Barriers to Water Demand Management: health - Beacon

WA7060/6

Barriers to Water Demand Management: health, infrastructure and maintenance Final A report prepared for Beacon Pathway Limited March 2010

The work reported here was funded by Beacon Pathway Limited and the Foundation for Research, Science and Technology

Barriers to Water Demand Management: health, infrastructure and maintenance: WA7060/6

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About This Report Title Barriers to Water Demand Management: health, infrastructure and maintenance

Author Dr. David Kettle, D&B Kettle Consulting Ltd Reviewer Dorothy Wilson, Beacon Water RTL, Lois Easton (Beacon Pathway), Vicki Cowan (Beacon Pathway), Stan Abbott (Massey University) Abstract This report documents the research findings from a literature review focussed on aspects related to rainwater tanks and greywater systems as part of the water supply demand management ‘tool box’. It discusses health risks, maintenance/ownership, centralised/decentralised, barriers to adoption and possible solutions.

While rainwater tanks for non-potable water uses (toilet, laundry and outdoor) are generally gaining greater acceptance in urban areas, use of rainwater for potable uses is not seen as acceptable at this stage. Greywater systems have less acceptance than rainwater tanks as there are greater uncertainties over health risks and ongoing maintenance. In both cases: proper installation, monitoring and regular maintenance are key issues.

One potential barrier to the uptake of both rainwater tanks and greywater systems is the possible revisions to the new Building Code that propose an unworkable and inappropriate single number as a water quality standard.

Reference Kettle, D. March 2010. Barriers to Water Demand Management: health, infrastructure and maintenance.Report WA7060/6 for Beacon Pathway Limited. Rights Beacon Pathway Limited reserves all rights in the Report. The Report is entitled to the full protection given by the New Zealand Copyright Act 1994 to Beacon Pathway Limited.

Disclaimer The opinions provided in the Report have been provided in good faith and on the basis that every endeavour has been made to be accurate and not misleading and to exercise reasonable care, skill and judgment in providing such opinions. Neither Beacon Pathway Limited nor any of its employees, subcontractors, agents or other persons acting on its behalf or under its control accept any responsibility or liability in respect of any opinion provided in this Report.


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Contents Prologue ........................................................................................................................................ 1 1 Executive Summary................................................................................................................ 2 2 Introduction............................................................................................................................. 5 3 Background............................................................................................................................. 6

3.1 Research Scope.............................................................................................................. 6 3.2 Research Method ........................................................................................................... 6

4 Technical Descriptions and Terminology............................................................................... 8 4.1 Water Supply Demand Management ............................................................................. 8 4.2 Rainwater Characteristics and Terminology.................................................................. 9 4.3 Wastewater Characteristics and Terminology ............................................................. 12 4.4 Water Reuse Characteristics and Terminology............................................................ 15 4.5 Infrastructure Characteristics and Terminology .......................................................... 16

5 Health Risks.......................................................................................................................... 19 5.1 Research Question ....................................................................................................... 19 5.2 Chapter Outline............................................................................................................ 19 5.3 Rainwater Tanks – New Zealand Specific................................................................... 19 5.4 Greywater Systems – New Zealand Specific............................................................... 28 5.5 Discussion.................................................................................................................... 35

6 Maintenance/Ownership ....................................................................................................... 41 6.1 Research Question ....................................................................................................... 41 6.2 Chapter Outline............................................................................................................ 41 6.3 Internationally Accepted Issues ................................................................................... 42 6.4 Low Impact Urban Design and Development ............................................................. 44 6.5 Glencourt Place............................................................................................................ 45 6.6 Talbot Park................................................................................................................... 49 6.7 Kapiti Coast District Council....................................................................................... 50 6.8 Tauranga City Council................................................................................................. 52 6.9 North Shore City Council ............................................................................................ 52 6.10 On-Site Wastewater Treatment.................................................................................... 53

7 Infrastructure – Centralised and Decentralised..................................................................... 55 7.1 Research Question ....................................................................................................... 55 7.2 Chapter Outline............................................................................................................ 55 7.3 Overview...................................................................................................................... 56 7.4 Financial Planning and Risk ........................................................................................ 57 7.5 Community and Watershed Impacts............................................................................ 59 7.6 On-site and Neighbourhood Impacts ........................................................................... 60 7.7 Capital and O&M Costs............................................................................................... 62 7.8 Infrastructure Synergies: benefits of integration.......................................................... 71 7.9 Management ................................................................................................................ 74


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7.10 Reliability, Vulnerability and Resilience..................................................................... 75 8 Summary Main Points and Conclusions............................................................................... 77

8.1 Health Risks................................................................................................................. 77 8.2 Maintenance/Ownership .............................................................................................. 79 8.3 Infrastructure – Centralised and Decentralised............................................................ 81 8.4 Conclusions.................................................................................................................. 83

9 References............................................................................................................................. 86 10 Appendix A: New Zealand Ministry of Health Documentation on Wastewater Re-use ...... 93 11 Appendix B: NSW Domestic Greywater Treatment Systems Guidelines.......................... 101

11.1 Source Documents ..................................................................................................... 101 11.2 Summary.................................................................................................................... 101 11.3 Greywater in Sewered Areas ..................................................................................... 103

12 Appendix C: Kapiti Coast District Council Water Demand Management ......................... 108 12.1 Source Documents ..................................................................................................... 108 12.2 Background................................................................................................................ 108 12.3 Proposed Plan Change 75 .......................................................................................... 117 12.4 Ongoing Work ........................................................................................................... 120


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Tables Table 1: Total Coliforms and E. coli. of Roof-Collected Rainwater.......................................... 11 Table 2: Comparison of greywater quality and sewage .............................................................. 12 Table 3: Typical BOD5 and SS Levels for Treated Domestic Sewage....................................... 14 Table 4: Australian NSW Greywater Reuse Compliance Criteria ............................................. 14 Table 5: Water Reuse Categories and Typical Applications...................................................... 15 Table 6: Example Total Coliforms and E.coli Tests for Roof-collected Tank Water after a First

Flush Diverter..................................................................................................................... 24 Table 7: Example Total Coliforms and E.coli Tests for Roof-collected Tank Water (Control

Tank) .................................................................................................................................. 25 Table 8: Untreated Greywater Characteristics ............................................................................ 33 Table 9: Comparative Untreated and Treated Greywater Quality (Leonard et al. 2006)............ 34 Table 10: Cost of Greywater System per Household/unit........................................................... 68 Table 11: Individual and Community Costs for Rainwater Tanks.............................................. 71 Table 12: Five Scenarios Modelled for the Kapiti District ....................................................... 110 Table 13: Greywater and Sewage Quality................................................................................. 112

Figures Figure 1: Dual Purpose Rainwater Tank Schematic (NSCC 2009) ........................................... 10 Figure 2: Some Essential Elements for Safe Rainwater Harvesting ........................................... 11 Figure 3: Schematic of Wastewater Treatment Systems used for Water Reuse ......................... 17 Figure 4: Earthsong E.Coli versus 7 day Rainfall Dec 2005 to May 2008 ................................ 26 Figure 5: Flow versus Capacity for Centralised and Decentralised Systems .............................. 57 Figure 6: Comparison of Capital Outlays for Hypothetical “Smallside, USA” .......................... 58 Figure 7: Differences in Total Lifecycle Costs for “Smallside, USA – Central System Costs

Minus Onsite System Costs................................................................................................ 58 Figure 8: Capital Cost per Service .............................................................................................. 63 Figure 9: Operating Cost per Service .......................................................................................... 63 Figure 10: Total System Cost per Service................................................................................... 64 Figure 11: Total cost of water for graywater scenarios versus number of connections .............. 65 Figure 12: Harvest efficiencies of natural and roof catchments.................................................. 66 Figure 13: Average Yearly Percentage of Water Supplied (at water use rate of 225 litres per

day) versus Rainwater Tank Size ....................................................................................... 72 Figure 14: Average Yearly Percentage of Water Supplied (at water use rate of 500 litres per

day) versus Rainwater Tank Size. ...................................................................................... 73


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Prologue Beacon Pathway sees water demand management (water efficiency) as a sensible and cost-effective approach for the wise management of water supply in New Zealand. In discussions with councils in different parts of the New Zealand, it has become clear that there are four steps that can be considered: 1) Councils’ management of its own infrastructure, water pressure reduction, intensifying

leakage programmes, energy-efficient management techniques etc 2) Councils’ metering and pricing mechanisms 3) Basic water-efficient technology for households - such as ‘gizmos’ water-efficient shower

heads, dual flush toilets, aerating faucets and small water barrels. 4) Higher cost household solutions such as sizable water tanks and grey water systems. Beacon has developed a range of tools to support councils implement water demand management: a decision making framework in Slowing the Flow; a resource manual to support more sustainable building (addresses all components of Beacon’s HSS); and an economic framework to value water demand management. Beacon’s homes research programme has developed advice for new build and renovation of existing homes which adopts existing water efficiency as standard to reduce water demand from homes. This research is to understand the barriers to the next step of augmenting council water supply with rainwater harvesting and re-use at the household level. Consistent advice and feedback from stakeholders during consultation on Beacon’s water research has identified three core issues as the main barriers: health; maintenance and infrastructure. This report is commissioned to improve the knowledge base and direct future activities at unlocking barriers to water efficiency techniques.


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1 Executive Summary This report documents research findings from a literature review on the health risks, maintenance/ownership and centralised/decentralised issues, barriers and possible solutions for the adoption of rainwater tanks and greywater systems as part of the water supply demand management ‘tool box’. The main conclusions from the report are: Rainwater tanks for non-potable water uses (toilet, laundry and outdoor) are generally gaining greater acceptance by the public and officials, with the following main issues:

Some health regulators believe that health risks are manageable for rainwater use as a non-potable water use. In New Zealand, at present, some health authorities believe that if water tanks are properly installed, labelled and maintained, they are safe to use for non-potable use - flushing toilets, laundry and garden use. Therefore urban dwellers need to be aware of the maintenance requirements and at this stage, rainwater use in the urban setting is not recommended for potable water.

Significant construction cost savings (up to 50%) can be realised by installing the rainwater tank and dual plumbing systems in new ‘greenfield’ developments compared to retrofitting existing ‘brownfield’ areas. Case studies in the Auckland area have shown dual purpose rain tanks and plumbing systems to save approximately 40% of the total household water usage.

Significant cost sharing is possible when incorporating synergies with stormwater management.

Possible region-wide benefits are possible with wide spread adoption by delaying the construction of new water supply head works infrastructure. Careful design of the rainwater tank system is necessary to achieve maximum benefits, such as a trickle feed ‘top up system’ so both the peak daily and average yearly water demands are reduced.

Neighbourhood options can show some cost savings. Rainwater tanks offer resilience to the water supply network to disruptions from natural

hazards Some new developments are mandating rainwater tanks for non-potable use and accepting

the relatively small cost premiums (compared to house and land costs) as a ‘resilient’ action to take.

Simple financial cost-benefit analyses show relatively long pay back periods of 20 to 30 years. However, these simple cost-benefit analyses fail to take into account any synergies and other social and environmental benefits (and costs) to the wider community (such as reduced stormwater discharges and the need for future water supply upgrades).

There is a potential barrier with the low one-single-number water quality standard of ‘not to exceed 10E.coli/100ml’ in the proposed revisions to the Building Code as it is unworkable and inappropriate and appears not to be based on any sound epidemiological studies or risk assessment. Water quality readings from ‘acceptable’ rain water tanks in NZ indicates that


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the readings are highly variable, very few rainwater tanks would meet this requirement, and if the water is for non-potable use it appears inappropriate to set such a low ‘not to exceed’ limit.

Greywater systems are still not widely accepted by the public or regulatory bodies, with the following main issues:

Have the advantage that they provide a reliable year round supply of non-potable water and reduce the water discharged from the house that requires treatment at a wastewater treatment plant.

If grey water systems are properly installed, labelled, monitored and maintained they have some acceptance in the urban setting if used for subsurface irrigation only, such as in the Kapiti Coast District Council’s Water Management Plan mandating all new development to include either a rain water tank or a rainwater tank and a greywater diversion device.

Greywater reuse systems (for irrigation and toilet flushing) have been installed in rural subdivision developments but they do not have the same degree of acceptance in the urban setting.

The concerns of ongoing maintenance have led to the concept of ‘decentralised construction with centralised management’ to get the best of decentralised construction technologies and centralised ‘microprocessor-based’ management systems.

Studies on greywater reuse systems have shown economies of scale in per-unit costs from individual households up to about 100 to 1,000 connections, then level off, and slightly increase again after 10,000 connections, but this varies with different treatment technologies.

However, greywater systems:

Have greater uncertainties over health risks. Are generally not accepted by the Ministry of Health for inside use for toilets, for example.

Have a large variation in system type and cost depending on the degree of reuse water quality treatment.

Have greater concerns over maintenance than rainwater tanks. As for rainwater tanks, the proposed revisions to the Building Code include a low, one-

single-number, but at a lower number of ‘not to exceed 1 E.coli/100ml’ for all greywater systems. This appears inappropriate given other international industry guidelines that recommend a three tiered system of increasing regulatory requirements to reflect varying size and risks to public health.


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Another point related to the inappropriate low number of 10 E.coli/100ml for rainwater and 1 E.coli/100ml for greywater is the comparison to the acceptable/green mode monitoring value (O.K for swimming) of ‘no single value greater than 260 E.coli/100ml’ from the freshwater recreational swimming guidelines (MfE 2003). Although the recreational swimming guidelines state that these guideline values cannot be applied to water uses other than recreational uses, it does highlight the inconsistency and difficulty of using E.coli as an indicator organism.


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2 Introduction Beacon’s goal is to bring the vast majority of NZ homes to a High Standard of Sustainability®, HSS® by 2012. It therefore set high level targets for each of its components of the HSS® (energy, water, indoor environment quality and materials). The water target relates to reticulated water supply to the residential built environment, setting a 40% reduction in demand from all homes and 50% reduction in council supply by 2012. At the level of the household, Beacon’s HSS water benchmark is 125litres/person/day.

Over the last five years, Beacon have produced a number of reports addressing the issues of water demand management. These include:

The Neighbourhoods Sustainability Framework, January 2006 Making Policy and Regulations Rain Tank Friendly, March 2007 Best Practice Water Efficiency Policy and Regulations, May 2008 Slowing the Flow: A Comprehensive Demand Management Framework for Reticulated

Water Supply, January 2008 Integrated Water Management (IWM) Design Criteria Report, July 2009 Building Sustainable Homes: A Resource Manual for Local Government, June 2009 Framework to value water demand management, with case study of Tauranga City Council,

2010. These reports are available from the Beacon website, www.beaconpathway.co.nz. Beacon’s current knowledge base has identified best practice water demand management. This includes the wide range of options, such as low flow shower heads, water efficient washing machines, water metering, rainwater tanks, greywater reuse and many others. Councils have been prioritised by Beacon as a key uptake channel and so most resources (e.g. the decision making framework in ‘Slowing the Flow’) have been directed at supporting improved council decision making. Beacon’s research has also quantified the value of adopting best practice water demand management (i.e. why should councils bother?).

Through a series of five Beacon workshops conducted in 2008, attended by utilities, policy, regulatory and communications staff, three areas were cited as barriers to the uptake of water supply demand management infrastructure options. These three areas were:

Health risks Maintenance/Ownership Infrastructure – centralised versus decentralised

This research was commissioned to improve Beacon’s knowledge of the impact of these three areas on the adoption of rainwater tanks and greywater systems for water demand management in New Zealand.

http://www.beaconpathway.co.nz/


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3 Background 3.1 Research Scope This report identifies the barriers to greater uptake of two key water demand management options available to homes and neighbourhoods, namely water tanks and grey water systems. It is now generally accepted that the technologies required to reduce water demand are readily available, but it is the perceived drawbacks/barriers which are limiting their uptake on a national scale. For this Beacon project, the two sources of water being considered for reducing household demand for reticulated water are:

Rainwater – through use of urban rainwater tanks Treated greywater (bathroom and laundry water) – through collection from individual

households This Beacon project specifically addresses three primary barriers to the uptake of rainwater and treated greywater use, those barriers having been identified in five Beacon workshops conducted in 2008, as:

Health risks – through the use of non-drinking water quality (rain water and/or greywater use) at the house or neighbourhood scale

Maintenance/Ownership – particularly where privately owned infrastructure (e.g. a rain water tank) is being used to provide a public infrastructure benefit (e.g. smaller reticulated pipe network)

Infrastructure – centralised and decentralised – the costs and benefits of many small local systems versus one centralised collection and treatment option. This is particularly relevant when looking at reuse of water (either rain water or greywater) where the potential users are located some distance from the one centralised treatment plant. Localised reuse options can be located closer to the end user.

3.2 Research Method Research was carried out through a literature review of national and international reports/findings found through an internet search, or recommended by other contacts made during the course of the work. Although the issues of greywater use and a revived urban rainwater harvesting focus are relatively new, there is an immense amount of literature published on these topics, with differing viewpoints. This brief report can therefore in no way present all the literature that is available, but best efforts have been made to present as wide a cross-section of viewpoints as possible and present the author’s synthesis of the information presented, primarily from an engineering standpoint.


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It is acknowledged that addressing these issues of water resource availability and use from a holistic or sustainability standpoint requires a broad cross-section of viewpoints and expertise. For example, with respect to health issues, these can be addressed from a number of different areas of expertise:

Social acceptability and uptake – people’s behaviour patterns and ability to ‘handle’ and adapt to new technologies and change what ‘they have always done’: This requires input from social scientists and behavioural change specialists.

Public health standpoint – human health issues and effect of differing levels of contaminants on human health: this requires expertise from human health professionals

Engineering standpoint – infrastructure constructability and operational issues and impacts on resulting water quality: this requires expertise from professional engineers

Risk standpoint – addresses both likelihood of occurrence and consequence of failure and the ability to assess different areas of risk (e.g. public health risk and engineering risk) and then combine to an overall risk assessment: requires a formal risk framework, such as that based on the Australian/New Zealand Risk Management Standard AS/NZS 4360:2004.

While this report’s author is an engineer, every effort has been made to present a summary of social, public health and risks aspects documented in the literature reviewed. Readers will notice that there is often contradictory information found in the literature, with not necessarily clear black and white answers. It is hoped that this report will improve the knowledge base around barriers to greater uptake of best practice water management and identify what is needed to overcome them.


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4 Technical Descriptions and Terminology For background it is useful to present a brief summary of the characteristics and terminology of water supply demand management, rainwater, wastewater, water reuse and infrastructure in order to understand the likely health risks, maintenance/ownership issues and different infrastructure options (i.e. centralised vs decentralised systems). A brief summary is presented in the following sections on: Section 4.1 – Water Supply Demand Management Section 4.2 – Rainwater Characteristics and Terminology Section 4.3 – Wastewater Characteristics and Terminology Section 4.4 – Water Reuse Characteristics and Terminology Section 4.5 – Infrastructure Characteristics and Terminology

4.1 Water Supply Demand Management Water supply demand management, or water conservation, has been viewed historically by the water industry as a standby or temporary measure that is utilised only during times of drought or other emergency water shortages. However, this limited view is changing, especially in cases where there is a need for a new water supply; demand management has been proven to be a viable long-term supply option (Vickers, 2001 cited in Metcalf & Eddy, AECOM 2006, Lawton, M. et al. 2008). The previous report prepared for Beacon Pathway Limited on water efficiency (Lawton, M. et al. 2008) provided a concise summary of the increasing awareness of the documented advantages and disadvantages of demand management. The full list of advantages and disadvantages will not be repeated here, but suffice to say they generally fall into the following broad categories:

Cost savings – such as reducing capital costs through delaying or eliminating expansion of water supply infrastructure reservoirs and/or pipelines, reducing wastewater operating costs through reducing wastewater volumes in the main trunk wastewater system, reduced energy and chemical inputs for the water supply system.

Building resilience – such as reducing competing demands for water in parts of the country where water resources are constrained, and the need to cope with greater variability in climate patterns.

Social/ethical considerations – to meet the goal of water resource sustainability it is necessary to ensure that water is used efficiently and the legislative requirement of the New Zealand Local Government Act sustainability principles across the four pillars of wellbeing – cultural, social, environmental and economic.

Perceived drawbacks – the lack of expertise in this new field, both from the water utility operator and the end users, amendments to existing regulations and codes of practice, health risks, new ownership, operating and maintenance requirements and responsibilities, and challenging ‘business as usual’ paradigm.


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This also leads to the changing role of water resources engineers and managers. Whereas twentieth century engineers and managers were trained to build dams, reservoirs and water and wastewater treatment facilities, today’s water professionals are confronted with the complex task of assessing the sustainability of water and its impact on society and the environment. In addition to considering technical and economic aspects of water management projects, today’s water professionals are becoming stewards of water resources for the current and future needs of humans and the environment. This new approach incorporates the principles of sustainability, environmental ethics and public participation. Public participation is increasingly being recognised as a vital component, especially with water reuse, as the public can often make or break a water reuse project if wrong information or misplaced perceptions take hold during the planning and design stages.

4.2 Rainwater Characteristics and Terminology For this Beacon project rainwater is considered in the context of ‘rainwater harvesting’ from urban roofs into a rainwater tank and using it for non-potable (toilet flushing, laundry and outdoor use) or potable (kitchen, shower and indoor taps) uses. While the concept of a rainwater tank is simple, in the rural/urban environment they can be differentiated into five generalised types (NSCC 2009):

Water Supply Tank – to provide the main water supply to a household in areas where non-potable and potable water supply is not available (generally in rural areas)

Single Purpose Rain Tank – to provide an alternative non-potable water supply to a household (and water bill savings where connected to a user pays mains water supply) and in doing so reducing the annual volume of stormwater runoff from the site.

Detention Tank – to reduce the peak flow of stormwater leaving a site by temporarily storing the rainwater in a tank and releasing it over time through a ‘small’ (10 to 20mm diameter) orifice during and after the rainwater event.

Dual Purpose Rain Tank – to provide both an alternative non-potable water supply to a household and to reduce the peak flow of stormwater leaving the site. This is achieved by having a ‘permanent’ storage volume in the bottom portion of the rainwater tank (below the small diameter orifice) and having the top part of the tank (above the small diameter orifice) provide ‘temporary’ storage to reduce the peak runoff from a rainfall event. (Refer Figure 1 below)

Rain Barrels – these are similar to Single Purpose Rain Tanks but smaller in scale (the size of say a 200 litre barrel rather than a say 3,000 to 10,000 litre rain tank).


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Figure 1: Dual Purpose Rainwater Tank Schematic (NSCC 2009)

While many rural parts of New Zealand rely on rainwater for both potable and non-potable uses, this Beacon project is primarily focused around the more readily acceptable (from health perspectives) non-potable water uses. Microbial growth in rainwater storage tanks can occur (Abbott 2006a):

If the water is physically dirty Regrowth of microbes associated with rotting vegetation Animals and/or decaying animal matter in the tank Biofilms on internal surfaces Nutrients in sediments in the bottom of the tank

Providing the rainwater is clear, has little taste or smell and is collected from a well-maintained system, it is probably safe and unlikely to cause any illness in most users (Cunliffe, 1998 and Gould, 1999, cited in Abbott 2006a). However, a number of national and international studies have shown that the microbiological quality of roof-collected rainwater is usually poor, often fails to meet drinking water standards and frequently there is evidence of faecal contamination in the stored roof water (Abbott 2006a). For example, in a five year study of the microbiological quality of roof-collected rainwater samples of 560 private dwellings in New Zealand (with little or no pre-treatment) measurement of the Total coliforms and E. coli gave the following results presented in Table 1 (Abbott et al. 2006b, Table 1):


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Table 1: Total Coliforms and E. coli. of Roof-Collected Rainwater

Range per 100ml (N = 560)

Total Coliforms Escherichia coli (E. coli)

0 – 10 179 (32%) 202 (36%)

10 – 20 34 (6%) 56 (10%)

20 – 60 50 (9%) 72 (13%)

60 – 100 67 (12%) 84 (15%)

100 – 200 62 (11%) 90 (16%)

> 200 168 (30%) 56 (10%)

Total coliforms and Escherichia coli (E. coli) are typically measured as indicator organisms for drinking water quality. E. coli is the bacterial indicator of choice in the Drinking Water Standards for New Zealand (Ministry of Health 2005), with a drinking water standard of less than 1 (one) organism per 100ml. The above table shows that about 65% of the roof-collected rainwater samples in this study are above 10 E.coli/100ml (Abbott et al. 2006b). Examples of some of the essential elements of the collection and storage system to ensure the best practical water quality are shown on the schematic below, Figure 2.

Figure 2: Some Essential Elements for Safe Rainwater Harvesting

(Rodney District Council, cited in Abbott 2008)


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4.3 Wastewater Characteristics and Terminology Some background terminology of wastewater characteristics and different degrees/types of treatment is useful, particularly when referencing health risks and maintenance requirements.

Wastewater, including any by-products, can be divided up into six broad categories: 1) Full domestic sewage (traditional combination of black and grey water) 2) Blackwater – consisting of only toilet flush water and kitchen wastewater containing food

waste. Typically higher in organic matter, nutrients and pathogens. 3) Greywater – from bathroom and washing facilities that does not contain concentrated

human waste (i.e. flush water from toilets) or food waste (i.e. kitchen sink). Examples include bath and shower water, hand wash water and laundry washwater.

4) Tradewaste water – from commercial or industrial processes 5) Treated effluent – the purified wastewater that is disposed of to the receiving environment 6) Sludge (biosolids) – by definition, purification of wastewater involves removal of

undesirable constituents and these are typically concentrated into an end by-product called sludge or biosolids.

For this report, the focus is on the treatment and reuse of the greywater portion of the wastewater, having a greater acceptability to the public as a reuse option than the more contaminated blackwater. In the same light, trade wastes have also been ruled out for treatment and reuse due to the higher risk of increased contaminants.

Comparison of greywater quality and sewage (black and grey water) is given below in Table 2 (NRMMC 2006, Australian Guidelines for Water Recycling: Managing Health and Environmental Risks (Phase 1), Table 3.10, page 116).

Table 2: Comparison of greywater quality and sewage

(NRMMC 2006)

Greywater Parameter

Range Mean Sewage

Escherichia coli (E.coli)/thermotolerant coliforms (per 100ml)

101 - 107 No value 106 - 108

Suspended solids (mg/L) 2 - 1500 99 100 - 500

BOD5 (mg/L) 6 - 620 430 100 - 500

Nitrite < 0.1 – 4.9 No value 1 - 10

Ammonia (mg/L) 0.06 – 25.4 2.4 10 - 30

Total Kjeldahl nitrogen (mg/L) 0.06 - 50 12 20 - 80

Total phosphorous (mg/L) 0.04 - 42 15 5 - 30

pH 5.0 – 10.0 8.1 6.5 – 8.5


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Of note from the above table are:

The parameters used in other parts of this report are the primarily coliforms, suspended solids and BOD5.

In the worst cases, concentrations of faecal micro-organisms (coliforms) are almost as high as those found in sewage.

The significantly wider range of values in greywater than that for sewage (e.g. for suspended solids and BOD the high and low values for greywater are both lower and higher than those for sewage)

The reason for this variation is that both microbial and chemical quality depend on human behaviour and individual control of materials discharged into greywater.

There is also terminology around the different degrees of wastewater treatment. Treatment of wastewater and its by-products, can be classified into seven types:

1) Preliminary treatment – the removal of “gross solids”. Examples are screening and grit removal.

2) Primary treatment – the removal of “settleable” solids by sedimentation or (for lighter than water fats and greases) flotation and surface skimming. Examples are conventional sedimentation and septic tanks.

3) Secondary treatment – the biological conversion of initially nonsettleable “dissolved” and “colloidal” solids into bio-floc that is settleable, and removal (typically by sedimentation). There are numerous biological/secondary process types.

4) Tertiary treatment – the removal of residual dissolved and non-settleable solids that are not removed by secondary treatment. An example is sand filtration.

