University of Groningen Emerging energy-efficient ... · The eight emerging technologies were estimated to have the potential to save close to 1300 GWh, mainly due to the software

University of Groningen

Emerging energy-efficient technologies for the Californian wastewater industrySlaa, Jan Willem

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CIO, Center for Isotope Research

IVEM, Center for Energy and Environmental Studies

Master Programme Energy and Environmental Sciences

Emerging energy-efficient technologies

for the Californian wastewater industry

Jan Willem Slaa

EES 2011-111 M


Master report of Jan Willem Slaa

Supervised by: Tengfang Xu (Lawrence Berkeley National Laboratory)

Prof. dr. H.C. Moll (IVEM)

Prof. dr. A.J.M. Schoot Uiterkamp (IVEM)


CIO, Center for Isotope Research

IVEM, Center for Energy and Environmental Studies

Nijenborgh 4

9747 AG Groningen

The Netherlands

http://www.rug.nl/ees/organisatie/CIO

http://www.rug.nl/ees/organisatie/IVEM

TABLE OF CONTENTS

1. Summary .................................................................................................................... 3

2. Introduction ............................................................................................................... 5 Water and Energy ....................................................................................................................5 Wastewater Treatment .............................................................................................................5 Emerging Energy-efficient Wastewater Technologies for California .....................................5

3. Research Scope .......................................................................................................... 7 Research Aim...........................................................................................................................7 Research Questions..................................................................................................................7 Research Boundaries................................................................................................................8 Research Methodology and Data Sources ...............................................................................8

4. Wastewater Treatment Processes .......................................................................... 11 Introduction............................................................................................................................11 Overview of Treatment Steps and Processes .........................................................................11 Energy Consumption .............................................................................................................12 Wastewater Pollutants and Industrial Wastewater Treatment ...............................................13

5. California Water System ........................................................................................ 17 Introduction............................................................................................................................17 Water Withdrawals by Sector ................................................................................................17 Residential Water Use ...........................................................................................................18 Commercial and Industrial Water Use...................................................................................19 Future Developments.............................................................................................................20

6. Californian Wastewater Industry.......................................................................... 21 Introduction............................................................................................................................21 California’s Wastewater Treatment Plants ............................................................................21 Energy in California’s Wastewater Treatment Plants............................................................22 Industrial Wastewater Treatment...........................................................................................23 Future Energy Use .................................................................................................................24

7. Results ...................................................................................................................... 25 Introduction............................................................................................................................25 Process Technologies.............................................................................................................25

Improved Sludge Dewatering by Novel Materials..............................................................25 Highly-efficient Submersible Mixers for Wastewater Pond Aeration ................................26

Reuse Technologies ...............................................................................................................27 Membrane Filtration to Reuse Wastewater for Cooling Tower Operations........................27 Wastewater Reuse System for Washing Methanol in Biodiesel Facilities..........................28 Advanced Treatment Technologies – Ozonation of Rinse Water .......................................29

Software Technologies ..........................................................................................................31 Computer Picked Bacteria for Better Biogas Generation in Wastewater Sludge Digestion31

Demand Response Technologies ...........................................................................................32 Solar Dish Engine to Offset Wastewater Peak Energy Demand.........................................32 Vanadium Redox Flow Batteries for Wastewater Load Management ................................33

Summary of Technology Assessments ..................................................................................33 Other Wastewater Technologies............................................................................................34

8. General Discussion .................................................................................................. 37

9. Conclusions .............................................................................................................. 39

10. Acknowledgments.................................................................................................... 41

11. References ................................................................................................................ 43

Appendix A: Californian Wastewater Treatment Plants.......................................... 47

Appendix B: Wastewater Scenarios California ......................................................... 49

Appendix C: Data Tables Emerging Technologies .................................................... 50

Appendix D: Energy Use Dutch Wastewater Sector ................................................. 58

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1. SUMMARY Wastewater treatment is of vital importance for protecting human health and minimizing the environmental impact of polluted water. Since the beginning of the 20th century public facilities have been installed globally which treat wastewater at a central location before discharge into the environ-ment. It is not often recognized, but there is a substantial amount of energy involved in the continued operation of wastewater treatment plants. The United States uses about 1-2 % of its national electric energy demand for this purpose, while in the Netherlands this value is about 0.6 %. In recent years improving the energy efficiency of economic sectors has become an important goal for the U.S. government due to rising energy prices and a decrease in domestic oil reserves. However, energy efficiency opportunities in the U.S. wastewater sector have often been overlooked. Implementing novel technologies is an approach to increase energy efficiency in industrial processes and whole industries is by implementing novel technologies. This thesis looked at the potential energy savings of eight emerging wastewater technologies in the American state of California for the year 2020, which recently acquired Public Interest Energy Research (PIER) grants from the California Energy Commission. These technologies varied in their applicability for the wastewater sector and were classified into four groups. The groups and technologies are listed below: • Process technologies (2: for improved sludge dewatering and enhanced mixing) • Reuse technologies (3: industry-specific technologies to reuse wastewater) • Software technologies (1: to enhance the bacterial composition for improved biogas generation) • Demand Response technologies (2: to offset peak energy demands) California is very involved in water-related energy-efficiency opportunities because of its climate and regular water shortages. Due to predicted population growth in the coming decades, stress on water resources will continue to rise. In recent years the state has tried to quantify the relation between energy use and water use in all sectors and found a large amount of energy use being related to water (about 19% of its electric energy use). Estimates vary, but up to half of Californian urban water will be treated at wastewater treatment plants, which can be between 5 and 6 billion m3. The wastewater sector in California contains approximately 600 wastewater treatment facilities and the 80 largest plants in capacity were studied in detail. Most plants treat wastewater up to a secondary level, which means treatment mainly targets solids and organic pollutants, although some plants have additional advanced treatment methods. Aeration and pumping account for the largest shares of energy use in wastewater treatment and the state has estimated that 2012 GWh is annually used for the Californian wastewater sector. From literature figures this would result in an average energy intensity of 0.4 kWh m-3 for the sector. However, there is significant uncertainty in the annual flows, the amount of energy being used and average energy intensities. Following a scenario from the California Department of Water Resources, it was estimated that around 3600 GWh will be used by the wastewater sector in 2020 with an average energy intensity of 0.5 kWh m-3. The eight emerging technologies were estimated to have the potential to save close to 1300 GWh, mainly due to the software technology which enhances the bacteria mix in wastewater treatment for onsite biogas fueled electricity generation. The potential for onsite electricity generation is large and can significantly reduce a plant’s energy expenditures. Other technologies have fewer potential for energy savings and because of the crude nature of the estimates, there is a large margin of uncertainty. Most technologies can be applicable to other states and countries, although some are suited at specific industrial sectors. This thesis emphasizes the uncertainties related to energy use in wastewater treatment plants at the state level and recommends further quantification of water flows and energy intensities of plants. While emerging wastewater technologies can clearly improve energy efficiency to a large extent, economic and technological barriers still exist for rapid uptake of these technologies.

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2. INTRODUCTION Water and Energy

Water is one of the most important substances on this planet as it is essential to sustain Earth’s ecosystems and the human population. Besides for survival, human societies use large amounts of water for a variety of reasons: e.g. sanitation, cleaning, heating, cooling, manufacturing and cooking amongst others. Virtually all of these applications draw on freshwater sources (on the ground or from the air as precipitation), which are unevenly spread around the globe and vary in both quantity and quality (Jackson et al., 2001). To replenish ground- and surface water levels in a sustainable way, wastewater should be treated before disposal. During the 20th century wastewater treatment facilities were installed in many countries for the sake of reducing infectious diseases and these have been a valuable addition to a region’s water system ever since. A substantial amount of energy is related to human water use, especially if the water system is located in an arid region. This is particularly visible in the American state of California, which has a large agricultural sector and a dry climate in the populous south (Eisenstein & Kondolf, 2008). California withdraws the largest amount of (fresh)water of any state in the United States (45.5 billion m3 in 2005) (Kenny et al., 2009) and uses much energy in its water system. Recent estimates on the relation between water and energy use have found that about 19% of Californian electricity use and 32% of Californian natural gas use is related to water (Klein, Krebs, Hall, O'Brien, & Blevins, 2005). For that reason efficiency gains in water systems can reduce both water and energy use. Wastewater Treatment When water is used in human society, it will generally become of a lesser quality due to some form of pollution. Therefore, wastewater treatment is an important final step in the human water system and aims to minimize the environmental impact of wastewater (also called sewage) as well as protecting human health. Due to the large and varied nature of wastewater, treatment either takes place at centralized collection plants or onsite. Being hailed as one of the hallmarks of human development, developed countries have an extensive sewage collection and treatment system in place. Nevertheless, many developing countries do not have an integrated wastewater treatment approach because of lack of funds and knowledge (Aiyuk, Amoako, Raskin, van Haandel, & Verstraete, 2004). Generally, wastewater treatment plants (WWTPs) are owned and run by a public institution like a municipality or a water district in the United States (Day, 2007). Their main target would be the treatment of municipal wastewater, which consists out of residential, commercial and institutional (governmental) water flows (Gibbs & Morris, 2004). Proper treatment implies lowering the concentrations of harmful compounds to a safe disposal. Industrial wastewater flows may require different treatment since they can have (much) higher concentrations of harmful substances and vary substantially over different industrial sectors (Wun Jern, 2006). Consequently, such wastewater might be treated onsite to levels safe for disposal instead of being discharged into the public sewer system. Another option is to treat industrial wastewater to a level where it can be discharged to the sewers after which it will be further treated to safe standards at a public WWTP. Emerging Energy-efficient Wastewater Technologies for California As wastewater treatment facilities constantly require energy for their operation, the energy expenditures of a facility might take up a large share of its operation costs (Carns, 2005; [EPA], United States Environmental Protection Agency, 2006). Consequently, there is a need for wastewater technologies which improve efficiency to reduce both economic and energy costs. Rising (fossil) energy prices and a decrease in domestic oil reserves are two important reasons why the United States have invested in the development of new energy-efficient technologies over the last three decades (Bang, 2010). Such technologies aim to use the available energy more efficiently, thereby reducing

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dependence on foreign energy sources and create a reliable, clean and affordable domestic energy system ([DOE], 2010). U.S. policy aims to implement such technologies in all sectors (residential, commercial, industrial, institutional) with different degrees of success (Andrews & Krogmann, 2009; McKane et al., 2009). Industrial sectors consume about one third of the country’s energy and are highly energy intensive, hence technology improvements can make a significant difference with regard to energy savings. Due to the fact that wastewater treatment is part of many industrial activities, but is not directly related to their main processes, it is often overlooked in terms of energy efficiency opportunities (Lekov et al., 2009). Many American states and countries around the world are busy with wastewater treatment developments. This thesis focuses on the American state of California, because it was the location where research took place and this research was partially funded by the California Energy Commission (CEC). In 2010 the CEC offered Public Interest Energy Research (PIER) grants to eight particular wastewater technologies and these were studied for this report. So far the CEC and the Californian Public Utilities Commission (CPUC) have mainly assessed the Californian wastewater industry in an integrative approach to include the whole human water cycle (Klein et al., 2005; Park & Bennett, 2010), but this thesis focuses solely on wastewater flows and wastewater treatment.

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3. RESEARCH SCOPE This chapter introduces the aim, questions and methods of this thesis, which assessed several emerging energy-efficient technologies for California’s wastewater industry in terms of energy savings potential, payback periods and other potential benefits. Because the main focus was on eight technologies which had received Californian state grants, this chapter also describes the boundaries of this research. Research Aim The aim of this research is to gain insight into the potential savings (energy and water) by emerging wastewater technologies to assess their applicability in California’s wastewater industry. The term wastewater industry is used to emphasize wastewater treatment as an industrial sector and therefore includes both public and private treatment facilities. While technology assessments are the primary target of this research thesis, the aim extends to presenting future scenarios for wastewater treatment in California and the potential savings the assessed technologies might have in the future. Due to the localized nature of this thesis, there is a likely bias to wastewater treatment processes commonly found in California and the United States in general. Nevertheless, the thesis also aims at increasing understanding of wastewater treatment and related energy use at a more general level. Research Questions In order to achieve the research aim, several research questions are addressed in this thesis. The main goal is to answer the following research question:

- What is the water and energy savings potential for California’s wastewater treatment industry by several emerging wastewater technologies1 in the year 2020?

The underlying research questions define the different topics which are presented in this thesis and help to answer the main question. These sub questions are:

- Out of which processes would a (Californian) wastewater treatment plant consist and how much energy is required for these separate steps? (Chapter 4)

- How much water and energy is used, treated and disposed in California’s wastewater industry? (Chapter 5 and 6)

- To what extent can the relation between energy and water use in wastewater treatment plants be quantified? (Chapter 6)

- What are the benefits of the emerging technologies compared to common practice and what would be the barriers for successful implementation? (Chapter 7)

- Would the potential water and energy savings be viable in other states and countries? (e.g. The Netherlands) (Discussion)

1 Mainly, the wastewater technologies which have received PIER grants from the California Energy Commission in December 2009 (Grant Solicitation PON-08-006).

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Research Boundaries Due to the complexity of hydrologic cycles, the research scope and its boundaries have to be defined carefully. First, this thesis has a strong focus on California because the studied technologies were assessed for their potential in this U.S. state. To broaden the perspective of this thesis, wastewater treatment in California was compared with wastewater treatment in The Netherlands to recognize common themes and specific differences, but only briefly. When no specific locations are named in this thesis, the aspects discussed will relate to the Californian situation. Secondly, this research does not include (drinking) water treatment technologies or the public water distribution system. Also, agricultural water use is largely excluded because most water in this (Californian) sector is for irrigation purposes and does not end up in wastewater treatment facilities. The focus lies on wastewater treatment processes and the amount of wastewater which is treated in California. These values are required to determine the present situation, which needs to be extrapolated to 2020 for the technology assessments. It is likely that water use in urban situations (commercial, residential and industrial) is also useful to compare the volume of water used with the volume of treated wastewater. Figure 3.1 summarizes the scope of this research and the steps which are touched upon. Wastewater recycling (or reuse) is of importance for three studied technologies, but is not discussed in the general description of wastewater treatment in California. Energy in this research mainly relates to electric energy, because the common indicator for the energy intensity of wastewater treatment in the United States is the amount of electricity needed per volume (kWh per million gallons). In this thesis the energy intensity is expressed in SI units and becomes kWh m-3. The reason for excluding non-electric energy is the comparatively small part is plays in wastewater treatment in the United States (Carlson & Walburger, 2007).

Research Methodology and Data Sources

During the course of this research, several stages were followed. Research commenced with obtaining the necessary background information on wastewater treatment by finding online scientific literature via the ISI Web of Science search database and books on wastewater treatment, which were found in the libraries of UC Berkeley and the University of Groningen.

Source Water Supply

Water Treatment

Water Distribution

End-use:

Agriculture

Commercial

Residential

Industrial

Wastewater Collection

Wastewater Treatment

Recycled Water Treatment

Recycled Water Distribution

Wastewater Discharge

Source

Figure 3.1 Research scope and boundaries (marked) for emerging wastewater treatment

technologies. Picture adapted from Klein et al. (2005).

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Secondly, data and literature was gathered describing California’s wastewater system by energy and water use. The most important data sources for this description were obtained from the U.S. Geological Survey, the California Energy Commission, the California Public Utilities Commission and LBNL expertise. Data had to be converted to SI units on many occasions. The purpose of data gathering was to establish the current base case for California’s wastewater treatment plants. In the end the Clean Watersheds Needs Survey by the Environmental Protection Agency provided the most detailed data on Californian wastewater treatment plants (see Appendix A). With these numbers on the amount of wastewater being treated and the average energy intensity, the validity of previous estimates could be discussed. Combined with the future water use scenarios of the California Department of Water Resources, the amount of treated wastewater and its related energy use in the year 2020 could be estimated. This estimate was used to assess potential energy savings (and water savings when possible) of the emerging wastewater technologies. Eight emerging wastewater technologies were studied. As many of them targeted a specific industrial sector, four groups were distinguished to establish different technological approaches to wastewater treatment. Process technologies targeted a specific treatment process for energy efficiency improvements. Reuse technologies aimed at reducing water use, thereby reducing energy costs in the whole water supply chain. The software technology made use of digital progress to enhance the digestion process for biogas generation. Demand Response technologies would offset peak energy demand of wastewater treatment facilities, thereby reducing financial and energetic costs. The eight technologies which were studied are the following:

• Novel materials for sludge dewatering (process technology) • High-efficiency mixers for wastewater pond aeration (process technology) • Wastewater reuse by membrane filtration for cooling tower operations (reuse technology) • Integrated system for water reuse from methanol strippers in biodiesel plants (reuse

technology) • Ozonation technologies for onsite water reuse (reuse technology) • Computer-driven microorganism addition (software technology) • Solar system to offset peak energy costs (demand response technology) • Vanadium Batteries for wastewater load management (demand response technology)

Information on these technologies was provided by the California Energy Commission during the course of this research. These grant proposals were read to assess the technologies’ potential for energy savings, but also for their costs (both capital and operation/maintenance costs) and their other benefits. After reading the proposals, literature was searched on these type of technologies and on possible improved data sources which could verify claims made in the grant proposals. The assessment was performed according to a procedure available at LBNL, which has been used to assess emerging energy-efficient industrial technologies in the past (Martin et al., 2000). The assessments resulted in a data table summarizing the findings. After both wastewater systems are well described and the technologies fully assessed, the research questions were answered. The results were discussed on the uncertainties and limitations of this research, but would also highlight the need for further research.