5) Advanced treatment – further treatment of the effluent by such methods as membrane filtration, activated carbon filtration, ion exchange and reverse osmosis. Advanced treatment can be capable of producing water of drinking quality.

6) Disinfection – typically applied to the primary, secondary, tertiary or advanced treatment effluents for the destruction/removal of pathogenic microbes. Examples are ultraviolet light (UV), chlorine and ozone.

7) Disposal of sludge – commonly taken to landfills or can be applied to pasture or forest land provided that it meets certain guidelines and/or additional treatment.

The quality of the wastewater effluent is commonly referred to in terms of biochemical oxygen demand (BOD5) and suspended solids (SS) in concentrations per million (ppm), milligrams per litre (mg/L) or grams per cubic metre (g/m3), (all of these parameters, ppm, mg/L and g/m3 are equal in number).

Definitions of these two terms are:

BOD5 – the amount of oxygen consumed by microbes in biodegrading organic matter. Typically measured as the oxygen consumed in 5 days at a constant temperature of 200C.


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SS – suspended solids, those solids in suspension (as distinct from in solution) that are of sufficiently large particle size (albeit microscopic) as to be removable on a fine laboratory filter.

Typical BOD5 (Biochemical oxygen demand, measured as the oxygen consumed in 5 days at a constant temperature of 200C) and SS (suspended solids) levels for different degrees of treated domestic sewage are presented in Table 3 (EcoWater – Waitakere City Council 1999):

Table 3: Typical BOD5 and SS Levels for Treated Domestic Sewage

Treatment Type BOD5 (ppm or mg/L) SS (ppm or mg/L)

Raw sewage 300 300

Preliminary treatment 300 300

Primary effluent 200 150

Secondary effluent 20 30

Tertiary effluent 10 10

Advanced effluent <1 <1

For comparison against guidelines for treated greywater, the compliance criteria from the Australian NSW guidelines for Total coliforms, BOD5 and SS are presented in Table 4 below (NSW Health 2005):

Table 4: Australian NSW Greywater Reuse Compliance Criteria

(NSW Health 2005)

Table 2 (NSW Health 2005): Compliance Criteria for Effluent Quality from DGTS According to Disposal/Utilisation Method

Disposal Method T. coliforms cfu/100ml

BOD5 mg/L

SS mg/L

Free Cl2 mg/L

Sub-surface irrigation

90% of samples < 20 < 30

Maximum threshold < 30 < 45

Surface irrigation

90% of samples < 30 < 20 < 30 > 0.2 - < 2.0

Maximum threshold < 100 < 30 < 45 < 2.0

Toilet / Washing Machine reuse

90% of samples < 10 < 10 < 10 > 0.5 - < 2.0



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It can be seen from the above terminology and examples, that the use of greywater for ‘non-people contact’ sub irrigation are less severe than for toilet flushing and other similar uses where there is greater likelihood of people contact.

4.4 Water Reuse Characteristics and Terminology As background information it is also prudent to give a brief summary of water reuse in general, before focussing specifically on rainwater tanks and greywater systems, particularly as there are a number of different end uses of this ‘non-drinking water quality’ water.

For the Beacon focus on the house and neighbourhood scale the different water reuse categories and their applications are summarised in Table 5.

Table 5: Water Reuse Categories and Typical Applications

Category Typical application

Landscape irrigation Residential

Parks

Non-potable urban uses Toilet flushing

Outdoor uses - exposed (e.g. washing the car from outdoor taps)

Outdoor uses – unexposed (e.g. subsurface irrigation)

Laundry clothes washing

Fire protection

Potable uses Blending in with ‘drinking water quality’ water supply

Standalone water supply for all uses – potable and non-potable

This variability of water quality and end uses requires a different approach to that of the design of one water quality for all uses (that is, the conventional potable water system design). The engineering issues for water reuse systems are:

Water quality Public health protection Wastewater treatment alternatives Pumping, storage and distribution system siting and design On-site conversions such as potable and non-potable plumbing separation Matching of supply and demand Supplementary and back up water supplies

The most common concern for water reuse projects is public health protection. For example, the Metcalf & Eddy textbook on water reuse (Metcalf & Eddy, AECOM 2006) states in Part 2: Health and Environmental Concerns in Water Reuse:


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‘While there is no reliable epidemiological evidence that the use of reclaimed water for any of its applications has caused a disease outbreak in the United States, potential transmission of infectious disease by pathogenic organisms is the most common concern in water reclamation and reuse.’

The factors affecting water reuse guidelines and regulations and water quality requirements are (Metcalf & Eddy, AECOM 2006, Table 4-1):

Public health protection – water reuse guidelines and regulations are directed principally at public health protection.

Use area controls - reclaimed water quality requirements are based on proper controls and safety precautions implemented at areas where the water is used.

Use requirements - physical, chemical, and/or microbiological quality may limit user or regulatory acceptability of reclaimed water for specific uses.

Environmental considerations – natural flora and fauna should not be adversely affected. Aesthetics - reclaimed water should be no different in appearance than potable water, that

is, clear, colourless and odourless. Political realities - Regulatory decisions may be influenced by public policy, public

acceptance, technical feasibility and financial considerations. The microbial and chemical constituents and physical properties of water that are of concern in water reuse applications are (Metcalf & Eddy, AECOM 2006, Table 4-2):

Microbiological constituents – bacteria, protoza, helminths and viruses Chemical constituents – biodegradable organics (BOD5), total organic carbon, nitrates,

heavy metals, pH, trace elements, disinfection by products and total dissolved solids. Physical properties – total suspended solids (TSS), turbidity and temperature.

Another important aspect of treatment for water reuse is the provision of multiple barriers; the principle of establishing a series of barriers to preclude the passage of pathogens and harmful organic and inorganic contaminants. For water reuse, barriers may take the form of:

Source control programmes designed to prevent the entrance of deleterious substances into the wastewater collection system that will inhibit treatment or may preclude reuse;

A combination of treatment processes wherein each provides a specific level of constituent reduction;

An environmental buffer, such as retention or storage ponds, dilution with freshwater, or soil-aquifer treatment that permits blending or equalising water quality.

4.5 Infrastructure Characteristics and Terminology When considering the centralised versus decentralised debate it is useful to briefly review the different types of infrastructure for the collection, treatment and distribution of urban water services, in terms of wastewater, stormwater and water supply.


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For example, in wastewater there are three different infrastructure systems, commonly referred to as centralised, satellite and decentralised systems. Centralised treatment plants are typically located at a low point in the drainage area, usually near the point of effluent disposal, and not necessarily at locations with the greatest potential for water reuse. In contrast, satellite systems are located in the upper reaches of the service area close to potential water reuse projects such as agricultural irrigation and recreational enhancement. Satellite systems take wastewater from the main collection system; treat it to the reuse grade, and the residuals produced in the treatment system are returned to the main collection system for treatment at the central treatment plant. Satellite systems effectively ‘mine’ the wastewater stream at locations closest to the water reuse sites. Decentralised systems are defined as the collection, treatment and reuse of wastewater from individual homes, clusters of homes, isolated or portions of communities at or near the point of wastewater generation. Often the term decentralised also includes the subset of satellite systems. For this report, the greywater devices are predominantly for the individual and community scale reuse systems. Examples of these different treatment systems are depicted in Figure 3 (Source: Metcalf & Eddy, AECOM 2006, Figure 6-12).

Figure 3: Schematic of Wastewater Treatment Systems used for Water Reuse


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Figure 3 gives examples of the three systems for water reuse as:

a) Centralised system – with a treatment plant upgrade to produce water for reuse. b) Satellite systems – for toilet flushing, water features and irrigation. c) Decentralised systems – individual on-site treatment with drip irrigation and community

treatment with landscape irrigation. The two other types of water infrastructure are stormwater and water supply. For stormwater, the conventional ‘centralised’ system comprises a pipe collection network, with or without stormwater treatment; stormwater treatment being mainly ‘end-of-pipe’ treatment systems such as wetlands and filter systems. The new ‘decentralised’ approach focuses on managing the stormwater ‘at the source’ and thus reducing the need for larger and larger pipes. Small scale ‘at-source’ stormwater treatment includes rainwater tanks, bio-retention devices such as rain gardens, permeable paving and grass swales. For water supply, the conventional ‘centralised’ systems generally collect water from watershed reservoirs, streams and lakes, groundwater wells and natural springs. Treatment is generally at a centralised municipal water treatment plant with distribution through a central pipe network. On the other hand, ‘decentralised’ systems focus on collecting water closer to the point of use. For this Beacon project the focus is on individual or community scale roof-collected rainwater tanks (predominantly for non-drinking purposes of toilet, laundry and outdoor) and greywater reuse (either for irrigation or toilet flushing).


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5 Health Risks 5.1 Research Question The Beacon research question to be answered for health risks is:

What is the nature and scale of the problem that on-site rainwater and greywater systems present NZ in terms of health risk?

This section presents the literature research carried out to help answer this question in the following topic areas: Rainwater Tanks:

Used for outdoor non-potable use – the garden, washing cars etc Used for indoor non-potable use – toilet and laundry Used for potable use – drinking water taps and bathroom

Greywater Systems:

On an individual site for sandy and clay soils; - Sub-surface irrigation - Toilet flushing

In a whole subdivision: for sandy and clay soils (i.e. the cumulative effect); - Sub-surface irrigation - Toilet flushing

5.2 Chapter Outline Section 5.3 presents the New Zealand specific literature review for rainwater tanks, and Section 5.4 for greywater systems. This literature research has raised a number of important issues with respect to barriers of including rainwater tanks and greywater reuse as part of the wider selection of demand management options. These issues are discussed in Section 5.5.

5.3 Rainwater Tanks – New Zealand Specific The health risks around roof-collected rainwater from on-site rainwater tanks are described below under the following headings specifically related to New Zealand based information:

Statutory Control The Ministry of Health and The Health Act Reported Health Incidents The Building Code Typical Roof-collected Rainwater Quality Example Existing Council Guidelines and Policies


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5.3.1 Statutory Control ‘Statutory control of individual water supplies falls under the Health Act 1956, the Local Government Act 2002, and the Building Act 2004. The Building Act requires premises to be provided with potable water for consumption, oral hygiene, utensil washing and food preparation and under Section 39 of the Health Act it is illegal to let or sell a house unless there is a supply of potable water. This means that the drinking water must not contain any contaminants that exceed the maximum acceptable values (MAVs), which in the case of Total coliforms and/or E.coli is less than 1 organism per 100ml (DWSNZ 2005)’ (Abbott 2008). However, it should be noted that the drinking water standards are less strict for private individual supplies servicing less than 25 people for less than 60 days a year. See sections below for further elaboration on individual statutory controls and documents. 5.3.2 The Ministry of Health and The Health Act An in-depth report prepared for Water Care Ltd and Beacon Pathway Ltd in March 2007, titled ‘Making Policy and Regulations Rain Tank Friendly’ (Lawton et al. 2007) specifically addressed relevant legislation, policy and regulations with respect to rainwater tanks. Section 3.4 of that report addressed the Health Act. Discussions with the Ministry of Health (MoH) and the Auckland Regional Public Health Service (ARPHS) in 2007 and further recent discussions in 2009/2010 indicate that the Health Act (1956) is unlikely to offer any legislative barriers relating to using rain water for non-potable uses provided suitable precautions are taken to ensure public health risks are appropriately managed. The three main precautions are to:

Minimise risk of using the non-potable rainwater for potable use, that is, for drinking water – to safeguard against this possibility all non-potable water outlets must be clearing labelled as not suitable for drinking and any non-potable pipelines are to be a different colour purple to distinguish them from pipes carrying potable water, and

Prevent possibility of the non-potable water contaminating the potable water source – to safeguard against this possibility all plumbing systems should have backflow protection as per the NZ Building Code (NZBC G12/AS1) which comprises of an ‘air gap’ and/or a backflow prevention device.

Ensure the rainwater collection and storage systems are adequately maintained and operated.

The Ministry of Health recommends using the public water supply, where available, for potable water use.


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5.3.3 Reported Health Incidents Although there have been numerous reports regarding the poor water quality of roof-collected rainwater supplies relatively few disease outbreaks linked to contaminated roof water have been reported (Abbott 2006a). Abbott 2006a cites numerous studies of reported health incidents, notably gastrointestinal diseases from pathogens such as Salmonella, Campylobacter, Giardia and Cryptosporidium (Koplan et al. 1978; Palmer et al. 1983; Broadhead 1988; Lester 1992; Crabtree et al. 1996; Eberhart-Phillips et al. 1997; Simmons and Smith 1997; Merrit et al. 1999; Tayloer et al. 2000; Simmons et al. 2001; Lye 2002; Thornley et al. 2003; Hoque et al. 2003). Full references are listed in the bibliography at the end of this report. However, it is the authors understanding that these reported health incidents have occurred where roof-collected rainwater has been used for potable drinking water purposes and not where it is used for non-potable non-drinking water only. This may be in part due to the practice of using roof-collected water only for non-drinking water purposes, which is a relatively new urban practice, and the fact that health surveillance data do not reflect the true nature of waterborne illnesses in the community as they usually only capture case-patients in contact with a health care facility. Similarly, a report prepared for the Ministry of Health by Environmental Science and Research Ltd, Estimation of the Burden of Water-borne Disease in New Zealand: Preliminary Report (Environmental Science and Research Ltd. 2007), states ‘there is ample evidence of waterborne disease outbreaks in New Zealand to indicate a significant risk of contracting gastro-intestinal disease from drinking water that is untreated or inadequately treated.’ The report gives an ‘average of 16.8 waterborne outbreaks (range from 6 to 27) occur annually, affecting an average of 145 cases/year (range from 18 to 370).’ 5.3.4 The Building Code It is the responsibility of the Councils to manage rainwater collection systems for non-potable use under the Building Act and/or Resource Management Act. Resource Consents are required if a proposed development infringes a rule set down in the local City/District Plan. Depending on the size and location of the rainwater tank, a resource consent may be required for issues such as; maximum building coverage, height-to-boundary limits, outdoor living and yard rules, modifications to a watercourse, installed within 20m of a stream, installing on steep slopes, and the removal of vegetation. All rainwater tanks require a building consent due to the household plumbing and drainage alterations required, except where tanks are installed for outside garden-use only. A building consent is approval from Council to carry out the proposed works at a specific site and is a legal requirement under the Building Act 2004, and it’s associated Building Code. Of interest to the rainwater harvesting building code requirements are the proposed revisions to the Building Code performance requirements that were initiated in 2006/2007 (Department of Building and Housing July 2007). At time of writing (March 2010) the author understands that


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the revisions are on hold, but they are of value as an indicator of thinking on these issues in 2007.

The proposed 2006/07 changes to the Building Code with respect to rainwater harvesting included Type 1 (clarifying the performance requirements that are either in the current Building Code or current Compliance Documents) and Type 2 (Substantive changes including changes to measures for performance requirements, changes to the scope of the requirements and different approaches to describing requirements) changes:

Type 1 change: Clarifying the distinction between drinking and non-drinking water systems (ibid, 2007, page 27) - ‘Where non-drinking water outlets are provided, a ‘non-drinking water’ sign or notice

shall be prominent at the outlet. - Water pipes and outlets with non-drinkable water shall be completely isolated from any

drinking water distribution system.’ Type 2 change: Raw water for other uses (ibid, 2007, page 53)

- ‘Raw water that is supplied from springs, bores and tank rainwater may be used for washing machines (excludes laundry tub), clothes washing, toilet flushing or irrigation.

- Raw water used for these purposes shall have low risk to human health from direct contact.

- The level of microbial indicators shall not exceed 10 E.coli/100ml (provided by Environmental Science and Research)’

Type 2 change: Distinguishing between drinking and non-drinking water systems (ibid, 2007, page 53) - ‘Water pipes with non-drinking water shall be continuously identified.’

All of the above changes are consistent with findings from the author’s literature review except for the level of microbial indicators being set to ‘shall not exceed 10 E.coli/100ml’. There are four primary concerns with this ‘not to exceed limit of 10 E.coli/100ml’ as a building consent control for non-potable household water use. These are: 1) It would be very difficult to enforce at a building consent level by building inspectors as to

enforce it correctly would require a number of microbial tests and can only be tested after the system has been installed and operating for some time.

2) What, where and when are they going to test the water? For example, would it be tested as it enters the tank, in the rain tank, as it leaves the rain tank, before or after the tank is topped up with potable water from the reticulated system, before or after a rain event, water from the outside tap, water in the toilet and how often it is to be tested?

3) The not-to-exceed 10 E.coli/100ml appears to be too strict from a practical point of view when looking at other guidelines and monitoring of existing rainwater roof-collected systems. The author certainly agrees to strict E.coli limits for potable drinking water, but questions a similar need for non-potable water uses such as flushing the toilet watering the garden, and washing the car. In addition, due to the inherent variability of E.coli readings, if an E.coli limit is to be used it would be more useful to have an acceptable range, such as,


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90% of samples not to exceed X, with a maximum threshold of Y rather than a single not-to-exceed value.

4) This not-to-exceed limit of 10 E.coli/100ml does not appear to be based on any sound epidemiological studies or risk assessment (Abbott 2010).

It is useful to view the appropriateness of the ‘not to exceed 10 E.coli/100ml’ standard for non-potable water uses in light of typical water quality readings from several examples in New Zealand, presented in the next section. 5.3.5 Typical New Zealand Roof-collected Rain Water Quality Some New Zealand studies on the microbiological quality of roof-collected rainwater and findings on the degree of maintenance carried out are presented below. The results that follow are for stand alone private supplies. 5.3.5.1 Study of 560 Private Dwellings

The sampling of roof-collected rainwater from 560 private dwellings in New Zealand by Abbott et al (2006b) (refer Section 3.2) showed that approximately 70% of those systems sampled would have failed the ‘not-to-exceed limit of 10 E.coli/100ml’. It is of interest to note that Abbott used a ‘somewhat arbitrary’ value of 60 E.coli or Total Coliforms per 100ml as an indicator of ‘compliance’ due to ‘some level of contamination in stored roof-collected rainwater is almost inevitable.’ Indeed, even using this higher limit of 60 E.coli/100ml, 40% of the samples were still noncompliant. These high levels can probably be explained by the fact that over 50% of the householders did not have even simple physical measures (such as gutter guards/screens and first flush diverters) in place to safeguard the water against microbiological contamination (Abbott 2006b). As with many systems, ongoing maintenance is the key to good performance. The Abbott 2006b study found the following lack of maintenance (Abbott 2006b):

10% did no gutter cleaning, the remainder did some gutter cleaning varying between 3 monthly (18%) to 2-yearly (15%) and periodically (20%).

50% didn’t know or did not do tank cleaning 50% did not have simple physical measures in place such as gutter guards, debris screens or

first flush diverters 60% did not have any form of treatment and of the 10% that filtered their water, 70% of the

filtered samples were in fact contaminated (not changing of filters is a very common issue). And Simmons et al (2000), cited in Abbott (2006b) found with 125 domestic roof-collected rainwater supplies from 4 rural Auckland Districts:

25% never cleaned the guttering 35% cleaned their storage tanks 43% has some type of water filtration system, with only 3% ever using chemical

disinfection


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5.3.5.2 Wairarapa

Dennis (2002), cited in Abbott (2006b) sampled roof-collected rainwater from 60 roofs in South Wairarapa, with the following findings:

Revealed E.coli transgressions in all samples on at least one occasion during a three-month period.

Most samples had total coliform counts of more than 500 per 100ml and in two samples E.coli counts of greater than 550 per 100ml

5.3.5.3 Lower North Island

Sedouch (1999), cited in Abbott (2006b) sampled roof-collected rainwater from 100 roofs in the lower half of the North Island, with the following findings:

18% complied with the 1995 NZ Drinking Water Standards 40% of samples failed “badly” with very high E.coli counts of greater than 150 per 100ml

5.3.5.4 Research by the Roof Water Research Centre, Massey University

The Roof Water Research Centre, Massey University, Wellington comprise a selection of six tanks varying in size from 5,000 to 25,000 litres collecting roof water from a roof area of approximately 200m2, with water sampling from four taps at various heights and the ability to test a variety of different products to enhance roof-collected rainwater and storage tanks. For example, in a trial of a first flush device carried out at the Roof Water Research Centre, Massey University, Wellington, the E.coli tests for 14 sampling dates between 21/03/2006 to 20/07/2006 were 0.0 (zero) for 10 dates, between 1 and 3 for three dates and 24 for one date, Table 6 (Abbott et al. 2006a, from Table 1):

Table 6: Example Total Coliforms and E.coli Tests for Roof-collected Tank Water after a First Flush Diverter

Tank 5 – Linked to first flush diverter Range per 100ml Total coliforms

(maximum value of 4 tests taken at different depths in the tank on each sampling date)

Number of sampling dates (% of sampling dates)

E. coli (maximum value of 4 tests taken at different depths in the tank on each sampling date)


0 0, 0, 0, 0, 0, 0 6 (43%) 0, 0, 0, 0, 0, 0, 0, 0, 0, 0

10 (71%)

1 - 10 2.0, 3.1, 1.0, 4.1, 1.0 5 (36%) 2.0, 1.0, 3.1 3 (21%)

10 - 20

20 - 60 25.9 1 (7%) 23.8 1 (7%)

60 - 100

100 – 200 117.8 1 (7%)

> 200 517 1 (7%)


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Table 7: Example Total Coliforms and E.coli Tests for Roof-collected Tank Water (Control Tank)

Tank 6 – Control tank Range per 100ml Total coliforms

(maximum value of 4 tests taken at different depths in the tank on each sampling date)


E. coli test results (maximum value of 4 tests taken at different depths in the tank on each sampling date)


0 0, 0 2 (14%) 0, 0, 0, 0, 0 5 (36%)

1 - 10 7.4, 1.0, 6.1, 4.0, 3.1 5 (36%) 4.1, 3.1, 2.0, 5.0, 3.0 5 (36%)

10 - 20 10.9, 10.9 2 (14%) 0 (0%)

20 - 60 53.7 1 (7%) 36 1 (7%)

60 - 100 86 1 (7%)

100 – 200 172.5, 101.4 2 (14%) 101 1 (7%)

> 200 488, 816 2 (14%) 816 1 (7%) Table 6 and Table 7 indicate that the first flush diverter significantly reduced the number of samples greater than 10 coliform units/100ml from 30 – 50% down to 7 – 20% for E.coli and Total coliforms respectively. Correspondingly, the number of samples with 0 coliform units/100ml increased from 36 – 14% up to 71 to 43% for E.coli and Total coliforms respectively. Similar reductions have also been measured for the case of two tanks in series. The majority of the sediments settle out in the first tank with improved water quality in the second tank. 5.3.5.5 Three-years of Monthly Water Quality Data from Earthsong Eco-Neighbourhood

The Earthsong Eco-Neighbourhood, Raunui, Waitakere City (www.earthsong.org.nz) is a communal co-housing project that has been going for approximately five years, consisting of 32 homes with seven 30,000 litre roof-collected rain water tanks. The rain water tanks feed non-potable water uses of toilet flushing, laundry and outdoor garden use, along with the hot water cylinders. The rainwater tanks do not have first flush diverters, but do have ‘tank vacuum’ systems that automatically suck the water (and debris) from the bottom of the tank every time the tank overflow pipe is activated by rainfall volumes. Typical weekly E.coli readings from each of the tanks is presented in Figure 4, plotted against the 7-day rainfall for the period from December 2005 to May 2008 (Allison 2010).

http://www.earthsong.org.nz/


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Figure 4: Earthsong E.Coli versus 7 day Rainfall Dec 2005 to May 2008

5.3.5.6 Comments

It is clear from the above examples (particularly the Rainwater Research Centre and Earthsong data) of typical rainwater quality that the proposed ‘not to exceed 10 E.coli/100ml’ standard for non-potable water uses would simply not work. For instance, the weekly monitoring of the rainwater in the Earthsong rain tanks since December 2005 show a wide range of E.coli results from less than 1 to 500 to 1,000, with some readings as high as 2,000. Note that in the five years since the Earthsong tanks have been operating there have been no reported health incidents from contaminated water supplies for the 32 homes (Allison 2010). 5.3.6 Example Existing Guidelines and Policies There are a number of existing guidelines and documents on rainwater collection and storage, although the majority of them have been focussed around households in non-reticulated areas that have to rely on roof-collected rainwater for both potable and non-potable uses. Examples of Ministry of Health publications are (Abbott 2008): Treatment options for small drinking water supplies (Ministry of Health, 2007; Code HP 4413). This booklet provides information about the supply of safe drinking water to small water supplies and describes the principles and methods of water treatment that are available to small supplies.


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Water collection tanks and safe household water. (Ministry of Health, 2006; Code 10148). This booklet gives a brief outline of the steps involved for the safe collection and storage of rainwater. Small, Individual and Roof Water Supplies - In Guidelines for drinking water quality management for New Zealand. (Ministry of Health, 2005 - Chapter 19). This is a very detailed 48-page chapter on the collection, storage and treatment of roof water. Household water supplies: The selection, operation, and maintenance of individual household supplies. (Ministry of Health, 2004; Code 4602). This book presents information on the supply of safe drinking water to households other than those connected to water town supplies. Information on water sources and treatment options have also been included. Public health risk management plan guide; roof water sources. (Ministry of Health, 2001; Version 1, Ref S1.2). This guide covers many of the causes of contamination of roof water and the preventive measures and corrective actions that are necessary to ensure the safety of the water supply. Included are contingency plans such as when roofs are contaminated by spraydrift, volcanic ash, and contingencies for water shortage events. A 2006 BRANZ bulletin No. 478 (Building Research Association of New Zealand) titled ‘Rainwater collection for domestic use’; gives an overview of the choice, design and installation of rainwater collection systems for the New Zealand home. The range of council documents available, varying from 2-page colour fold out brochures to 100-page technical guidelines is given below. These include: Southland District Council (Sarfaiti, 1997, cited by Abbott 2008). This non-mandatory code was developed for the Southland District Council for use as a building compliance guidance document for the “potable water” requirement of the Building Act. Kapiti Coast District Council – Developed the “Kapiti Coast Rainwater and Greywater Code” to provide performance solutions to meet the statutory requirements of the Kapiti Coast District Plan and the New Zealand Building Code (refer Appendix C for details of rainwater harvesting and greywater use plan change) North Shore City Council – Developed the “Rain Tank Guidelines” (NSCC 2009), a comprehensive 100-page document for both potable and non-potable rainwater harvesting Rodney District Council – “Rainwater Tanks for Non-drinking Water Purposes”, a 2 page fold out colour brochure with basic information for general public dissemination.


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Examples of how some councils (Auckland City, North Shore City, Tauranga City and Kapiti Coast District Council) are managing rainwater tanks in their region are given in Sections 6.6 to 6.10 on management issues.

5.4 Greywater Systems – New Zealand Specific The health risks of greywater systems are described below under the following headings specifically related to New Zealand based information:

Statutory Control The Ministry of Health and the Health Act Reported Health Incidents The Building Code Typical Greywater Quality Example Existing Council Guidelines and Policies

5.4.1 Statutory Control As with rainwater tanks, statutory control of any greywater diversion, collection, treatment and irrigation system discharging into the ground must comply with the Resource Management Act 1991, the Building Act 1991 and the Health Act 1956. Systems must comply with District Plan regulations, and, for instance in the Auckland Region, comply with the Auckland Regional Council’s Technical Publication 58 (ARC TP58 2004) on on-site wastewater systems: design and management manual. See sections below for further elaboration on individual statutory controls and documents. 5.4.2 The Ministry of Health and the Health Act While there are no guideline documents from the Ministry of Health around greywater reuse, the increasing interest by the public and professional bodies around sustainable water resources has meant an increase of interest in the reuse of greywater. Although black and grey water reuse systems have been installed in New Zealand over the last 15 years (personal communication with Innoflow Technologies Ltd, Technical Manager 14 January 2010) these systems have predominantly been in rural settings of cluster housing developments, often with restrictions on the volumes of wastewater that can be discharged to the environment. However, greywater reuse in the urban setting is still relatively new with few examples. This increase in interest in greywater reuse over the last five years has prompted the Ministry of Health to clarify its position with regard to the re-use of wastewater (including both black and greywater). To ensure consistency throughout New Zealand, the preferred protocol when requesting information on Ministry of Health policies is to go through the Regional Public Health Service, the service responsible for policy implementation. Documents and position statements obtained from the Auckland Regional Health Service and the National Co-ordination Unit located in Christchurch are attached in Appendix A for information. These documents include:


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Letters of clarification on “Re-Use of Wastewater – Ministry of Health Policy” and “Dual

Water Supplies in Residential Dwellings”, dated 2005 and 2006, from Paul Prendergast, Principle Public Health Engineer, Public Health Directorate, and

Position Statement on Greywater Re-use in Auckland, by the Auckland Regional Public Health Service

In short, the Ministry of Health does not support the re-use of wastewater within the residential environment. The reasons are given in the letter from Paul Prendergast, titled “Dual Water Supplies in Residential Dwellings”, dated 27 June 2005, which was sent to public health services throughout New Zealand. This letter presents the Ministry of Health’s two principles with regard to wastewater as being:

‘The treatment and discharge methods used for sewage effluent should provide the best method of protecting the public health. That is the public health is paramount.