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4. WASTEWATER TREATMENT PROCESSES Introduction

Ultimately, the goal of each wastewater treatment plant is universal: treating wastewater to an extent at which it can be safely disposed into the natural environment. However, due to the large variety in wastewater characteristics (different pollutants with different concentrations) several processes have been developed over the last hundred years. This chapter presents a brief overview of the main processes and the amount of (electric) energy which is consumed during treatment to answer the first subquestion presented in the research scope (chapter 3). Pollutants in wastewater can be classified in four different types: organic contaminants, pathogens, nutrients and synthetic chemicals ([EPA], United States Environmental Protection Agency, 2004). For each of these pollutants there are different reasons to lower their concentrations. Organic waste (and ammonia) for example is converted to common gasses like carbon dioxide and nitrogen when dissolved oxygen is present. Large wastewater concentrations of these compounds would therefore reduce the oxygen available in water for species and could lead to mass fish mortality. Pathogens like bacteria or viruses should be avoided in discharge streams as they can invoke disease in species close to the wastewater stream. High nutrient concentrations can lead to massive algae growth and synthetic chemicals may have toxic, adverse effects on ecosystems. Not only might these pollutants affect aquatic life, but as water is continuously cycled through hydrological cycles they might end up in tap water or food. For these reasons, treating wastewater is beneficial for both humans and the environment.

Overview of Treatment Steps and Processes Several treatment processes exist and there are also several methods to categorize these. In this thesis the more common categorization by the stage or level of treatment is used (Brown, 2009), which separate the total wastewater treatment system in four consecutive steps (Figure 4.1). Generally, a plant with advanced treatment has all of the previous steps and this holds for secondary and primary treatment plants too. Occasionally, one step might be absent due to a specific setup of the plant, but this is rare and could not be found in the largest Californian wastewater treatment facilities. The preliminary treatment step is largely universal across wastewater treatment plants and its purpose is to remove larger solids from the stream to prevent damage to equipment further downstream. Larger solids like plastic items, leafs and metals parts are removed by using simple screens, while grit and sand removal sections may also be installed in this step.

Preliminary treatment

Primary treatment

Secondary treatment

Tertiary (advanced)

treatment

Screens (Primary) clarifiers Trickling Filters Biological Nitrification Grit/sand removal Activated Sludge Biological Denitrification Rotating Biologic Nutrient (P) removal Contactors (Secondary) clarifiers

Figure 4.1 Wastewater treatment steps and examples of associated processes. Every wastewater

treatment plant can have a different setup.

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Actual water treatment begins with settling or sedimentation of dissolved and suspended solids in a large tank (clarifier) (Nemerow et al., 2009). Most small solids will sink down over time and form sludge on the bottom. This physical-chemical treatment method accounts for the primary wastewater treatment step and yields two outflows: primary sludge and clarified effluent. Sometimes chemicals are added to improve flocculation of metals and other particles, making their removal by sedimentation easier (Kurniawan, Chan, Lo, & Babel, 2006). After primary treatment the wastewater effluent has lost most of its solids content, but retains a high concentration of organic material. Secondary treatment aims to reduce organic compounds by facilitating bacterial breakdown. There are two general categories for this biological treatment step: attached growth and suspended growth systems (Water Environment Federation, 2009). In attached growth systems, the bacteria are located on a medium over which wastewater is led. The presence of oxygen from the air enables the bacteria to consume the organic compounds and grow. Two main technologies using attached growth treatment are trickling filters (oxidizing beds) and rotating biological contactors ([EPA], United States Environmental Protection Agency, 2004). Suspended growth takes place by bacteria that are not attached to a medium, but which are found in the wastewater flow as suspension. One of the most common processes of this type is the activated sludge (AS) process (Stephenson & Blackburn, 1998). Again, oxygen is needed for this aerobic process and therefore aeration of the water stream is required. Sometimes pure oxygen is used instead of air, which enhances bacteria growth but is more expensive and requires additional energy for its generation (Stephenson & Blackburn, 1998). Not all biologic treatment methods are aerobic processes. In some cases (e.g. when organic concentrations are very high) anaerobic bacteria are used and in recent years anaerobic processes have developed as energy efficient alternatives or supplements to aerobic processes (Stephenson & Blackburn, 1998). Secondary treatment is commonly concluded by another sedimentation step to remove more solids (Water Environment Federation, 2009). This secondary sludge is partially lead back to the aeration tank in the AS process to maintain the activated sludge concentration (U.N. Economic and Social Commission for Western Asia, 2003). Tertiary treatment is less common and is therefore often referred to as advanced treatment. This can encompass a variety of processes aimed at specific wastewater streams and/or discharge requirements. For example, disinfecting methods to kill off pathogens by use of chlorine, ozone or UV radiation are occasionally classified as advanced treatment. Tertiary treatment methods aim at reducing the nitrogen (N) and phosphor (P) content of the effluent, as well as some final solid removal ([EPA], United States Environmental Protection Agency, 2004). Due to more stringent environmental regulations, these processes have become more common in recent times (Brown, 2009). In general most wastewater treatment plants will have preliminary, primary and secondary treatment technologies installed in varying complexity and efficiency further downstream. Energy Consumption

Like most processes, wastewater treatment requires the input of energy. However, absolute energy use can vary significantly due to the level of treatment of a plant, but also because of wastewater characteristics, location and plant size (Water Environment Federation, 2009). Depending on the equipment of a specific wastewater treatment plant it can use both electrical power and fossil fuels (mostly natural gas). Electric energy accounts mostly for the total energy consumption of a plant. An U.S. survey amongst national wastewater treatment plants showed 86 percent of them having an electricity consumption accounting for over 80 percent of their total energy consumption (Carlson & Walburger, 2007). For this reason only electricity consumption is considered in this thesis. Electricity is mostly employed for two uses: aeration and pumping (Brown, 2009). Improving pumps and aeration equipment can therefore result in significant electricity savings. Simple treatment systems will be the least energy intensive as less pumping energy is required, while the energy intensity increases with more advanced treatment methods (Water Environment Federation, 2009). The most common indicator for the energy intensity of a wastewater treatment plant in American literature is the electric energy per wastewater volume (kWh m-3). In other countries the energy

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intensity for wastewater treatment processes is often expressed in electric energy per population equivalent (kWh p.e.-1). A population equivalent (sometimes also found as person equivalent in literature) represents a certain volume of wastewater with an average organic content (BOD5 of 54-60 g L-1). However, due to different definitions such energy intensities can often not be compared accurately. An overview of different energy intensities for different plant sizes and plant types is given in Table 4.1. This shows electricity use can differ a factor four between the smallest, most advanced plant (0.78 kWh m-3) and the largest plant with a basic approach (trickling filter, 0.18 kWh m-3). Depending on the type of plant the relative share of the main electricity consuming processes changes also. Table 4.2 shows the shares in different wastewater treatment plants with the same size. More advanced treatment plants use relative less electricity for wastewater pumping, dissolved air flotation (a clarifying process) and for anaerobic digestion. Other processes make up about one fifth of the electricity use of a plant and consist out of several other processes: e.g. lighting and electrical applications in the plant’s buildings, primary and secondary clarifiers and sludge handling processes. Wastewater Pollutants and Industrial Wastewater Treatment While electricity use of wastewater treatment plants is largely related to their size, wastewater characteristics contribute also to the amount of electricity used. For example, plants for domestic wastewater treat a complex mixture of pollutants, but these are more diluted compared to industrial wastewater streams. It is estimated that domestic wastewater consists for 99 percent out of water (Wun Jern, 2006), so pollutants will have low concentrations. In industrial wastewater streams pollutant concentrations can be several orders of magnitude larger and may require much more energy per volume compared to domestic wastewater.

Table 4.1 Electricity use of different wastewater treatment processes. (Derived from

Appendix C in Water Environment Federation (2009) with 1 gallon = 3.785 dm3.)

Treatment process 3,800 19,000 190,000 380,000

Trickling Filter 0.48 0.26 0.18 0.18

Activated Sludge 0.59 0.36 0.28 0.27

Advanced without Nitrification 0.69 0.42 0.32 0.31

Advanced with Nitrification 0.78 0.51 0.42 0.41

Electricity use (kWh m-3)

Size (m3 / day)

Table 4.2 Share of electricity use of different processes in a 38,000 m3 / day wastewater treatment plant.

(Derived from Appendix C in Water Environment Federation (2009) with 1 gallon = 3.785 dm3.)

Process: Trickling Filter Active Sludge

Advanced with

Nitrification

Wastewater Pumping 16% 12% 8%

Aeration (diffused air) N/A 44% 30%

Biological Nitrification N/A N/A 19%

Dissolved Air Flotation 21% 15% 11%

Anaerobic Digestion 13% 12% 9%

Trickling Filters 30% N/A N/A

Other 20% 17% 22%

Electricity use (kWh m-3) 0.23 0.32 0.47

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Wastewater characteristics are mainly determined by two concentration values; the biological oxygen demand over 5 days (BOD5) and total suspended solids (TSS), but there are more properties which can be measured and might require specific treatment methods. Some of these are shown in Table 4.3 with typical domestic wastewater values. Industrial wastewater streams have a larger variety in their characteristics as water streams are less diluted and might contain high concentrations of certain pollutants, depending on the type of industry (Wun Jern, 2006). Food processing plants for example can have BOD5 and TSS concentrations which are one or more orders of magnitude larger than the domestic wastewater values presented in Table 4.3 (Lekov et al., 2009). Other industries can have high concentrations of volatile organic compounds (e.g. chemical industry), which may require additional treatment methods like steam or air strippers (Stephenson & Blackburn, 1998). Industrial wastewater can be fully treated onsite before discharge into a natural water body, but also disposal to the sewer is possible. However, higher concentrations may cause the wastewater treatment plant at the end of the sewer to react differently and therefore

Characteristic Description

Average

Concentrationa

Effluent

standardsb

Biologic Oxygen Demand

(BOD5)

Difference between initial

dissolved oxygen concentration

with the concentration five days

later after aerobic bacterial

degradation of organic

compounds.

190 30

Chemical Oxygen Demand

(COD)

Oxygen concentration which can

be oxidized chemically. This

concentration is larger than the

BOD5, because also inorganic

compounds are oxidized.

430 -

NitrogenAmount of nitrogen containing

materials.40 -

Phosphorus

Amount of phosporus con-

taining materials, which can

contribute to eutrophication.

7 -

Total Suspended Solids (TSS)Amount of visible, suspended

solids.210 30

Oil and Grease (O&G) Amount of hydrocarbons. 90 10

pH

Value for the acidity or basicity

of (waste) water. Scale: 0 - 14

(neutral pH=7).7.5

c6 - 9

c

Table 4.3 Wastewater characteristics with average concentration for domestic wastewater and effluent

standards in San Francisco, California.

a In mg/L, except for pH. Data is for untreated, medium strength residential wastewater. (Lekov, Thompson, McKane, Song, & Piette, 2009; Metcalf & Eddy Inc., 2003) b Maximum allowed average effluent concentrations over a thirty day period in the San Francisco region. (Lekov et al., 2009) c No concentration, but pH level (unitless). Average value is for domestic community wastewater. (Nemerow, Agardy, Sullivan, & Salvato, 2009)

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equalization of the wastewater stream may be required (Nemerow, 2007). For that reason industries can have early wastewater treatment onsite to reduce concentrations to levels which can be handled with more ease at the final wastewater treatment plant (Wun Jern, 2006). However, little information on the flow magnitudes of whole industrial sectors can be found in literature. This chapter has presented an overview of wastewater treatment processes, pollutants and the most common indicators for wastewater strength from an American perspective. Currently, energy use in wastewater treatment is not directly related to wastewater characteristics, although effort has been put recently into developing a benchmarking tool which related wastewater energy use to BOD5-concentrations (Carlson & Walburger, 2007). Energy use can roughly be related to a plant’s capacity and the type of treatment involved. Large trickling filter facilities use least electric energy per volume, while small advanced treatment facilities may use four times as much relatively. Both the benchmarking tool of Carlson and Walburger (2007) and the average energy intensity per plant size/-type are used in chapter 6 for an approximation of the electric energy use in California’s wastewater industry.

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5. CALIFORNIA WATER SYSTEM

Introduction California is one of the largest American states in land area and is the most populous state with over 37 million inhabitants. Due to the fact that the majority of inhabitants are living in the Southern part of California, while most precipitation falls in the Northern part, water infrastructure and planning is of high priority there (Eisenstein & Kondolf, 2008). Especially, because significant population growth is expected in the coming decades which will drive water demand to higher levels and climate change might diminish natural water sources from the Californian mountains of the Sierra Nevada. This chapter presents an overview of the Californian water system by sector water demands and the size of all water flows through the state. It should be noted that the sum of water use also places a significant burden on the state’s energy demand. A report by the Californian Energy Commission reported water-related energy use to represent 19 percent of the state’s electricity use and 30 percent of its natural gas use (Klein et al., 2005). To conclude this chapter future water scenarios according to the California Department of Water Resources will be discussed to establish the reference water scenario for assessment of the emerging technologies.

Water Withdrawals by Sector One of the most striking aspects of the Californian water balance is its variability and the frequent occurrence of a net water shortage (see Table 5.1). The average natural addition of water is about 250 billion m3 of which the large share is precipitation in the form of rain, snow and hail ([DWR], Department of Water Resources, 2009c). Of this total water balance some ten to fifteen percent is consumptive use2. In years with below average precipitation like 2002-2004 the water balance may be negative, up to half the consumptive use in 2004 for example. This emphasizes California’s stress on natural water resources and its consequent drought problems in shortage years. If one looks closer at the consumptive use, the relative size of different sectors can be seen. Table 5.2 shows the differentiated applied water use in the year 2005. Applied water use is larger than consumptive water use alone, because the former also includes reuse and is thereby a closer approximation of the actual water flows in a year. It can be seen that the majority of applied water use is for growing agricultural crops. This is because California has a very large agricultural sector which is located in the Central Valley and requires substantial irrigation water. As mentioned in the

2 Water which can no longer serve as a source of supply, i.e. cannot be reused.

Table 5.1 Total water balances in California during dry (2002 to 2004) and wet years (2005).

2002 2003 2004 2005

Precipitation 197 227 230 311

Inflow neighboring states 8.1 7.0 7.2 6.5

Total addition 205 234 237 317

Evaporation 114 120 142 207

Outflow neighboring states 1.0 1.4 1.0 1.7

Outflow salt sinks (e.g. ocean) 66 86 76 74

Consumptive use 36 33 36 30

Total withdrawal 217 241 254 312

Net balance -12 -6 -17 5

Year

Annual water flow in California (billion m3)

18

Research Boundaries (Chapter 3) agricultural water flows will not be addressed because irrigation water is taken up by the crops, evaporates into the air or sinks into the earth and is therefore not treated as wastewater. Non-agricultural sectors are classified as urban water use and make up about a quarter of the total applied water volume (10.4 billion m3, see Table 5.2). The majority of water is used in the residential sector for both indoor and outdoor applications, while commercial and industrial sectors are smaller. About ten percent of urban water use is for large landscaping purposes, which can vary from watering city parks to erosion control ([DWR], California Department of Water Resources, 2010) Reducing urban water use and improving the water efficiency is an important point in Californian state policy and estimates have been presented which can reduce urban water use to two thirds of current values (Gleick et al., 2003). Most residential, commercial and industrial water will end up in sewer systems and be treated at a collective public wastewater treatment plant. In California onsite residential wastewater treatment is small compared to other U.S. states (Gibbs & Morris, 2004). Still, not all urban water will end up in a plant because not everything is collected in the sewage systems and pipes are aging with frequent leaks. Another complicating factor is the amount of rain, snow and hail (storm water) which can end up in the wastewater collection system. Although many Californian cities have separated storm water collection systems with a runoff to lakes and seas ([Caltrans], 2003), some storm water might end up in the sewers thereby blurring the figures. It is uncertain to what extent this is an important issue. The EPA estimated the annual wastewater flow through Californian wastewater plants to be 5.0 billion m3. Of this volume 0.33 billion m3 was expected to originate from industry.