No sewage treatment system entirely protects public health and all systems can fail. Therefore, it has always been a prime public health measure to separate people from contact with sewage effluent as much as is practicable.’

Prendergast, in his cover letter titled ‘Re-Use of Wastewater – Ministry of Health Policy’, states:

‘The very high failure rates of on-site wastewater systems in New Zealand is such that we can have no confidence of wastewater re-use within a residential situation where poorly treated effluent will often be in contact with people. The above is not a technology issue but the high failure rate is largely a people and management problem.’

The Auckland Regional Public Health Service (ARPHS) Position Statement (Appendix A) acknowledges that the drive to manage water demand has meant that the practice of re-using greywater is gaining in popularity. However, the statement goes on to say that:

‘……the wide range and competency of system-types, the lack of a comprehensive risk monitoring framework for systems in New Zealand, lack of auditing of practice and the potential for human health risk meant that ARPHS do not support greywater re-use in the domestic setting.’

The ARPHS position statement goes on to say that:

‘While ARPHS holds a view on the concept of greywater re-use, it has no regulatory involvement in approving, monitoring or remedying greywater systems. ARPHS provides public health advice. There may be limited uses (e.g. subsurface irrigation) where health risks could be reduced by:

• Design of the system by a specialist engineer; • Utilising a risk management framework; • Regular monitoring by the appropriate TA.’


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5.4.3 Reported Health Incidents It is acknowledged that it is very difficult to establish a cause and effect from greywater use, as there are potentially many sources of disease and health surveillance data do not reflect the true nature of waterborne illnesses in the community as they usually only capture case-patients in contact with a health care facility. However, there is clear evidence of poor performance and management of existing individual ad-hoc residential greywater systems with samples taken “after” treatment not being able to meet guideline values as those suggested by the U.S. EPA or the Australian NSW guidelines (Leonard and Kikkert 2006). Of the 31 greywater sites sampled by Leonard et al., occupants from only half the sites had a good understanding of their system and/or kept it well maintained and 24% of the sites were poorly maintained. Refer Section 5.4.5 for a summary of the greywater quality sampled by Leonard et al. before and after greywater treatment. 5.4.4 The Building Code As for rainwater tanks, wastewater systems require a building consent, approved by the local Council and is a legal requirement under the Building Act 2004, and its associated Building Code. Of interest to the greywater reuse building code requirements are the proposed revisions to the Building Code performance requirements that were initiated in 2006/2007 (Department of Building and Housing July 2007). At time of writing it is the author’s understanding that the revisions are on hold, but they are of value as an indicator of thinking on these issues at 2007. The proposed 2006/07 changes to the building code with respect to greywater reuse are ‘Type 2 changes’ (Substantive changes including changes to measures for performance requirements, changes to the scope of the requirements and different approaches to describing requirements) and consist of (ibid, 2007, page 54):

Buildings may recycle greywater for re-use within a building in toilets and for outdoor re-use on a property (for example, irrigation).

The level of pathogens in greywater for re-use as measured by microbial indicators shall be less than 1 E.coli/100ml.

The quality of greywater water shall be monitored and the system maintained as a specified system.

Again, as for the proposed changes to the building code for rainwater harvesting, the above changes with respect to the first and third points (re-use for toilets and outdoor re-use; and monitoring and maintenance) are consistent with the authors literature review, but the second point on a microbial indicator level of less than 1 E.coli/100ml is at variance with some other literature. It is acknowledged that the above second point was referenced to two documents (that being the United States Environmental Protection Agency (2004) 2004 Guidelines for water reuse. EPA/625/R-04/108 US EPA Washington August 2004; and the National


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Guidelines for Water Recycling Managing Health and Environmental Risks. Natural Resource Management Ministerial Council Environmental Protection and Heritage Council Nov 2006), but the 1 Ecoli/100ml limit is contrary to the Australian New South Wales Health, Domestic Greywater Treatment Systems Accreditation Guidelines (NSW Health 2005), summarised in more depth in Appendix B. These NSW guidelines appear to give a more practical range of microbial levels based both on the frequency of testing and the type of end use. For example, the NSW guidelines give three levels of T.coliforms based on disposal methods of:

Sub-surface irrigation – no T.coliforms level (but does have BOD5 and Suspended Solids limits)

Surface irrigation – T.coliform levels of less than 30 cfu/100ml for 90% of the samples and a maximum threshold value of 100 cfu/100ml.

Toilet/Washing Machine reuse - T.coliform levels of less than 10 cfu/100ml for 90% of the samples and a maximum threshold value of 30 cfu/100ml.

It is also worthy of note that NSW Health randomly nominates a minimum of 10% of installed sites, operating for a minimum of 6 months, as sites for monitoring. The explanation given in the proposed building code review document for the proposed changes acknowledges that some submitters to the first discussion document expressed the view that Code requirements, in line with sustainable development objectives, should encourage the adoption of greywater on-site systems. However, the assessment of the current situation as given in the Department of Building and Housing 2007 document states (Department of Building and Housing 2007):

‘We consider that greywater could be recycled in commercial, industrial and other buildings where monitoring can take place as part of a compliance regime. But we do not consider that the management of greywater recycling in domestic buildings would be likely to provide adequate safeguards against disease transmission. The performance of treatment systems would need to be verified. We do not envisage greywater recycling for domestic use being economic, nor necessary in New Zealand for water conservation. We have used the same indicator as for raw water – E.coli/100ml. E.coli is a measureable indicator of pathogens. However, the level set for greywater is more stringent than for raw water. [Author insert: greywater reuse level is 1 E.coli/100ml compared to the raw water level of 10 E.coli/100ml] The different values take into account the risk of associated pathogens (bacteria and/or viruses). Greywater must be very well treated because the source cannot be controlled.’

As for the above rainwater harvesting comments on building code performance monitoring, from the authors standpoint, using E.coli does not appear to be the most practical measuring system from a building inspector’s point of view. An alternative that the author has become aware of in discussions with a local wastewater treatment manufacturer/installer/maintenance


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operator is the measuring of chlorine residuals (personal communication with Innoflow Technologies Ltd, Technical Manager 14 January 2010). Chlorine residual testing is a much simpler test than for coliforms, which can easily be done by a Building Inspector on site with an immediate result, using a chlorine test strip. Innoflow Technologies have been installing wastewater reuse systems (primarily in rural areas for body corporate or similar community sysetms) for the last 15 years and have approval from the respective Regional Public Health Services under the following conditions (Hawthorne 2010):

Only use wastewater reuse for toilet flushing, not for gardens. Regular weekly testing of chlorine residuals (not less than 0.5 mg/L) Sometimes request 1 or 3-monthly coliform testing

The testing of chlorine residual instead of E.coli would also be more in line with the existing New Zealand Auckland Regional Council Technical Publication No. 58 (TP58), ‘Onsite Wastewater Systems: Design and Management Manual’ (ARC 2004), which gives guideline values of less than 15 mg/L BOD5, less than 15 mg/L TSS and a minimum 0.5 mg/L chlorine residual. 5.4.5 Typical Greywater Quality A summary of “before” and “after” treated greywater sites in New Zealand are given in the conference paper ‘Efficacy of Greywater Treatment in New Zealand’ (Leonard and Kikkert 2006). Leonard et al. expanded their previous 2005 work with sampling from twenty four further greywater reuse sites around New Zealand. Microbial indicators (such as E.coli) and other performance indicators (such as BOD5) were measured in order to provide a picture of greywater characteristics in New Zealand, and the effectiveness of greywater treatment systems. A variety of greywater systems were identified and sampled, including constructed wetlands, screening, chlorination, composting toilets and some had no treatment at all. A variety of greywater samples were taken, from before and after treatment, from different greywater streams (i.e. laundry, kitchen, bathroom) and from sludge in the bottom of the greywater tanks. Microbial indicators measured to indicate the presence of potentially pathogenic microbes were Escherichia (E.coli) and enterococci (bacterial indicators), Clostridium perfringens spores (indicative of protozoan removal) and F-RNA phage (a virus which infects E. coli). As might be expected, untreated greywater showed a wide range of values due to the widely varying sources within the home, from kitchen, laundry and bathroom. For instance the median, maximum and minimum values for E.coli, Total coliforms, TSS and BOD5 are given below in Table 5-3 (Leonard et al. 2006, Table 1).


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Table 8: Untreated Greywater Characteristics

(Leonard et al. 2006) E. coli

(cfu/100ml) Total coliforms (cfu/100ml)

TSS (mg/L) BOD5 (mg/L)

Median 1480 2,850,000 129 190

Maximum 14,000,000 790,000,000 795 3,500

Minimum 1 1 0.5 3.7

95 percentile 2,922,000 600,500,000 579 639

N (no. of samples)

32 32 30 30

Raw sewage median conc

5,000,000

The above table shows the range of contaminant levels that a treatment system may have to deal with. Of interest, is that the maximum greywater concentrations for E.coli are similar to the median concentrations for raw sewage (Leonard et al. 2006). These values are also of a similar order of magnitude to the range given in the Australian Guidelines for Water Recycling given previously in Table 2. Leonard also presented data for treated greywater. Although sampling “before” and “after” treatment may not relate exactly to each other due to the variable length of time for water to pass through the treatment system, it is useful to get a general indication of probable treatment efficiencies. Indeed, in three of the eleven treatment systems sampled, the median concentrations of E.coli were greater “after” treatment than “before”. Of the eleven sites, five gave treated Total coliforms of less than 10 cfu/100ml (meeting the NSW Total coliforms guideline value of < 10, but failing the EPA guideline of less than 1 cfu/100ml). Leonard also noted that where the E.coli values were low, the treatment system was not effective against F-RNA phage or C. perfringens spores, indicating that if E.coli were the only indicator measured, it could overestimate the effectiveness of the treatment system. The range of treated greywater sampling test results for E.coli and Total coliforms for selected systems sampled are shown below in Table 9, compared against the untreated ranges from Table 5-3 above (Leonard et al. 2006, Tables 1 and 2):


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Table 9: Comparative Untreated and Treated Greywater Quality (Leonard et al. 2006)

E. coli (cfu/100ml) Total coliforms (cfu/100ml) Untreated Treated Untreated Treated

Median 1480 470 2,850,000 78,000

Maximum 14,000,000 300,000 790,000,000 1,180,000,000

Minimum 1 0.5 1 5

95 percentile 2,922,000 278,400 600,500,000 550,000,000

N (no. of samples) 32 13 32 13 Table 9 shows that the treated levels of E.coli and Total coliforms were less than the untreated, except for the maximum Total coliforms which were higher for the treated. This may have been owing to growth in the system or inherent variability in the samples (Leonard et al. 2006). 5.4.6 Example Existing Council Guidelines and Policies A summary of some regional council guidance on greywater reuse are presented below, resourced from Ormiston Associates Ltd report titled ‘Greywater Reuse in Single Dwellings Review for Kapiti Coast District Council’ (Ormiston 2008, pages 19-20): ‘Auckland Regional Council Auckland Regional Council TP58 provides guidance for greywater reuse on individual properties. TP58 stresses that it is critical that any reuse is managed in a manner to sustain public health and the environment. TP58 accepts that greywater may be suitable for subsurface irrigation of gardens, fruit trees and shrubs but not root crops. The reuse of greywater for manual watering in the garden is not a permitted activity but is cautiously allowed under the consenting process. The minimum treatment standard for greywater required for subsurface irrigation is a septic tank and effluent outlet filter with discharge to trench. Discharge to pressure compensating dripper irrigation requires at least secondary treatment (20:30 BOD5:SS) to minimise emitter blockage. Greater Wellington Regional Council Wellington Regional Council allows the discharge of greywater onto or into land as a permitted activity where,

The daily discharge volume is less than 2,000 litres The disposal is more than 20metres from surface water; and The discharge does not cause ponding on, or runoff from the disposal area.

The Greater Wellington Regional Council refers designers to ARC TP58 (2004) (ref 1) for design guidance for greywater treatment and land disposal system design.


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Environment Bay of Plenty Environment Bay of Plenty allows greywater reuse as a permitted activity where,

The daily discharge is less than 1,000 litres The greywater is only for lawn and garden watering The greywater must be discharged within 24 hours of production The discharge shall not result in ponding, runoff or objectionable odour. The minimum treatment required is a settlement tank with an effluent outlet filter. The irrigation line is to be no less than 200mm in depth and Have a minimum of 600mm separation from the groundwater table.

It is also a requirement that each greywater system design includes management for times when greywater is not able to be discharged.’

5.5 Discussion The above literature research of health risks has highlighted several issues and probable barriers to the implementation of rainwater tanks and greywater reuse, most noticeably around greywater reuse. The significant issue around maintenance and operation of these systems is acknowledged by all and is covered in Section 7: Maintenance/Ownership. This discussion section more focuses on the issue of how to assess the health risk of a given installed system and the best way to address these health risks from a building consent perspective as the approval of such systems generally falls to a building inspector during an onsite inspection. 5.5.1 Rainwater Tanks First, with respect to rainwater tanks, there is general acceptance that there may be health risks with using roof-collected rainwater for drinking water. While there are still more than 10% of New Zealanders relying solely on roof water for their drinking water, the Ministry of Health recommends using the public water supply, where available, for drinking water use. Therefore to achieve Beacon’s goals of reducing household demand for reticulated water, an excellent first step is to consider roof rain water for non-drinking water purposes, such as toilet flushing, laundry and outdoor use, when considering it as a water demand management option. One of the main issues of concern is the ability of the general public to operate and maintain their own rainwater system. However, there appears to be general agreement that, with ongoing educational efforts, the majority of people can be educated enough to maintain their systems adequately for non-drinking water purposes, as opposed to drinking water quality. Where there is more disagreement is to do with the costs and benefits of such a practice, this issue is covered in Section 6: Infrastructure – centralised vs decentralised. However, the main area highlighted by the research that could provide a significant barrier is in setting of appropriate guideline values for non-drinking water quality parameters. There are no national standards for non-drinking water (as opposed to the National Drinking Water Standards), but the closest attempt at setting such guidelines has been in the proposed revisions


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to the Building Code that were initiated in 2006/2007. While it is understood that these revisions have been put on hold for now, it is important to highlight what was proposed in 2007 and how it would likely be a significant barrier. As detailed in the above Section 5.3.4: The Building Code, the primary concern is around setting a ‘not to exceed limit of 10 E.coli/100ml’ as a building consent control for non-potable household water use. The four primary reasons given in section 5.3.4 are repeated below for completeness: 1) It would be very difficult to enforce at a building consent level by building inspectors as to

enforce it correctly would require a number of microbial tests and can only be tested after the system has been installed and operating for some time.

2) What, where and when are they going to test the water? For example, would it be tested as it enters the tank, in the rain tank, as it leaves the rain tank, before or after the tank is topped up with potable water from the reticulated system, before or after a rain event, water from the outside tap, water in the toilet and how often it is to be tested?

3) The not-to-exceed 10 E.coli/100ml appears to be too strict from a practical point of view when looking at other guidelines and monitoring of existing rainwater roof-collected systems. The author certainly agrees to strict E.coli limits for potable drinking water, but questions a similar need for non-potable water uses such as flushing the toilet watering the garden, and washing the car. In addition, due to the inherent variability of E.coli readings, if an E.coli limit is to be used it would be more useful to have an acceptable range, such as, 90% of samples not to exceed X, with a maximum threshold of Y rather than a single not-to-exceed value.

4) This not-to-exceed limit of 10 E.coli/100ml does not appear to be based on any sound epidemiological studies or risk assessment (Abbott 2010).

The author acknowledges that he is not experienced in microbiology, and so is not qualified to propose what a suitable guideline value should be, but feels strongly that for a national guideline and/or building code to be accepted, and enforced, it must have practical guideline values that make sense. For example, from a building inspectors point of view, the author would suggest that guidelines around the most suitable constructed installation (such as the inclusion of leaf guards, first flush diverters, removal of overhanging trees etc), similar to the Ministry of Health guidelines for rural households that need to rely on rainwater for drinking water purposes, would be more useful to assess the overall health risks to the individual household compared to some technical highly variable microbial test, that is only an indicator test anyway, for pathogens that may be present that are the real health risk.


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5.5.2 Greywater Reuse Greywater reuse is the more contentious issue (compared to rainwater harvesting) and has been receiving significant attention in recent years, nationally and internationally, particularly in periods of drought (e.g. Australia). This interest in greywater, compared to rainwater harvesting, has gained significance as the effectiveness of rainwater harvesting in times of drought has come into question. In addition, while rainwater harvesting reduces the reticulated water supply, it does not actually change the wastewater discharged from the household. Whereas greywater reuse provides both a reliable year round supply of extra water and reduces the water discharged from the house that requires treatment at a wastewater treatment plant. However, these additional benefits need to be balanced against the additional health risks from the more contaminated greywater source compared to roof-collected rainwater. This appears to be the major barrier: how to assess the most appropriate health risk for a given situation, for the highly variable nature of greywater. There is some concern over the perception that greywater is relatively benign and that recycling is safe (Leonard 2006, MRMMC 2006). As was shown in Table 2 of Section 3.3: Wastewater Characteristics and Terminology, greywater quality is highly variable with, in the worst cases, concentrations of faecal microorganisms almost as high as those found in sewage (black water and greywater). The variability of greywater quality is also greater than that of sewage. This complicates the determination of health-based targets and has both negative and positive impacts on the setting of guideline values as described briefly below from the Australian Guidelines for Water Recycling. The Australian Guidelines for Water Recycling describes these issues in its Section 3.7.2: Calculation of microbial health-based targets for greywater used as a source of recycled water (MRMMC 2006). Some of these issues also apply to large scale wastewater treatment systems, but as you will see from some of the points below, some issues are specific to assessing the health risks to individual household systems. The Australian Guidelines lists some of these issues as (MRMMC 2006, page 116):

There is limited water quality data available, and the data relates to measurement of indicator organisms such as E.coli and thermotolerant coliforms, little or no data are available on presence of specific pathogens

One study (Ottoson and Stenstrom 2003, cited in MRMMC 2006) has suggested that indicator organisms might regrow due to the presence of organic material, leading to an overestimation of faecal contamination. However, the authors also considered that there could be a regrowth of pathogenic bacteria such as Salmonella and Campylobacter.

The variability in individual domestic systems will be greater than that in large systems. In large decentralised greywater schemes it may be possible to test for pathogens, but for

most greywater schemes a modified approach needs to be adopted to determine performance targets.


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The Australian Guidelines goes on to explain that, for instance, this wide variability of greywater water quality means that the conventional 95th percentiles or medians which are used for assessing microbial quality are not recommended; 95th percentiles are likely to be very conservative and to overestimate general levels of microbial contamination, and the use of medians may underestimate contamination by discounting peak values. Means were considered to provide a balanced assessment of microbial contamination. The guidelines then explain how a reduced correction factor could then be applied to greywater schemes as opposed to sewage. The guidelines (ibid, page 117) suggest ‘a further decrease in ‘log reduction requirements’ for on-site greywater systems serving single domestic dwellings. These systems represent a lower risk than those servicing multiple dwellings due to the lack of exposure of third parties either directly or through cross-connections.’ Australia has not set a national greywater standard yet for onsite greywater, but it would probably be based on the New South Wales standards (given in Appendix B) (Leonard 2010). Perhaps one of the most comprehensive sources of information on greywater systems is Oasis Design (www.oasisdesign.net). On their Gray Water Policy Center site they recommend U.S states to use the Arizona graywater laws. While California were the first state to implement greywater laws, they are now outdated and the more recent Arizona laws are recommended. New Mexico has copied Arizona and Texas is considering them (last updated 8/12/2009). What Oasis like about the Arizona laws is the three tiered approach to scrutinizing grey water systems:

First tier systems for less than 400 gallons per day (1,800 litres per day) that meet a list of reasonable requirements are all covered under a general permit without the builder having to apply for anything.

Second tier systems process over 400 gallons a day (1,800 litres per day), or do not meet the list of requirements, as well as commercial, multi-family, and institutional systems.

Third tier systems are over 3,000 gallons a day (13,000 litres per day). Regulators consider each of them on an individual basis.

As presented in more detail in Section 5.4.2: The Ministry of Health and The Health Act, The Ministry of Health does not support the reuse of wastewater (black or grey) within the residential environment. As for rainwater harvesting for non-drinking water uses, the issue is compounded by not having any national guidelines, but Regional Public Health Services, such as Auckland, do have a Position Statement stating that they ‘do not support greywater re-use in the domestic setting’. This position statement was largely the result of a statement/letter from the Ministry of Health’s Paul Prendergast, Principle Public Health Engineer in 2005 and 2006. However, in the authors opinion, a key issue in this Ministry of Health correspondence (as outlined in Section 5.4.2 of this report) was the statement that the problem of high failure rates of on-site wastewater systems in New Zealand (and hence having no confidence in wastewater reuse systems) ‘is not a technology issue but the high failure rate is largely a people and management problem’.

http://www.oasisdesign.net/


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As for rainwater harvesting, in the absence of a national greywater guideline/standard, the best surrogate to indicate how, at a national level, they want to address this high failure rate is to look at what was proposed in the revised Building Code of 2006/2007. In those revisions the proposal was to provide for only one level of treatment (compared to the more reasonable and recommended three-tier approach or Arizona, USA stated above) and control the level of pathogens in greywater for re-use by measuring the microbial indicator of E.coli, with a value of less than 1 E.coli/100ml. The reason given for this lower level of 1 coliform/100ml compared to the raw water (rainwater) value of 10 coliform/100ml was stated as to account for the risk of associated pathogens (bacteria and/or viruses). Note that the drinking water standards are also an E.coli of less than 1 coliform/100ml. Another point of interest is where E.coli are used as indicators in the Microbiological Water Quality Guidelines for Marine and Freshwater Recreational Areas (MfE 2003). The author fully recognisees and notes that the marine and freshwater guidelines specifically state that ‘These guidelines cannot be applied to water uses other than recreational use.’ and ‘These guidelines cannot be directly used to determine water quality criteria for wastewater discharges’, because these are only indicator organisms, but nevertheless some comments are included here to highlight the inherent difficulties in using ‘indicator organisms’ and begs the question as to if E.coli is the most appropriate water quality test for a greywater (or rainwater non-potable use) guideline. For example, the recreational water quality guidelines give a method for estimating a ‘Suitability for Recreation Grade’ for freshwater sites that is based on both the susceptibility to faecal influence (based on a ‘Sanitary Inspection Category’ of very low to very high) and a microbiological assessment category (based on four grades of E.coli counts per 100ml of <=130, 131-260, 261-550, and >550). In addition, the guidelines propose a three-tier management framework for monitoring beaches for recreational swimming based on bacteriological (E.coli) indicator values of:

Acceptable/Green Mode: No single sample greater than 260 E.coli/100ml Alert/Amber Mode: Single sample greater than 260 E.coli/100ml Action/Red Mode: Single sample greater than 550 E.coli/100ml.

These freshwater guidelines highlight the difficulty of using E.coli as an indicator organism as acceptable levels for recreational swimming are in the order of 130 to 260 E.coli/100ml, and yet the proposed acceptable level for flushing the toilet is an E.coli count of less than 1 (the level for the NZ Drinking Water Standards)? Therefore, in the author’s interpretation, the approach to set only one very low E.coli level is an unreasonable solution given the range of scales of grey water systems and is essentially a technology fix to what is predominantly not a technology problem but a people and management problem. It is also appears not to take into account the issues highlighted in the Australian Guidelines mentioned above around the high variability and the need to use mean values, the ability to use a ‘reduced correction factor’ for greywater compared to sewage, and a further reduction in ‘log reduction requirements’ for individual on-site systems compared to


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large scale multiple dwelling systems. Such factors could be included if a tiered system, such as in the Arizona greywater laws, and the NZ freshwater guidelines, was adopted. Also, from a sustainability point of view, which has as one of its core principles the need to change peoples behaviours, to ‘solve’ the problem of malfunctioning greywater systems we need to focus on these people and management issues, not only the technology. The management issues have been recognised as a specific barrier and are addressed more fully in the subsequent section 7.


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6 Maintenance/Ownership 6.1 Research Question The Beacon research question to be answered for maintenance/ownership at the lot and neighbourhood scale is:

What are the ongoing maintenance and ownership issues of on-site water management as compared to centralised infrastructure?

6.2 Chapter Outline This section presents the maintenance/ownership management issues from the following sources. (Note the costs of ongoing management are included in Section 7 on centralised and decentralised infrastructure): Section 6.3 Internationally Accepted Issues; presents a brief generally accepted summary of the ongoing management issues of decentralised systems from an international perspective – taken from the internationally recognised text book on small and decentralised systems by Crites and Tchobanoglous (1998). Sections 6.4 to 6.10 focus on local New Zealand examples of handling maintenance and ownership issues around the Beacon interests of rainwater tanks and greywater reuse systems. Section 6.4 Low Impact Urban Design and Development (LIUDD),( New Zealand wide); highlights the findings from a six-year research program (2003 – 2009), funded by the New Zealand Foundation of Research, Science and Technology. While this programme was on low impact stormwater devices rather than the Beacon focus on the water demand aspects, it has been included here as the installations of low impact stormwater devices involve small, on-site devices, equivalent to the management of general decentralised systems. In addition, the LIUDD program included the use of on-site rain water tanks (focussing on their stormwater management benefits), and so is equally applicable to the management issues of locating and maintaining rainwater tanks for demand management. Section 6.5 Glencourt Place,(Auckland); has been included as a unique rainwater tank project that included the planning, design, gaining public approval, construction, monitoring and public response to the retrofitting of 22 rainwater tanks in a built up residential area of North Shore City. The project was initiated in 2001, constructed in 2005 and monitored from 2006 to 2009. While the primary driver for the project was for stormwater mitigation, a major part of the project included the installation of dual purpose rainwater tanks (tanks used both for rainwater use as non-potable household water and stormwater detention) and so is very applicable here.


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Section 6.6 Talbot Park, (Auckland); has been included as an example of a new development including rainwater tanks where they were installed as part of community renewal project initiated by Housing New Zealand Corporation in 2001 as part of promoting a more sustainable approach to redevelopment projects. The rainwater tanks supplied non-potable water for toilet flushing and garden irrigation. Section 6.7 Kapiti Coast District Council; has been included as it is the first New Zealand council to formally adopt the mandatory installation of rainwater tanks and/or greywater devices on all new developments as part of its demand management strategy and so is directly applicable to this Beacon project. Due to this unique opportunity, further descriptions of this project are included in Appendix C. Section 6.8 Tauranga City Council; has been included as a typical example of a council with a focus on demand management (Beacon has worked with the council on its demand management strategy) and in the process of trying to define rain water tank non-potable water use and greywater policy in the district. Section 6.9 North Shore City Council (Auckland); has been included as an example of a council that has already installed over 4,000 on-site devices, including rain water tanks and rain gardens. Again, while these devices have been primarily installed for their stormwater management benefits, many of the rainwater tanks have also had a rainwater harvesting component of them supplying toilet, laundry and outdoor water use, and hence applicable here. Section 6.10 On-site Wastewater Treatment (New Zealand wide); has been included as although not specifically including rainwater tanks or greywater devices, many of the same management issues of on-site rainwater tanks and greywater devices have been experienced by councils with the management of their on-site wastewater treatment systems over many years. Valuable lessons can be learnt from regulating on-site wastewater treatment systems and applied to rainwater tanks and greywater systems. 6.3 Internationally Accepted Issues Internationally, the recognised text on small and decentralised wastewater systems by Crites and Tchobanoglous (1998) have devoted a whole chapter on management. They state that the purposeful management of decentralised wastewater systems must be undertaken to:

Overcome the stigma of failed onsite systems. Obtain costs savings by using many recently developed technologies. Allow for the development and testing of new technologies. Encourage the orderly development of unsewered areas in the context of a sustainable

environment.