Residential Water Use The residential sector accounts for the largest share of applied urban water use with 3.4 billion m3 for indoor use and 4.0 billion m3 for outdoor use (Table 5.2). In the interior setting half of the water is used in toilets and showers, while the other half is about evenly spread over taps, washing machines and leaks (Gleick et al., 2003). During the last decades interior water use has almost stabilized over the whole state, which means water use per capita is slowly declining. The reduction is largely

Table 5.2 Applied Californian water use in 2005 per urban sector.

a Water which can be reused ([DWR], 2009) b Total volume of treated wastewater in California according to the Clean Watersheds Needs Survey of the Environmental Protection Agency ([EPA], U.S. Environmental Protection Agency, 2008a)

Californian Water Flows per

Sector 2005

(billion m3)

Residential-interior 3.4

Residential-exterior 4.0

Commercial 1.3

Industrial 0.6

Energy Production 0.2

Large Landscaping 0.9

Total Urban 10.4

Agriculture crop production 34.0

Total applieda

44.3

Wastewater treatedb

5.0

19

attributed to conservation measures and improved water efficiency. Interior water will largely end up in the sewers and therefore be treated at a public wastewater treatment plant. Outdoor water use is mainly for watering lawns and gardens, but the exact numbers for this use are uncertain due to varying calculation methods and lack of real data (Gleick et al., 2003). Nevertheless, it is a significant number with the same order of magnitude as interior water use. In recent years project have been developed in California which reuse treated wastewater for landscaping purposes, but residential landscaping is still hard to address effectively. Like agricultural water use, most outdoor water will end up in crops, sink into the earth or evaporate and the amount ending up at a wastewater treatment plant will be much smaller compared to indoor water.

Commercial and Industrial Water Use

Residential water use has been studied extensively over the last decades (Zhang & Brown, 2005). Less studied is water use in non-residential settings like stores, factories and offices. In California the first statewide assessment of commercial, institutional and industrial water use was carried out only in the first years of the new millennium (Gleick et al., 2003). This assessment reported a total Californian water use in these sectors of about 3 billion m3, almost two thirds for the commercial/institutional sector and one third for the industrial sector. In the former case schools, restaurants, offices and golf courses are attributed as the sectors which use the larger share of the whole sector. It can be assumed most water (except for golf courses) would end up in the sewers. In the industrial sector there are several industries using substantial amounts of water. The larger industrial sectors like food processing, petroleum refining and high tech industries account for the majority of this use. One extensive study on water use in Californian industries was performed at the beginning of the 1990s to establish the impact of water shortages on industry (Wade, Hewitt, & Nussbaum, 1991). Industrial water use was determined over the year 1989 and resulted in a water use of 0.4 billion m3. Since that study, no specified industrial studies were done before the study by Gleick et al. (2003). Here, water use had increased to 0.8 billion m3 following from data for the year 2000. More recently, a number of close to 1.0 billion m3 was reported (Isaac, 2008). Another uncertain aspect of industrial water use is how much water ends up in the (municipal) sewage systems and the quantity which is treated onsite. Industrial wastewater can have significant different characteristics compared to domestic wastewater, making onsite (pre-)treatment necessary at times. Table 5.3 gives an overview of the different available industrial data. For extrapolation of industrial water data to the year 2020, the ratio of industrial use to total urban applied water use in 2000 is used. This ratio of 7.5 percent is assumed to remain constant in the development of future scenarios.

1989 1995 2000 2005 2006

Total industrial 0.40 0.78 0.82 0.13 0.96

Dairy processing - 0.02 0.02

Meat processing 0.01 0.02 0.02

Fruit/Veg processing 0.03 0.11 0.09

Beverage processing 0.05 0.06 0.07

Refining 0.16 0.13 0.10

High Tech 0.05 0.09 0.09

Paper - 0.03 0.03

Textiles - 0.03 0.04

Fabricated metals 0.01 0.02 0.02

Unaccounted 0.10 0.31 0.34

Source:Wade

(1991)

Gleick

(2003)

Gleick

(2003)

Kenny

(2009)

Isaac

(2008)

Industrial water use in California (billion m3)

Year

Table 5.3 Water use in Californian industrial sectors (when available) over the last two

decades.

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Future Developments

Two important factors for future Californian water demand are population increases and climate change. The most recent Californian Water Plan has developed three scenarios up to 2050: Current Trends (a.k.a. business as usual), Slow and Strategic Growth (preferred scenario), Expansive Growth (worst scenario) ([DWR], Department of Water Resources, 2009b). In all scenarios urban water use is higher in 2050 compared to the 2005 Water Plan figures (Table 5.1) ranging from 11 to 20 billion m3 annually. For this thesis the expected water demand in 2020 is used and shown in Table 5.4. Industrial water use is extrapolated by a fixed ratio of 7.5 percent of total urban water use, as mentioned in the previous paragraph. What is apparent from these number is the wide range of future water flows. An important factor might be future climate change, which could have strong negative impacts on California’s future water resources (Vicuna, Maurer, Joyce, Dracup, & Purkey, 2007). It is also noteworthy that no scenario expects an absolute decline from current values. These scenarios are relevant for California’s wastewater industry also, because they highlight the increase in water demand and hence, an increase in treated wastewater. Quantifying the future amount of treated wastewater is complicated by efficiency of future wastewater treatment plants, but because the amount will be larger and strict environmental regulations require more advanced treatment levels, the amount of energy required in wastewater treatment is very likely to rise. The following chapter will present an overview of current energy use in the Californian wastewater sector and will make an estimate of the use in 2020.

Total

Urban Industry

Total

Urban Industry

Total

Urban Industry

Current

Trends10.4 0.8 13.3 1.0 17.5 1.3

Strategic

Growth10.4 0.8 11.3 0.8 11.7 0.9

Expansive

Growth10.4 0.8 14.8 1.1 22.1 1.7

2005 2020 2050

Projected future urban and industrial water use

in California (billion m3)

Year

Table 5.4 Urban and industrial water use projections for 2020 and 2050. These are

derived from the California Department of Water Resources.

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6. CALIFORNIAN WASTEWATER INDUSTRY Introduction

California started its modern-day development when gold was discovered halfway during the 19th century. The state’s dry climate forced pioneering Americans to build up an extensive water infrastructure with many pipelines and water towers, but also with aqueducts and long-distance canals (Gleick et al., 2003). Simultaneously came the rise of water and wastewater treatment facilities and these became larger when cities continued to grow (Day, 2007). Approximately 600 wastewater treatment facilities are located in California, over 3.5 percent of the U.S. total ([EPA], U.S. Environmental Protection Agency, 2008a; Gibbs & Morris, 2004). Most Californian wastewater treatment plants are small, but 34 have capacities over 76,000 m3 per day ([EPA], U.S. Environmental Protection Agency, 2008a) (for details on the largest Californian plants, see Appendix A). California also has the most households connected to the sewage systems (90 percent) of all American states, because residential wastewater treatment with e.g. septic tanks is limited (Gibbs & Morris, 2004). Therefore, onsite treatment in this chapter solely refers to treatment which takes place at industrial sites. This chapter presents an overview of California’s wastewater industry, its energy use and discusses the likely magnitude of onsite, industrial wastewater treatment. California’s Wastewater Treatment Plants

There is a wide variety in California’s wastewater plants, both in size and in type. The largest one is the Hyperion facility in Los Angeles with an average daily wastewater flow of 1.3 million m3 and a dry-weather capacity of 1.7 million m3 per day, serving some four million residents. All large plants are located close to California’s major cities. Of the ten largest plants, six are situated in the greater Los Angeles area, two in the San Francisco Bay area and the other two serve San Diego and Sacramento.

Treatment Level #

Only Preliminary Treatment 2

Primary Treatment 4

Secondary Treatment 37

Advanced Treatment 37

Total: 80

California's Largest Wastewater

Treatment Plants

Type of Secondary Wastewater T reatment

20%

11%

3%

1% 5%60%

Activated Sludge Clarification

Trickling Filter Pond

Sedimentation No secondary treatment

Figure 6.1 Treatment level and type of secondary treatment (when applicable) of the 80 largest

Californian wastewater treatment plants by capacity (> 76.000 m3 per day). ([EPA], U.S.

Environmental Protection Agency, 2008a)

22

Figure 6.1 shows the plant types of the eighty wastewater treatment plants with the largest capacity. Almost all plants provide secondary treatment and the activated sludge process features in the majority of the facilities, while some plants use older trickling filters. Many facilities also have advanced treatment methods ranging from bio filters and chemical addition to biologic nitrification/denitrification processes (see Appendix A). In general the Californian wastewater sector has a mix of secondary and advanced treatment plants, probably due to strict effluent regulations and environmental awareness. The majority of these plants are still owned publicly by either a municipality or a water district. Some plants have been sold to private companies such as Veolia. Little information is available on the number of plants which have been sold to private firms and there is a worldwide debate whether utilities like wastewater treatment plants are better off in public or in private hands (Day, 2007).

Energy in California’s Wastewater Treatment Plants

In the last decades Californian authorities have recognized the significant share which water use plays in the state’s energy use. In 2005 the California Energy Commission (CEC) published a major study to identify the relation between water and energy use and found lots of energy being related to the use of water (Klein et al., 2005). The wastewater treatment system was attributed to use 2012 GWh of electric energy per year, which is about one percent of the total state’s electricity use. Since that report both the CEC and the California Public Utilities Commission (CPUC) have been studying the embedded energy use in water systems. In 2010 the CPUC published a major study on Californian water and wastewater treatment facilities, covering about a third of the whole state (Park & Bennett, 2010). Its over-arching goal was to develop energy intensities for different components in the water cycle and establish whether they had a large variety or not. This report found the energy intensity of wastewater treatment plants ranging from 0.13 to 0.90 kWh per m3. The upper value was caused by a Southern plant which treated wastewater well beyond state requirements. However, these values did exclude the energy use related to wastewater pumping. When gravitational flow could be used this amount could be very close to zero, but in coastal communities where wastewater had to be pumped uphill, energy use could reach an additional 0.12 kWh per m3.

According to the methodology presented in chapter 5 with either BOD5-concentrations or average energy intensities for specific plant types and sizes, new estimates on California’s electricity use by wastewater treatment plants were constructed (Table 6.1). This shows lower values for the Californian wastewater industry compared to the estimate of the California Energy Commission (2012 GWh) (Klein et al., 2005) which was upheld by the CPUC (Park & Bennett, 2010). The estimation of 2005 was based on an average energy intensity of 0.66 kWh m-3 (2500 kWh / million gallons), but this value was later expected to be too high because of oversimplifications and corrected to 0.50 kWh m-3 (1911 kWh / million gallons) (Navigant Consulting Inc., 2006). The former estimate with a total electricity use of 2012 would yield a total annual Californian wastewater flow of 3.0 billion m3, while

Water flow

(Gm3)

Energy

use

(GWh)

Energy

intensity

(kWh m-3)

CEC 5.0 2012 0.40

BOD 5.0 1505 0.30

6.0 1736 0.29

Benchmark 5.0 1387 0.28

6.0 1502 0.25

California's wastewater

industry

Table 6.1 Estimates on energy use of the Californian wastewater sector and the average wastewater

treatment energy intensity which follows from these estimates. Flow data is derived from [EPA]

(2008) (capacity and actual flow)

23

would yield an annual flow of 4.0 billion m3. However, flow data from the Clean Watersheds Needs Survey by the Environmental Protection Agency show an annual flow of 5.0 billion m3 and a total dry weather capacity of 6.0 billion m3. Therefore, either the average energy intensity of all Californian wastewater treatment plants would be much lower or the total annual electric energy use of the sector would need to be larger than 2012 GWh. Compared to the average energy intensity of the wastewater sector in The Netherlands (0.37 kWh m-3, see appendix D), the Californian wastewater sector has comparable values (see Table 6.1). The BOD-values of the largest Californian wastewater treatment plants can be found in Appendix A. What is apparent from these figures is the larger energy intensity and BOD-reduction of advanced treatment plants. The variation of energy intensity ranges from 0.20 kWh m-3 (primary treatment plant) to 0.65 kWh m-3 (advanced treatment plant). Therefore, the future wastewater scenarios for California were calculated with varying sector wide energy intensities between 0.2 and 0.6 kWh m-3 (see appendix B). The total electric energy use of the Californian wastewater sector is 1505 GWh according to this methodology, which is lower than CEC estimates. However, the question is whether industrial wastewater (pre)treatment is taken into account in the CEC estimate of 2012 GWh and if all plants were included in the Clean Watersheds Needs Survey of the U.S. Environmental Protection Agency. Industrial Wastewater Treatment There are some factors which create uncertainty in estimates on energy use of California’s wastewater sector. One of these is the lack of data on the industrial wastewater flows (Lekov et al., 2009). Another aspect is the amount of storm/rainwater which enters the sewage system and is treated in these plants. The best data available for the Californian industry is from 1989 and found two thirds of industrial water use being discharged into the sewer system (Wade et al., 1991). Based on a small set of survey results over half of the wastewater discharge would receive a form of pretreatment. Petrochemical industries were responsible for the large share of pretreatment. With average energy intensities and flows from Table 5.3, estimates of industrial wastewater treatment before discharge are derived to assess the amount of electric energy involved in industrial wastewater treatment (Table 6.2). Because it is unsure to what extent industrial wastewater is (pre) treated onsite, these figures might add to the total electricity use in the Californian wastewater industry. When all industrial water undergoes wastewater treatment with a high energy intensity (0.6 kWh m-3), close to 500 GWh might be involved. However, due to the lack of insight into onsite wastewater (pre) treatment, this value can only be an indication. The energy intensity of industrial wastewater flows might be (much) higher compared to residential wastewater due to higher concentrations of pollutants, but this is an uncharted area. Recently, the lack of water use in U.S. industrial sectors has lead to new methodologies in estimating industrial water use (Blackhurst, Hendrickson, & Vidal, 2010). This discussion also hopes to raise the issue of industrial wastewater treatment into attention.

100% 75% 50% 25%

0.2 164 123 82 41

0.3 246 185 123 62

0.4 329 246 164 82

0.5 411 308 205 103

0.6 493 370 246 123

Energy

Intensity

(kWh m-3)

Percentage treated

Electricity Use Industrial Wastewater (GWh)

Table 6.2 Electricity use associated with California’s industrial wastewater treatment by using

common energy intensities. If no industrial wastewater is pretreated or disposed onsite, this is

included in general figures. Otherwise, it might add to the total picture.

24

There is some industrial wastewater data available from the EPA’s Clean Watersheds Needs survey because some municipal wastewater treatment facilities distinguish a municipal and an industrial stream, but it is unsure if this applies for all facilities. The total industrial wastewater stream was estimated at 0.33 billion m3 annually. Compared to the 1989 value of 0.26 billion m3, this would indicate small growth over two decades.

Future Energy Use To assess the emerging technologies in the wastewater industry and their potential in 2020, it is necessary to establish a base electricity use in this year. The previous paragraphs have sketched the large uncertainties in future water flows, current energy intensities and the possible exclusion of electric energy used in industrial pretreatment facilities, which emphasizes the inaccurate nature of this base. However, the developments of larger wastewater facilities to advanced treatment methods and the population development justifies the expectation of reasonable growth in energy intensity and flow size in California’s wastewater industry. Therefore, the business-as-usual scenario of the California Department of Water Resources is followed with an average energy intensity of 0.5 kWh per m3 (see Figure 6.2). With these figures, California’s wastewater sector would account for 3595 GWh of electric energy use in the year 2020. This figure will be used to assess the possible impact of emerging wastewater technologies in the next chapter.