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Crites and Tchobanoglous recommend the formation of both private and public decentralised wastewater management (DWM) districts and agencies with typical functions including:

Inventory System design and installation Plan review and construction inspection Inspections Notification Certification/permitting (issuing of 1- or 2-year permits to operate) Water quality monitoring Reporting (annual reports) Education

The requirements for a successful DWM district or agency were listed as:

Regulatory authority Well-developed rules and regulations Authority to correct a failed system Trained personnel Economic feasibility Well-designed and –constructed onsite systems Well-informed public

Crites and Tchobanoglous suggest two methods to finance the DWM programs, districts and agencies; revenue-based financing or benefit assessment financing. Revenue-based financing: Methods that involve borrowed funds repaid from revenue of the wastewater management enterprise. Benefit Assessment financing: The costs of the facilities or needed improvements are levied against each property within the area of benefit, according to direct benefit afforded to each property, typically levied based on an equivalent dwelling unit. The next logical step is the centralisation of information collection and control. That is, ‘decentralised construction with centralised management’. This can be effectively managed through remote sensing and control by a microprocessor-based control panel, being the next best thing to having a full-time wastewater treatment plant operator at each site.


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6.4 Low Impact Urban Design and Development 6.4.1 Background A significant New Zealand project focussing on low impact design stormwater devices was the Low Impact Urban Design and Development (LIUDD) six-year research programme (2003 – 2009), funded by the New Zealand Foundation of Research, Science and Technology. The purpose of the programme was to facilitate the uptake and implementation of low impact design policies and practices. 6.4.2 Relevance to Beacon As for this Beacon project, the LIUDD project identified that ensuring the devices are well maintained and operated correctly was a significant potential barrier to their uptake. The project provided guidance, in the form of a ‘checklist’, to highlight key considerations around the issues of design, responsibility, mechanisms to ensure ongoing operation and maintenance and tools to support implementation. The project referred to this as how to design ‘maintenance smart systems.’ This highlights the importance of considering the operational and maintenance issues at the initial planning and design stages, and not just at the end of the process, after the devices have been constructed. In addition, particularly as many of these on-site, decentralised systems are relatively new, it is equally important to think about how their performance is going to be monitored. The monitoring ‘feedback loop’ is vital to ensure the ongoing improvement of such devices in future installations. The check list of the design process for developing maintenance smart (LIUDD) devices and programmes to support and monitor their performance was (Puddephatt and Heslop 2008): Design process

Design objective – What is the purpose of the device? Device selection – Is the device appropriate for this purpose and in this location? Integrated approach – Who should contribute to the design of the device? Design for maintenance – What features will support ease of maintenance?

Responsibility for operation and maintenance

Private or public ownership – Who will be responsible for the ongoing operation and maintenance of the device?

Contribution to design – Can the long term owners contribute to the design of the device? Information management – How will information about the device and maintenance

requirements be managed? Mechanisms to ensure operation and maintenance

Legislative requirements (design and installation) – Building Act, Resource management Act, Regional Plans, District Plans, Bonds.

Legislative requirements (operation and maintenance) – By-laws, District Plans. Outsourcing responsibility – Third party maintenance.


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Warranty period – Ability to check performance before accepting ownership. Asset handover process – Handover from private to public ownership.

Support for implementation

Guidelines and checklists – For design, construction, maintenance and inspection. Templates (e.g. operation and maintenance plans) – To support the development of clear

instructions and provision of required information. Education and skills development – Build the capability of professions responsible for

designing, constructing and maintaining devices. Certified contractors – Guidance for device owners.

Another example of the LIUDD research work that is applicable to the Beacon ownership issues is their work on managing devices on multi-owned residential sites (Lysnar 2007). Lysnar et al looked at a number of legal options including incorporated societies, limited companies, bodies corporate, trusts, land covenants and memoranda of encumbrance. However, the unpacking of the private governance of common-property features revealed a complex web of accountabilities and relationships in relation to law, private property rights and regulation. One of the main conclusions was that closer scrutiny by policy makers, councils and other stakeholders is necessary to avoid problems in the future. One lawyer warned that this ownership/maintenance issue could become the next ‘leaky building crisis’. In his view, too often, the use and management of commonly owned assets or activities were not established with rules that were secured by effective legal instruments and procedures in perpetuity. Another lawyer commented that the question of how to limit liability in such multi-owned developments was a ‘time bomb’ waiting to happen. Lysnar et al identified the critical elements to ensuring the long term future of such sites as:

The quality of decision-making by various parties as the entity is created and rules developed.

The physical design of the devices and the consent conditions imposed by councils. The ability of owners to manage and maintain their commonly-owned devices, whether this

is achieved by engaging experienced contractors or by the owners themselves. 6.5 Glencourt Place 6.5.1 Background This project comprised the retrofitting of 22 ‘dual purpose’ rain water tanks in the upper reaches of a developed residential catchment (lot sizes of 700 to 1200m2) in North Shore City (Meritec 2002, Meritec 2003, Tian et al. 2003 and Irvine 2009). The upper catchment comprised approximately 50 land owners, with only partial stormwater reticulation, draining into an under-sized downstream stormwater reticulation system. The two options considered were: 1) Install full reticulation to the 50 properties and enlarge existing downstream pipe network, 2) Construction of ‘dual purpose’ rain water tanks along with some drainage swales and minor

piping works. (Computer modelling of the rain water tanks showed that the installation of


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20 rain water tanks reduced the peak stormwater flows down to a level that could be handled by the existing downstream pipe network, that is, the downstream pipe work did not have to be enlarged for this option, provided enough landowners agreed to the installation of the rain tanks).

Rough order capital costs estimates showed that the cost of both options was similar, at around $500,000. Essentially, the money saved from not having to enlarge a length of downstream piping and the reduced on-site piping paid for the additional cost of the rainwater tanks. Refer section 7 for further breakdown of capital and maintenance costs. 6.5.2 Relevance to Beacon This project is useful for Beacon as it has included the planning, design, gaining public approval, construction, monitoring and public response to the retrofitting of the 22 ‘dual purpose’ rainwater tanks that were used for household non-potable water uses. While the primary driver was for stormwater management (the top two thirds of the tank was for ‘temporary’ storage with a small 10mm diameter orifice to mitigate the peak stormwater flows during a rainfall event), the bottom one third was used as ‘permanent’ storage to provide non-potable water to the toilet, laundry and outdoor use. The responsibilities (includes carrying out the required work and paying for the costs) of the council and land owners was: Responsibility Council Land Owners

Initial Capital Costs Yes

Ownership Yes

Regular Inspections Yes

First 3-years Maintenance Yes

4 years + Maintenance Yes

Renewal Yes

The ownership/operation process: Because Council did not have legal power to enforce the property owners to accept the rain tank proposal, a three-stage consultation/sign-off process was carried out on a one-to-one basis to explain the uniqueness of the project to each land owner and to get their final agreement and sign-off.

Stage 1 – Initial Scoping to check feasibility and acceptance of the public - Document the existing situation - Fully explain the proposal and reasons behind the investigation. - Answer any questions/record any concerns that the landowner may have. - Seek support for the rain tank option from the landowners.


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The general response during the first stage was positive, with 80% of those interviewed supporting the rainwater tank proposal. This gave confidence to the Council to proceed to Stage 2 with the rain tank proposal.

Stage 2 – To confirm support and signing of preliminary approval form - Confirm Council’s proposal - Clarify the concerns raised during the first stage consultation (primarily around where

to locate the tank, on-going maintenance, Council’s motive and collective responsibility)

- Carry out survey and design - Confirm the support from the property owner. - Those who did not support the rain tank were required to sign a ‘non-approval’ form to

avoid future possible disputes with new property owners asking why they did not have a rain tank and that any future stormwater problems within that property should be solved by the property owner.

The Stage 2 responses from 32 properties were; 15 (47%) signed the preliminary approval forms, 12 (38%) undecided but leaning to positive and 5 (15%) negative responses.

Stage 3 – Final agreement and sign-off Countersigning final agreement letter, accepting that:

- Use the installation for its required purpose and in accordance with Council’s bylaws - Maintain in good operating condition and replace when necessary - Installation becomes your property and Council has no ongoing responsibility (except

for initial 3yr maintenance period) - Council and agents have access to property - Any stormwater pipelines will become public drains.

As noted above, the final number of rain water tanks installed was 22, approximately 50% of those properties approached. Legal Opinion Because it was recognised that properly maintaining the system was a key factor for its success, legal opinion was obtained on two issues:

What documentation would be required in order to record and implement the proposed arrangement – namely supply of the raintank system by the Council, but being the landowner’s responsibility to carry out the necessary on-going maintenance and renewal works.

How to enforce the landowner’s obligations. Legal opinion stated that a letter from Council to the landowner, countersigned by the landowner to indicate acceptance of the raintank system and associated responsibility, should be


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adequate. For ongoing responsibility of future landowners, legal opinion also indicated that Clause 22.6.4 of the NSCC Stormwater Management Bylaw would oblige the landowner, whoever that may be from time to time to maintain the device in good operating condition. Clause 22.6.4.states:

“You must maintain the pipes, gutter, down pipes, catchpits, detention tanks (if any) or any other components of your approved stormwater system on your premises in good operating conditions, at the designed hydraulic capacity and in compliance with any requirements set by us.”

For more certainty, it is possible to register a memorandum of encumbrance on the title deed, and also ensure that any LIM (Land Information Memorandum) report on the properties identifies the existence of the raintank and the ongoing maintenance requirements. Landowner’s feedback of operating system Two survey questionnaires were sent to the tank landowners, one in April 2006, one year after construction (6 landowners replied, 27% return) and again in October 2007, two and a half years after construction (8 landowners replied, 36% return). Ten landowners (45%) replied either in 2006 or in 2007. Replies to the following questions were:

Was the raintank more – about the same – less work than you expected? More - 0 to 30%; About the same – 65 to 75%; Less – 0%

Ease of raintank use? Not easy enough – 10%; Fair – 25 to 75%; Excellent – 25 to 50%

Would you recommend to a friend? Yes – 50 to 70%; No – 0 to 25%

The operation issues and maintenance problems raised by the landowners included:

Gutter blockages and blockages/cleaning of filters due to leaves was the most common problem (particularly the small tea tree leaves were the most problematic)

Where trees were present, gutters had to be cleaned out every 1-2 months compared to 6-12 months where there are no trees.

High gutters meant maintenance was difficult and potentially dangerous Possible increase in mosquito’s Washing machine filter needed cleaning due to small debris getting through raintank filters Continuous filling from mains water supply – the NAS valve (ball cock) malfunctioned on

three of the installations and did not shut itself off when being filled from mains supply. Option is to make the overflow pipe visible so it could be seen if it was continuously overflowing.

When raintank is out of water, public have to pay for pump and for the water. Height of raintank too high for practical maintenance Cleaning of their raintank was too inaccessible Two owners blocked the small diameter orifice located part way up the tank (for stormwater

detention) as they wanted to use the entire tank storage volume for non-potable water use in the household. Some owners thought the 1/3 household (bottom storage part for water use)


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and 2/3 council (top part for stormwater detention) was ‘unfair’, and would have liked a 50/50 split.

Some water quality issues noted were - Discolouration of water in the toilet cistern (x 3) - Leaves appearing in the toilet cistern (x 1) - Staining of clothes in the washing machine and leaves appearing (x 1)

Some asked for additional and larger signs to distinctly show the outside taps, laundry or garage taps were not for drinking

Some concern of the asbestos/fibro-cement roofs impact on water quality but not considered a problem as water was not used for drinking.

Cleaning tank of debris – suggested using the product on the market that sucks the water from the bottom of the tank when it overflows.

On a couple of occasions the raintank operation and maintenance manual was not passed on to the new owners.

Inconvenience of power outages when pump does not work and have to bucket water to toilet cistern.

Suggestion to install a smaller tank, with no pump, that was used as gravity feed for outdoor use only. This would alleviate the pump ‘down time’ concerns (but would mean less water savings)

Question of fixing holes in guttering was raised as it is stretching how much the council should pay for on private property.

Reduced flooding and drier back yards were noticed by the property owners. Since the tanks have been installed there have been no reports to the Council Actionline of flooding.

Good to streamline the consenting process if possible. A lot of these issues could be addressed if the raintanks were installed at the time of house

construction. One of the recommendations was to try to make the systems ‘simpler’ to reduce

maintenance and the likely replacement costs. Many of these issues are familiar to rural landowners that have grown up depending on rainwater capture for some, or all of their water supply, but are new to urban dwellers who are used to just turning on the tap and not having to worry where the water is coming from. 6.6 Talbot Park 6.6.1 Background Background: The Talbot Park development is a community renewal project initiated by Housing New Zealand Corporation in 2001, comprising 167 Housing New Zealand Corporation residential units, up to four storeys, over 5 hectares. It is a low socio-economic area with a high dependency on social assistance. The project master plan was multifaceted including the principles of community development, affordable and appropriate community services and facilities, etc.


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6.6.2 Relevance to Beacon Of interest for this Beacon project is the installation of rainwater tanks for non-potable water supply by an overarching owner (Housing New Zealand Corporation). In this case, as water usage is paid for by Housing NZ, the focus is on tenant participation with use of the rain tanks and education of the importance of conserving water. The rain tank use is only for toilet cistern and external taps. Laundry use was not included as there were some cultural concerns raised from Maori and Polynesian tenants during the initial stages of the project. Nine rainwater tanks were installed, one in each of four pensioner single bedroom units, four family homes and in a large apartment block with a large tank (30,000 litres) to serve twenty-four 2-bedroom units. At Talbot Park, Housing New Zealand has been trialling two rain tank systems for houses and single level units for topping up the tank when it is low on rainwater: 1) Manual – tenants are responsible for switching over to the mains when the tank is low.

However, experience has shown that since the tenant is not paying for the water there is little incentive to switch it back again, and so often remains on the mains supply

2) Automatic – through a floating ‘ball-cock’ valve system. However, these systems have proven to fail frequently, not coming on and hence the rain tank runs dry and needs a plumber to come at get the system operating again.

From the experience of these two systems, they are favouring the manual option, with a focussed tenant education programme to bring them on board and understand the environmental benefits of using rain water. Landcare Research has completed a monitoring programme in 2009 to measure how much water is being used from one of the raintanks. The feedback from this has been positive with tenants in favour of the rain tank system appreciating the wider environmental benefits. They are also happy to use the rainwater for the toilet and outdoor uses.

6.7 Kapiti Coast District Council 6.7.1 Background Due to future projected water supply shortages the Kapiti Coast District Council assessed a number of different options and after extensive analysis and public consultation initiated Plan Change 75 – Water Demand Management. The plan change mandated either rainwater storage tanks (connecting to toilets and outdoor taps) with a total volume of not less than 8,000 litres or a rainwater tank of 4,000 litres and a complying greywater diversion device (that is, diversion to sub-surface irrigation, but NOT for reuse in the toilet) on new developments. The plan change went through an environment court hearing in April 2009 and was approved with some minor modifications. 6.7.2 Relevance to Beacon The Kapiti Coast District Council plan change presents a unique opportunity to examine the process of mandating the installation of rainwater tanks and/or greywater devices on all new


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development as a water demand management strategy. This is a first for New Zealand. For this reason additional explanation of the process, reports published and feedback is summarised in Appendix C. For regulatory control of the rainwater tanks and greywater diversion devises the council has produced two relevant documents, the Kapiti Coast Rainwater and Greywater Code and the Water Demand Management Declaration of Compliance. These two documents are examples of the regulatory documentation to control the design, installation and maintenance of these systems. The Kapiti Coast Rainwater and Greywater Code is a 20-page document adopting the same structure as the New Zealand Building Code; Objective, Functional requirements and Performance criteria. This will maintain the standards set by the Code while allowing for innovation in materials and methods. Performance Criteria and Acceptable Solutions are given for:

Part 1: Sustainable water supplies for new dwellings in reticulated areas - Reduce peak reticulated water used by household by 30%, while - Protecting reticulated water supply and household from cross contamination; and - Preventing unacceptable risk to the receiving environment

Part 2: Rainwater systems - Includes typical details for a dual supplied rainwater tank - Criteria for installation, capacity and water quality protection measures, system

materials, tank stands, tank openings and tank overflow/point of discharge. Part 3: Greywater diversion devices

- Criteria for design, installation and maintenance. - Only for residential dwellings that generate up to 2,000 litres per day

Part 4: Greywater land application systems - Criteria for design, installation and maintenance - Set back distances, loading rates, environmental constraints, site suitability assessment,

discharged a minimum of 100mm below ground surface The Water Demand Management Declaration of Compliance, is a 10-page document that tabulates:

- The chosen solution (raintank or raintank/greywater diversion) - Statement confirming plumbing and water uses - Greywater irrigation calculation sheet - Worked examples - Example Plumbing and Drainage Plan.

The actual management regime to ensure the systems are operating properly has not yet been finalised but they are looking at it for the 2012/2013 year and is likely to comprise (Thompson 2010):

Homeowner payment and/or council rate


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Likely to affect around 200 homes per year Inspections would be carried out by council staff member (estimated at 0.5 fte) Likely to undertake an initial inspection one year after code compliance certificate of

construction to ensure the system is installed correctly and that the landowner understands how the system works. Then set up a triennial inspection, similar to the proposed standards for onsite wastewater.

If complaints arise from greywater entering neighbours property then council’s compliance team would respond.

6.8 Tauranga City Council 6.8.1 Relevance to Beacon Tauranga City Council is an example of a ‘typical’ council with a focus on water demand management and in the process of trying to define rain water tank non-potable reuse and greywater policy and documentation. Tauranga City Council has recently completed a 2-page brochure on using rainwater for outdoor, toilet and laundry based on current regulation including information on:

example tank sizes and percent water supplied Requirements for backflow prevention Signage, maintenance. What can you use rainwater for (watering garden/lawn, washing vehicles, toilet, laundry) When a building consent and/or resource consent is required Typical drawing on system components (tank, piping, first flush diverter etc.)

They have just started working on developing greywater guidelines but these are a lot more complicated and uncertain. Two significant barriers identified was the lack of a national guideline and the ability to define/handle the possible health risks (Bowles 2010). 6.9 North Shore City Council 6.9.1 Background North Shore City Council has about 4,000 properties with one or more on-site stormwater devices (primarily rainwater tanks and rain gardens). 6.9.2 Relevance to Beacon While these devices have not been primarily installed for water demand management, but for stormwater management, many of them comprise a rainwater harvesting component (for non-potable water uses of outdoor, toilet and laundry) and the council are attempting to address these ongoing operational and maintenance issues. They have produced A5 size, 15 to 20 page ‘booklets’ which the land owner fills out, with information of the purpose, operation, maintenance requirements, safety considerations, trouble shooting, contact details and typical drawings for their three types of on-site devices (Rainwater Tanks, Detention Tanks and Rain


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Gardens). Currently all these devices are entered in to the Property Information Register, along with other property information such as flooding and unpaid rates. The LIM (Land Information Memorandum) references to the Property Information Register. North Shore City Council do not have a formal maintenance procedure but have been working on a developing a 2-year mandatory maintenance procedure (Wallace 2010). To address the ongoing operation/maintenance issues the council was developing a recording system (using their new ‘Pathway’ software module) where by each landowner of an on-site system would be responsible for paying (through a ‘targeted’ rate) for regular 2-year inspections and reporting to council by approved inspectors, and the ongoing council administration. The system would be implemented through the development of a by law, and be similar in concept to the existing targeted rates on, for example, swimming pool fence inspections (required 3-yearly) and commercial building warrant of fitness’s for lifts etc (required yearly). The estimated landowner costs were in the order of $150 to $200 for the approved 2-yearly inspection and reporting and $40 per year as a targeted rate for council administration. The council had estimated that it would require up to an additional 2 - 4 full time employees to administer the procedure. However, the project has been put on hold as it will be a decision for the new one ‘Auckland Council’. 6.10 On-Site Wastewater Treatment 6.10.1 Relevance to Beacon While on-site wastewater treatment systems are different from rainwater tanks and greywater systems, they can provide an insight in to problems and possible solutions to handling private systems that have public health risks. Indeed, one of the reasons for the Department of Health’s caution with allowing greywater reuse systems is the historical lack of private landowners being able to maintain and operate their on-site wastewater treatment systems. If they can not manage an on-site wastewater treatment system, they are very likely not going to be able to maintain a greywater reuse system. In the survey of 31 New Zealand greywater systems, Leonard and Kikkert (Leonard and Kikkert 2006) found that only halve of those surveyed had a good working knowledge of their systems and kept them well maintained. Leonard and Kikkert concluded that the lack of maintenance and the low level of treatment used in New Zealand means that on-site greywater systems present a high risk to public health and the environment. This lack of private maintenance of on-site wastewater systems has been acknowledged by councils and ‘solutions’ have been put in place, such as: Waitakere City Council – have required now for about the last 10 years that all on-site wastewater systems be serviced by an approved contractor at 3-yearly intervals and a report submitted to Council, paid for by the landowner.


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The Environmental Bay of Plenty – The On-Site Effluent Treatment Regional Plan (2006) has a permitted activity rule identifying the site owner as responsible for maintenance activities of the on-site effluent treatment system, requiring regular servicing and maintenance of the system and that records of maintenance activities and a certificate of performance be lodged with the council. Failure to provide information to the council or maintenance records that demonstrate below average performance are identified through the compliance monitoring process and followed up by the council.


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7 Infrastructure – Centralised and Decentralised

7.1 Research Question The Beacon research question to be answered for the centralised and decentralised debate is:

What is the experience, from NZ and internationally, of costs and benefits of centralised and decentralised water supply infrastructure and how these findings might inform debate in NZ for improved demand management.

7.2 Chapter Outline The debate over centralised and decentralised infrastructure is such an all encompassing broad area of discussion that to keep the discussion focussed this chapter initially gives a very brief overview to three key issues (Section 7.3 Overview);

Considering all ‘three-waters’, The inclusion of more than just financial costs and benefits, and The consideration of both centralised and decentralised.

The next sections (Section 7.4 to 7.10) then uses the subject headings of the in depth Rocky Mountain Institute 180-page report on ‘Valuing Decentralised Wastewater Technologies, A Catalog of Benefits, Costs and Economic Analysis Techniques’ (Rocky Mountain Institute 2004) to describe how the centralised/decentralised issues impact on water demand management in New Zealand, specifically with respect to rainwater tanks and greywater reuse. Under each of the headings are two sections: 1) General trends – taken from the Rocky Mountain Institute report 2) Relevance to NZ demand management – how these general trends impact on demand

management in New Zealand. These subsequent sections present the summary of the centralised/decentralised issues in terms of comparing the potential benefits and costs (or advantages and disadvantages) of decentralised systems relative to centralised systems, using the same terminology as that adopted in the Rocky Mountain Institute report, that is (Rocky Mountain Institute 2004, page 9):

Decentralisation Benefit: Where smaller scale tends to produce a benefit or save on a cost relative to larger scale.

Decentralisation Cost: Where smaller scale tends to produce a cost relative to larger scale, or fails to obtain a benefit available at a larger scale.

Decentralisation consideration: Where there is no clear tendency for smaller scale to be beneficial or costly relative to larger scale.


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7.3 Overview There have been numerous papers and text books written on decentralised and centralised water infrastructure systems, with the majority of them being focussed around managing wastewater. However, a lot of these same findings for wastewater systems can be applied to the relatively new decentralised areas of stormwater (often referred to as ‘Low Impact Design’) and water supply. It is in this area of decentralised water supply (water demand management) that this Beacon project is focused on, that is, rain water tanks for non-potable household use and greywater reuse. But it is important to note that in the new sustainability and ‘good governance’ paradigm an integrated approach is necessary. This means integration in terms of:

The 3-waters (water supply, stormwater and wastewater) – for example maximum benefit from the installation of rainwater tanks can often come when they are designed as ‘dual purpose’, that is, used both for stormwater detention and water supply; and, greywater reuse to reduce water supply demand also has a positive benefit of reducing the net wastewater volumes discharged from a site into the wastewater collection and treatment system.

The inclusion of more than just ‘financial’ costs and benefits – many of the social, cultural and environmental ‘costs and benefits’ can not easily be seen in financial terms, although being just as important, if not more important to the long term ecological sustainability of the planet. For example, in the previous Beacon report titled ‘Integrated Water Management (IWM) Design Criteria Report (Kettle 2009), different demand management options were assessed against a total of 31 criteria, under the following 11 categories:

Water Quantity Water Quality Nutrient Cycle Material Cycle

Cultural Issues Resilience Technical Issues Governance

Social Energy Economic

The consideration of both centralised and decentralised – an integrated approach looks at the best overall system, which can in many cases be a combination of both centralised and decentralised systems, so we should see these as complimentary technologies rather than only one or the other. For example, an existing undersized centralised system can be made to operate a lot more efficiently if, say, some of the wastewater loads from site specific areas where there is potential for wastewater reuse have reduced discharges to the existing centralised system. Upgrading existing centralised systems may also be more cost-effective if smaller ‘decentralised technologies’, such as small diameter pipelines with onsite storage are used.


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7.4 Financial Planning and Risk 7.4.1 General Trends Decentralised systems offer financial planning and risk benefits through:

Smaller faster to build modules of capacity allows closer matching of growing demand to system capacity, and therefore saves three different kinds of costs (refer Figure 5, Rocky Mountain Institute 2004, Figure 8-1, p. 17): - The costs of the increased lead time of slower-to-build central resources - The cost of idle capacity that exceeds current needs - The cost of overbuild capacity that remains idle

Figure 5: Flow versus Capacity for Centralised and Decentralised Systems

Financial risk is reduced with the decentralised system as the flexibility allows managers to adjust capital investments, more exactly tracking the unfolding future both in terms of ‘trapped equity’, allow upgrades to be focussed on a small subset of the community’s capacity and to develop and deploy future advances in new technologies.

Debt Financing costs are generally less for decentralised systems.

Debt financing costs are generally not taken into account in conventional engineering benefit/cost NPV (Net Present Value) estimations. This is especially important when comparing systems with markedly different capital cost distributions, such as centralised systems with larger single upfront costs compared to decentralised much smaller costs distributed over many years.


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The Rocky Mountain Institute gave an example of a hypothetical town (referred to as “Smallside USA”) which was to grow from 500 to 1,600 homes over a 30-year period (Pinkham et al. 2004 cited in Rocky Mountain Institute 2004). The capital and O&M costs were chosen to represent typical centralised/decentralised systems and that they had the same conventional engineering NPV, refer Figure 6 (Rocky Mountain Institute 2004, Figure 8-4, p. 35)

Figure 6: Comparison of Capital Outlays for Hypothetical “Smallside, USA”

However, when debt financing costs were taken into account, the total life cycle costs (Capital, O&M, Management and Financing costs) were quite different, with the centralised system costing $33M compared to a lower decentralised cost of $25.6M, a net difference of $7.4M in favour of the decentralised system, refer Figure 7 (Rocky Mountain Institute 2004, Figure 8-5, page 36):

Figure 7: Differences in Total Lifecycle Costs for “Smallside, USA – Central System Costs Minus Onsite System Costs


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The Rocky Mountain Institute report goes on to explain that the results are essentially the same whether the onsite alternative involves ownership of the on-site systems by the town, or ownership by the residential property owners (even when taking into account the differential between interest rates paid by residents and by the town, assumed lower due to access to cheaper capital). 7.4.2 Relevance to NZ Demand Management The benefits of small incremental costs compared to large centralised expenditure in New Zealand demand management can be seen in the deferral of future major infrastructure upgrades. Two New Zealand examples are given below for Tauranga and Waitakere City Councils. Tauranga City Council Metering and other water demand management initiatives enabled Tauranga City Council to defer investment in a new $40 million water source by 10 years and has meant that existing water resources will be able to serve more than 50,000 additional people in future years (Lawton et al. 2008.) A recent economic study commissioned by Beacon has further defined the benefit to ratepayers and the community of $53.3M (in 2009 terms) over those ten years (Market Economics 2010) Waitakere City Council A Water Demand Management Plan carried out by Meritec for Waitakere City Council in 2001 (Meritc 2001) indicated that a water demand management reduction of 20% over 10 years differed future capital works for water supply and wastewater by 13 years (note that demand management impacts on both water supply and wastewater infrastructure through reduced water usage). Therefore, for an annual 2% reduction in water use, a 1.3 year deferral could be expected, which lead to an annual savings of approximately $600,000 due to deferral of water supply and wastewater capital works costs. 7.5 Community and Watershed Impacts 7.5.1 General Trends Many of these impacts are difficult to put a monetary value on, but are important in an ‘integrated’ approach. They were listed as (Rocky Mountain Institute 2004, p. 41-68):

Decentralisation Benefit: - Can accommodate (and control) varying growth in different areas at different times - Promotes ‘cluster’ developments - Support of local economies - Fairness and equity - Greater public understanding/participation

Decentralisation Consideration:

- Large centralised systems may impact local hydrology


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- Greater or lesser public health risks (refer previous Section 5) 7.5.2 Relevance to NZ Demand Management One example of these community and watershed impacts is the Kapiti Coast District Council’s Sustainable Water Use Strategy (Kapiti Coast District Council 2003). Some of the conclusions from this strategy were:

Water Management is an issue for all the Kapiti Coast communities to address (not just the past focus on only the Waikanae, Paraparaumu and Raumati supply issues).

Water Management must be a partnership between Council and iwi, who have a kaitiaki (guardian) role (a specific New Zealand focus), and with local communities.

Water Management must take account of the natural capacities of local environments – the need for more information on all of the catchments.

Development Futures must be understood and managed in relation to this natural capacity – it was agreed that more understanding was needed in the areas of residential growth and economic development.

Efficiency of water use systems: Future adaptability – agreed to take a longer term view and to develop non-potable supply ‘systems’ that reduce unnecessary reliance on the more expensive potable supply systems.

7.6 On-site and Neighbourhood Impacts 7.6.1 General Trends These are implications that are experienced by community members mainly at the scale of individual properties or neighbourhoods, and can include both tangible and intangible costs (Rocky Mountain Institute 2004 page 69-80):

Decentralisation Costs - Difficulty of and time spent on maintenance - Inconveniences of limitations on garbage disposals, washing machines etc.:

decentralised systems are more likely to have restrictions on what can be sent down the pipe.

- Private property rights and resistance to intrusion of outsiders into backyards - Regulatory burdens: centralised systems relieve users from the responsibility of

ownership of a decentralised system. - Lower perceived property value: The property value of a decentralised system can be

lower (depending on the type of system as an on-site septic tank and drain field would have a greater impact than a ‘storage tank’ collected effluent decentralised system). The Rocky Mountain Institute cited a report by Nelson et al. (Nelson et al. 2000, p. 5-2) of a survey of 95 residents (age 55 to 69), with homes ranging in value from $250-$300,000 in Plymouth, USA. Ninety percent responded that homes on a sewer have higher value than homes on septic systems, with an average perceived price differential of $9,250.


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Decentralisation Consideration - Public resistance by neighbouring property owners are more likely with large

centralised systems, but resistance to several smaller decentralised systems may still be prevalent depending on the type of decentralised system.

- Aesthetics: Visual Impacts – these may occur with any system - Aesthetics: Noise – noisy or quiet systems are dependent on technology chosen - Aesthetics: Odour: Odour control is typically less of a concern with smaller systems - Affordability: depending on chosen system - Construction impacts: In retrofit and repair/replacement situations, disruption to

properties varies depending on the system. Repair/replacement of centralised large pipelines can be more disruptive than smaller decentralised collection system, however, repair to onsite treatment/storage systems on each property can be more disruptive to the general public than repairs at one centralised treatment plant.

7.6.2 Relevance to NZ Demand Management One New Zealand example of the impacts on individuals and a neighbourhood is the Glencourt Place rainwater tank retrofit project in North Shore City, presented previously in Section 6.6. The feedback received from the landowners 1 and 2 ½ years after construction of water tanks used for non-potable water (toilet, laundry and outdoor) related to the above points was:

Difficulty and time on maintenance – 2-story roofs and accessibility issues made maintenance difficult and increased time on gutter maintenance compared to previous situation with no raintank.

Inconveniences - leaves and debris getting through to toilet cisterns and laundry machine in some instances.

Intrusion into backyards – retrofitting rain water tanks meant that locations were often not very accessible to ongoing council inspectors.

Regulatory burdens – ownership of the system was transferred over to each landowner, with them being responsible for ongoing operation, maintenance and renewal.

Lower perceived property value – no feedback was noted on this issue. Public resistance – extensive meetings/discussions with individual owners was necessary as

the initial public resistance in some cases was with a ‘distrust’ of council. They wanted to know what was in it for council and why they were doing it?

Aesthetics – size and location of tanks were often an issue. Affordability – some comments were received about a less costly option of just a gravity

tank for outdoor use compared to the more complicated and expensive system of dual plumbing and a pump to supply toilet and laundry water.

Construction Impacts – several comments were received about the time it took the contractor to install the tank system, especially if small retaining walls were necessary to support the tanks due to the sloping ground.


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7.7 Capital and O&M Costs 7.7.1 General Trends This is perhaps the area of most discussion and debate. This section includes conventional capital and operations and maintenance costs (O&M) calculated by traditional engineering economics. These costs are distinct from financial planning costs and risks addressed previously in section 7.5. The important aspect of these Rocky Mountain Institute costs is their relative values with increasing number of services/connections. Example New Zealand costs are presented in Section 7.7.2. One of the most important concepts to understand with respect to costs, and take into account when considering centralised and decentralised systems at different scales, is the inherent economies of scale with treatment facilities compared to the diseconomies of scale with collection/transportation systems. One comprehensive study carried out by Clark in Adelaide, Australia (Clark 1997, cited in Rocky Mountain Institute 2004) examined the capital and operating costs of four different wastewater collection and treatment sizes from 20,000 to 190,000 services (connections). Clark’s findings are presented in the following figures, Figure 8 to Figure 10. The most important points from these figures are:

Figure 8: Capital Costs per service shows: - Clear economies of scale for treatment plants (steep downward grade from 1 to 100 -

1,000 services) - Clear diseconomies of scale in sewer pipelines (moderate upward grade from 1 to

10,000 services) - Connections and pumps are relatively flat and small in value


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Figure 8: Capital Cost per Service

(Rocky Mountain Institute 2004, Figure 11-8)

Figure 9: Operating Costs per service shows: - Clear economies of scale for treatment plants (steep downward grade from 1 to 10,000

services) - Sewer pipelines, connections and pumps are relatively constant and small in value.

Figure 9: Operating Cost per Service



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Figure 10: Total annualised capital and operating costs per service - Middle line (for Clark’s lot density) shows majority of economies of scale occurs from

1 to 100 services. - Effect of increasing lot density (lower line with increased density by a factor of 5)

shows greater economies of scale (reduced from $600 to 400 per service), but still with the majority of these savings occurring from 1 to 100 – 1,000 services.

- Effect of lowering lot density (upper line with reduced density by a factor of 5, a factor of 0.2) shows a slight reduction from 1 to 100 services, then a slight increase and levelling off to approximately the initial cost of service for 1 service. Lower density has the effect of increasing per service pipe lengths, which creates a greater diseconomy of scale for the pipe network, and thus a greater total cost than those at higher density.

Figure 10: Total System Cost per Service

(Rocky Mountain Institute 2004, Figure 11-10) One of the significant outputs from Clark’s work is the levelling of total annualised costs beyond the 100 to 1,000 services. This means that when considering an integrated approach for areas greater than 100 to 1,000 services, other non-cost factors may and perhaps should predominate in decision making. However, for large greywater systems, instead of levelling off at higher number of services, the unit costs tend to increase at higher numbers due to the ‘double penalty’ in the diseconomies of pipe networks, due to the dual distribution system of potable and non-potable pipe networks. A specific example related to greywater cited by the Rocky Mountain Institute report was that of Booker (1999). Booker estimated the cost benefit of the reduction in potable water demand by five slightly different systems of recycling greywater for toilet, laundry and garden watering


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across a scale from 12 to 120,000 households. Figure 11 (Rocky Mountain Institute 2004, Figure 12-1) shows the total cost of water supplied for the five systems levels off between 1,200 and 12,000 household connections, and then rises for 120,000 connections. The minimum estimated cost of water produced by a reclaimed greywater system was $0.50/m3, which was cheaper than the Australian prices for potable water (e.g. $0.70 to $0.80/m3 in Melbourne in 1999).

Figure 11: Total cost of water for graywater scenarios versus number of connections


The additional benefits to the direct economic incentives of cheaper water of reducing the demand on potable water supplies and reducing wastewater flows to sewage treatment plants would also need to be factored in to a full integrated approach. The cost of water produced at a scale of 120 homes is about twice the cost at 1,200 homes, but could still be economic in areas with scarce water and high costs to develop new supplies. However, the steep rise in the cost of water as scale decreases to 12 homes indicates that a scale of service much below 100 homes may not be economic (Rocky Mountain Institute 2004). In terms of centralised and decentralised water supply networks, the most significant work has been that carried out at The University of Newcastle by Dr. P. J. Coombes and others, albeit for Australia with greater water demand pressures than in New Zealand. One situation, often overlooked, is the difference in yields from a roof catchment compared to a watershed catchment. Error! Reference source not found. shows that the efficiency of a water supply catchment (where significant amounts are taken up by the vegetation before it enters the storage lake or reservoir) is considerably less than a roofed catchment feeding a rainwater tank (where losses from spills etc are significantly less (Coombes 2002). Coombes noted that this also shows that in dry Australian years (where rainfall is less than 500mm) the annual runoff in water supply catchments, in this situation, would be insignificant.


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Figure 12: Harvest efficiencies of natural and roof catchments

(Coombes et al 2002)

In the same study, Coombes et al (2002), presented a methodology for evaluating the regional economic benefits due to implementation of source control measures for two case studies in the Lower Hunter and Central Coast regions of New South Wales, Australia. Coombes demonstrated that the use of rainwater tanks to supplement mains water supply for toilet, hot water and outdoor uses can significantly reduce demands on mains water supply and stormwater discharges. For the Lower Hunter region with an urban population of about 450,000 it was shown that the use of rainwater tanks could delay the construction of new water supply headworks infrastructure by up to 34 years. Similar results were found for the Central Coast region (Coombes 2002). Coombes also showed that compared with the traditional provision of mains water and stormwater disposal, the use of rainwater tanks along with other source control measures can produce present worth savings to the Lower Hunter region conservatively estimated to be up to $67 million. 7.7.2 Relevance to NZ Demand Management Studies on costs in the New Zealand environment of rainwater tanks and greywater systems are presented below under three headings; General cost implications of varying scales, greywater systems and rainwater tanks.

General Cost implications of varying scales The above noted trend of reduced costs down to a levelling off point is also reported by Hedgeland (Hedgeland 2009) using New Zealand data. Hedgeland showed a decrease in both decentralised systems (grinder pump and ‘STEP/G’ systems) and conventional centralised systems at approximately 1000 EP (Equivalent population based on 5 persons/property, that is, 1000EP is equivalent to 200 properties or services). Hedgeland states that costs for cluster systems in his calculations have assumed a maximum cluster plant size of 1000EP, beyond this reductions in cluster treatment are usually off-set by bulk conveyance costs, which are site specific.


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However, it should be noted that these cost trends are also technology and system specific; cost information in the literature can often be contradictory. Examples of greywater and rainwater tanks are given below.

Greywater Costs Examples of three different NZ greywater systems are given below; ‘Innoflow’, ‘Ecoplus’ and ‘WaterLillie’. The ‘Innoflow’ system is applicable at both the individual and neighbourhood scale, but the other two systems, ‘Ecoplus’ and ‘WaterLillie’ are only applicable at the individual lot level. An example of a different cost trend is with the local NZ manufactured ‘Innoflow’ system, where the cost differential of their greywater/blackwater reuse systems are not very ‘scale dependent’ because of the modular nature of the treatment system. For instance, the respective rough order costs for different scales of ‘Innoflow’ treatment systems are in the order of (Hawthorne 2010), (2009/10 prices): Individual, single owner Greywater reuse to toilets: Capital installed costs of $15,000 to $20,000 Blackwater reuse to toilets: Capital installed costs of $20,000 to $25,000 Maintenance contract of $300 per year. For 20 to 30 households, greywater reuse Treatment at site (primary treatment in tanks at each lot) at $8 to $9,000 per lot Treatment plant (secondary treatment in one central plant) at $10,000 per lot Recycle/reuse part at $1,500 per lot Total ‘community scale’ at $19,500 to $20,500 For greater than 40 households, greywater reuse Treatment at site (primary treatment in tanks at each lot) at $8 to $9,000 per lot Treatment plant (secondary treatment in one central plant) at $6 to $8,000 per lot Recycle/reuse part at $1,000 per lot Total ‘community scale’ at $15,000 to $18,000 It should be noted that the above ‘Innoflow’ greywater/backwater reuse systems are of high treatment quality (with design BOD5 (Biochemical oxygen demand) and TSS (Total Suspended Solids) of less than 5, and automatic chlorine dosing systems, (Hawthorne 2010)), compared to less expensive lower treatment quality systems such as the:

- ‘Ecoplus’ (www.ecoplus.co.nz) capital cost of $2,750 (treatment by aeration and a flow filter, with manual weekly addition of chlorine tablets) for greywater reuse for irrigation and toilet (with BOD5 in the order of 30 to 100, and TSS of 10 to 100 (ESR 2008))

http://www.ecoplus.co.nz/


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- ‘WaterLillee’ (www.watersmart.co.nz) capital cost of $2,000 (with very limited treatment from a stainless steel filter and temporary storage) with the water only being used for subsurface irrigation.

Brown (2009) uses the costs and water saving benefits of the above ‘ecoplus’ system to show that the on-site system has a significantly higher NPV (Net Present Value) than other local and central greywater systems. The purchase cost, operational cost (per annum) and NPV of the on-site (using the ‘ecoplus’), local and central (based on limited literature for local scales of around 200 connections and central systems for cities) are presented below (Brown 2009, Table 4):

Table 10: Cost of Greywater System per Household/unit

(Brown 2009, Table 4)

On-site Local Central (3)

Purchase Cost $4,250 $3,550 (2) $7,680

Operational Cost (per annum)

$65 $108 (2) $269 (estimated)

Net Present Value $6,568 $1,024 ($3,438)

(1) Numbers in brackets represent a loss (2) Figure based on limited information (3) Prices based on approx. average of existing schemes

Rainwater Costs

Another important issue when considering cost/benefits analyses is whether it is a new ‘greenfield’ situation (when the system can be designed and built along with the rest of the house) compared to a ‘brownfield’ retrofit situation (where the plumbing and location of the device(s) have to be done as an after thought. This is very clear in the case of rainwater tanks, particularly when they are installed for non-potable reuse. The costs to retrofit rain water tanks (of 6,000 to 9,000 litres storage) is in the range of $7,500 to $10,000 (Glencourt Place), where as in a greenfield situation they are in the order of $3,000 to $5,000 (Talbot Park, Hobsonville Land Company). This obviously makes a significant difference to the net present value calculations. For example, costing information from the Glencourt Place project showed that these relatively high retrofitting ‘dual purpose’ rain tank costs were due to having to retrofit the dual plumbing into the house, redirection of some of the downspouts and the difficulty of locating the tanks with requirements for some small retaining walls.

http://www.watersmart.co.nz/


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In terms of ongoing costs, the Glencourt project estimated the power and ongoing maintenance costs at an average of $50/annum, with the average annual replacement costs at $100 (assuming a 25 year tank life and $2,500 replacement costs). With annual cost savings from a reduced water bill (from the using of the rainwater for toilet, laundry and outdoor) measured at approximately $100 to $135 per annum per household, it can be clearly seen that in the brownfield situation, the savings are insufficient to pay off the capital cost of the installation. In such cases the retrofit project has to have other synergies, such as stormwater benefits, as discussed further in Section 7.8 below. The Glencourt project also showed that initial maintenance costs and council inspections can be relatively expensive. The first 3-years maintenance, paid for by the council, was approximately $50,000, or $2,300 per house over the 3-year period. The $50,000 comprised $30,000 on four-monthly inspections and reporting, and $20,000 for additional maintenance costs (including cleaning sediment out of 3 tanks, changing buteline pipes to copper pipes, fixing leaks, new spouting and downpipes). However, in the greenfield situation, an increasing number of new developments are starting to mandate the installation of rainwater tanks for non-potable water use in all new homes. In addition to the Kapiti Coast District Council Plan Change (discussed previously and in Appendix C), other councils in the Auckland area are also taking it up. Two significant ‘greenfield’ developments in North Shore City (development of 250 hectares in Long Bay, North Shore City Council 2009) and Waitakere City (development of 111 hectares into mixed housing by the Hobsonville Land Company, www.hobsonvilleland.co.nz) are both mandating the installation of rainwater tanks (in sizes of 3,000 to 5,000 litres) for non-potable water uses of toilet, laundry and outdoor on all new developments. In both the North Shore and Waitakere City examples, while some cost benefit analyses were carried out, it was generally accepted that there would be a small cost premium (relative to the cost of land and house purchase) for the installation of rainwater tanks , but that it was ‘the right thing to do’, in terms of long term sustainability issues around using our finite freshwater resources for the most appropriate use (for example, do we need to use treated drinking water quality water to flush the toilet?). An example of neighbourhood scale efficiencies with rainwater tanks is the Earthsong Eco-Neighbourhood (www.earthsong.org.nz) example given in the previous Beacon Integrated Water Management (IWM) Design Criteria Report (Kettle 2009). In this example, the Earthsong development had seven 30,000 litre rainwater tanks (and pumps) to serve 32 houses. All units have a dual water supply system. The kitchen sink and bathroom basin cold supply is always direct from the council water main. All other taps (all hot water, and bath, shower, toilet, laundry and outside taps) are supplied by the rainwater tanks. The cost comparisons of the Earthsong communal tanks and a 3,000 litre tank on an individual house were estimated using the following costs,

http://www.hobsonvilleland.co.nz/

http://www.earthsong.org.nz/


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Table 11:


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Table 11: Individual and Community Costs for Rainwater Tanks

3,000 litre tank on individual homes Earthsong communal tanks

Capital Cost $3,500 $100,000 for 7 tanks and accessories, divided by 32 houses = $3,100 per house.

Power cost Est. 200kWh/year @ $0.17 per kWh = $34 per year.

Estimated as 50% of individual homes, = $17 per year.

Maintenance Cost Assume plumber visit once each 7 yrs @ $100 per visit, say $15 per hh per yr. (could be on the low side?)

Est. at $300 per year, for 32 houses = $9.40 per hh per yr.

Water savings Saving of 200 to 300 litres per household per day @ $1.50/m3 = $100 to $150 per hh per yr

The above table shows that the Earthsong development had slightly less per unit capital and ongoing costs, but with the relatively low price of water at $1.50 per cubic metre, the pay back periods were still relatively long at 20 to 30 years.

7.8 Infrastructure Synergies: benefits of integration 7.8.1 General Trends The Rocky Mountain Institute refers to these as ‘economies of scope’. Referring to efficiencies that are gained when businesses or other institutions provide multiple functions which generate economies of scale in combination, for example, combined water and wastewater (Rocky Mountain Institute 2004, pp 121-134). Decentralisation Benefits

Decentralised wastewater systems provide opportunities for cost-effective reuse of water at the site or neighbourhood scale, although, on-site or cluster systems may not provide the quantities of water necessary for large water uses such as industrial facilities.

Decentralised systems allow for closer control of sources of wastewater and can therefore

more easily target low contaminated sites (e.g. residential compared to the more highly contaminated industrial sites)

Decentralisation Considerations

Integration of wastewater and stormwater collection and treatment can be considered over a range of scales.


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7.8.2 Relevance to NZ Demand Management Examples of where integration of rainwater tanks and greywater systems are a benefit to demand management can be seen in:

Integration of rainwater tanks and greywater systems: For example, Kapiti Coast District Council where the Plan Change 75 – Water Demand Management mandated either: - rainwater storage tanks (connecting to toilets and outdoor taps) with a total volume of

not less than 8,000 litres, - or a rainwater tank of 4,000 litres and a complying greywater diversion device (that is,

diversion to sub-surface irrigation, but NOT for reuse in the toilet).

Integration of rainwater tanks and stormwater (with integration of Council and Landowner responsibilities and costs): For example, Glencourt Place (refer Section 6.5 Glencourt Place) where the savings in stormwater infrastructure upgrading costs essentially paid for the installation of the rain water tanks (paid for by Council), with the ongoing operational and maintenance costs being paid for by the reduced water bills (paid for by the landowner).

Integrated design of the rain tank system: The installation of ‘dual purpose’ tanks

demonstrates the need to fully understand how the ‘total rain tank system works’. For example, Figure 13 for 225 litres/day water use and the North Shore City yearly rainfall pattern, shows the greatest reuse benefit comes in the first 3,000 litres of storage volume. For example, for the 250m2 roof and 225 litres per day water use, 3,000 litres of storage provides 90% of the average yearly water use, while increasing to 4,500 litres only increases the percentage used up to 95%. That is, increasing the tank size from 3,000 to 4,500 litres of storage only achieves an additional 5% of the average yearly percent of water supplied (from 90% to 95%).

Average Yearly Percentage of Water Supplied (Water Use of 225 litres per day)

0%

20%

40%

60%

80%

100%

120%

0 5000 10000 15000 20000 25000 30000

Rainwater Tank Capacity

Ave

rage

Yea

rly %

of W

ater

Su

pplie

d 150m2 Roof250m2 Roof500m2 Roof

Figure 13: Average Yearly Percentage of Water Supplied (at water use rate of 225 litres per day) versus Rainwater Tank Size


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It therefore made sense to install 6,000 to 9,000 litre tanks, with only using the bottom 3,000 litres for non-potable water use and the greater top 3,000 to 6,000 for the volumes required for stormwater attenuation. The other important aspect is the need to reduce peak water supply demand as well as the average yearly water use. Council water supply infrastructure design is predominantly based on peak water demands. Therefore, to achieve maximum benefits the tank refill from the mains (in times that the rain tank is empty) should be via a ‘trickle feed’ to ensure it has minimum impact on the reticulated water supply peak demand. Another aspect of rainwater tank design is the question of what size of tank is required to supply both potable and non-potable water use. Taking 500 litres/day total potable and non-potable water use and the North Shore City rainfall pattern as an example, Figure 14 shows the same shape as for the 225 litres per day water use (Figure 13) but indicates storage volumes greater than 25,000 litres would be required to supply 100% of the 500 litres per day water use. Indeed, homeowners often install at least two 30,000 litre tanks to reduce the number of ‘dry days’ throughout the year. While actual numbers will vary for different regions of New Zealand depending on rainfall patterns, they will show the same trends of an initial steep part of the curve up to 3,000 to 4,500 litres of storage with a flattening off after 4,500 to 10,000 litres of storage.

Average Yearly Percentage of Water Supplied (Water Use of 500 litres per day)

0%

20%

40%

60%

80%

100%

0 5000 10000 15000 20000 25000 30000

Rainwater Tank Capacity

Ave

rage

Yea

rly %

of W

ater

Su

pplie

d 150m2 Roof250m2 Roof500m2 Roof

Figure 14: Average Yearly Percentage of Water Supplied (at water use rate of 500 litres per day) versus Rainwater Tank Size.

Integration of water demand management and wastewater: For example, the added benefit

from greywater reuse systems for toilet flushing is that it reduces both the water supply demand and the wastewater volumes discharged


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7.9 Management Management activities ensure the system is properly designed, constructed, operated and maintained to meet the specified performance requirements. Many operators of small systems suffer from inadequate institutional capacity (technical, managerial and financial capacity) and cannot properly operate and maintain their systems, or plan and budget for future upgrades and rehabilitation. This has lead to a lot of attention being placed at management guidelines, policies and regulations. Refer to Section 6 which specifically addresses operating and maintenance issues of centralised versus decentralised systems. Of interest in the Rocky Mountain Institute (2004) report is their reference to the U.S. Environmental Protection Agency set of five ‘management models’ depending on the scale, complexity and/or environmental sensitivity increases (U.S. Environmental Protection Agency 2003, p5, cited in Rocky Mountain Institute 2004):

Management Model 1 – “Homeowners Awareness” for treatment systems owned and operated by individual property owners in areas of low environmental sensitivity. For conventional systems that require little owner attention. Regulatory authority mails maintenance reminders to owners at appropriate intervals to help ensure that timely maintenance is carried out.

Management Model 2 - “Maintenance Contracts” specifies program elements and activities where more complex designs are employed to enhance the capacity of conventional systems to accept and treat wastewater. Because of treatment complexity, contracts with qualified technicians are needed to ensure proper and timely maintenance.

Management Model 3 - “Operating Permits” specifies program elements and activities where sustained performance of treatment systems is critical to protect public health and water quality. Limited-term operating permits are issued to the owner and are renewable for another term if the owner demonstrates that the system is in compliance with the terms and conditions of the permit. Performance-based designs may be incorporated into programs with management controls at this level.

Management Model 4 - “Responsible Management Entity (RME) Operation and Maintenance” specifies program elements and activities where frequent and highly reliable operation and maintenance of decentralized systems is required to ensure water resource protection in sensitive environments. Under this model, the operating permit is issued to an RME instead of the property owner to provide the needed assurance that the appropriate maintenance is performed.

Management Model 5 - “RME Ownership” specifies that program elements and activities for treatment systems are owned, operated, and maintained by the RME, which removes the property owner from responsibility for the system. This program is analogous to central sewerage and provides the greatest assurance of system performance in the most sensitive of environments.


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7.10 Reliability, Vulnerability and Resilience 7.10.1 General Trends In the Rocky Mountain report this was given a separate section because of its importance and need to clarify definitions and distinction between reliability, vulnerability and resilience. The report gave the following definitions to clarify concepts related to wastewater reliability (Rocky Mountain Institute 2004, page 143):

Performance refers to required or desired results of wastewater treatment systems: a level of nutrient removal, pathogen reduction or elimination, etc. Performance levels are often defined by regulatory effluent standards.

Reliability is the rate or probability over time of attaining a performance level under a given set of operating conditions.

Failure occurs when a system does not meet desired performance levels. Typically the term is reserved for serious deviations from desired performance levels and not used for expected stochastic fluctuations outside of the desired performance range.

Vulnerability is the susceptibility of a system to disruptions exogenous to those standard operating conditions.

Resilience is the ability of a system to recover from disruptions or perturbations. (Often, the wider resilience term includes the reliability and vulnerability issues as well).

The Rocky Mountain Institute makes the important point that when reviewing reliability and related issues it is important to consider whether the comparison is made on the assumption of good operation and maintenance, or on actual historical evidence. While there is considerable evidence that many onsite and cluster systems are not properly maintained, the same argument could be made for many small community centralised wastewater systems that are poorly maintained. Large centralised systems often have maintenance issues around sewer overflows (from stormwater infiltration etc) which are not as predominant with decentralised systems. The Rocky Mountain Institute concludes by saying that system planners should (ibid, page 144):

‘Review the reliability aspects of different systems based on an assumption of proper operation, maintenance and management, and should specify the institutional arrangements necessary to ensure those activities are carried out and their costs are supported.’