0

1000

2000

3000

4000

5000

6000

7000

2000 2005 2010 2015 2020 2025 2030 2035 2040 2045 2050 2055

Year

Electric energy use (GWh)

Expansive growth Slow/Strategic Current Trends

Figure 6.2 Visualisation of future electric energy use in the Californian wastewater sector among

different scenarios with an average energy intensity of 0.5 kWh m-3

.

25

7. RESULTS Introduction

To address energy use in wastewater treatment, technologies are being developed which improve the energy efficiency of wastewater systems. This chapter presents eight of these emerging technologies which recently acquired funds from the Californian Energy Commission. Some technologies are suited for specific industrial sectors in California (e.g. the food processing sector), while others can be applied in most wastewater treatment processes. As mentioned in the research methodology in chapter 3, four types of technologies are distinguished and they will be treated in this order. First, there are two process technologies which aim to improve (parts of) the wastewater treatment process. These type of technologies often enhance machinery or reduce their loads. Machinery is an important factor in wastewater treatment, because pumps and motors make up a large share in wastewater energy use (Water Environment Federation, 2009). A second type of technologies facilitates some sort of water reuse during wastewater treatment, thereby reducing the energy intensity of water flows. Such technologies can be specific to some industrial processes, which is the case in the three technologies presented here. The third type results from the large improvements made possible by biotechnology and computer development; software technologies. In this case it is software which would enhance biogas generation by improving the bacterial mix. Biogas generation can be a large potential for the large energy efficiency advances in wastewater treatment sectors. Finally, there are technologies which have the goal to balance energy demand and supply more efficiently in wastewater treatment facilities. Two of these technologies will be presented. The data tables of these technologies can be found in Appendix C. After the eight technologies have been described and discussed for the Californian state, other technological developments are briefly discussed. Together they serve as an overview for the future challenges and possibilities in treating more wastewater with less energy. Process Technologies

Improved Sludge Dewatering by Novel Materials

In Chapter 4 the main wastewater pollutants were discussed. Among these are organic waste, pathogens and nutrients containing phosphorus or nitrogen. Pathogens can be removed with relative ease by chemicals or radiation, but organics and nutrients require substantial treatment before the pollutants leave the wastewater as common gasses (e.g. nitrogen and carbon dioxide) or solid waste. However not all waste can be fully reduced to common gasses and for a large extent they end up as solids at the bottom of clarifiers, together with bacteria. This solid mixture is referred to as sludge and while it was not discussed so far, sludge handling can consume about 10 to 40 % of the energy use of a wastewater treatment plant due to extensive pumping and sludge disposal (Rajagopalan, 2009). Sludge is partially formed during primary treatment in which suspended solids are slowly separated from the water stream in large sedimentation or clarifying tanks. This process can be performed by gravity only, but can be aided by addition of chemicals which result in increased settling of solids. The current secondary treatment standard makes use of activated sludge to remove the organic substances after which the effluent stream again passes another clarifier. The majority of large Californian wastewater treatment plants make use of activated sludge treatment (see Figure 6.1) ([EPA], U.S. Environmental Protection Agency, 2008a). Substantial amounts of wet sludge (1-2% solid content by weight) are generated in these plants and need to be disposed. Before disposal however, the sludge needs to be stabilized (reduction of odor and living microorganisms) and decreased in volume. In general, sludge is first thickened by gravitational or mechanical forces which increased the solids content to 3-5% (Rajagopalan, 2009). Subsequently, it can be dewatered by drying beds, belt filter presses and/or centrifuges to obtain solids content between 20 and 30%. In the

26

past however, sludge dewatering was sometimes deemed to be unnecessary as it involves significant energy costs and transport to offsite disposal sites was inexpensive. Because environmental sludge requirements have become more stringent, transport has become more expensive and available land for sludge disposal is diminishing, sludge dewatering is becoming common. To achieve a higher solids content and hence a more efficient sludge dewatering process, formation of solid flocks in the wastewater stream should be improved. One common approach to achieve these higher solids content is adding chemicals (cationic polymers, polyelectrolytes, salts) to the clarifying tank. Recently, efficiency was enhanced further by adding nanoscale (1-100 nm) alumina particles alongside the polymer to the thickened sludge. This resulted in improved sludge conditioning and dewatering in some specific cases (Wang, Hung, & Liu, 2007). The mechanism behind this has been compared with the addition of β-cyclodextrin to paper mill sludge, which yielded occasional dewatering improvements (Hartong, Abu-Daabes, Le, Saidan, & Banerjee, 2007). Nevertheless, in bench-scale studies with alumina particles solid content of the dewatered sludge increased significantly according to the PIER grant proposal for this technology (Rajagopalan, 2009) and currently the concept is being used for field testing at California’s second largest public wastewater treatment facility: the Joint Water Pollution Control Plant in the greater Los Angeles region. When the lab-scale energy savings of 30% are applicable for the larger wastewater treatment plants, about 21 GWh of electricity could be saved on the state level in 2020. Also, less natural gas may be used as higher solids content reduce the thermal energy required for possible sludge drying. The gas savings are neglected in the energy benefits shown in the data table (Appendix C), because of the uncertain quantity of sludge which is dried in California. To apply this technology at a large scale, will require some additional developments. First of all, the technology needs to be demonstrated to work efficiently with a variety of alumina particles and sludge loadings to proof the principle idea. Secondly, there appears to be a difference between optimum polymer doses (20 kg/dry ton) and the doses at which the particle addition has benefits (3.5-7 kg/dry ton). It is uncertain whether this affects the control of the process. Further, its economics are not yet known in detail. The proposal indicated that the technology is economically viable when the nanoscale additives cost less than 250% of the aluminum salt, but assessing the viability of these costs lies beyond the scope of this research. Improving sludge processes in wastewater treatment plants is an important field which has only gained attention in more recent years (Neyens, Baeyens, Dewil, & De heyder, 2004). Sludge dewatering is an interesting option and while the optimal chemical mix for sludge conditioning is yet to be found (Novak, 2006), nanoscale particles might be able to improve this mix. Currently however, evidence is inconclusive to support the larger applicability of this technology. Its implementation will depend on the results of the Joint Water Pollution Control Plant field test. If successful, this technology could improve energy efficiency of the wastewater’s sludge line significantly.

Highly-efficient Submersible Mixers for Wastewater Pond Aeration

Another area of interest is small scale treatment plants and the opportunities to increase energy efficiency at these sites. Small scale onsite treatment is an alternative when discharge to sewers is expensive or not possible. For residential rural households septic tanks are often used in the United States (Gibbs & Morris, 2004; Nemerow et al., 2009), but another traditional onsite method is the stabilization pond ([EPA], United States Environmental Protection Agency, 1983). These ponds treat wastewater in large basins or ponds (sometimes also called lagoons), which are designed with a common average residence time of 1-4 weeks. If the wastewater load is not too high, facultative ponds without aeration equipment can be used. However, many wastewater streams require artificial oxygen addition (aeration) to keep the bacteria alive. California currently has at least 150 aerated wastewater stabilizations ponds out of some 400 in total (Nelson, 2005).

27

Single wastewater treatment ponds have a low energy intensity compared to large advanced treatment plant, but are sometimes compared to trickling filter plants (0.25 kWh m-3) ([EPA], United States Environmental Protection Agency, 1983). To a large extent this is due to the electricity required for operating the aerators. Most aerators function both as aerator and as mixer in the wastewater pond and this might result in suboptimal working conditions (Oppenheimer, 2009). Aerators are mainly found in two types: surface aerators and aspirating aerators. The former pumps water into the air, while the latter pumps air into the water. In both cases there are limitations to the water depth which can be fully aerated and lower levels could still lack oxygen. Improvement of aeration efficiency would lead to a reduction in electricity use. One of the approaches to achieve such improvement is by replacing traditional water aerators by submerged water circulators or mixers. Better mixing would yield a more dynamic water surface, which would enhance oxygen transfer to the water. Recently, an efficient submerged water mixer has been developed and demonstrated satisfying water mixing properties in water towers with large temperature variation over the year. The main reason for these results would be in the design of the impeller. Based on computational fluid dynamics studies, the design was optimized to obtain uniform flow patterns and eliminate water gradients. The technology has been demonstrated successfully at a wastewater pond of a Californian winery and is currently being extended (Oppenheimer, 2009). Successful development of such improved mixers would also be aided by a short payback period of investment. In the assessment the period was as short as half a year3. Nevertheless, the combination of mixing and aeration is a complex issue and might present future challenges (Sardeing, Poux, Melen, Avrillier, & Xuereb, 2005). Oxygen transfer rates by water mixers could be lower, compared to aerators. This particular water mixer requires a minimum depth of 2.4 m for optimal working and some ponds might not be this deep. Also, water circulation can have unforeseen side effects. A recent study showed improved bacterial growth (which was beneficial in this case) due to wastewater circulation (McGarvey, Miller, Lathrop, Silva, & Bullard, 2009). However, a large and rapid increase in bacteria can also ‘choke’ the treatment process. Therefore, further studies would be helpful in establish the effects of the high efficient water mixer on wastewater ponds. On a state level, the impact of the technology might be limited. There are 400 wastewater ponds in California (Nelson, 2005), but there is an uncertainty in this number due to the lack of an exact recording system in the state (Oppenheimer, 2009). Also, the ponds are generally small and may treat a limited amount of water (possibly less than 0.5 billion m3 annually, which is the base case in the assessment). Small scale ponds treat a relatively low amount of wastewater (<10 % of the state total) and have a low average energy intensity, so even significant efficiency increases will have a small effect on the state level. This is not to say, such improvements are not worthwhile and will definitely contribute to reducing energy costs (the assessment estimate is 29 GWh in 2020). It only highlights the different scales of wastewater treatment and the energy use related to treatment. Reuse Technologies

Membrane Filtration to Reuse Wastewater for Cooling Tower Operations

One of the largest industries in California is the fruit and vegetable processing sector due to the size of the state’s agricultural sector. In 2008, 38.1 million tonne of agricultural products were harvested in the state ([CDFA], 2010). Because of the sector’s large size significant amounts of energy and water are used. It is estimated that the fruit and vegetable industry in California accounts for 86 million m3 of water use annually (Gleick et al., 2003) and there are plenty of methods to address both energy use and water efficiency (Masanet, Worrell, Graus, & Galitsky, 2008). A straightforward approach to achieve improved water- and energy efficiency would be to reduce water consumption by recycling or reusing water. One of these solutions is using treated wastewater

3 With an industrial electricity purchase price of $ 0.12 per kWh in California.

28

as cooling water. There is a clear demand for cooling water in many fruit and vegetable processing plants because these operate at low temperatures to decrease product decay and water is one of the main working fluids for cooling purposes. Often, cooling towers are used and when they would apply treated wastewater instead of high quality tap water, economic costs would go down. Also, there is a reduction in energy use embedded in the decrease of water and wastewater flow. This design will be tested at an onion processing plant in Oxnard, California. The grant proposal expects a reduction in water consumption by 20 percent and its wastewater discharge to the city sewer by 25 percent (A. Hill, 2009). However, the wastewater requirements for cooling tower operations are stricter than regular discharge requirements since discharged wastewater might cause biofouling and corrosion inside the tower. A way to achieve wastewater of the appropriate quality would be to treat it further after the onsite wastewater plant. One promising technology would make use of membrane filters, although this solution should not use too much energy (Mirza, 2008). The purpose of these filters is to exclude suspended solids, microbes and organics by their size, while molecular water can proceed unhindered. There are several degrees of membrane separation processes, which are qualified by the size of the materials they exclude. Microfiltration covers the materials between 0.1 and 10 micrometer, while nanofiltration aims for materials between 0.5 and 10 nanometer (A. Hill, 2009). In between is the field of ultrafiltration, which partly overlaps both microfiltration and nanofiltration areas though boundaries might vary. Beyond nanofiltration one can use reverse osmosis to filter even the smallest compounds. However, this is no simple size exclusion filtration and costs considerably more energy (Hilal, Al-Zoubi, Darwish, Mohamma, & Abu Arabi, 2004). It is therefore not attractive to use in applications like cooling tower operations. In the assessment estimates from the California Public Utility Commission (CPUC) on electric energy costs for water supply, distribution and final treatment were used (1.19 kWh m-3) (Park & Bennett, 2010). The cooling tower from the Oxnard plan uses about 38,000 m3 annually (French, Hamman, Katz, Kozaki, & Frew, 2010) and according to CPUC data for microfiltration the energy costs would decrease by 82% (new energy use is 0.21 kWh m-3). The new electric energy costs are related to the pressure drop of the membrane. At the state level such savings could add up to 52 GWh in 2020 (appendix C). Such a reuse technology might lead to a reduction in both water consumption and energy use, but especially the latter is hard to quantify. Another disadvantage might be the capital costs related to the membrane installation, because the assessment results in a payback period of around 7 years (French et al., 2010). Finally, maintenance of the membrane in case of fouling might also diminish potential. However, the technique might also be applicable to other industries which use cooling towers and have a wastewater flow with a relatively clean effluent, enlarging its prospective energy and water savings.

Wastewater Reuse System for Washing Methanol in Biodiesel Facilities

Another wastewater reuse opportunity lies in the biodiesel sector. In recent years biofuels have gained much attention because of their ‘green’ promise for replacing fossil transportation fuels. Also, biofuels would reduce the dependence on foreign oil sources in the United States. Large-scale cultivation of food-crops for biofuel production would have negative impacts on global food prices however and a large debate on the best biofuel remains (Escobar et al., 2009; Naik, Goud, Rout, & Dalai, 2010). Of the two most common ones, bioethanol and biodiesel, the latter has a higher net energy gain and its environmental impact is lower (J. Hill, Nelson, Tilman, Polasky, & Tiffany, 2006). In California eleven biodiesel plant have been constructed in the last decade and annually about 50 million gallons of biodiesel are consumed in-state (Orta & Zhang, 2010). Although these numbers are likely to grow, energy efficiency improvements would help sustained growth of the sector because it would reduce dependence on fluctuating diesel prices.

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Biodiesel production uses considerable amounts of water, especially for washing impurities like glycerol, methanol, soap and salts (Guay, 2009). Currently, washing with solid absorbents is not fully developed yet (Guay, 2009; Liu, Musuku, Adhikari, & Fernando, 2009). It is estimated that up to two cubic meters wash water are used per cubic meter of produced biodiesel for sufficient impurities removal. These impurities result in wash water with a very high biologic oxygen demand (BOD) and BOD-concentrations are much higher compared to conventional wastewater streams (Jaruwat, Kongjao, & Hunsom, 2010). A closed cycle solution would be to treat wash wastewater to a level where it can be used for washing once again. Because the pollutants have varying properties, several treatment steps would be required before water could actually be reused. Two steps are needed to reduce the BOD level and this can be done by ultrafiltration (which removes soap and oil) and reverse osmosis (which removes salt and glycerol) (National Center for Appropriate Technology, 2009). The effluent of these two processes is a mixture of methanol and water, which can be readily distilled in a stripping column to remove methanol. While some water will be lost during these processes, it is estimated 85% of the wash water stream can be reused (Guay, 2009). This would result in an equivalent reduction in water consumption and a consequent reduction of energetic costs in the water supply and treatment chain. However, installation of these steps creates new energy requirements. Ultrafiltration may have a low energy intensity, but reverse osmosis requires significant amounts of energy depending on the quality of separation. Also, distillation requires a heat source (e.g. steam) which costs additional energy to generate. In the assessment these heating costs are neglected and only electricity consumption of ultrafiltration (0.21 kWh m-3) and reverse osmosis (0.41 kWh m-3) according to the 2010 CPUC report is considered (Park & Bennett, 2010). Without heating costs, the overall energy gain would be about 32 percent. However, the current scale of production is so small that even if the production doubles in 2020 net energy savings on a state level will still be negligible (0.15 GWh). Payback periods are unknown and are likely to depend on the water and wastewater charges of the local water utility. Another important aspect which has yet to be clarified is what will be done with the other waste streams of the treatment steps. It could be that some waste streams might actually be pure enough to be sold for further refining (methanol, glycerol), but if this would not be the case it must still be disposed with likely discharge costs involved. The methanol is very likely to be of high enough quality for other uses as it is the pure distillate of the methanol/water mixture, for other compounds this is less clear. In general, the future outlook for reusing washing water in biodiesel methanol strippers is limited. This is in part due to the stagnation of the biodiesel industry (Orta & Zhang, 2010), but also because of the costs associated with the wash water treatment steps. Especially, the net energy gain is unclear because of the additional energy requirements of the technologies which will be installed. Energy gains and cost-effectiveness will be improved in arid regions where the water supply and treatment chain is more energy intensive and more costly, as wash water reuse will decrease the water consumption of a biodiesel plant and reduce its costs related to water supply and discharge. Successful implementation of a wash water reuse system is therefore likely to depend on its location.