7.10.2 Relevance to NZ Demand Management General comments on the reliability, vulnerability, resilience and cost of failure for rainwater tanks and greywater systems are summarised below.

Reliability, as a function of proper operation and maintenance is covered in Section 6. Reliability of the chosen treatment process is very system specific.

Vulnerability of rainwater tanks and greywater reuse systems from ‘exogenous disruptions’ (that is, disruptions coming from outside the system) are:


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- Less vulnerable to natural hazards and rain water tanks may very well be able to supply water (even if it has to be boiled for drinking water) to householders in the case of disruption to the main reticulated system.

- More vulnerable to system misuse as a change in water quality into the system (cleaning the roof and not diverting the poor quality water away from the rainwater tank, or putting some chemicals down the wastewater going to the greywater system) have more of an impact on the individual system and does not get levelled out like in a centralised system.

- Individual greywater systems, if dependent on treatment for toilet use, are more vulnerable to the final treatment system, especially the ongoing maintenance of UV systems or the chlorine dosing system, particularly if it is not automated and depends on the landowners weekly addition of chlorine tablets.

- More vulnerable to inadvertent interference if the onsite systems are not properly located and known to the landowner, especially if the rainwater tank or greywater system is buried, with no indication of where they are.

Resilience of the rainwater system and greywater system to recover from disturbances of repair, treatment process reaction to influent variability, and the diversity of technologies within the overall system are: - More resilient to repair as in most cases repair can be done by a ‘well informed’

landowner, or at least the local plumber. - More or less resilient to influent variability depending on the relative scales of the

influent variability to the system size. For instance, a major chemical spill into the reticulated water supply could spread more widely throughout the network system than if it had only affected the onsite systems in its immediate spill area.

- There are an increasing diversity of technologies that can be installed on rain water tanks that control the water quality throughout the water path from the correct roofing material (non zinc), gutter leaf guards, downpipe leaf guards, first flush devices in the downpipes, filters at the exit of the downpipe into the tank, ‘tank vac’ systems that suck out the debris in the bottom of the tank, and ‘floating’ intake pipes that only collect the ‘cleaner’ water about a 100mm below the surface.

Costs of failure, due to the reliability, vulnerability and resilience of the systems are likely to be less because the consequences of small, widely distributed failures of localised rainwater tanks and greywater systems are limited compared to the consequences of large, centralised failures.


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8 Summary Main Points and Conclusions This section presents a summary of the main points for each of the three areas of health risks (8.1), maintenance/ownership (8.2) and centralised/decentralised infrastructure (8.3), with respect to the projects focus on rainwater tanks and greywater systems. Concluding remarks are given in Section 8.4.

8.1 Health Risks 8.1.1 Rainwater Tanks While the Ministry of Health recommends using the public water supply, where available, for potable water use, there is general acceptance of using rain water for non-potable uses (toilet, laundry and outdoor), provided suitable precautions are taken to ensure public health risks are appropriately managed, such as:

clearing labelling non-potable water outlets as not suitable for drinking and any non-potable pipelines are a different colour purple

provide backflow prevention (backflow device or ‘air gap’) to prevent possibility of the non-potable water contaminating the potable water source.

Ensure systems are adequately maintained and operated. Reported health incidents have been where roof-collected rainwater has been used for potable drinking water purposes and the author is unaware of any incidents regarding non-potable water. The proposed changes to the Building Code (currently put on hold) propose a ‘raw water’ (water from springs, bores and tank rainwater) quality guideline of ‘not to exceed 10 E.coli/100ml’ which appears to be unworkable and inappropriate for the following reasons:

Difficulty to enforce at a building consent level by building inspectors due to the number of microbial tests required.

Difficulty of consistency in when and where to sample from (e.g. where the rainwater enters the tank, in the tank, or when it leaves the tank, at the outdoor tap or in the toilet, before or after rain events)

A range, such as 90% of samples not to exceed X, with a maximum threshold of Y is more meaningful than one single number.

The value of ‘not to exceed 10 E.coli/100ml’ is inappropriate given actual values obtained from working rainwater tank systems that have appropriate measures such as leaf guards, first flush diverters and/or ‘tank vac’ systems that give readings in the 100s and sometimes as high as 1,000 to 2,000.

The not to exceed limit of 10 E.coli/100ml does not appear to be based on any sound epidemiological studies or risk assessment (Abbott 2010).


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Another issue related to the inappropriate low value of 10 E.coli/100ml (and applicable to the proposed 1 E.coli/100ml for greywater) is the comparison to the acceptable/green mode monitoring value (O.K. for swimming) of ‘no single value greater than 260 E.coli/100ml’ from the freshwater recreational swimming guidelines (MfE 2003). Although the recreational swimming guidelines state that these guideline values cannot be applied to water uses other than recreational uses, it does highlight the inconsistency and difficulty of using E.coli as an indicator organism. There are a number of guidelines prepared by the Ministry of Health (predominately around the supply of safe drinking water) and a range of council documents varying from 2-page brochures to 100-page technical guidelines. 8.1.2 Greywater Systems There are no guideline documents from the Ministry of Health around greywater reuse, but the recent increase in interest in the last 5 years has prompted some letter of clarification and ‘Position Statements’ (such as that from the Auckland Regional Public Health Service which states ‘….the wide range and competency of system-types, the lack of a comprehensive risk monitoring framework for systems in New Zealand, lack of auditing of practice and the potential for human health risk meant that ARPHS do not support greywater re-use in the domestic setting.’ One point of interest from the Ministry of Health correspondence was the statement that the problem of high failure rates of on-site wastewater systems in New Zealand (and hence having no confidence in wastewater reuse systems) ‘is not a technology issue but the high failure rate is largely a people and management problem’. While the author is unaware of any reported health incidents from wastewater reuse systems, there is clear evidence of poorly managed systems which reinforce the issue of a ‘people and management problem’. As for rainwater, the proposed revisions to the Building Code give an allowable level of pathogens in greywater for re-use as measured by the microbial indicator of E.coli, with a level of less than 1 E.coli/100ml. The explanation in the code states that, ‘…the level set for greywater is more stringent than for raw water. The different values take into account the risk of associated pathogens (bacteria and/or viruses). Greywater must be very well treated because the source cannot be controlled.’ One of the problems with the monitoring of greywater is its very high variability, with its lower range similar to ‘raw water’ (that from springs, bores and rainwater tanks) but its upper range close to that of blackwater. However, as stated in the Australian Guidelines, the nature of greywater and its variability means that the same methodology that is applied to general wastewater (blackwater) can not necessarily be applied to greywater.


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As for rainwater tanks, the proposed one single not to exceed number (of 1 E.coli/100ml) proposed in the revised Building Code for all sites does not appear to be the most appropriate and the author would propose an alternative three-tiered approach to account for different risk levels at different scales, as used in Arizona, U.S.A. and recommended by the comprehensive greywater site, Oasis Design (www.oasisdesign.net). The three Arizona greywater tiers are:

First tier systems for less than 400 gallons per day (1,800 litres per day) that meet a list of reasonable requirements are all covered under a general permit without the builder having to apply for anything.

Second tier systems process over 400 gallons a day (1,800 litres per day), or do not meet the list of requirements, as well as commercial, multi-family, and institutional systems.

Third tier systems are over 3,000 gallons a day (13,000 litres per day). Regulators consider each of them on an individual basis.

8.2 Maintenance/Ownership It is internationally and nationally accepted that maintenance and ownership (ongoing management) of decentralised systems is one of the most important issues around the implementation and ongoing reliability of decentralised systems versus centralised systems (Rocky Mountain Institute 2004, Crites and Tchobanoglous 1998, Leonard and Kikkert 2006, Abbott et al. 2006b, Abbott 2008a, Abbott 2008b, Puddephatt and Heslop 2008 and Scott 2008). In fact, two New Zealand lawyers responding to issues of managing on-site devices on multi-owned residential sites have commented that this is a ‘time bomb’ waiting to happen and could become the next ‘leaky building crisis’(Lysnar et. al 2007). These concerns over ongoing management of decentralised systems have led to the concept of ‘decentralised construction and centralised management’. This has the potential for the best of both worlds, the best of decentralised collection/treatment/reuse/disposal technologies with the best of centralised ‘microprocessor-based’ management systems. The Low Impact Urban Design and Development (LIUDD) project used a term called ‘maintenance smart systems’. This emphasised the importance of considering the maintenance issues throughout the entire design/build process, including design for maintenance, defining the responsibilities and mechanisms to ensure proper operation and maintenance, and the necessary support for the implementation and monitoring stages. The Glencourt Place project demonstrated that a relatively long 3-stage public consultation process was necessary and the co-signing of legal documents (by Council and landowner) were required to ensure the landowner fully understood the project and took over the ownership and ongoing operation/maintenance of the rainwater tank after the initial council funded 3-year maintenance period. The main landowner’s feedback of the rainwater collection and use system (supplying both non-potable water use and stormwater benefits) in two questionnaires sent out one-year and two and a half-years after construction were:

http://www.oasisdesign.net/


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Excessive leaves and debris blockages, sometimes discolouring and appearing in toilet (x 3) and laundry water (x 1).

Concerns by landowners over ability to maintain systems – two story gutter very high and dangerous to clean, height of rain tank, inaccessible rain tank covers, need to clean out debris inside the tank (most noticeable in heavily treed areas).

Suggested smaller tank just for outdoor gravity use then would have a ‘simpler’ system with no pumps and indoor plumbing. (This option is available as one of the Beacon demand management options but has less water demand benefits).

The two sets of questionnaires received from 30% of the landowners revealed - 65 to 75% of responses said the maintenance was about as they expected, with 0 to 30%

saying it was more than expected - 25 to 75% of responses rated the ease of use as ‘fair’, 25 to 50% as excellent, and 10%

as not easy enough. - 50 to 75% of responses said they would recommend it to a friend, 0 to 25% said they

would not. The Talbot Park example was for a new community renewal development where nine rainwater tanks were installed by the owners, Housing New Zealand Corporation (HNZC), one in each of four pensioner single bedroom units, four family homes and in a large apartment block with a large tank (30,000 litres) to serve twenty-four 2-bedroom units. In this case, as water usage is paid for by Housing NZ, the focus is on tenant participation with use of the rain tanks and education of the importance of conserving water. The rain tank use is only for toilet cistern and external taps. Laundry use was not included as there were some cultural concerns raised from Maori and Polynesian tenants during the initial stages of the project. The feedback from this project has been positive with tenants in favour of the rain tank system appreciating the wider environmental benefits. The Kapiti Coast District Council developed a Rainwater and Greywater Code (adopting the same structure as the New Zealand Building Code with Objectives, Functional Requirements and Performance Criteria) to maintain the proper standards while allowing for innovation in materials and methods. Actual ongoing management regime has not yet been finalised, but it is likely that an initial council inspection would be carried out 1 year after construction to ensure that the system is installed correctly and the landowners understands how the system works. This would be followed up with 3-yearly inspections, similar to the proposed national standards for onsite wastewater. Payment would be by homeowner and/or council rates. Tauranga City Council was an example of a ‘typical’ council who are currently addressing water demand management in that they have developed and distributed a ‘brochure’ with information on using rainwater tanks for non-potable water use but are ‘struggling’ with developing a greywater brochure due to lack of national guidance and the ability to define/handle the possible health risks.


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North Shore City Council is an example of a council that already has over 4,000 on-site devices (rainwater tanks and rain gardens) that have formally recorded the location of them on the Property Information Register (that is referenced to in the LIM, Land Information Memorandum, report) but have yet to implement a process for ongoing inspections. The council had plans to implement a system, through a new by law, that would require 2-yearly maintenance inspections by an approved plumber/inspector and council administration, all paid for by the landowner (similar to the existing swimming pool inspections carried out on a 3-yearly cycle), but the process was put on hold with the implementation of the new one ‘Auckland Council’. The management systems currently being used to ensure the proper functioning of on-site wastewater treatment systems (such as 3-yearly approved contractor inspections and reporting) can be used as examples for ongoing management of rainwater tanks and greywater systems.

8.3 Infrastructure – Centralised and Decentralised The impacts of the decentralised rainwater tanks and greywater systems relative to centralised systems in improving demand management in New Zealand are listed under six headings:

Financial Planning and Risk - Smaller modules of increasing capacity (at the individual or neighbourhood scale)

allows closer matching of growing demand to system capacity. - Financial risk is reduced as flexibility allows managers to adjust capital investments to

actual future demands. - Debt financing costs are less for many small capital investments compared to one large

upfront capital expenditure. - Small incremental savings can defer future major infrastructure upgrades with

significant financial savings.

Community and Watershed Impacts - Decentralised water management has more meaning for individual communities with

their specific needs and environmental constraints.

On-site and Neighbourhood Impacts - Difficulty and amount of time spent on maintenance. - Intrusions into private property. - Initial public resistance. - Aesthetics can be an issue. - Affordability issues. - Construction impacts can vary with many small sites compared to one central site.


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Capital and O&M Costs - Economies of scale with treatment facilities (larger scale treatment plants have a lower

per unit cost). - Diseconomies of scale with collection/transportation systems (larger pipe network

systems have a greater proportion of the more expensive larger pipes). - Due to these conflicting economies of scale, decentralised systems generally decrease in

per unit costs up to about 100 to 1,000connections, and then level off, and/or slightly increase after 10,000 connections, but this varies with different treatment technologies and systems.

- Significant cost savings (from $7,500 - $10,000 down to $3,000 - $5,000) can be made if rainwater tanks are designed and installed in ‘greenfield’ (new) developments compared to higher retrofitting costs

- The relative low cost of reticulated water supplies (Typical savings of $80 to $130 per household per year by supplying rainwater for non-potable uses) and highly variable ongoing operation, maintenance, and management of individually owned systems (in the range of $20 to $200 per household per yr) tend to give long pay back periods of 20 to 30 years.

- However, an increasing number of new greenfield developments are mandating the use of rainwater tanks for non-potable water use because it is ‘the right thing to do’ in terms of long term sustainability issues around using our finite freshwater resources and accepting that a relatively small cost premium (compared to the cost of land and house purchase) is ‘worth it’.

- Greywater systems have a large variation in system type and cost depending on degree of treatment, from little to moderate treatment systems of $2,000 - $3,000 to relatively high treatment systems in the range of $15,000 - $20,000.

Infrastructure Synergies: benefits of integration

- Integration of rainwater tanks and greywater systems can be used - Integration of rainwater tanks and stormwater make for a more cost efficient solution

(with integration of Council and Landowner responsibilities and costs) - Integrated design of the rain tank system can ensure maximum benefits for least costs - Integration of water demand management and waste water with greywater toilet reuse

systems reduce both the water supply demand and the wastewater volumes discharged.

Reliability, Vulnerability and Resilience - Reliability is primarily covered under the management issues addressed in Section 6. - Less vulnerable to natural hazards - More vulnerable to system misuse, variable inputs and lack of maintenance - More resilient to repair - Increasing resilience of rainwater tank water quality with an increasing number of water

quality treatment devices that can be installed along the whole water path from the water falling on the roof, gutters, downpipes, tank water storage and use.


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The costs of failure due to the reliability, vulnerability and resilience of the system are probably less (on the assumption that proper management systems can and will be put in place) because the consequences of small, widely distributed failures of localised rainwater tanks and greywater systems are limited compared to the consequences of large, centralised failures.

8.4 Conclusions The main barriers, and possible solutions and advantages, to wider adoption of rainwater tanks and greywater systems as part of the demand management ‘tool box’ have been identified as: Rainwater Tanks Rainwater tanks for non-potable water uses (toilet, laundry and outdoor) are generally gaining greater acceptance by the public and officials:

Health risks are generally manageable for non-potable water use: While the Ministry of Health recommends using the public water supply, where available, for potable water use, there is general acceptance of using rain water for non-potable uses provided suitable precautions are taken to ensure public health risks are managed.

Maintenance/Ownership needs careful consideration: While maintenance and ownership issues for rainwater tanks are not as much of an issue as for greywater systems, urban dwellers need to be aware of the basic requirements and the correct choice of the increasing number of devices coming onto the market to help ensure as clean as water as possible.

Not recommended for potable water use: At this stage, roof-collected rainwater is not recommended for potable water in the urban setting due to possible health risks and the large size tanks (one or two 30,000 litre tanks) that would be necessary to supply both potable and non-potable water uses in most parts of the country. A relatively small rain tank (3,000 to 5,000 litres) can supply up to 80% of the non-potable household water uses, depending on specific rainfall patterns.

Greenfield cost savings: Significant cost savings of up to 50% (from $7,500 - $10,000 down to $3,000 - $5,000) can be realised by installing the rainwater tank and dual plumbing systems in new ‘greenfield’ developments compared to retrofitting existing ‘brownfield’ areas.

Synergies with stormwater management: Significant cost sharing, particularly for capital costs, can be made when the rainwater tanks are also designed for stormwater management.

Possible region wide benefits: One Australian study indicated that wide spread adoption of rainwater tanks over regional populations of 450,000 could delay the construction of new water supply head works infrastructure by up to 34 years.

Detailed design required for maximum benefits: Careful design of the rainwater tank system is necessary to achieve maximum benefits, such as a trickle feed ‘top up system’ so both the peak daily and average yearly water demands are reduced.

Neighbourhood options: Some cost savings can be made with neighbourhood communal developments where tank and pumping costs can be shared among near by households.


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Offers resilience to centralised systems: to disruptions from natural hazards and from breakdowns in the centralised system.

Some new developments are mandating rainwater tanks: Two new significant greenfield developments in Auckland (100 to 250 hectares) have accepted a small cost premium (relative to the cost of land and house purchase) for the mandatory installation of rainwater tanks for non-potable water uses on the grounds that it was ‘the right thing to do’ in terms of long term sustainability of our finite freshwater resources and using water for its most appropriate use (we do not need to flush our toilets with high quality drinking water).

Pay back periods: Simple cost-benefit analyses show that when considered on their own as a supply of non-potable water (toilet, laundry and outdoor) to individual households, without any other synergies, they have a relatively long pay back period of 20 to 30 years. This is due to the relative low cost of reticulated water supplies (typical savings of $80 to $130 per hh per year) and highly variable ongoing operation, maintenance, and management costs of individually owned systems (in the range of $20 to $200 per hh per yr). However, it is important to note that simple cost benefit analysis used to generate “payback” calculations mask the wider value of water demand practices to the whole value chain. As is common with many household interventions to improve performance, the cost is born by home owners while the benefit accrues to the wider community (via improved environment), councils and water providers. Incentives provided by the government’s Warm Up NZ initiative for insulation and clean heating are a response to this in the energy component of household performance. Recognition of value to the nation, region and household of better water management at homes and neighbourhoods is less well advanced in NZ.

Possible barrier with proposed new Building Code water quality standards: While the proposed revisions to the NZ Building Code are on hold it is important that the current proposal for a rainwater quality standard of ‘not to exceed 10 E.coli/100ml’ is not adopted as it is unworkable and inappropriate due to the difficulty of enforcement, a one-single-number rather than a range, and does not appear to be based on any sound epidemiological studies or risk assessment (Abbott 2010).

Greywater Systems: Greywater systems are still not widely accepted by the public or regulatory bodies.

Some acceptance if used for subsurface irrigation only: If greywater systems are properly installed, labelled, monitored and maintained they have some acceptance in the urban setting if used for subsurface irrigation only, such as in the Kapiti Coast District Council Plan Change 75 which mandates rainwater tanks and/or greywater diversion (for subsurface irrigation) for all new developments as part of its water demand management plan.

Acceptance is system dependent: Given the wide range of treatment systems and varying water reuse options, the acceptance of each system is dependent on the type of system and how the water is being reused.

Have been used in rural subdivisions: Greywater (and black water) reuse systems (for irrigation and toilet flushing) have been installed in rural subdivision developments but they do not have the same degree of acceptance in the urban setting.


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Provide reliable year round supply: Have the advantage that they provide a reliable year round supply of non-potable water and reduce the water discharged from the house that requires treatment at a wastewater treatment plant.

Greater concerns over maintenance than rainwater tanks: The lack of landowner maintenance of on-site wastewater systems is often used as a reason for not allowing greywater systems. However, this can be addressed with the right combination of council inspections and a regulated maintenance regime.

Decentralised construction and centralised management: The concerns over ensuring appropriate long term maintenance has lead to these complementary systems of having the best of decentralised collection/treatment/reuse/disposal technologies with the best of centralised ‘microprocessor-based’ management systems.

Centralised and decentralised economies/diseconomies of scale: Centralised systems show economies of scale for treatment facilities (larger treatment plants have lower per unit cost) but diseconomies of scale for collection pipe networks (larger pipe network systems have a greater proportion of the more expensive larger pipes).

Net economies of scale vary with increasing population: Studies have shown that greywater reuse systems generally decrease in per unit costs from individual households up to about 100 to 1,000 connections, then level off, and slightly increase again after 10,000 connections, but this varies with different treatment technologies.

Less public acceptance than rainwater tanks: In general greywater systems are less accepted than rainwater systems due to their higher health risks and general lack of public knowledge/interest.

Large variation in system type and cost: Costs vary depending on the degree of reuse water quality treatment. From little to moderate treatment systems of $2,000 - $3,000 to relatively high quality treatment systems in the range of $15,000 - $20,000. Thus when comparing systems it is important to not only include the ‘simple financial benefits and costs’ but also the social and environmental benefits (and costs) to the wider community.

Greater uncertainties over health risks than for rainwater tanks: due to high water quality variability and associated pathogens.

Non acceptance by Ministry of Health for greywater re-use in the domestic setting. Possible barrier with proposed new Building Code water quality standards: As for

rainwater tanks, the proposed revisions to the Building Code include a low, one-single-number, but at a lower number of ‘not to exceed 1 E.coli/100ml’ for all greywater systems. Having only one not to exceed number does not appear the most appropriate approach for handling the variety of different systems and system scales with their respective varying risks. A more appropriate three tired system of increasing regulatory requirements, similar to that in Arizona and other US states includes a first tier for systems covered under a general permit, a second tier where they do not meet the list of general first tier requirements, and then a third tier that are considered on an individual basis.


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9 References Abbott, S.E., B.P. Caughley, et al. (2006a). A Systematic Evaluation of Measures for Improving the Quality of Roof-Collected Rainwater. Presented at the NZWWA 48th Annual Water Conference and Expo, Christchurch, New Zealand, October 2006. Abbott, S.E., J. Douwes et al. (2006b). A Survey of Microbiological Quality of Roof-collected Rainwater of Private Dwellings in New Zealand. In Proceedings: Water 2006 International Conference Hyatt Regency Hotel, Auckland, New Zealand. Abbott, S. (2008a). Rainwater Harvesting in Urban Environments – Why Not?. Presented at the New Zealand Water and Wastes Association’s 50th Annual Conference, Christchurch Convention Centre, Christchurch, 25th September 2008. Abbott, S. (2008b). Microbiological health Risks of Roof-Collected Rain Water. Presented at the American Rainwater Catchment Systems Association’s National Conference, 15 to 18th September 2008, Sheraton Delfina Hotel, Santa Monica, California. Abbott, S. (2010, March). Senior Lecturer, Microbiological & Communicable Diseases; Director, Roof Water Research Centre; Institute of Food Nutrition & Human Health, Massey University Wellington. Personal communication to David Kettle. Allison, R. (2010, January). Earthsong Eco-Neighbourhood project manager. Personal communication and information to David Kettle. ARC – Auckland Regional Council. (2004). Technical Publication 58 (TP58), On-site Wastewater Systems: design and management manual, 3rd edition, 2004. Booker, N. 1999 (November). "Estimating the Economic Scale of Greywater Reuse Systems." CSIRO Molecular Science. CSIRO Internal Report FE-88. Bowles, Celia (2010, January). Tauranga City Council. Personal communication to David Kettle. Brown, C. (2009). Recycled Water: Risks, benefits, economics and regulation by system scale. New Zealand Land Treatment Collective Conference Proceedings (Technical Session 30): Recycling of Water. Taupo 25-27 March 2009. Broadhead, J. (1988). Occurrence of Legionella species in tropical rainwater cisterns. Caribbean Journal of Science. 24; 71-73.


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Clark, R. 1997. "Water Sustainability in Urban Areas: An Adelaide and Regions Case Study. Report Five: Optimum Scale for Urban Water Systems." Adelaide, Australia: South Australia Department of Environment and Natural Resources. Draft. Combes, P. J., Kuczera, G., Kalma, J.D., Argue, J.R. (2002). An evaluation of the benefits of source control measures at the regional scale. Urban Water, 4, pp 307-320. Crites, R. and G. Tchobanoglous (1998). Small and Decentralised Wastewater Management Systems. McGraw Hill. Cunliffe, D. (1998). Guidance on the use of rainwater tanks. National Environmental Health Forum Monographs, Water Series 3. Public and Environmental Health Service, Dept. of Hu man Services, P.O. Box, Rundle Mall SA 5000, Australia. Crabtree, K., Ruskin, R., Shaw, S. and J. Rose. (1996). The detection of Cryptosporidium oocysts and Giardia cysts in cistern water in the U.S. Virgin Islands. Water Research. 30; 208-216. Davies, C.M, Long, J.A., Donald, M. and N.J. Ashbolt. (1995). Survival of faecal microorganisms in marine and freshwater environments. Applied and Environmental Microbiology. 61; 1888-1896. Dennis, J. (2002). A survey to assess the bacterial quality of roof-collected rainwater in the Wairarapa. BhlthSc 214.318 Environmental Health Research Project. Massey University, Wellington. Department of Building and Housing 2007. Building for the 21st Century. Review of the Building Code. Performance Requirements July 2007. Downloaded from www.dbh.govt.nz/bcr-2007-consultation , 13 January 2010. Eberhart-Phillps, J., Walker, N., Garret, N., Bell, D., Sinclair, D., Rainger, W. and M. Bates. (1997). Campylobacteriosis in New Zealand: results of a case control study. Journal of Epidemiology and Community Health. 51; 686-691. EcoWater – Waitakere City Council (1999). Draft Guidelines for Best Practice Water management, Part of the Comprehensive Urban Stormwater Management Action Strategy to Demonstrate Best Sustainable Practice project, funded by the Ministry for the Environment Sustainable management Fund, Waitakere City Council, Auckland, NZ. Ensslin, C.H. (2005). Rainwater tanks in series. Master of Science Thesis. Loughborough University, England.

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ESR - Environmental Science and Research Ltd. (2007). Estimation of the Burden of Water-borne Disease in New Zealand: Preliminary Report. Prepared for the Ministry of Health, Wellington: Environmental Science and Research Ltd. ESR – Environmental Science and Research Ltd. (2008). Letter to Derry and Elizabeth Gordon, dated 14 August 2008, with results from sampling the ‘Ecoplus’ greywater recycling system on three sampling dates. Evans, C.A., Coombes, P.J. and R.H. Dunstan. (2006). Wind, rain and bacteria: The effect of weather on the microbial composition of roof-harvested rainwater. Water Research. 40; 37-44. Fleming, J. (2000). Risk perception and domestic roof-collected rainwater supplies. Master of Public Health Thesis. Auckland University, New Zealand. Gould, J. (1999). Is rainwater safe to drink? A review of recent findings. Proceedings of the 9th International Conference on Rain Water Cistern Systems, Brazil, September. Hawthorne, Brent (2010, January). Technical Manager, Innoflow Wastewater Specialists, Dairy Flat, Auckland, New Zealand. Personal communication and information to David Kettle. Hedgeland, Ray (2009, December). Director Environmental Department, Fraser Thomas Ltd, Papatoetoe, New Zealand. Personal communication and information to David Kettle. Hoque, M.E., Hope, V.T., Scragg, R. and T. Kjellstrom. (2003). Children at risk from giardiasis in Auckland: a case-control study. Epidemiol. Infect. 131; 655-662. Irvine, J. (2009). Raintank Pilot Project Report, Glencourt Place, Draft, North Shore City Council. Kapiti Coast District Council. (2003). Water Matters: Kapiti Coast District Sustainable Water Use Strategy, January 2003. Kettle, D. (2009). Integrated Water management (IWM) Design Criteria Report. Report WA7090/3 for Beacon Pathway Limited, July 2009. Koplan, J., Deen, R., Swanston, W. and B. Tora. (1978). Contaminated roof-conducted rainwater as a possible case of an outbreak of Salmonellosis. Journal of Hygiene. 45; 303-309. Krishna, J. (1993). Water quality standards for rainwater cistern systems. Proceedings of the 6th International Conference on Rain Water Cistern Systems, Nairobi, Kenya. 389-392 Lawton, M. et al. (2008). Best Practice Water Efficiency Policy and Regulation. Report WA7060/3 for Beacon Pathway Limited.