Advanced Treatment Technologies – Ozonation of Rinse Water

As mentioned in the previous two reuse technologies, treating wastewater flows to a level where it can be reused would have energy savings for the Californian water supply and treatment system, while reducing water consumption at a local level. An option to treat industrial wastewater is by disinfecting the effluent. In many wastewater treatment facilities this is already common at the end of treatment. Although definitions vary, disinfection is sometimes qualified as part of tertiary or advanced treatment and aims to kill of pathogens and microorganisms ([EPA], United States Environmental

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Protection Agency, 2004). Similar to the membrane filtration technologies (page 30), disinfecting wastewater in fruit and vegetable processing industries would be an interesting option. The fruit and vegetable processing industry of California is the largest in the United States due to the size of the state’s agricultural sector (38 million tonnes of agricultural products) ([CDFA], 2010). Further processing steps after the harvest depend on the large variety of fruit and vegetable end products (e.g. cans, frozen, fresh). For treatment of many fresh-cut fruits and vegetables a large quantity of water is necessary to rinse the product from dirt and other pollutants like pathogens or microorganisms, which could cause decay of the food product. Currently, rinse water may act both as a conveyor to transport the fruits or vegetables to the next process, as well as for washing. To restrict microorganism growth, the washing water is mostly chilled, especially in the case of fresh cuts and antimicrobial chemicals like chlorine and organic acids may be added (Biswas, 2009). After a certain time period this rinse water needs to be refreshed and residual water is mostly disposed to the sewage system for municipal wastewater treatment. An alternative would be to make use of advanced treatment technologies for disinfection. These have attracted attention in recent years and can generally be classified in membrane filtration-, UV radiation- and advanced oxidation processes (AOPs) (H. Zhou & Smith, 2001). Such treatment can be beneficial in the food processing sector because it might enable the direct reuse of effluent water (Shon, Vigneswaran, & Snyder, 2006). The most studied alternative to conventional disinfection technologies is ozonation. This is an advanced oxidation process which uses the reactive ozone gas to degrade organic compounds (H. Zhou & Smith, 2001). As ozone (O3) decomposes readily to oxygen, no harmful residues will result in ozonation processes, which is an advantage over chlorine use. Also, some microorganisms are better disabled by ozone than by chlorine (Olmez & Kretzschmar, 2009). A disadvantage of ozonation would be the financial and energetic costs of ozone generation. Ozone is commonly generated onsite, because of the risks associated with ozone handling (explosions). Ozone technology has been demonstrated at some food processing plants in California for the flour production and fresh cut vegetables processing (Biswas, 2009). Especially the latter case has gained some attention, because during implementation it was realized water use was reduced by about 60% due to fewer flume water replacements (Strickland, Sopher, Rice, & Battles, 2007). The system still used some chlorine, but the whole system was a worthwhile investment with a payback period of less than two years. Different from the other reuse technologies, there were direct energy reductions at the plant level. In the old practice, rinse water was replaced by completely emptying the conveyor and fresh rinse water needed to be chilled again. With less frequent rinse water replacements, energy costs for chilling declined resulting in lower energy, water and wastewater disposal costs. The assessment has been based on the specific example of the fresh cut vegetable plant which replaced chlorination by ozonation. Because these did not have energy intensities in the previously mentioned CPUC report, they could not be directly compared to the energy intensity of the water supply and treatment chain. Following the grant proposal the estimate is based on a 50 percent reduction of water consumption which results in 0.59 kWh m-3 savings and this would translate to 6 GWh for California in 2020. This method neglects savings by the reduction in chilling energy and therefore potential might be larger. Advanced treatment technologies like ozonation can improve the energy efficiency of the Californian food processing industry. Water chilling is a significant energy cost of this industry and any technology which can reduce water use and chilling energy is likely to result in energy savings. However, ozone generation is an energy intensive process and might limit the net potential if all factors are included. Still, productivity gains and improved economics can make this a worthwhile approach in California’s food processing industry.

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Software Technologies

Computer Picked Bacteria for Better Biogas Generation in Wastewater Sludge Digestion

One of the most effective technologies to reduce energy consumption of a wastewater treatment plant, is by making use of the biosolid waste to generate biogas (mainly methane). This gas can be used to drive a turbine and generate onsite electricity for the plant operations, while surpluses might be sold to the electricity grid. Biogas is formed by anaerobic bacteria and this anaerobic digestion process has been established in wastewater treatment facilities (Lettinga, 1995). Nevertheless, natural bacteria only convert the organic sludge materials partly (60%) to natural gas (Braaksma, 2010). Improvement of this process can increase energy efficiency of a plant and make it a useful investment for more plants . Currently, wastewater sludge is thickened and pretreated before actual digestion takes place (Appels, Baeyens, Degreve, & Dewil, 2008). Therefore, a significant share of biogas is lost. To illustrate some current challenges, the digestion process will be described briefly. In general, four important digestion steps can be identified. First, suspended organics are hydrolyzed so that all organic materials are in solution. Further degradation (acidogenesis and acetogenesis steps) takes place which results in organic acids and gasses like hydrogen and carbon dioxide. These materials are then converted in the final step to methane and carbon dioxide. Currently, the rate determining step is the initial hydrolysis step. All these steps are facilitated by anaerobic bacteria (Angenent, Karim, Al-Dahhan, & Domiguez-Espinosa, 2004). To improve the efficiency of anaerobic digestion several approaches have been examined. Sludge pre-treatment by radiation for example, to ease the hydrolysis step, or co-digestion which digests several substrates simultaneously. The approach which is presented on this page addresses the bacteria which perform the digestion processes. Choosing the appropriate bacteria can enhance sludge conversion to biogas and recently, software has been developed to match wastewater characteristics with certain bacteria. Such computer-assisted bio-engineering has demonstrated large conversion gains by adding the most suited bacteria mix in laboratory settings (C. Zhou, 2009). Wastewater treatment facilities could improve energy efficiency to a large extent if methane production would rise drastically as to generate electricity or heat offices/processes. Principally, this technology could reduce energy costs for wastewater treatment radically. This can be seen from the assessment, where potential energy savings of 30 percent in the larger wastewater treatment plants (80%) could lead to over 850 GWh of savings in 2020 for California. However, the technology still has to be developed to a commercial scale. At the moment field tests of the technology are to be performed at the Dublin San Ramon Service District wastewater plant to show whether the technology can actually be implemented on a plant level (C. Zhou, 2009). In this test no genetically modified bacteria will be used, which might make the biogas increase modest. The technology is expensive because of the significant costs associated with bacteria acquirement, but might still have a payback period of some three years with the significant production increase on a bench scale level. It is most likely that such technologies will aid large wastewater treatment plants primarily and smaller plants will follow later. While the technology has yet to be developed further for large scale, commercial application, the principle is straightforward and could be made possible in the next decades. If so, the impact of this technology in the wastewater sector can be very large.

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Demand Response Technologies

Solar Dish Engine to Offset Wastewater Peak Energy Demand

While the emerging energy-efficient wastewater technologies which have been presented so far focused on wastewater treatment processes or reuse, the last ones draw attention to future interactions/fluctuations between energy supply and demand. Wastewater treatment plants have been studied for their energy loads over time (Park & Bennett, 2010) and agencies studying forms of energy storage or renewable energy sources occasionally try to demonstrate their technology in combination with such a plant. The first example is the solar power dish engine and makes use of the sun as an renewable source for energy. Such energy sources have received major attention in the last decades as potential new sources of electricity and especially the sun is seen as an important future supplier of energy due to the enormous amount of energy it emits. Several methods exist, but the main approach to solar electricity has been by developing photovoltaic cells (Gratzel, 2001). Another method however, concentrates sunlight with mirrors or lenses to create high temperatures which may drive turbines or engines. Such solar thermal energy designs have been installed for larger plants, compared to average photovoltaic sizes, at sunny locations (Ridao, Garcia, Escobar, & Toro, 2007). The solar power dish engine is a design which makes use of concentrated solar power, collects this with a large dish and drives a Stirling engine at the focal point. A multitude of these devices can produce a significant amount of energy during daylight hours when the dish is tracking the sun. Arguably, the potential for this sort of technology may be very large, but has met with unfortunate market conditions in the past (Mills, 2004). In the last ten years however, solar power dish engines have become commercially available and are being build on ‘cloudless’ locations, for example in the U.S. states of Nevada and California. The intermittency of the power generation remains a disadvantage, although heat is stored more easily compared to electricity. An interesting approach is to use the solar dish engines at locations where peak energy consumption takes place during the day. This is an example of a demand response technology which acts when electricity consumption is rising to ‘shave’ the peak energy demand. Wastewater treatment plants have a larger demand in the daytime (Lekov et al., 2009; Park & Bennett, 2010) and can be a viable option for peak shaving. Currently, this technology is not commercially available for wastewater treatment plants and demonstration at a Californian wastewater treatment facility is not yet started (Loge, 2009). The demonstration project involves 1 MW of energy producing solar engine dishes and about 330 dishes need to be built to achieve this output. For the assessment on energy savings in California’s wastewater industry, the estimates of the grant proposal are being used (25 percent reduction of utility-supplied energy) (Loge, 2009). When these savings can be achieved in 25 percent of all the wastewater treatment plants by 2020, it could have an energy saving potential of 225 GWh in California. Limitations are the large capital investments and the plant’s characteristics. The current demonstration is not yet economical at an industrial electricity price of $ 0.12 per kWh and requires federal loans. Additionally, not every plant is large enough for this technology and the location will also be important. Not all plants have sufficient land available around the plant and not all locations have an optimal amount of sun. Nevertheless, in dry, arid regions where energy and water prices are highest it can be expected to be economical first.

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Vanadium Redox Flow Batteries for Wastewater Load Management

Another demand response technology focuses on a pivotal, but complex issue in electric engineering: storing electricity on a large scale (Lee & Gushee, 2008). One of the challenges encountered when handling fluctuating electric energy sources and/or demands, is to maintain a stable grid which provides sufficient electric energy regardless of weather or unexpected peaks. This issue is especially important with an increasing share of renewable energy supply in a state’s or nation’s total energy supply, as the amount of wind or sunshine will cause larger fluctuations in some climates. When electric energy could be stored, peak demands could be met more easily again. Batteries work fine in small systems but have yet to deal with cost, charging time and lifetime issues at a grid order or magnitude. One of the promising novel battery designs to overcome these issues are vanadium redox flow batteries. As mentioned during discussion of the previous technology, wastewater treatment is one of the areas in which electric energy storage would facilitate larger energy efficiency. Wastewater load is not continuous and stable over the day and in the year, but has periods during the day in which treatment is more intensive than at other moments (Park & Bennett, 2010). Limiting the purchase of more expensive electricity at peak moments by energy storage would reduce the costs of a wastewater treatment facility. Also, it might help in the possible implementation of onsite biogas generators as digested sludge gas would now harness energy which could be stored and used later (Appels et al., 2008). The plant’s ability to practice facility load management and demand response opportunities would increase its efficiency and reduce its operating costs. Vanadium redox flow batteries (VRBs) have been developed since the 1980s (Skyllas-Kazacos & Robins, 1988) and have a strongly distinctive operation mode compared to regular batteries mentioned. The reason for this is the ability of vanadium to act both as an anode and a cathode. In such systems the electrolyte is a vanadium-sulphuric acid solution without solids and its lifetime can be very long (Blanc, 2009). Another advantage is that such a battery system can be monitored in real-time due to the accessibility of the fluid, so the amount of energy which is stored is clearer. However, the system has a low energy density and can therefore result in large installations. Also, the costs for implementing these systems is unsure. Currently, a new demonstration project is planned at the Californian wastewater treatment plant in Pleasanton (Dublin San Ramon Service District) (Toca, 2009). In this plant (molten carbonate) fuel cells have been installed, which would be more effective when an electric energy storage system would be in place. Such a system could be able to diminish purchase from the electricity grid by 25 percent. Especially, since the fuel cells are run on digested sludge biogas this could reduce energy consumption of wastewater treatment facilities by roughly the same number. The assessment estimates significant energy savings on a plant level, but a limited number of plants where this system can actually be installed as it needs an anaerobic digestion systems with fuel cells (10 percent expected in 2020). Consequently, the state’s energy savings by this technology in 2020 are estimated at 90 GWh. Summary of Technology Assessments The eight studied wastewater technologies show large variation in their energy savings potential for California (Table 7.1), but also highlight the variety of the wastewater sector. Several technologies are designed for certain types of treatment plants (e.g. lagoons, plants with anaerobic digestion) or for a sector specific process (e.g. rinse water in the food processing industry). Consequently, technologies which are not bound to specific plants or sectors (the software and demand response technologies) have the highest energy savings potential on a state level in these assessments. However, the latter technologies currently have problems because of their higher costs compared to standard practices.

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In 2020, following the Current Trends scenario of the California Water Plan ([DWR], Department of Water Resources, 2009a) and the conclusion of Chapter 6, the savings potential of these eight technologies combined is close to 1300 GWh. This would be about a third of the total electric energy consumption of California’s wastewater industry in 2020 and it is mainly due to the large potential with the improved biogas generation technology (~ 850 GWh). Due to the uncertainty in many factors and the crude nature of this estimate, there remains ample room for discussing its validity. However, it emphasizes the technological possibilities which are emerging in the wastewater sector and especially the opportunity to generate biogas for onsite electricity generation. The largest energy efficiency increase of the sector can be made when digester technology becomes economically and technically feasible for more plants. Other efficiency increases are smaller and are either because of wastewater reuse or because of improvements in equipment (mixers) and processes (sludge dewatering). Potential for energy savings is no guarantee for actual implementation of emerging energy efficient technologies (McKane et al., 2009). Barriers exist in the form of poor economics, risks associated with tentative investments and a lack of incentives for change. In the Californian wastewater industry these barriers can be recognized. During the course of this research, some technology developers were contacted and generally answered that successful demonstration would still take time and financial resources. In the past the wastewater sector was also often overlooked in energy efficiency opportunities (Lekov et al., 2009) and consequently adaption of emerging energy efficient technologies has lagged until about a decade ago. It is possible that the public nature of most Californian wastewater treatment plants played a role in a lack of investments, but there is no hard evidence to support this. However, these eight technologies have shown the diversity of approaches to improve energy efficiency in California’s wastewater industry. Since attention to energy efficiency has risen in the last decade in the United States and the California state identified the relation between water conservation and increased energy efficiency, some barriers might be overcome in the coming years. Other Wastewater Technologies

To conclude the chapter an overview is given on some energy efficiency measures for wastewater treatment plants which have been assessed according to Dutch experiences and some technologies which were listed by the U.S. Environmental Protection Agency. Together with the previous eight technologies which were studied in detail this gives an overview of the technological developments and future issues in modern wastewater treatment systems. Table 7.2 presents an overview of measures which were assessed by a Dutch engineering company and have significant energy savings

# Measure / Technology

Rough Energy

Savings Calculation

(GWh)

Potential for

Energy Savings

Costs compared

to standard

Current Market

Penetration

1Novel materials for sludge

dewatering 21 Low medium none

2 Wastewater pond mixers29 Medium low low

3Reuse wastewater by

membrane filtration 53 Medium medium low

4 Biodiesel methanol strippers0 Low medium none

5 Ozonation treatment6 Low low low

6Improve bacteria mix for

biogas generation 863 High medium medium

7 Solar power dish engines225 High high low

8 Vanadium redox flow batteries90 Medium high low

Table 7.1 Overview of the eight emerging PIER-funded wastewater technologies and their potential

in California.

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(over 1 percent) with small payback periods (Geraats et al., 2010). Compared to the eight technologies which were assessed in the previous paragraphs, these are straightforward measures which can improve energy efficiency instead of novel technologies. What is apparent from this overview is the amount of possible energy savings in common wastewater treatment plants. Most of these measures are process improvements which enhance sludge handling and general aeration issues. It can serve as a reminder that some efficiency improvements can be made just by adapting motors and aeration equipment (Water Environment Federation, 2009). Other measures can be linked to previous technology discussion. One of the largest energy savings is possible by adding polymers to primary clarifiers. Not only does this reduce energy costs for sludge dewatering as was seen in the nanoscale particle addition technology (page 26), but it can also improve biogas quality for digestion purposes. Again, implementing digesters for biogas fueled electricity generation can largely enhance the energy efficiency of a wastewater treatment plant. Also, better mixers and reduction of propellers remain important. Technologies were listed by the EPA to identify current developments and changes in industrial processes ([EPA], U.S. Environmental Protection Agency, 2008b). Some issues which were identified were: upgrading old plants, nutrient removal (and recovery), using automated process controls and treatment which would enable wastewater reuse. This confirms the trend of wastewater treatment plants to include advanced treatment (nutrient removal) methods and the opportunity to implement emerging energy efficient technologies when upgrading old plants.

Measure: Energy Savings

Payback

Period Type of Plant

Polymer addition for improved primary settling

and improved biogas10-20% <5

Secondary with

biogas digester

Automate aeration rate by oxygen concentration 10-20% <5Advanced with

nutrient removal

Lower standard oxygen concentration 5-10% 0 Common

Enhance sludge loading/production 5-10% 0 "

Improve oxygen transfer efficiency (alpha factor) 5-10% 0 "

Automate aeration rate by ammonium/nitrate

concentration5-10% <5

Advanced with

nutrient removal

Built-in alarm in case of excessive aeration 1-5% <5 Common

Use bump aeration instead of propellers 1-5% 0 "

Stop use propellers during aeration 1-5% 0 "

Use digester heat as buffer 1-5% 0Secondary with

biogas digester

Mix digesters by mixer instead of gas 1-5% <5 "

Automate aeration rate by redox measurement 1-5% <5Advanced with

nutrient removal

Optimize sensor quantities and locations 1-5% <5 "

Frequent sensor calibration 1-5% <5 "

Table 7.2 Overview of energy efficiency measures in wastewater treatment plants with energy savings

over 1% and small payback periods according to Dutch experiences (Geraats, Schelleman, &

Geilvoet, 2010).

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While technologies may be specific to certain plants, sectors, climates and countries, the results of this research are valuable to regions outside California which have constructed a modern wastewater infrastructure in the last fifty years. They underline opportunities for improved energy efficiency, which will be more important in the coming decades, especially when advanced, more energy intensive processes are required for pollutant removal. A characteristic of California are the drought problems it frequently faces and which explains special interest in technologies which reduce both energy and water use. Maintaining an efficient water and wastewater infrastructure is more pressing in a dry state with a large agricultural sector. In The Netherlands for example, water scarcity is a comparatively small problem, but reducing energy consumption in water and wastewater processes has been targeted in the last years (Geraats et al., 2010). Therefore, the majority of the eight technologies presented in this chapter, might still be interesting for The Netherlands and other countries. The three wastewater reuse technologies might have little impact on a national level, in particular when the type of industries are only slightly present but can still be important for these industries worldwide. Process technologies can be applicable outside the Californian state borders as well and this also holds for the software technology which improves the bacteria mix. Only the solar power technology seems limited by location rather than type of plant or sector. This assessment of technologies and the discussion above have emphasized the challenges, developments and opportunities of the Californian wastewater sector in particular and for many modern wastewater systems in general. Emerging technologies can clearly aid in improving energy efficiency, but require further quantification of their possibilities and should not be considered to be applicable to the whole range of wastewater systems. Costs might limit uptake of emerging technologies until payback periods reach levels acceptable for investment, but technological development is necessary for future wastewater treatment plants.

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8. GENERAL DISCUSSION The goal of this research was to gain insight into California’s wastewater treatment sector, its energy use and opportunities for improved energy efficiency. The results from the study were mixed however, due to the number of uncertainties related to actual wastewater treatment figures, energy intensities and data availability. This discussion shows issues which came up during the course of this research. In the last decades more data has become available on water use and disposal in California. The U.S. Geological Survey presents regular overviews of water withdrawals in American states and the California Department of Water Resources publishes detailed water flows in its regular and extensive State Water Plans, which have been presented in chapter 5. Nevertheless, data on disposal is less detailed and less certain. For California, the best data source was the Environmental Protection Agency’s Clean Watersheds Needs Survey which measures flows in all wastewater treatment facilities. However, the distinction between the plant’s capacity and its actual flow is not always made. Therefore, actual wastewater flows might be slightly lower than presented in this study, although this might be compensated by energy use related to industrial wastewater treatment which may not be accounted for yet. The latter is hardly documented with only a twenty year old report present on the Californian industrial flows. On a national level even less data is available, as the survey on detailed industrial water use was terminated in the 1980s. To assess the energy savings potential of technologies, a benchmark was required with average energy intensities of wastewater treatment plants. A variety in figures can be found, but most lead back to a 15 year old study and are not fully applicable to the current wastewater sector of California. What can be seen is a wide range of energy intensities (the lowest and highest values differ almost one order of magnitude), reflecting the different plant setups and local conditions. Because average energy intensity, the amount of treated wastewater and the contribution of industrial wastewater is unsure, it is difficult to quantify the electric energy used in California for wastewater treatment. These issues have been recognized in the United States earlier and an attempt was made to develop a benchmark related to organic content (BOD5) and flow sizes (Carlson & Walburger, 2007), but due to the low number of surveys being returned and large variety in the results uncertainty is still present. It is also unclear to what extent sludge treatment is included in energy benchmarks, because sludge handling and disposal require significant amounts of energy. Another issue with wastewater flow data is the amount of storm water (i.e. rain and snow) which enters into the system. While some cities have separate sewage pipes for storm water and for urban wastewater, others are combined and treat storm water together with wastewater. Little figures on this issue are available, so it is not known whether this is an influential factor or not. A similar issue is the amount of leaks in the sewage systems. Looking at the percentage of urban water which is treated, there are significant losses. For a major part this is due to evaporation and outdoor use, but leaks can play a significant role. There is little to suggest water reuse is common at a residential level, although this could be a reason for lower wastewater disposal compared to water withdrawal in industrial sectors. Data sources are often from different years and especially in the state of California where water supply and demand can vary substantially, this can be another source for data errors. Still, general trends are reasonably consistent and it is expected that such errors would not create as much uncertainty compared to uncertainties in wastewater flows and energy intensities. The assessment of the eight wastewater technologies for California in 2020 is based on several estimates related to their applicability, their savings and the base case. For applicability this is often an educated guess by the author loosely based on current Californian wastewater sector or other Californian sources. Savings have been estimated by crude calculations and are regularly based on expected savings in the grant proposals, which might be tinted by optimism (Martin et al., 2000). The total savings are dependent on the base case and due to data availability this could not always be the

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3595 GWh estimate presented in chapter 6. Technologies which did have the estimated 2020 base case were slightly favored as a result. With wastewater reuse technologies, energy savings were dependent on the value for the water supply and treatment chain and this value can also vary significantly. For these reasons, the assessment should be interpreted as crude estimates which only emphasize possible energy savings. It is however possible to discuss the choice of the California Energy Commission to select these eight specific technologies. From the assessment follows that some technologies might have significant potential energy savings in 2020, while others have low potential. Especially, the biodiesel technology is of interest in this light as the potential is virtually non-existent due to the small size of the sector. When only potential energy savings and cost-effectiveness would be taken into account, it appears to be better to focus on cross-cutting emerging technologies with multiple benefits. Most uncertainties sketched in the paragraphs above underline the difficulties in quantifying links between water use and energy use. Because of these uncertainties and the large variety in data, it was not deemed necessary to establish error margins or perform sensitivity analysis. The results should therefore be assessed qualitatively. One of the research questions asked to what extent the relation between these factors can be quantified in wastewater treatment plants. The clear answer from this discussion is only to a qualitative level or a broad quantitative range. Higher water flows involve more pumping and aeration for example, but there appears to be no well defined relations. An alternative to induce energy efficiency in wastewater treatment plants might actually be to compare equipment instead of plants. Having discussed the uncertainties of this research, this study hopes to highlight important issues related to energy use in the wastewater sector in general. It would be highly recommend to quantify average energy intensities and the size of industrial wastewater (pre) treatment in further studies.

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9. CONCLUSIONS This research aimed to identify the water and energy savings potential for California’s wastewater treatment industry in 2020 by implementing a specific set of emerging wastewater technologies. While there is a significant uncertainty in the amount of water and energy which is currently used for wastewater treatment and plenty of uncertain estimates in the technology assessment, crude approximations were determined. The energy savings potential for the eight wastewater technologies is close to 1300 GWh in 2020, when about 3600 GWh of electric energy will be used for wastewater treatment in that year with an average energy intensity of 0.5 kWh m-3. The water savings potential has not been developed, because it would only extend to technologies which reuse wastewater. Wastewater treatment plants consist out of a varying number of steps, but most larger plants in California treat wastewater to a secondary level with the activated sludge process. Such treatment plants are sufficient in reducing the organic content to effluent standard. Some plants have advanced treatment methods, which enable further reduction of organic content and proper removal of nutrients as well. More advanced treatment plants require more energy, which is largely (over 80%) in the form of electricity and therefore gas use is not discussed in this thesis. Most electricity is used for aeration and pumping, but its relative shares are dependent on the type of plant and its capacity. The average electricity use of common wastewater treatment processes varies between 0.18 and 0.78 kWh m-3, although more variation is possible. The Californian wastewater industry treats about 5.0 billion m3 annually and according to several Californian state reports it uses 2012 GWh to achieve treatment. However, there are large uncertainties in water and energy use estimates, because of differing energy intensities and lack of consistent data. To establish water and energy use in 2020 an average energy intensity of 0.5 kWh m-3 was used and by using water use scenarios of the California Department of Water Resources, the estimate for the total annual electric energy use of the wastewater sector became about 3600 GWh. The Californian wastewater industry would treat 7.1 billion m3 wastewater in that year. Emerging wastewater technologies can improve energy efficiency of the wastewater sector and thereby reduce future energy expenditures in California. In this thesis, eight technologies were assessed in detail for their potential in California in 2020. These technologies were categorized in four classes: process technologies, reuse technologies, software technologies and demand response technologies. Process technologies address energy efficiency by improving equipment or processes and are not bound to California. Wastewater reuse technologies are especially suited for California, because water scarcity is a pressing issue in this state and yield energy savings on the state’s water infrastructure level instead of on the local level. These savings are therefore harder to quantify. The studied software technology enhances bacteria mix and can improve the largest opportunity for wastewater treatment plants: onsite biogas fueled electricity generation. This technology alone was assessed to have about 850 GWh savings potential of the 1300 GWh in total for California in 2020. Demand response technologies implement a more flexible electricity grid and can thereby create significant energy savings for wastewater treatment plants. Common barriers to implementation of these technologies are poor economics, investment risks and lack of incentives to change current processes. This thesis addressed a large number of issues related to modern day wastewater treatment and challenges it faces. While emerging technologies can aid the sector in improving its energy efficiency, changes take time and there is a lot of uncertainty in determining reference levels in term of energy intensity and current water use. Future research should continue with benchmark studies on these issues, which would reduce uncertainties in current practices and thereby create opportunities to quantify efficiency opportunities with more accuracy.

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41

10. ACKNOWLEDGMENTS At the end of this master thesis I have to thank several people for giving me the opportunity to perform the study largely abroad at the wonderful Lawrence Berkeley National Laboratory (LBNL). First of all, I want to thank Tim Xu who was my supervisor in Berkeley. Tim, I have thoroughly enjoyed participating in the Emerging Technologies project and must say that I learned a tremendous amount on energy use in California and the United States, in particular of its industrial sectors. Having somewhat of an engineering background I was glad to enrich this background by the wide variety of technologies studied. Unfortunately, the wide variety kept me sometimes too far from studying the wastewater sector for this report, but I think we made the best of it. I would also like to thank the whole International Energy Studies group of Jayant Sathaye at the LBNL. I have clearly benefited from research which has been performed here in the past and present. Next to that, I enjoyed the occasional group lunches and the insights it provided in local and U.S. policies. One person I should mention in particular is Barbara Adams, who was very helpful in guiding me trough the paper work to actually get into the States and all the red tape which had to be dealt with later. During my research into wastewater in the United States and California, I have had fruitful discussions with Edward Vine, Larry Dale and Richard Brown at the LBNL. They confirmed some of the thoughts I had and also provided me with additional literature which was very helpful for the development of this thesis. Being a former employee of both the Center for Energy and Environmental Sciences (IVEM) at the University of Groningen and the LBNL, Klaas Jan Kramer was the first person I actually contacted in the San Francisco Bay Area and I am very grateful for that as it led me to Tim Xu. Klaas Jan, I have also enjoyed the social stop-bys when you were at the Berkeley Lab and all the other social events for which you invited me. This started with watching World Cup football matches together with the Dutch expat community at the Dutch consulate when you and your family where not even there, but also with some dinners at your place and a ‘hockey’ game at the end. Thanks for all! There are many persons who made my residence in Berkeley even more enjoyable. My house mates (Atma, Scott and Edna), friends I made at the International House (Meghan, Marieke, Brian, Nandor, Martin, Ipek, Özge, David, Karin and many others) and our little Groningen community; Wendy, Frans and Stella. Wendy and Frans also thanks for letting me stay at your apartment before I found a room. Having mentioned most people in Berkeley, I would like to conclude by thanking my supervisors in Groningen: Henk Moll and Ton Schoot Uiterkamp. Henk, I am very grateful for the supporting emails you send and the confidence that I could make it all work pretty much on my own. Of course, I also greatly appreciate the (rapid) comments on this thesis and its development. Ton, thanks for the comments on this thesis and the willingness to give feedback in a relative short time span. That wraps up this thesis and my master program Energy and Environmental Sciences at the University of Groningen. It has been a great learning experience altogether, which I will remember very fondly!

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43

11.REFERENCES Aiyuk, S., Amoako, J., Raskin, L., van Haandel, A., & Verstraete, W. (2004). Removal of carbon and

nutrients from domestic wastewater using a low investment, integrated treatment concept. Water Research, 38(13), 3031-3042.

Andrews, C. J., & Krogmann, U. (2009). Technology diffusion and energy intensity in US commercial buildings. Energy Policy, 37(2), 541-553.

Angenent, L. T., Karim, K., Al-Dahhan, M. H., & Domiguez-Espinosa, R. (2004). Production of bioenergy and biochemicals from industrial and agricultural wastewater. Trends In

Biotechnology, 22(9), 477-485. Appels, L., Baeyens, J., Degreve, J., & Dewil, R. (2008). Principles and potential of the anaerobic

digestion of waste-activated sludge. Progress In Energy And Combustion Science, 34(6), 755-781.

Bang, G. (2010). Energy security and climate change concerns: Triggers for energy policy change in the United States? Energy Policy, 38(4), 1645-1653.

Biswas, P. (2009). Advanced Water Treatment Technologies for Onsite Water Reuse. In Emerging Technologies Demonstration Grant Program (Ed.): California Energy Commission.

Blackhurst, M., Hendrickson, C., & Vidal, J. S. I. (2010). Direct and Indirect Water Withdrawals for US Industrial Sectors. Environmental Science & Technology, 44(6), 2126-2130.

Blanc, C. (2009). Modeling of a Vanadium Redox Flow Battery Electricity Storage System. Ecole Polytechnique Fédérale de Lausanne, Lausanne, Switzerland.

Braaksma, A. (2010). G-gas: from Groningen gas to Green gas? An assessment of the Dutch green

gas potential and its delivery to the natural gas system based on Groningen gas quality. University of Groningen, Groningen, Netherlands.

Brown, R. (2009). Energy Efficiency and Renewable Energy Technologies in Wastewater Management, Subcommittee on Water Resources and Environment. Washington, DC: U.S. House of Representatives.