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Lawton, M., Birchfield, D and Kettle, D. (2007). Making Policy and Regulation Rain Tanks Friendly. Report PR205/1 for Beacon Pathway Limited. Leonard M. and H.Kikkert (2006). Efficacy of Greywater Treatment in New Zealand. Institute of Environmental Science and Research Ltd. (ESR), Christchurch, New Zealand. The Water Conference 2006, New Zealand Water & Wastes Association 48th Annual Conference and Expo, Christchurch, 11-13 October, 2006. Leonard, M., D. wood & A. Skinner (2009). How Efficient is On-site Water Reuse as a Water Management Option. Institute of Environmental Science and Research Ltd. (ESR), Christchurch, New Zealand. New Zealand Water & Wastes Association 51st Annual Conference and Expo, Rotorua, 2009. Leonard, M. (2010, January). Institute of Environmental Science & Research Ltd (ESR), Christchurch, New Zealand. Personal communication to David Kettle. Lester, R. (1992). A mixed outbreak of cryptosporidiosis and giardiasis. Update. 1; 14-15. Lye, D.J. (2002). Health risks associated with consumption of untreated water from household roof catchment systems. American Water Resources Association. 38; 1301-1306. Lysnar, P., J. Dixon, C. Dempsey, M. van Roon (2007). Managing ‘Low Impact’ Features on Multi-owned Residential Sites. 5th South Pacific Stormwater Conference, 16-18 May, 2007, Sky City Convention Centre, Auckland, New Zealand. Market Economics (2010). The Value Case for Water; Report 1: Literature Review, Report 2: A Framework for Valuing Water Demand Management, Report 3: Tauranga City Case Study: summary report. Reports prepared for Beacon Pathways Ltd. Meera, V. and M. Mansoor Ahammed. (2006). Water quality of rooftop rainwater harvesting systems: a review. Journal of Water Supply and Technology. AQUA. 55.4; 257-269. Meritec (2001). Water Demand Management Plan. Prepared by AECOM (formerly Meritec Ltd) for Waitakere City Council, October 2001. Meritec (2002). Glencourt Place/Seaview Road, Glenfield: Flood Mitigation Discussion Document. Prepared by AECOM (formerly Meritec Ltd) for North Shore City Council, July 2002. Meritec (2003). Glencourt Place/Seaview Road, Glenfield: Stormwater Mitigation Final Design Report. Prepared by AECOM (formerly Meritec) for North Shore City Council, April 2003.


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Merrit, A., Miles, R. and J. Bates. (1999). An outbreak of Campylobacter enteritis on an island resort, North Queensland. Communicable Disease Intelligence. 23; 215-219. Metcalf & Eddy, AECOM (2006). Water Reuse: Issues, Technologies and Applications. Written by Asano, T., F. Burton, et al. Mc Graw Hill Ministry of Health. (2004). Household water supplies: the selection, operation, and maintenance of individual household supplies; Code 4602. Ministry of Health. Wellington. New Zealand. Ministry of Health. (2005). Drinking-water standards for New Zealand 2005. Ministry of Health. Wellington, New Zealand. Ministry of Health. (2006). Water collection tanks and safe household water; Code 10148. Ministry of Health. Wellington. New Zealand. Mithraratne, N. and R. Vale (2006). Life-cycle Resource Efficiency of Conventional and Alternative Water Supply Systems. 12th Annual International Sustainable Development Research Conference, 6-8 April 2006, Hong Kong. Centre for Urban Ecosystem Sustainability, Landcare Research, Auckland, New Zealand Ministry of Health. (2009). Annual Review of Drinking-Water Quality in New Zealand 2007/08. Wellington: Ministry of Health. Nelson, V., S. Dix, and F. Shephard. 2000 (September). "Advanced On-Site Wastewater Treatment and Management Market Study, Volume I: Assessment of Short-Term Opportunities and Long-Term Potential." Palo Alto, California: Electric Power Research Institute. 1000612. North Shore City Council. (2009). Text Resulting from Environment Court Interim Decision A078/2008 of 16 July 2008, Proposed Plan Change 6, Long Bay Structure Plan Stage 2, Rebuttal Version, 2 November 2009. NRMMC (2006). Australian Guidelines for Water Recycling: Managing Health and Environmental Risks (Phase 1). A publication of the Natural Resource Management Ministerial Council, the Environment Protection and Heritage Council and the Australian Health Ministers Conference. Editing by Biotext Pty Ltd, Canberra, November 2006. NSCC - North Shore City Council. (2009). Rain Tank Guidelines, Second Edition, September 2009. NSW Health (2005). Domestic Greywater Treatment Systems Accreditation Guidelines. Part 4, Clause 43(1), Local Government (Approvals) Regulation, 1999. February 2005.


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Ormiston Associates Ltd. (2008). Greywater Reuse in Single Dwellings, Draft, Reference 2069/2879. Review for Kapiti Coast District Council. Palmer, S.R., Gully, P.R., White, J.M., Pearson, A.D., Suckling, W.G., Jones, D.M., Rawes, J.C. and J.L. Penner (1983). Waterborne outbreak of Campylobacter gastroenteritis. Lancet. 1; 287-290. Pinkham, R.D., J. Magliaro, and M. Kinsley. 2004. "Case Studies of Economic Analysis and Community Decision Making for Decentralized Wastewater Systems." Project No. WU-HT-02-03. Prepared for the National Decentralized Water Resources Capacity Development Project, Washington University, St. Louis, Missouri, by Rocky Mountain Institute, Snowmass, Colorado. Puddephatt, J and V. Heslop (2008). Guidance on an Integrated Process; Designing, operating and Maintaining Low Impact Urban Design and Development Devices, Prepared by Jane Puddephatt and Viv Heslop, July 2008 for the Low Impact Urban Design and Development (LIUDD) project, Auckland, New Zealand. Rocky Mountain Institute. (2004). Valuing Decentralised Wastewater Technologies: A Catalog of Benefits, Costs, and Economic Analysis Techniques. Prepared by the Rocky Mountain Institute for the U.S. Environmental Protection Agency, November, 2004. Copyright © 2004 Rocky Mountain Institute. Scott, K. (2008). Down the Drain: Control and Ownership of the ‘Problem’ of Stormwater. ASA, AAS & ANZASA International Anthropology Conference ‘Ownership and Appropriation’, 8-12 December 2008, University of Auckland, Auckland, New Zealand. Sedouch, V. (1999). Total coliform and faecal coliform detection in roof water: comparison of membrane filtration with Colilert methods. BappSc 3330 NBSEH Environmental Health Research Project. Massey University, Wellington. Simmons.G. and J. Smith. (1997). Roof water probable source of Salmonella infections. The New Zealand Public Health Report. 4; pp 5. Simmons, G., Gould, J., Gao, W., Whitmore, J., Hope, V. and G. Lewis. (2000). The design, operation and security of domestic roof-collected rainwater in rural Auckland. Proceedings of the Water 2000 Conference ‘guarding the global resource’ New Zealand Water and Wastes Association. Auckland. Session 3; Pp 1-16. Simmons, G., Hope, V., Lewis, G., Whitmore, J. and W. Gao. (2001). Contamination of potable roof-collected rainwater in Auckland, New Zealand. Water Research. 35;1518-1524.


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Taylor, R., Sloan, D., Cooper, T., Morton, B. and I. Hunter. (2000). A waterborne outbreak of Salmonella Saintpaul. Communicable Disease Intelligence. 24; 336-340. Tian, F, A. Vosloo, R. Hawthorne and D. Kettle (2003). Non-technical Issues Surrounding the Use of Raintanks to Mitigate Flooding Problems in a Developed Urban Area. Presented at the 3rd South Pacific Conference on Stormwater and Aquatic Resource Protection, 14-16 May 2003, Auckland, New Zealand. Thompson, B. (2010, February). Water Use Coordinator, Kapiti Coast District Council. Personal communication to David Kettle. Thornley, C.N., Simmons, G.C., Callaghan, M.L., Nicol, C.M., Baker, M, Gilmore, K.S. and N.K. Garret. (2003). First incursion of Salmonella enterica serotype DT160 into New Zealand. Emerging Infectious Diseases. 9; 493-495. U.S. Environmental Protection Agency. 2003b (March). "Voluntary National Guidelines for Management of Onsite and Clustered (Decentralized) Wastewater Treatment Systems." Washington, D.C.: Office of Water and Office of Research and Development. EPA-832-B-03-001, available at http://www.epa.gov/OWOWM. html/mtb/decent/download/guidelines.pdf. Vickers, A. (2001). Handbook for Water Use and Conservation, WaterPlow Press, Amherst, MA. Walker, T.J. (1997). A study to evaluate the physical fitness of roof catchment water supples in the rural district of Pauatahanui. BappSc NBSEH 3330 Environmental Health Research Project. Wellington Polytechnic. Wallace, Ian (2010 February). Environmental Services, North Shore City Council. Personal communication to David Kettle. Yaziz, M.I., Gunting, H., Sapari, N. and A. W. Ghazali. (1989). Variations in rainwater quality from roof catchments. Water Research. 23; 761-765.

http://www.epa.gov/OWOWM


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10 Appendix A: New Zealand Ministry of Health Documentation on Wastewater Re-use

This Appendix contains Ministry of Health documentation on wastewater re-use obtained by the author in January 2010. The attached documents and their sources are:

Two Ministry of Health clarification letters in 2005/06, written by Paul Prendergast, Principal Public Health Engineer, Public Health Directorate, following a number of questions from different parties on wastewater reuse issues. These two letters were obtained from Denise Tulley, Community and Public Health, Christchurch, by the author on 17 January 2010. The two attached letters are:

“Re-Use of Wastewater – Ministry of Health Policy” (a cover letter to the following letter), (dated 2005/6?)

“Dual Water Supplies in Residential Dwellings”, dated 27 June 2005.

The third attached document is the Auckland Regional Public Health Service’s “Position Statement on Grey Water Re-use in Auckland’, received from Shannon Palmer, Health Protection Officer, Acting Technical Manager Drinking Water, Assessment Unit – Auckland, by the author on 18 December 2009.


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PH20-14-3

Mr Greg Hill General Manager Policy and Planning Auckland Regional Council Private Bag 92012 AUCKLAND Dear Greg Re-Use of Wastewater – Ministry of Health Policy Following a number of questions from different parties, I would like to clarify to the Auckland Regional Council the Ministry of Health’s position with regard to the re-use of wastewater (including greywater). Following a request from the public health services last year, the Ministry’s position was put in a letter to the District Health Boards for their Designated Officers under the Health Act 1956 (Medical Officers of Health and Health Protection Officers) to use when advising local authorities (regional and territorial) of the Ministry’s policy. I have attached a copy of the letter sent to the Auckland Regional Public Health Service. The letter was also copied to other public health services in New Zealand. The Ministry of Health does not support the re-use of wastewater within the residential environment and the reasons for this are explained in the attached letter. It is a basis of protecting a community’s public health that people are separated from possible contact with contaminated water. The very high failure rates of on-site wastewater systems in New Zealand is such that we can have no confidence of wastewater re-use within a residential situation where poorly treated effluent will often be in contact with people. The above is not a technology issue but the high failure rate is largely a people and management problem. I represented the Ministry on the joint Australian/New Zealand Standard 1547 from 1995 to 2000 and I am on the new Standards Committee reviewing that Standard. The Standard recognised that the major problem with on-site systems was the lack of ongoing maintenance and management. The Standard sought regulatory authorities in this area to require regular compliance checking and compliance certificates. Whilst the above standard is being reviewed, the Committee has already concluded that 1547 will not be expanded to cover re-use of greywater as this is outside the scope of the Standard and some of the jurisdictions involved would not support 1547 if greywater was added. Until such requirements for managing on-site systems are regulated in New Zealand nationally, the Ministry of Health considers the risks of re-using wastewater (where the water quality will usually be poor) is not worth the risks involved.


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Also attached for your information is a paper prepared for the Ministry by Margaret Leonard of ESR. You will see from this paper that ESR had difficulty finding many greywater re-use operations, largely because the local authorities could not supply the information on where they were. Even where local authorities grant consents with satisfactory conditions attached, these had not been monitored and some consent holders simply decided to stop complying with the conditions. A number of the systems in the ESR report were on Waiheke Island. Whilst the Ministry of Health has adopted AS/NZS 1547, it notes the Auckland Regional Council’s design manual TP 58 shares many features and a similar philosophy to the Standard. As a design manual, TP 58 is therefore supported by the Ministry of Health. Notwithstanding the above advice from the Ministry of Health, if a regulatory authority does decide to grant consent to re-use wastewater (including greywater), then the requirements of TP 58 are the minimum that should be required. My understanding is that in the preparation of TP58, the Medical Officer of Health and the Auckland Regional Public Health Service were consulted and their advice adopted in that document as well as for your rules in the regional plan which cover the re-use of wastewater/greywater. Where consent is given for re-use of wastewater, it is then very important that regular monitoring of the effluent quality by the consent authority is carried out. Yours sincerely Paul Prendergast Principal Public Health Engineer Ministry of Health

Cc Te Miha Ua-Cookson

Manager Health Environments Auckland Regional Public Health Service Private Bag 92-605 Symonds Street AUCKLAND


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27 June 2005 PH20-14-3

Te Miha Ua-Cookson Manager Health Environments Auckland Regional Public Health Service Private Bag 92-605 Symonds Street AUCKLAND Dear Te Miha Dual Water Supplies in Residential Dwellings You have asked a number of questions relating to the use/re-use of water for non-potable purposes within residential dwellings and properties. These are questions relating the re-use of wastewater but also stormwater or other sources of water for non-potable uses. The questions are therefore partly related to wastewater re-use but also, where dual pipe systems are involved, they relate to drinking-water and the risks to the drinking-water supply. A number of questions you ask do not have specific Ministry of Health (MoH) policies and have to be looked at case by case. The current MoH policy on re-use of wastewater within the home is: The Ministry of Health has stated:

“……….. two principles that should be followed : • The treatment and discharge methods used for sewage effluent should

provide the best method of protecting the public health. That is the public health is paramount.

• No sewage treatment system entirely protects public health and all systems can fail. Therefore, it has always been a prime public health measure to separate people from contact with sewage effluent as much as is practicable.

a) Ministry of Health does not support reuse of wastewater within a

residential property because in NZ the risks are not justified by the need. No matter what performance parameters are specified, the high failure rate of many primary on-site treatment systems discharging into poor soils means that inevitably householders will come into contact with poorly treated or untreated effluent. Public health is best protected by separating people from possible contact with sewage effluent.

b) Under no circumstances should potable reuse of wastewater be considered in a residential situation.”


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My understanding is that this policy was reproduced in the latest TP58 by the Auckland Regional Council. The policy is of-course related to the re-use of wastewater from septic tanks or more advanced on-site systems. Your questions cover a wide range of alternative water sources from low quality or treated effluent to groundwater that is near potable quality. Your question ask guidance on:

• Acceptable sources of water for non-potable use • Acceptable non potable uses of recycled water

This clearly depends on three aspects. What the water is to be used for, where, and what quality it is. You have listed a number of possible sources for this water, namely; roof water, stormwater, shallow groundwater, grey water, and wastewater. For the grey water and wastewater re-use the MoH policy above covers those situations. The Ministry of Health advises against the use of recycled water domestically with dual supplies. This is because of the risks of cross connection with potable water supplies. In addition, because in small systems it will be difficult to ensure reliable recycled water quality, domestic use represents an unnecessary hazard. We also have concern with wastewater re-use for the garden unless it can be ensured children, pets etc cannot get access to irrigated areas and also any use on vegetables. Environmental Science and Research Ltd’ (ESR) microbiological water quality monitoring has shown that indicator bacteria and even F-RNA phage are present in some greywater systems. As phage appears to only be present in sewage (unlike indicator bacteria) it can be seen that some types of greywater systems will contain pathogens. Restricting what occurs on site is impossible. For roof water (by which I mean you are including the stormwater collection ie. It is not stormwater off the street) use within the section may be fine if:

• It is not part of a dual supply (ie totally separate system) • There is no possibility of children etc drinking from taps. That is they

are placed too high for example. Colour coding and signs do not work for children (or some adults).

You have mentioned water use from the Mt Wellington Quarry. Is this the same as the Three Kings Quarry supply that was proposed to supplement Auckland water some years ago and to which full treatment was provided (my Auckland geography getting a little rusty)? This was close to potable before treatment and the roof tank comments above would be applicable. For the above (roof water, groundwater) with dual water supply systems:


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This is now a water supply question related to the risk of cross contamination. You have mentioned ‘non-potable water for flushing toilets probably poses minimal risks to public health provided there are adequate measures in place to prevent cross contamination’. The problem is that it is very difficult to ensure no cross contamination occurs and the Netherlands recently stopped allowing this to happen because of cross contamination incidents that occurred in a more regulated society than we have here. Where good quality non-potable water is used in a dual water supply I would consider that the risks would need to be assessed as part of the Public Health Risk Management Plan (PHRMP) for the water supply. This would need to consider a number of aspects including the quality of water, uses, type of backflow prevention device, ability for the device to be checked that it is working and how often it is inspected. My view is that the backflow preventers would need to be testable and checked (in each house) annually. Less than this will probably result in demerit marks for the distribution zone of that drinking-water supply unless each house has a testable backflow preventer at the toby, which is tested. This should be discussed with your drinking-water assessors (DWAs). You mention North Shore City Council has allowed dual pipe systems with roof tanks. You also need to check with the DWAs if this has been taken into account in the grading of the distribution zones of that water supply. The use of non-potable water of the above quality (not wastewater) for laundries and outside taps would have similar risks to a house on a roof tank as far as direct exposure pathways are concerned. Again a PHRMP approach may be useful here. If it is plumbed in to a dual supply then the above comments are relevant. Your final question asks about your responsibilities under legislation for non-potable water supplies and potential liability. The Ministry Of Health cannot supply legal advice to public health services who are advised to obtain their own. The responsibilities of the designated officers under the Health 1956 and the Water Supplies Protection Regulations 1961 apply. There is also the question of the liability of a council that allows dual systems if contamination occurs. A current issue is the liability question with councils who supply water, knowing it does not comply with DWSNZ and issuing boil water notices over a period of years (and therefore not a temporary/emergency measure) also knowing it will be largely ignored and resulting in illness. One council in the South Island is contemplating this at the present time after a case of E.Coli 0157. Such liability advice can only be obtained from a legal opinion and ultimately from a decision of the courts. I hope this has gone some way to answering your questions. Yours sincerely Paul Prendergast Principal Public Health Engineer Public Health Directorate


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11 Appendix B: NSW Domestic Greywater Treatment Systems Guidelines

11.1 Source Documents NSW Health (2000a). Domestic Greywater Treatment Systems Accreditation Guidelines (April 2000), Local Government (Approvals) Regulation 1999. NSW Health (2000b). Greywater Reuse in Sewered Single Domestic Premises. April 2000. A document focussed on greywater reuse in sewered areas. NSW Health (2005). Domestic Greywater Treatment Systems Accreditation Guidelines. Part 4, Clause 43(1), Local Government (Approvals) Regulation, 1999. February 2005. Sydney Water (2004). Information for Plumbers – Domestic Greywater Reuse. Plumbing Policy Standards and Regulation. May 2004 (a 4-page summary document)

11.2 Summary The NSW Health Department define greywater as that component of sewage which does not come from a toilet or urinal. Greywater is therefore the wastewater which is generated from:

shower bath tub spa bath hand basin laundry tub kitchen sink dishwasher clothes washing machine

In NSW a domestic greywater treatment system (DGTS) are designed to treat and disinfect greywater or components of greywater so that it may be applied to:

a surface or sub-surface irrigation area and/or reused for toilet flushing and laundry use in the household.

Before local councils can approve the installation of a DGTS, it must be accredited by the NSW Health Department. The most recent accreditation guidelines are those dated February 2005 (NSW Health 2005). Some of the more relevant design criteria are:

The DGTS shall be designed to treat the greywater waste stream from a minimum of 8 persons and a maximum of 10 persons, based on a minimum daily flow of 90 litres per person per day.

Where it is intended to install a DGTS in a sewered area, the DGTS shall be capable of connection to the sewer such that: - An overflow to the environment will not occur should there be a failure of the DGTS; - The operator may direct greywater to the sewer during periods of rain or other

circumstances adverse to the discharge of treated greywater.


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The testing of the DGTS shall be carried out over a continuous 26 week period and comprise (NSW Health 2005):

Table 1 (NSW Health 2005): Frequency of Sampling

Parameter Influent Effluent

Prescribed (must be analysed)

Thermotolerant coliforms (faecal coliforms)

Every 12 days Every 6 days

BOD5 Every 12 days Every 6 days

SS Every 12 days Every 6 days

Free chlorine (where used) Every 12 days Every 6 days

Optional (manufacturer to nominate)

TKN Every 12 days Every 6 days

TN Every 12 days Every 6 days

TP Every 12 days Every 6 days

Free chlorine (or residual of any other chemical disinfectant)

Every 12 days Every 6 days

The compliance criteria for T. coliforms, BOD5 and SS are (NSW Health 2005):

Table 2 (NSW Health 2005): Compliance Criteria for Effluent Quality from DGTS According to Disposal/Utilisation Method

Disposal Method T. coliforms cfu/100ml

BOD5 mg/L

SS mg/L

Free Cl2 mg/L

Sub-surface irrigation

90% of samples < 20 < 30

Maximum threshold < 30 < 45

Surface irrigation

90% of samples < 30 < 20 < 30 > 0.2 - < 2.0


Toilet / Washing Machine reuse

90% of samples < 10 < 10 < 10 > 0.5 - < 2.0

Maximum threshold < 30 < 20 < 20 < 2.0 NSW Health randomly nominates a minimum of 10% of installed sites, operating for a minimum of 6 months, as sites for monitoring.


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11.3 Greywater in Sewered Areas NSW have a specific document to address greywater reuse in sewered areas (areas with a reticulated wastewater system) titled Greywater Reuse in Sewered Single Domestic Premises (NSW Health (2000b). The document considers the reuse of greywater in single domestic premises in sewered areas based primarily on public health considerations according to the characteristics of greywater. Environmental aspects are also considered. The document lists the key differences between greywater and blackwater as:

Greywater contains only about 1/10 of the nitrogen (nitrite and nitrate) as does blackwater Because blackwater (containing faecal material) is excluded from greywater there is a

decreased load of faecal pathogenic organisms. The organic content of greywater decomposes more rapidly than blackwater and

assimilation is assisted even further when greywater is reused by direct application in the root zone.

The document notes the detrimental effects from the storing of greywater, other than temporarily in a surge tank, unless adequately treated. When greywater is stored it turns septic giving rise to offensive adours and provides conditions for micro-organisms to multiply. Thermotolerant coliforms have been found to multiply by 10 to 100 times during the first 24 to 48 hours of storage before gradually declining. Significant levels of pathogens have been found in stored greywater after eight days. In these sewered areas, there are two types of greywater reuse practice:

Greywater diversion devices which simply divert greywater (excluding kitchen wastewater) without storage or treatment

Domestic greywater treatment systems which collect, store and treat greywater (which may include kitchen wastewater) to a higher standard.

Greywater diversion devices do not treat greywater but, depending on the greywater source, as a minimum, be coarse screened to remove materials that may clog pumps, block pipes or place too great a pollutant load in the soil for its treatment. For domestic greywater treatment systems, various treatment systems include settling of solids, floatation of lighter materials, anaerobic digestion in a septic tank, aeration and clarification to treat the gross pollutant nature of wastewater. The final treatment of disinfection (e.g. chlorine) is used to treat micro-organisms rather than the gross pollutants and depends on the prior treatment processes for its efficiency.


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The document gives examples of different ‘Greywater Diversion Devices’ and ‘Domestic Greywater Treatment Systems’ as: Greywater Diversion Devices (GDD). There are two types:

Gravity Diversion Devices – a gravity diversion device incorporating a hand activated valve, switch or tap which is fitted to the outlet of the waste pipe of the plumbing fixture such as a laundry tub. The plumbing diversion device can be switched by the householder to divert greywater from the laundry tub by gravity directly to the diversion line and the dedicated land application system instead of the sewer. The greywater must not be stored.

Pump Diversion Devices – a pump diversion device incorporates a surge tank to cope with sudden influxes of greywater for distribution by a pump to a sub-surface land application system. The surge tank must not operate as a storage tank. The greywater should be screened as it enters the surge tank. The coarse screens must be cleaned regularly and the surge tank flushed periodically.

Domestic Greywater Treatment Systems (DGTS). A DGTS collects, stores, treats and may disinfect all or any of the sources of greywater. A DGTS requires a certificate of accreditation from NSW Health. It is important to note their cautionary text in relation to the operation and maintenance of wastewater systems, the document states:

It is well recognised that householders, unless dedicated to wastewater reuse practices, do not necessarily maintain their wastewater management systems unless there is a system of audit. It is essential that councils institute an on-site wastewater management strategy which initially considers the impacts of greywater reuse in their areas before allowing greywater reuse and secondly, rigidly enforces an operating licence by a system of regular audit.

The document lists the following public health considerations:

The health status of the household is usually reflected in the wastewater produced although a household enjoying good health will still excrete pathogenic micro-organisms which are part of the normal flora of the gut.

Greywater is contaminated with human and animal excretions from bathing, food preparation and from clothes washing.

All forms of greywater are capable of transmitting disease. Disease transmission is principally through the faecal-oral route where the greywater may

be directly ingested through contaminated hands, or indirectly ingested through contact with contaminated items such as grass, soil, toys, garden implements, and diversion or treatment devices while they are being serviced.

Care must be taken to ensure that there is no cross connection between the greywater reuse system and the water supply so that the drinking water is not inadvertently contaminated.


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The potential to transmit disease must be minimised by: - Minimising human contact with untreated greywater, i.e. subsurface utilisation - Placing barriers between the greywater and people (and their pets) to minimise exposure

to greywater by containing greywater in vessels or tanks as it is utilised. - Disinfection to an even higher standard of utilisation in toilet and urinal flushing or

laundry use. - Sign posting the land application system to advise that greywater is being reused and

that contact must be avoided. - Using a dedicated land application system not used for recreation such as a childrens’

play area, BBQ are etc. - Not storing greywater except for surge attenuation, unless treated and disinfected. - Preventing surface ponding or surface run-off of greywater and confining greywater

within the disposal area. - Not irrigating greywater during periods of wet weather. - Distinguishing plumbing which contains recycled water and to prevent cross connection

to the potable water supply. - Maintaining a connection to the sewer so as to enable isolation of the land application

system. - Installing a backflow prevention device on the potable water supply when greywater is

used for toilet flushing. - Not irrigating raw or treated greywater on edible plants which are consumed raw.

The document lists the following environmental considerations:

One of the most important concepts is that of “Ecologically Sustainable Development”, defined as “using, conserving, and enhancing the community’s resources so that ecological processes, on which life depends, are maintained, and the total quantity of life, now and in the future can be increased.” The four principles to achieve this being: - The precautionary principle – if there are threats or serious irreversible environmental

damage, lack of full scientific certainty should not be used as a reason for postponing measures to prevent environmental degradation;

- Intergenerational equity – the present generation should ensure that health, diversity and productivity of the environment is maintained and enhanced for the benefit of future generations;

- Conservation of biological diversity and ecological integrity; and - Improved valuation and pricing of environmental resources.