[Caltrans], California Department of Transportation. (2003). Statewide Storm Water Management

Plan. Sacramento: California Department of Transportation. Carlson, S. W., & Walburger, A. (2007). Energy Index Development for Benchmarking Water and

Wastewater Utilities (No. CEC-500-01-041). Denver, CO: Awwa Research Foundation. Carns, K. (2005). Bringing Energy Efficiency to the Water and Wastewater Industry: How do we get

there? Proceedings of the Water Environment Federation, 2005, 7650-7659. [CDFA], California Department of Food and Agriculture. (2010). California Agricultural Production

Statistics 2008. Sacramento, CA: California Department of Food and Agriculture. Day, T. J. (2007). A Systems Approach to the Privatization and Outsourcing of Publicly Owned

Treatment Works. Stevens Institute of Technology, Hoboken, NJ. [DOE], U.S. Department of Energy. (2010). About DOE. Retrieved 6 October, 2010, from

http://www.energy.gov/about/index.htm [DWR], California Department of Water Resources. (2010). 20x2020 Water Conservation Plan.

Sacramento, CA: California Department of Water Resources. [DWR], Department of Water Resources. (2009a). California Water Plan: Update 2009 - Integrated

Water Management - Volume 1 - The Strategic Plan (No. Bulletin 160-09). Sacramento, CA: State of California, Department of Water Resources.

[DWR], Department of Water Resources. (2009b). California Water Plan: Update 2009 - Integrated

Water Management - Volume 2 - Resource Management Strategies (No. Bulletin 160-09). Sacramento, CA: State of California, Department of Water Resources.

[DWR], Department of Water Resources. (2009c). California Water Today. In California Water Plan:

Update 2009 - Integrated Water Management - Volume 1 - The Strategic Plan (Vol. 4, pp. 1-66). Sacramento, CA: State of California, Department of Water Resources.

Eisenstein, W., & Kondolf, G. M. (2008). Planning Water Use in California. ACCESS, 33(Fall), 8-17. [EPA], U.S. Environmental Protection Agency. (2008a). Clean Watersheds Needs Survey: U.S.

Environmental Protection Agency.

44

[EPA], U.S. Environmental Protection Agency. (2008b). Emerging Technologies for Wastewater

Treatment and In-Plant Wet Weather Management (No. EPA 832-R-06-006). Washington, DC: U.S. Environmental Protection Agency.

[EPA], United States Environmental Protection Agency. (1983). Design Manual: Municipal

Wastewater Stabilization Ponds (No. 625/1-83-015). Washington, DC: United States Environmental Protection Agency.

[EPA], United States Environmental Protection Agency. (2004). Primer for Municipal Wastewater

Treatment Systems (No. 832-R-04-001). Washington, DC: United States Environmental Protection Agency.

[EPA], United States Environmental Protection Agency. (2006). Wastewater Management Fact Sheet:

Energy Conservation (No. 832-F-06-024). Washington, DC: United States Environmental Protection Agency.

Escobar, J. C., Lora, E. S., Venturini, O. J., Yanez, E. E., Castillo, E. F., & Almazan, O. (2009). Biofuels: Environment, technology and food security. Renewable & Sustainable Energy

Reviews, 13(6-7), 1275-1287. French, L. A., Hamman, L., Katz, S., Kozaki, Y., & Frew, J. (2010). Zero Waste Strategies and

Innovation for Sustainability. Santa Barbara, CA: Bren School of Environmental Science & Management.

Geraats, S. G. M., Schelleman, F. J. M., & Geilvoet, S. (2010). Guideline for Energy Efficiency in

Wastewater Treatment in Turkey (No. I&M-1016744-BG). De Bilt, The Netherlands: Grontmij Nederland.

Gibbs, M. J., & Morris, M. (2004). Water and Energy: Improving the Efficiency in the Use of Two

Critical Resources. Washington, DC: United States Environmental Protection Agency. Gleick, P. H., Haasz, D., Henges-Jeck, C., Srinivasan, V., Wolff, G., Cushing, K. K., et al. (2003).

Waste Not, Want Not: The Potential for Urban Water Conservation in California. Oakland, CA: Pacific Institute.

Gratzel, M. (2001). Photoelectrochemical cells. Nature, 414(6861), 338-344. Guay, C. (2009). Integrated System for Reducing Water Consumption and Wastewater Discharge of

Biodiesel Production Facilities in California. In Emerging Technologies Demonstration Grant Program (Ed.): California Energy Commission.

Hartong, B. H., Abu-Daabes, M., Le, T., Saidan, M., & Banerjee, S. (2007). Sludge dewatering with cyclodextrins. Water Research, 41(6), 1201-1206.

Hilal, N., Al-Zoubi, H., Darwish, N. A., Mohamma, A. W., & Abu Arabi, M. (2004). A comprehensive review of nanofiltration membranes:Treatment, pretreatment, modelling, and atomic force microscopy. Desalination, 170(3), 281.

Hill, A. (2009). Reclamation of Wastewater for Cooling Tower Operations at the Gills Onion Processing Plant in Oxnard, California. In Emerging Technologies Demonstration Grant Program (Ed.): California Energy Commission.

Hill, J., Nelson, E., Tilman, D., Polasky, S., & Tiffany, D. (2006). Environmental, economic, and energetic costs and benefits of biodiesel and ethanol biofuels. Proceedings Of The National

Academy Of Sciences Of The United States Of America, 103(30), 11206-11210. Isaac, R. (2008). Estimated Water Use on Large Projects in 2004-2006 (No. CRB-08-012).

Sacramento, CA: California Research Bureau. Jackson, R. B., Carpenter, S. R., Dahm, C. N., McKnight, D. M., Naiman, R. J., Postel, S. L., et al.

(2001). Water in a changing world. Ecological Applications, 11(4), 1027-1045. Jaruwat, P., Kongjao, S., & Hunsom, M. (2010). Management of biodiesel wastewater by the

combined processes of chemical recovery and electrochemical treatment. Energy Conversion

And Management, 51(3), 531-537. Kenny, J. F., Barber, N. L., Hutson, S. S., Linsey, K. S., Lovelace, J. K., & Maupin, M. A. (2009).

Estimated Use of Water in the United States in 2005 (No. 1344). Reston, VA: U.S. Geological Survey.

Klein, G., Krebs, M., Hall, V., O'Brien, T., & Blevins, B. B. (2005). California's Water – Energy

Relationship (No. CEC-700-2005-011-SF). Sacramento, CA: California Energy Commission.

45

Kurniawan, T. A., Chan, G. Y. S., Lo, W. H., & Babel, S. (2006). Physico-chemical treatment techniques for wastewater laden with heavy metals. Chemical Engineering Journal, 118(1-2), 83-98.

Lee, B. S., & Gushee, D. E. (2008). Electricity Storage: The Achilles' Heel of Renewable Energy. Chemical Engineering Progress.

Lekov, A., Thompson, L., McKane, A., Song, K., & Piette, M. A. (2009). Opportunities for Energy

Efficiency and Open Automated Demand Response in Wastewater Treatment Facilities in

California - Phase I Report (No. LBNL-2572E). Berkeley, CA: Lawrence Berkeley National Laboratory.

Lettinga, G. (1995). Anaerobic-Digestion And Waste-Water Treatment Systems. Antonie Van

Leeuwenhoek International Journal Of General And Molecular Microbiology, 67(1), 3-28. Liu, S. T., Musuku, S. R., Adhikari, S., & Fernando, S. (2009). Adsorption of glycerol from biodiesel

washwaters. Environmental Technology, 30(5), 505-510. Loge, F. J. (2009). Demonstration of Mid-Scale Concentrated Solar Power - Dish/Engine (CSP-D/E)

System to Offset Peak Energy Cost at a Wastewater Treatment Facility. In Emerging Technologies Demonstration Grant Program (Ed.): California Energy Commission.

Martin, N., Worrell, E., Ruth, M., Price, L., Elliott, R. N., Shipley, A. M., et al. (2000). Emerging

Energy-Efficient Industrial Technologies (No. LBNL 46990). Berkeley, CA: Lawrence Berkeley National Laboratory.

Masanet, E., Worrell, E., Graus, W., & Galitsky, C. (2008). Energy Efficiency Improvement and Cost

Saving Opportunities for the Fruit and Vegetable Processing Industry (No. LBNL-59289-Revision). Berkeley, CA: Lawrence Berkeley National Laboratory.

McGarvey, J. A., Miller, W. G., Lathrop, J. R., Silva, C. J., & Bullard, G. L. (2009). Induction of purple sulfur bacterial growth in dairy wastewater lagoons by circulation. Letters In Applied

Microbiology, 49(4), 427-433. McKane, A., Desai, D., Matteini, M., Meffert, W., Williams, R., & Risser, R. (2009). Thinking

Globally: How ISO 50001 - Energy Management can make industrial energy efficiency

standard practice (No. LBNL-3323E). Berkeley, CA: Lawrence Berkeley National Laboratory. Metcalf & Eddy Inc. (2003). Wastewater Engineering, Treatment and Reuse: McGraw-Hill. Mills, D. (2004). Advances in solar thermal electricity technology. Solar Energy, 76(1-3), 19-31. Mirza, S. (2008). Reduction of energy consumption in process plants using nanofiltration and reverse

osmosis. Desalination, 224(1-3), 132. Naik, S. N., Goud, V. V., Rout, P. K., & Dalai, A. K. (2010). Production of first and second

generation biofuels: A comprehensive review. Renewable & Sustainable Energy Reviews,

14(2), 578-597. National Center for Appropriate Technology. (2009). The Sidestreams of Biodiesel Production - A

Curriculum for Agricultural Producers. Retrieved 19 October, 2010, from http://attra.ncat.org/attra-pub/PDF/sidestreams.pdf

Navigant Consulting Inc. (2006). Refining Estimates of Water Related Energy Use in California (No. CEC-500-2006-118). Sacramento, CA: California Energy Commission.

Nelson, K. L. (2005). Small and Decentralized Systems for Wastewater Treatment and Reuse. In H. Vaux, J. Crook & R. Parkin (Eds.), Water Conservation, Reuse, and Recycling: Proceedings of

an Iranian-American Workshop (pp. 54-66). Washington, DC: National Academies Press. Nemerow, N. L. (2007). Industrial waste treatment: Contemporary Practice and Vision for the

Future. Oxford: Butterworth-Heinemann. Nemerow, N. L., Agardy, F. J., Sullivan, P., & Salvato, J. A. (Eds.). (2009). Water, Wastewater, Soil

and Groundwater Treatment and Remediation. Hoboken, NJ: John Wiley & Sons. Neyens, E., Baeyens, J., Dewil, R., & De heyder, B. (2004). Advanced sludge treatment affects

extracellular polymeric substances to improve activated sludge dewatering. Journal Of

Hazardous Materials, 106(2-3), 83-92. Novak, J. T. (2006). Dewatering of sewage sludge. Drying Technology, 24(10), 1257-1262. Olmez, H., & Kretzschmar, U. (2009). Potential alternative disinfection methods for organic fresh-cut

industry for minimizing water consumption and environmental impact. Lwt-Food Science And

Technology, 42(3), 686-693.

46

Oppenheimer, J. (2009). High-Efficiency Submersible Mixers for Wastewater Pond Aeration. In Emerging Technologies Demonstration Grant Program (Ed.): California Energy Commission.

Orta, J., & Zhang, Z. (2010). 2009 Progress to Plan: Bioenergy Action Plan For California (No. CEC-500-2010-007). Sacramento, CA: California Energy Commission.

Park, L., & Bennett, B. (2010). Embedded Energy in Water Studies - Study 2: Water Agency and

Function Component Study and Embedded Energy-Water Load Profiles. Sacramento, CA: California Public Utilities Commission.

Rajagopalan, G. (2009). The Use of Novel Nanoscale Materials for Sludge Dewatering: A Field Demonstration. In Emerging Technologies Demonstration Grant Program (Ed.): California Energy Commission.

Ridao, A. R., Garcia, E. H., Escobar, B. M., & Toro, M. Z. (2007). Solar energy in Andalusia (Spain): present state and prospects for the future. Renewable & Sustainable Energy Reviews, 11(1), 148-161.

Sardeing, R., Poux, M., Melen, S. P., Avrillier, P., & Xuereb, C. (2005). Aeration of large size tanks by a surface agitator. Chemical Engineering & Technology, 28(5), 587-595.

Shon, H. K., Vigneswaran, S., & Snyder, S. A. (2006). Effluent organic matter (EfOM) in wastewater: Constituents, effects, and treatment. Critical Reviews In Environmental Science And

Technology, 36(4), 327-374. Skyllas-Kazacos, M., & Robins, R. (1988). All-vanadium redox battery. United States: Unisearch Ltd. Stephenson, R. L., & Blackburn, J. B. (1998). The Industrial Wastewater Systems Handbook. New

York, NY: Lewis Publishers. Strickland, W., Sopher, C. D., Rice, R. G., & Battles, G. T. (2007). Six Years of Ozone Processing of

Fresh Cut Salad Mixes. Paper presented at the IOA Conference and Exhibition, Valencia, Spain.

Toca, C. (2009). Application of High Capacity Electric Energy Storage via Vanadium Redox Flow Batteries, in conjunction with Fuel Cells, to a Wastewater Treatment Facility. In Emerging Technologies Demonstration Grant Program (Ed.): California Energy Commission.

U.N. Economic and Social Commission for Western Asia. (2003). Waste-Water Treatment

Technologies (No. E/ECSWA/SPDP/2003/6). New York, NY: United Nations. Vicuna, S., Maurer, E. P., Joyce, B., Dracup, J. A., & Purkey, D. (2007). The sensitivity of California

water resources to climate change scenarios. Journal of the American Water Resources

Association, 43(2), 482-498. Wade, W. W., Hewitt, J. A., & Nussbaum, M. T. (1991). Cost of Industrial Water Shortages:

California Urban Water Agencies. Wang, Z. S., Hung, M. T., & Liu, J. C. (2007). Sludge conditioning by using alumina nanoparticles

and polyelectrolyte. Water Science And Technology, 56(8), 125-132. Water Environment Federation. (2009). Energy Conservation in Water and Wastewater Facilities.

New York, NY: McGraw-Hill. Wun Jern, N. (2006). Industrial Wastewater Treatment. London: Imperial College Press. Zhang, H. H., & Brown, D. F. (2005). Understanding urban residential water use in Beijing and

Tianjin, China. Habitat International, 29(3), 469-491. Zhou, C. (2009). CASCADE Clean Energy System for California Energy Commission PIER ETDG

in Water and Waste Water Projects. In Emerging Technologies Demonstration Grant Program (Ed.): California Energy Commission.

Zhou, H., & Smith, D. W. (2001). Advanced technologies in water and wastewater treatment. Canadian Journal of Civil Engineering, 28, 49-66.