Wastewater generation should be minimised for three important reasons - To conserve drinking water as a precious natural resource; - To ensure that wastewater does not overload the installed greywater management

system, which may then cause a public health risk, cause environmental damage or reduce neighbourhood amenity;

- To minimise land requirements for a greywater reuse system Domestic wastewater may harm the environment by:

- Overloading the land application system with nutrients;


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- Exceeding the hydraulic loading the land application system with water causing run off of polluted water to stormwater drains, rivers, streams and other peoples property;

- Raising the water table which may affect foundations of houses and causes the soil to become permanently boggy;

- Causing the soil to become permanently saturated, prevent plants from growing and cause odours;

- Altering the soil salinity; - Altering the soil permeability; - Changing the soil pH; - Altering the soil electrical conductivity; - Altering the soil sodicity; - Altering the soil cation exchange capacity; - Altering the soil phosphorous sorption capacity; - Altering the soil dispersiveness; - Degrading the soil with chemical impurities which affect the properties of the soil to

assimilate nutrients or water. The soil ecosystem must be capable of absorbing, assimilating or treating the chemical

impurities and nutrients without medium term and long term degradation of the soil, or the environment - The choice of cleaning products may influence the environmental impact of greywater.

Only genuine biodegradable products and products with low phosphorous should be used.

The document lists the following health and environmental performance objectives for over the short and long term:

Prevention of public health risk Protection of lands Protection of surface waters Protection of ground waters Conservation and reuse of resources Protection of community amenity.

The document also highlights the importance of education as it is not simply a matter of install and forget. They require constant monitoring and maintenance.


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NSW also has detailed legislative requirements. A summary of the legislative requirements per relevant authority and greywater system are given in the table below. Legislative Process Relevant

Authority Greywater Diversion

Device

Greywater Treatment

System

Land Application

System Carry Out Sewerage Works Approval

Local Gov’t x

Installation Approval Local Gov’t x x Accreditation NSW Health x x Operation Approval Local Gov’t Materials Authorisation DLWC1 x x 1: DLWC = Department of Land and Water Conservation


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12 Appendix C: Kapiti Coast District Council Water Demand Management

12.1 Source Documents BRANZ 2008. Water Use in Auckland Households. Auckland Water Use Study. BRANZ Project Number EC1356, 17 October 2008 Commissioners Report and Recommendation (2009). Proposed Plan Change 75 to the Kapiti Coast District Council District Plan – Water Demand Management, Hearing Date April 27-28 2009. Kapiti Coast District Council (2003). Water Matters, Kapiti Coast District Council Sustainable Water Use Strategy. Kapiti Coast District Council (2009). Kapiti Coast Rainwater and Greywater Code. Leonard. M. and Kikkert H. (2006). Efficacy of Greywater Treatment in New Zealand. The Waterconference 2006, NZWWA’s 48th Annual Conference and Expo, Christchurch, NZ, 11-13 October 2006. Ormiston Associates Ltd. (2008). Greywater Reuse in Single Dwellings, Draft, Reference 2069/2879. Review for Kapiti Coast District Council. Sinclair Knight Merz (SKM) (2008). Greywater Reuse Risk Assessment, Revision 1, 19 May 2008. Report for Kapiti Coast District Council. Sinclair Knight Merz (SKM) (2009). Kapiti Water Re-use Assessment. PURRS modelling of raintank & greywater effectiveness for the Kapiti Coast. Report for Kapiti Coast District Council. Thomson, Emily (2009). Statement of Evidence of Emily Thomson. Proposed Plan Change 75 to the Kapiti Coast District Council District Plan – Water Demand Management, Hearing Date April 27-28, 2009.

12.2 Background In January 2003 the Kapiti District Council published their Sustainable Water Use Strategy; the Council’s vision for the management of water use in the district over the next fifty years. Central to the Strategy is the belief that there is considerable room within each catchment within the next fifty years for any further development if demand for water is reduced and there is careful management of water storage. The two key themes in the strategy being:


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1) Ensure water supplies that meet the needs of the local communities for the next 50 years; 2) Ensure residents use the town supplied water responsibly outdoors and indoors, with good

knowledge and maximising opportunities in using efficient appliances and the use of non-potable supplies to offset dependence on town supplied water.

The key long term issue for the Kapiti District is that of demand management, both of average water use and peak demand. Average water use is important for managing the total water resource, whereas peak demand is more critical when stress is placed either on the water resource or the capacity of the pipe network. From a statutory planning perspective peak demand is of greater importance for Kapiti as the consented volume of water that can be extracted from the river and/or borefield is limited to 23,000 m3/day The outcome of the 2003 Water Matters Sustainable Water Use Strategy was the Proposed Plan Change 75 to the Kapiti Coast District Council District (KCDC) Plan – Water Demand Management. The draft 2007 Plan Change 75 suggested a typical raintank of 10,000 litres. However, with additional analysis to quantify the benefits of the 10,000 litre rainwater tanks it became apparent that while a rainwater tank is an efficient way of reducing average water consumption, it achieves very little in terms of reducing peak summer demand in the Kapiti District due to the relatively high summer time peaks from outdoor garden irrigation. After discussions and further research, SKM introduced greywater recycling as an option for peak demand management. In response to these findings KCDC prepared a revised plan change 75 which proposed two alternative options: 1) A 10,000 litre rainwater tank for toilet flushing and outdoor use, or 2) A 4,500 litre rainwater tank for toilet flushing and outdoor use and a greywater dispersal

system for outdoor subsoil irrigation. However, in response to the concerns raised over greywater reuse in the current review of the building code (currently on hold at time of writing (March 2010)), and due to the clear benefits of incorporating greywater into future urban development, KCDC commissioned SKM to carry out a risk assessment on the proposed greywater irrigation system from an engineering perspective. Ormiston and Associates were also engaged to carry out a risk assessment from a public health perspective. A summary of the three relevant reports prepared for the plan change are presented below. The three reports being: 1) Kapiti Water Re-use Assessment (SKM 2009) – the running of the ‘PURRS’ integrated

water cycle modelling software to determine the most effective size rainwater tank and greywater system to reduce both average water use and peak demand.


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2) Greywater Reuse in Single Dwellings (Ormiston Associates 2008) – a public health risk assessment of the diversion and reuse of greywater for on-site irrigation of lawns and gardens.

3) Greywater Reuse Risk Assessment (SKM 2008) – an engineering risk assessment focussing on environmetal aspects of greywater reuse.

12.2.1 Kapiti Water Re-use Assessment (SKM 2009) The purpose of this investigation was to assess how using rainwater and greywater can create savings to the mains supplied water in the Kapiti District. Five scenarios were modelled, as summarised in Table 12:

Table 12: Five Scenarios Modelled for the Kapiti District

Water Source Scenario Potable Mains Supply Raintank Greywater

1. Business as usual All

2. Toilet & Outdoors Kitchen, bathroom, laundry, hot water

Toilet and outdoor irrigation

3. Toilet, Laundry & Outdoors

Kitchen, bathroom, hot water

Toilet, laundry and outdoor irrigation

4. Toilet from raintank, Outdoors from greywater

Kitchen, bathroom, laundry, hot water

Toilet Outdoor irrigation from greywater from bathroom and washing machine

5. Toilet and laundry from raintank, Outdoors from greywater

Kitchen, bathroom, hot water

Toilet and laundry Outdoor irrigation from greywater from bathroom and washing machine

The effectiveness of the above scenarios is dependent on the existing water uses. For instance, Kapiti District have a relatively high summer outdoor water use, compared to other areas such as Auckland. For modelling purposes the Kapiti District average indoor usage throughout the year was taken as approximately 250 litres/person/day, which increased to a maximum of around 400 litres/person/day in January due to an additional 150 litres/person/day being for outdoor usage (an average October to March summer usage of 350 litres/person/day and average April to September winter usage of 270 litres/person/day). This compares to an Auckland average of approximately 175 litres/person/day for winter and 180 litres/person/day for summer (BRANZ 2008). The results of the modelling showed:

For average water demand example: - 12,000 litre rain tank supplying toilet and outdoor demand, the mains water demand was

reduced from an average of 300 down to 200 l/p/d.


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- With additional subsurface greywater irrigation system the average daily mains water demand was further reduced to approximately 140 l/p/d.

For peak water demand example: - 12,000 litre rain tank toilet and outdoor (and laundry), the peak mains water demand is

only reduced by less than 2 l/p/d to a peak of approx 510 l/p/d, because demand in Kapiti is highly seasonal with water use peaking in summer, aligning with less rainfall and hence not enough rainwater in the tank.

- With additional subsurface greywater irrigation system, the outdoor demand for water is essentially removed and the 1-year return period peak demand is reduced from 510 l/p/d to 245 l/p/d.

When comparing a 12,000 litre rainwater tank that supplies the toilet, laundry and outdoors versus a 4500 litre rainwater tank supplying toilet and laundry and a greywater system reusing household water in the garden achieves: - Similar average water savings - The 4500 raintank/greywater system peak demand is approx 60% that of the 12,000 litre

rainwater tank only option. 12.2.2 Greywater Reuse in Single Dwellings – Ormiston Associates 2008 This document (Ormiston Associates 2008) reviewed the potential benefits and risks from diversion and reuse of greywater sourced from single dwellings connected to the Kapiti Coast District community sewer for on-site irrigation of lawns and gardens. The report included a literature review and reporting on greywater composition, diversion methods, treatment and reuse options, regional plan compliance, risks and recommendations for implementation in Kapiti District. One point of note in the Ormiston report is in the executive summary that points out that:

‘The general public generally perceive greywater as being safe with little more risk than water sourced from roof water collection and storage tanks.’

and then goes on to state that research shows a different perspective:

‘Research into greywater composition both overseas and in New Zealand has shown that contaminants and bacteria levels are similar to blackwater and that greywater poses no less a risk to public health and the environment than blackwater.’

The public health risk from greywater reuse include those caused by disease causing organisms (bacteria, protozoa, viruses and parasites) sourced from the bathroom and laundry. The Ormiston report presents a table from Australian sources demonstrating, that in many cases, the range in quality is not that different between greywater and sewage (Ormiston 2008, page 12, Table 3.3: table reproduced below).


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Table 13: Greywater and Sewage Quality

Greywater Parameter Range Mean

Sewage

Escherichia coli/Thermotolerant coliforms/100mls

101 - 107 No value 106 - 108

Suspended Solids (mg/l) 2 - 1500 99 100 – 500

BOD (mg/l) 6 - 620 430 100 – 500

Nitrite (mg/l) <0.1 – 4.9 No value 1 – 10

Ammonia (mg/l) 0.06 – 25.4 2.4 10 – 30

TKN (mg/l) 5.0 – 10.0 12 20 – 80

Total Phosphorous (mg/l) 0.04 - 42 15 5 – 30

pH 5.0 – 10.0 8.1 6.5 – 8.5

Sulphate (mg/l) 7.9 - 110 35 25 – 100

Conductivity (mS/cm) 325 - 1140 600 300 – 800

Hardness (mg/l) 15 - 55 45 200 – 700

Sodium (mg/l) 29 - 230 70 70 – 300 The Ormiston report also presented the findings from a New Zealand greywater reuse study carried out by Leonard & Kikkert (Leonard M. and Kikkert H. 2006) comprising sampling of 31 greywater systems around New Zealand. The conclusions from this study were:

None of the greywater treatment systems provided a treatment system that could remove microbial indicators.

Only half those surveyed had a good working knowledge of their systems and kept them well maintained.

The lack of maintenance and the low level of treatment means that on-site greywater systems present a high risk to public health.

It is recommended that greywater reuse not be used as an option for managing areas where on-site sewage disposal is problematic, or for reducing section sizes in subdivisions. It is not efficacious to use on-site greywater recycling to solve these problems owing to the high cost to individuals, low level of treatment provided, poor maintenance of on-site systems and consequently, the risk to public health and the environment.

With respect to the Beacon project on possible greywater reuse the one aspect raised by the Ormiston report was the issue of reusing treated greywater inside the dwelling. Although the Ormiston report states that the reuse of greywater inside individual dwellings for toilet flushing was outside the scope of their review (Ormiston 2008, page 6), one of their conclusions was that no greywater reuse should be allowed inside a dwelling or for any other outside purposes other than primary treated greywater for subsurface irrigation or secondary treated greywater for surface irrigation (Ormiston 2008, page 44, ii), iii), iv)). The report states that even though some Australian States (Canberra, NSW and Queensland) allow the reuse of secondary and


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disinfected greywater inside the dwelling for toilet flushing and laundry and outside the dwelling for washing vehicles and paths, Ormiston Associates consider the environmental and public health risks for Kapiti District of allowing such reuse ‘far exceed the benefits and strongly recommended that such use be disallowed’ (Ormiston 2008, page 18). Ormiston Associates reasoning was stated as (Ormiston 2008, page 18):

‘We believe this to be an extremely high risk strategy as the effectiveness of an individual homeowners treatment and disinfection system cannot be guaranteed. Adults and children will have direct contact with the reuse water particularly with the use of outside hoses for washing pavement and vehicles. Additionally there is an extremely high risk that there will be direct runoff to stormwater drains and curb side drains and ultimately surface water. Although the greywater may be secondary treated and disinfected there is still a risk of pathogens and it will still include a significant concentration nutrients (nitrogen and phosphorus) and salts that will impact on surface water. We believe the environmental and public health risks far exceed the benefits and strongly recommend that such use be disallowed.’

The Ormiston Associates conclusions and recommendations were: ‘6. Conclusions and Recommendations i). Greywater is not a low risk option for water conservation as it contains a significant concentration of bacteria and contaminants potentially having a significant impact on public health and the environment. ii). Primary treated greywater reuse should be restricted to the subsurface irrigation of gardens. iii). Secondary treated greywater could be reused for surface irrigation of gardens however the cost to homeowners for system installation may be prohibitive. iv).No greywater reuse should be allowed inside a dwelling or for any other outside purposes other than irrigation described in (ii) and (iii) above. v). All greywater reuse systems should only be designed by suitably qualified professionals following an assessment of peak daily greywater production and surface and subsurface investigations for design of the irrigation system. vi). The greywater system must be subject to a building permit process. vii) The homeowner must be educated on the operation of the greywater system and hold a current maintenance contract with an approved maintenance provider. viii). A paper trail system warning potential purchasers that the property has an on-site greywater reuse system must be implemented. The new owner should have the option for continuing operation of the system or return to a fully sewered property operation.


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ix). A surface and groundwater monitoring regime should be developed to assess both short and long term public health and environmental impacts from greywater reuse. x). Greywater reuse is not a cheap option to reduce potable water consumption and there will be setup and ongoing costs for the homeowner and Kapiti Coast District Council. xi). The provision of reticulated sewers to communities for the removal of public health risks provides a significant improvement in public health and reduction in risk to public health and the environment. The reintroduction of on-site irrigation of greywater could have a public health impact. A comprehensive management system overseen by Council will in our opinion be crucial for the success of greywater reuse. xii). Individual on-site wastewater treatment and land disposal is practiced in many small communities throughout New Zealand without the collapse in public health that is predicted by researchers. However homeowners must take responsibly for their on-site systems and this should be accompanied by an ongoing education programme for the success of this initiative.’ 12.2.3 Greywater Reuse Risk Assessment – SKM 2008 In response to the concerns over greywater reuse in the review of the New Zealand Building Code, and due to the clear benefits of incorporating greywater into future urban development (refer Kapiti Water Re-use Assessment PURRS water use modelling, SKM 2009 above), Kapiti District Council commissioned SKM to carry out a risk assessment on the widespread greywater reuse from an engineering perspective. A separate public health risk assessment was cariied ou by Ormiston Associates (refer Greywater Reuse in Single Dwellings, Ormiston Associates 2008 above). The council raised seven key issues they wanted addressed in the SKM engineering perspective risk assessment. These seven issues, with their summarised response are listed below.

1. What impact will greywater have on the different Kapiti Soils? – Greywater will typically affect the soil either chemically or hydrologically.

a. The build up of sodium, chloride and boron (household detergents contain boron and water softeners contain sodium and chloride) in soil are of concern as these ions can be phototoxic in high concentrations.

b. High sodium concentrations can result in deterioration of the soil structure and decrease the soils infiltrability.

c. A positive long term outcome of greywater application is that the organic layer would build up from the nutrients present in the greywater.

d. A pH of range 4.5 to 8.5 is suitable depending on the plants, greywater will typically increase pH.


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e. If greywater is discharged year round it may lead to the soil becoming permanently boggy.

f. Greywater reuse should not be permitted in extended periods of wet weather. g. Areas of high ground water levels will need to be taken into consideration. h. SKM recommends that greywater systems have a soil moisture probe to

automatically divert the greywater to the sewer when the soil is saturated. 2. Is greywater reuse suitable in all soils and terrain? – Greywater reuse in not suitable

on all sites and terrain. a. There is a risk of erosion and run-off on slopes of more than 20%. b. Exclude areas of known slope instability. c. If depth to rock is too shallow it can result in water logging as water sits on top

of the rock. Fractures and faults may act as preferential pathways for the greywater to contaminate underlying groundwater.

d. Maintain sufficient buffer distances to ensure greywater does not seep into a water body (Greater Wellington Regional Council provisions require a minimum distance of 20m.

3. What process can the Council implement to ensure the greywater discharge will not cause damage to the soil or cause surface flooding? –

a. Carefully prepared GIS plan to identify areas not suitable for greywater irrigation.

b. Restrictions placed on the application rates of greywater on a given site with a given soil type.

c. Any new greywater system must be commissioned through a building consent process whereby physical aspects of the system can be inspected by qualified council staff.

4. What impact will greywater have on the water use and disposal over time? – a. The impact of a greywater system is mainly noticed during peak water demand

when the mains water demand will be reduce by 43%. b. Wastewater flows will be reduced by up to 68% during the summer months. c. However, during these summer months sections of the wastewater network

piping system may not have enough volume to achieve self cleansing velocities. 5. Are the provisions in the Greater Wellington Regional Council “Discharge to

land” provisions adequate to protect the water cycle? – a. The allowable maximum daily volume of 2,000 litres of greywater is too high

to effectively or safely govern greywater use due to the large area required to infiltrate this volume of greywater in, for example, medium density housing areas.

6. What source control measures can people do to reduce impact of greywater on natural systems? –

a. Source control is a vital part of the sustainability of greywater reuse. b. It must be ensured that any greywater reuse system can be simply switched over

to the sewer, preferably automatically (with a manual override).


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c. During the period of mid autumn to mid spring the reuse system should constantly be diverted to the sewer to ensure the ground does not become overloaded hydraulically, from increased rainfall.

d. People will need to be educated to switch over their reuse system to the reticulated sewer when ever using harsh chemicals.

e. Literature suggesting the selection of low phosphorous, sodium and nitrogen laundry detergents are used.

f. Education programmes to educate people what not to tip down the drain, e.g. paints.

7. Is the NSW Health document suitable in avoiding, mitigating or remedying the risks greywater poses to the wider environment? –

a. While both the NSW Health document (NSW 2000 and 2005) and the more recent Queensland Government document (Queensland, 2007) are informative, SKM believe that in general terms, both codes are too permissive for use in New Zealand.

b. SKM recommends KCDC initially implement the low risk subsurface trickle irrigation system and as research is undertaken on the impacts associated with this solution, this could be reviewed and a more permissive code developed.

The SKM report final recommendations were (SKM 2008, page 31):

• ‘KCDC must prepare their own regulations and a code of practice tailored to the Kapiti Coast focusing on one technology (sub surface irrigation, with soil moisture probe and automatic diversion).

• Installation of greywater systems must be part of the building consent process and be inspected by trained council staff.

• Sources of Greywater should not include any water from the Kitchen, Toilet or the Laundry sink.

• Public education will be vital to the sustainability of greywater reuse. • A study to establishing the true concentrations of various constituents in greywater

would make greywater reuse management more effective. • Preliminary and ongoing soil and drinking water source testing, must be

implemented • The preparation of GIS plans can be used to identify areas that are or are not

suitable for greywater reuse from the range of criteria identified in this report and of ongoing testing.

• Further work must be done on the effect of increased solids and fats content of wastewater on receiving private laterals and public sewers during periods of intense greywater reuse.

SKM believes a properly installed and maintained subsurface greywater irrigation system can successfully isolate or minimise the risks highlighted in this and the Ormiston and Associates report, in areas where greywater reuse is deemed appropriate.’


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12.3 Proposed Plan Change 75 This summary of the proposed plan change 75 has been taken from two documents:

Statement of Evidence of Emily Thomson, Senior Urban Planner for the Kapiti Coast District Council, and

Commissioners Report and Recommendation The purpose of the plan change is to manage outdoor water use to all residential zones from non-potable sources and is part of a range of measures being undertaken by Council. The plan change aims to facilitate a reduction in the average summer water use (November to April) from new dwellings to 400 litres per person per day, and the average water use (year round) to 300 litres per person per day for new dwellings. The plan change proposed to achieve a 30% saving from the summer average water use on new development by requiring all new developments to install one of two acceptable solutions, those being:

A 10,000 litre rainwater storage tank which would provide water for outdoor use and for the flushing of toilets.

A smaller 4,000 litre rainwater storage tank for these uses and a greywater irrigation system for outdoor subsoil irrigation.

The objective and policies of the proposed plan change were (Commissioners Report 2009, page 12-14):

‘Objective 4.0 - Water Demand Management To reduce the potable water demand from residential development on the public potable water supply and reticulation network by 30% from the 2007 average, in order to avoid the need to find new sources of supply, reduce peak stormwater discharges from residential areas and to aid in the improvement of the community's resiliency in the event of a natural disaster. Policy 1: Ensure that the impacts of new residential development on the public potable water supply and reticulation network are reduced by approximately 30% per household by installing rainwater storage tanks or water re-use systems to supply water for toilets and all outdoor non-potable uses. Policy 2: Ensure that public health is not compromised from cross-contamination from the use of non-potable water in residential situations by requiring separation between potable and non-potable systems, including backflow prevention and by providing an adequate public potable water supply to ensure sufficient supply for potable uses.

Potable water is treated to meet Ministry of Health standards for safe drinking water. This treatment and the extensive reticulation network is costly to manage. Much of this highly treated water is being used for residential garden irrigation and flushing toilets. These are uses that do not require this standard of water.


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All new rain water storage tanks and water re-use systems will have the ability to be supplemented by the public water supply system to ensure there will be enough water for reasonable use thereby ensuring that peoples' health and wellbeing will not be adversely affected. The "restricted” potable water top-up to the rainwater storage tank will be “restricted” to ensure that residents will receive a consistent and regular supply on a daily basis. This will also help to reduce the very high 'peak' volumes that are sometimes required from the public water supply network. Greywater re-use or similar systems that provide an alternative supply for outdoor irrigation will enable the Council's objectives to be met if used in conjunction with a suitable rain water storage tank. Greywater systems are available that use only the cleaner sources of greywater from bathroom sinks and laundries) for outdoor irrigation into the subsoil. As the greywater used by these systems is relatively clean and would not come into contact with people, there are few public health risk concerns.’

The commissioners’ recommendation, after taking into account all the submissions, was to accept the proposed plan change with some minor modifications. The issues around the proposed plan change that are relevant to this Beacon project on health, infrastructure and maintenance relate to the initiation of a plan change to mandate the use of rainwater tanks for non-potable water use and greywater reuse for irrigation on all new developments. This is a first for the mandating of greywater reuse for irrigation in medium density residential housing and only the second known instance of mandating rainwater tanks for urban non-potable water use. The other case of mandating rainwater tanks for non-potable water use in new medium to high density residential development is for the Proposed Plan Change 6, Long Bay Structure Plan Stage 2, for a new greenfield development in North Shore City, Auckland. The issues raised by submitters to the plan change, and addressed by the commissioners, that are relevant to this Beacon project are summarised below. Cost of Implementation Fifty three submitters were concerned that the provisions would add between $8,000 to $10,000 to a new home at a time when Government policy aims to reduce the cost of home ownership. The commissioners’ acknowledged that the plan change will add to the cost of building a home, but the cost is approximately 3% of the cost of building an average sized house, and was considered a relatively small cost to ensure water is available for all outdoor and some indoor uses. The commissioners also acknowledged a number of benefits, including:

• ‘New home owners will be exempt from outdoor water restrictions; • New home owners will have an emergency water supply in the event of a natural

disaster;


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• Guaranteed level of service (with 600 lpd top up) versus the 1000 l/d limitation for recent developments on rural land;

• There will be the potential to recover costs when the house is sold; • Reducing reliance on potable water; • Allowing for continued growth within the district (alongside other measures).’

Rainwater storage tank size Fifty three submitters and 43 further submitters had concerns around sizing of proposed measures being based on an average 200m2 house with 3 occupants, with no allowance for varying house sizes and occupancy. The commissioners’ considered that it was best to use an average house as a basis for a permitted activity standard rather than having complicated standards relating to house size, number of bedrooms or bathrooms as the size of a house often has little relationship to its use. Alternative water demand management Fifty one submitters and 43 further submitters believed that water metering would achieve the same, if not more water savings (30 to 50% water savings) and only cost $2.8M district wide and $350 per home. The commissioners’’ agreed that water metering and subsequent pricing can be a very effective demand management tool. The plan change was intended to complement water meters, by providing a means by which householders can achieve savings. The plan change also works as a stand alone measure. The subject of water meters lies outside the scope of the Plan Change and should be considered separately as part of the LTCCP (Long term Council Community Plan). Greywater Four submitters and two further submitters expressed concerns over the timing of completion of the greywater irrigation system to the finish of the house, that the approval process is complicated and that treated greywater be used for toilet flushing. The commissioners’ agreed that a greywater irrigation system was the most effective option in periods of drought. They agreed that the installation method was complicated but needed to ensure that the systems are safe. They were impressed with the alternative “Eco-plus” greywater recycling system to the toilet and noted that this system could provide a relatively low cost alternative system to meet the objectives. Such alternative systems can be considered as a restrict ted discretionary activity. They acknowledged the need for ongoing maintenance and monitoring of non-potable water systems and that this is likely to have costs for Council. Health risks Two submitters and two further submitters were concerned about potential adverse health effects from contact with greywater; members of the public need to be adequately informed of risks and maintenance requirements; the greywater systems need to be monitored and adjusted


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to prevent flooding with excess groundwater and/or stormwater; they need an external verification process to ensure correct installation and ongoing maintenance; greywater irrigation was for single domestic properties only and not for communal gardens; that the cost of installing the greywater systems and health risks will outweigh any benefits. The commissioners’ agreed that there are potential health risks, but that these had been addressed through the Councils risk assessment reports; there are some risks of chemical contamination with greywater and that to minimise this risk, the water from the most likely source, the laundry sink, should go directly to the sewer system (as suggested by SKM risk assessment report); the Council will put measures in place to ensure systems are maintained into the future; greywater should not be disposed of to communal areas and is only possible for dwellings with private outdoor areas, which have sufficient space to accommodate the irrigation. Visual effects Fifty four submitters objected to the visual pollution from water tanks in yards. The Commissioners noted that the variety of tank designs available on the market today, and that a rainwater tank can be buried or formed into a patio, bladder tanks can fit under decks and ‘slimline’ tanks can form fences or fit under the eaves of the house. Even standard round tanks can be used which can be incorporated into gardens or in utility areas. They noted that the tank sizes proposed are not significantly larger than a garden shed.

12.4 Ongoing Work Due to the concerns of possible chemical and biological contamination of the soils from greywater irrigation the Council are providing some funding (along with a small amount also from Beacon Pathways Ltd) to a research project to measure contaminants (EC, pH, cations, nitrate and phosphate, faecal coliforms and E.coli, Salmonella and F-RNA phage) in two soil types (sandy and clay) for three varying greywater treatments of: 1) Control – good quality greywater (very low microbes and chemicals) 2) Poor quality greywater in terms of high microbes and high chemicals (worst case) 3) Poor quality greywater in terms of microbes but low concentrations of chemicals. The results of this study are expected in the later half of 2010.