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APPENDIX A: CALIFORNIAN WASTEWATER TREATMENT PLANTS

Name facility Secondary Advanced

Flow (Mm3

per year)

Design

(Mm3 per

year)

BOD in

(mg L-1)

BOD out

(mg L-1)

Energy

intensity

(kWh m-3)

Hyperion WWTP Clarification N/A 638 638 323 20 0.23

Joint WPCP

Activated Sludge +

100% O2 N/A 445 536 402 7 0.35

Point Loma WWTF N/A N/A 254 332 295 94 0.20

Sacramento Regional WWTF Clarification Membrane Filtration 228 250 280 10 0.29

OCSD WWTP No. 2 Clarification N/A 209 232 260 48 0.21

San Jose/Santa Clara WPCP Activated Sludge

(Activated Bio-)

Filter 198 231 387 4 0.41

OCSD WRP No. 1 Clarification N/A 122 124 260 48 0.21

San Jose Creek WRP Activated Sludge

Biologic

Denitrification 115 145 287 3 0.50

East Bay MUD Main WWTP

Activated Sludge +

100% O2 N/A 111 166 380 18 0.36

Southeast WPCP Clarification N/A 111 117 300 30 0.25

Fresno-Clovis Regional WRF

Activated Sludge +

Trickling Filter Activated Sludge 104 111 300 20 0.28

D.C. Tillman WRP Activated Sludge Chem. Addition 81.5 88.4 365 3 0.45

Stockton Regional WWCF Trickling Filter

(Activated Bio-)

Filter 76.0 76.0 245 2 0.29

Central Contra Costa WWTF Clarification N/A 68.2 75.2 194 7 0.30

MEXICALI WWTF Activated Sludge N/A 62.2 34.5 203 7 0.23

TIJUANA WWTF N/A N/A 55.3 55.3 203 7 0.30

IEUA Regional Plant No.1 Activated Sludge

Biologic

Denitrification 53.6 60.8 400 2 0.65

Riverside Regional WQCP Pond + Clarification Lagoon 46.3 55.3 288 4 0.42

Los Coyotes WRP Activated Sludge

Biologic


Alvarado WWTF

Activated Sludge +

Clarification N/A 41.4 45.6 203 7 0.32

North City WRP Clarification

(Activated Bio-)

Filter 39.4 41.4 203 7 0.31

San Bernardino WRP

Activated Sludge +

Clarification

Biologic


Encina WPCF Clarification N/A 36.2 49.7 253 8 0.38

Palo Alto Regional WQCP Activated Sludge

(Activated Bio-)

Filter 35.9 47.0 263 2 0.50

Modesto WWTF Clarification Biologic Nitrification 35.6 35.6 203 7 0.37

SOCWA WWTF

Activated Sludge +


Oxnard WWTP Activated Sludge N/A 30.9 43.8 203 7 0.36

MRWCPA WWTF

Trickling Filter +


S BAYSIDE WWTP

Activated Sludge +

Clarification

(Activated Bio-)

Filter 29.0 33.2 203 7 0.34

SUNNYVALE WWTF Pond Oxidation Ditch 28.9 33.1 203 7 0.34

Long Beach WRP Activated Sludge

Biologic


Oceanside WPCP N/A N/A 24.9 30.4 203 7 0.35

Fairfield-Suisun WWTP Activated Sludge

(Activated Bio-)

Filter 24.2 31.1 203 7 0.36

Laguna Wastewater Treatment Plant Activated Sludge

Activated Carbon +

UV 24.2 29.4 203 7 0.35

Bakersfield WWTP #2

Trickling Filter +


Oro Loma WWTF

Activated Sludge +


Hale Avenue RRF Sedimentation Chem. Addition 21.6 24.2 203 7 0.34

SANTA CRUZ WWTF

Trickling Filter +


NAPA SANIT. DIST WWRF Activated Sludge

(Activated Bio-)

Filter 20.7 21.7 203 7 0.33

L.A.-Glendale WRP Clarification Chem. Addition 20.7 20.7 203 7 0.33

Delta Diablo Sanitation Dist. WWTF Activated Sludge

Actiflo (chem.prec.

a.o.) 19.6 22.8 203 7 0.35

Valencia WRP Activated Sludge

Biologic


48

Hayward WPCF

Trickling Filter +


Michelson WRP Activated Sludge N/A 18.7 20.7 203 7 0.35

Lancaster WRP Activated Sludge

(Activated Bio-)

Filter 18.2 22.1 203 7 0.36

VSFCD WWTF

Trickling Filter +


San Mateo WWTF

Activated Sludge +


Visalia WWTP

Activated Sludge +

Trickling Filter N/A 16.6 22.9 203 7 0.39

ANAHEIM FOREBAY WWRF Activated Sludge N/A 16.4 16.4 203 7 0.34

Temecula Valley Regional WRF Activated Sludge Chem. Addition 15.9 16.8 203 7 0.34

Bakersfield WWTP #3

Trickling Filter +


Perris Valley Regional WRF Activated Sludge Chem. Addition 15.5 15.3 203 7 0.34

SO SF-SAN BRUNO WWTF Activated Sludge N/A 15.2 18.0 203 7 0.36

Latham WWTP Activated Sludge N/A 15.1 18.0 203 7 0.37

Dry Creek WWTP

Trickling Filter +

Clarification Chem. Addition 14.9 25.2 203 7 0.31

Victor Valley Regional WWRP

Activated Sludge +

Clarification Chem. Addition 14.8 15.2 203 7 0.34

IEUA Regional Plant No.5 Clarification

(Activated Bio-)

Filter 14.5 20.7 203 7 0.40

Hill Canyon WWTP Activated Sludge

(Activated Bio-)

Filter 14.2 16.6 203 7 0.36

Moreno Valley Regional WRF Activated Sludge Phospor Removal 14.1 16.6 203 7 0.37

Ventura Water Reclamation Facility Activated Sludge

Biologic


Burbank WRP Activated Sludge N/A 13.8 15.2 203 7 0.36

Dublin-San Ramon WWTF Activated Sludge Extended Aeration 13.7 22.8 203 7 0.43

San Luis Rey WWTP

Activated Sludge +


Tapia WRF Activated Sludge Chem. Addition 13.1 22.1 203 7 0.43

Palmdale WRP Activated Sludge

(Activated Bio-)

Filter 12.7 20.7 203 7 0.43

Corona WWTF #1 Clarification

(Activated Bio-)

Filter 12.4 20.0 203 7 0.42

Simi Valley WWTP Activated Sludge

(Activated Bio-)

Filter 12.4 17.3 203 7 0.40

Pomona WRP Activated Sludge

Biologic


SANTA BARBARA WWTF Clarification N/A 12.2 15.2 203 7 0.38

San Jacinto Regional WRF N/A N/A 12.0 15.3 203 7 0.39

IEUA Carbon Canyon WRF Clarification

(Activated Bio-)

Filter 12.0 14.1 203 7 0.37

South Bay WRP Clarification

(Activated Bio-)

Filter 11.7 20.7 203 7 0.44

PALM SPRINGS WWRF Trickling Filter N/A 11.5 15.1 203 7 0.28

Whittier Narrows WRP Activated Sludge

Biologic


SAN PABLO WWTF

Activated Sludge +


INDUSTRIAL SHORE SUB FAC Activated Sludge N/A 10.3 17.4 203 7 0.44

Rialto WWTP Activated Sludge Equalization 10.2 14.8 203 7 0.41

Pleasant Grove WWTP Clarification N/A 9.7 16.6 203 7 0.45

RICHMOND WWTF

Activated Sludge +


TURLOCK WWTF Activated Sludge Biologic Nitrification 7.97 20.45 203 7 0.65

49

APPENDIX B: WASTEWATER SCENARIOS CALIFORNIA

SS CT EG SS CT EG

2005

0.2 1126 1228 1438 1603 1270 1899 2394

0.3 1689 1843 2157 2404 1905 2848 3590

0.4 2252 2457 2876 3206 2541 3798 4787

0.5 2815 3071 3595 4007 3176 4747 5984

0.6 3378 3685 4314 4809 3811 5696 7181

Year and ScenarioEnergy

Intensity

(kWh m-3)

Electricity Use in Californian Wastewater Industry (GWh)

20502020

Electricity use of the Californian wastewater sector according to urban water use developments from the most recent State Water Plan ([DWR], 2009) and a range of possible average energy intensities.

50

APPENDIX C: DATA TABLES EMERGING TECHNOLOGIES

Units NotesNovel Sludge Dewatering Materials

WW-JW1

Improve dewatering efficiency by nanoscale particles

Market Information:

Industries NAICS 22132End-use(s)Energy types

Market segment2020 basecase GWh Estimate from thesis Slaa 2011Reference technology

DescriptionThroughput or annual operating hours hours Assuming 90% uptime

Electricity use GWh Water Environment Federation 2009Fuel use MBtu

Primary Energy use MBtuNew Measure Information:

DescriptionElectricity use GWh 30% reductionFuel use MBtu

Primary Energy use MBtuCurrent status

Date of commercializationEstimated average measure lifetime YearsSavings Information:

Electricity savings kWh/% 21.08 30%Fuel savings MBtu/% 0.00 0%

Primary energy savings MBtu/% 0.18 30%Penetration rate

Feasible applications % Larger plants

Other key assumptions for savings

Electricity savings potential in 2020 GWhFuel savings potential in 2020 TBtu Primary energy savings potential in 2020 TBtu Cost Effectiveness

Investment cost $

Type of costChange in annual costs (O&M/other benefits) $ Dependent on nano additive costs

Cost of conserved energy (electricity) $/kWhCost of conserved energy (fuel) $/MbtuCost of conserved energy (primary energy) $/Mbtu

Simple payback period YearsInternal rate of return %Key non energy factors

Productivity benefits

Product quality benefits Higher sludge thermal contentEnvironmental benefits Decrease sludge transportOther benefits

Current promotional activity H,M,LEvaluation

Major market barriers

Need for demonstration, requires sub optimum polymer

dose

Likelihood of success H,M,LRecommended next steps

Data quality assessment E,G,F,PSources:

2020 basecase Slaa 2011

Basecase energy use Water Environment Federation 2009New Measure energy savings Grant Proposal (Rajagopalan 2009)

Lifetime Author's EstimateFeasible applications EPA 2008

CostsKey non energy factors Grant Proposal (Rajagopalan 2009)Principal contacts

Additional notes and sources

Technical

LowSuccesful demonstration

Fair

SomewhatSomewhat

Low

N/AN/A

N/A

N/AN/AN/A

210

0.18

N/A

30

Low

80%

0.00

0.42Field Test

2012

0.00

0.597

Sludge Dewatering aided by added chemicals and nanoscale particles49.18

3595

Sludge Dewatering aided by added chemicals7884

70

Wastewater treatmentMotor and Drives

Electricity

Retrofit

51

Units NotesHigh efficient wastewater pond mixer

WW-JW2

Improved design in wastewater pond mixer results in better aeration and mixer with lower electricity costs

Market Information:


Market segment2020 basecase MGDReference technology

DescriptionThroughput or annual operating hours MGD

Electricity use kWhFuel use MBtu


DescriptionElectricity use kWh

Fuel use MBtuPrimary Energy use MBtuCurrent status

Date of commercialization For freshwater stratification applicationsEstimated average measure lifetime YearsSavings Information:

Electricity savings kWh/% 500 50%

Fuel savings MBtu/% 0 0%Primary energy savings MBtu/% 4 50%

Penetration rateFeasible applications %Other key assumptions for savings

Electricity savings potential in 2020 GWhFuel savings potential in 2020 TBtu

Primary energy savings potential in 2020 TBtu Cost Effectiveness

Investment cost $Type of costChange in annual costs (O&M/other benefits) $

Cost of conserved energy (electricity) $/kWhCost of conserved energy (fuel) $/Mbtu

Cost of conserved energy (primary energy) $/MbtuSimple payback period Years

Internal rate of return %Key non energy factors

Productivity benefitsProduct quality benefits Stratified effluentEnvironmental benefits

Other benefits Less noiseCurrent promotional activity H,M,LEvaluation




2020 basecase Nelson 2005

Basecase energy use EPA 1983New Measure energy savings Proposal (Oppenheimer 2009)

Lifetime Author's EstimateFeasible applications Nelson 2005

Costs Proposal (Oppenheimer 2009)Key non energy factors Paxwater.com; Proposal (Oppenheimer 2009)Principal contacts


Wastewater treatmentUtilities

Electricity

Replace on failure400

Energy use of aerated pond by surface or aspirating aerator1

1,0000

9

Energy use of new PAX water mixer with improved design500

0

4Commercialized

200720

Low40%

290

0.25

10000Full

21900200

55090.5

219%

NoneSomewhat

None

SomewhatHigh

Limited market

MediumDemonstration no side-effects

Fair

52

Units NotesMembrane Filtration for Wastewater Reuse

WW-JW3

Micro-/nanofiltration of wastewater effluent to use for cooling tower operation

Market Information:


Market segment2020 basecase MG 10% total water use in food processingReference technology

DescriptionThroughput or annual operating hours MG




Fuel use MBtuPrimary Energy use MBtuCurrent status For other applications, proposal estimate: 2015

Date of commercialization Estimated average measure lifetime Years Author's EstimateSavings Information:

Electricity savings kWh/% 37,000 82%


Penetration rateFeasible applications % Equivalent cooling (34 F) estimated in 50% plants




Investment cost $Type of costChange in annual costs (O&M/other benefits) $ Savings water and wastewater costs




Productivity benefitsProduct quality benefitsEnvironmental benefits Reduces wastewater load and discharge

Other benefitsCurrent promotional activity H,M,LEvaluation




2020 basecase Gleick 2003

Basecase energy use CPUC 2010New Measure energy savings CPUC 2010

Lifetime Author's EstimateFeasible applications Author's Estimate

Costs French 2010Key non energy factors French 2010, Proposal (Hill 2009)Principal contacts


Low

Significant

None

(Energy) costs + fouling

LowSuccesful demonstration

Good

None

18166.7

8%

None

Full

60000N/AN/A

52.7

00.45

400000

20

Low50%

068

Commercialized

N/A

0

384

Using membrane filtered wastewater for cooling tower operation

8,000

2851

Using fresh water for cooling tower operation10

45,000

Food ProcessingProcess Cooling

Electricity

Retrofit

53

Units NotesBiodiesel Wastewater Reuse

WW-JW-4

Treating biodiesel wastewater for reuse in washing step

Market Information:


Market segment2020 basecase MG Orta 2010 (doubling of current production in CA)Reference technology

DescriptionThroughput or annual operating hours MG

Electricity use kWh Park 2010Fuel use MBtu


DescriptionElectricity use kWh 85% reduction - costs RO, ultrafiltration

Fuel use MBtu Heating costs?

Primary Energy use MBtuCurrent status

Date of commercializationEstimated average measure lifetime YearsSavings Information:










Productivity benefitsProduct quality benefits Increases purity methanol wastestreamEnvironmental benefits Embedded energy savings in water chain

Other benefits Might be applicable to other water reuse opportunitiesCurrent promotional activity H,M,LEvaluation




2020 basecase Orta 2010

Basecase energy use Park 2010New Measure energy savings Park 2010

Lifetime Author's EstimateFeasible applications Orta 2010

CostsKey non energy factors Orta 2010, Proposal (Guay 2009)Principal contacts


Biodiesel productionUtilities

Electricity

New100

Single use of water for washing1

4,5000

38

Treating wastewater with filtration, RO and distillation before leading it back to washing process3045

0

26Field Test

201330

Low100%

0.150

0.0012

N/AN/A

N/AN/AN/A

Significant

SomewhatLow

N/A

N/AN/A

SomeNone

Lack of biodiesel growth

LowShow energy improvement

Poor

54

Units NotesAdvanced Wastewater Treatment Technologies

WW-JW5

Addition of ozone to flume and rinse water decreases microbial growth and energy use in water chilling

Market Information:


Market segment2020 basecase GWh Shoemaker 2006Reference technology

DescriptionThroughput or annual operating hours MG 10% of sector total (Gleick 2003)

Electricity use GWhFuel use TBtu

Primary Energy use TBtu New Measure Information:

DescriptionElectricity use GWh 50% reduction (1:1 water use : chilling energy use)

Fuel use TBtu Primary Energy use TBtu Current status

Date of commercialization Author's EstimateEstimated average measure lifetime Years Author's EstimateSavings Information:

Electricity savings GWh/% 6.42 0%

Fuel savings TBtu/% 0.00 0%Primary energy savings TBtu/% 0.05 50%

Penetration rateFeasible applications % Applicable to most plants




Investment cost $ Demonstration in salad producing industry, StricklandType of costChange in annual costs (O&M/other benefits) $




Productivity benefits Less water per product, less maintenanceProduct quality benefits Fewer chlorine residuesEnvironmental benefits Embedded energy savings in water chain

Other benefits Lower health-risk employeesCurrent promotional activity H,M,LEvaluation

Major market barriers Grant Proposal (Biswas 2009)

Likelihood of success H,M,L Significant benefitsRecommended next steps On energy savings


2020 basecase Shoemaker 2006

Basecase energy use Gleick 2003, Grant Proposal (Biswas 2009)New Measure energy savings Grant Proposal (Biswas 2009)

Lifetime Author's EstimateFeasible applications Grant Proposal (Biswas 2009)

Costs Strickland 2006Key non energy factors Grant Proposal (Biswas 2009)Principal contacts


Lack of understanding

MediumMore research

Fair

SomewhatSignificant

SomewhatLow

26087911.8

55%

Significant

Full

112300N/AN/A

60

0.055

200000

30

Low90%

0.000.05

Field Test

2012

0.00

0.11

Addition of ozone to flume and rinse water to increase time water can be used6

800

Chlorination of flume and rinse water2851

13

Fruit/vegetable processingProcess Cooling

Electricity

Retrofit

55

Units NotesCASCADE system for enhanced biogas generation

WW-JW6

Improving bacteria mix to enhance biogas generation in sludge generation, combined with biogas reactor for onsite electricity generation

Market Information:


Market segment2020 basecase GWh Estimate from thesis Slaa 2011Reference technology

DescriptionThroughput or annual operating hours MGD




Fuel use MBtuPrimary Energy use MBtuCurrent status

Date of commercialization EstimatedEstimated average measure lifetime YearsSavings Information:










Productivity benefits More rapid biogas generationProduct quality benefits Higher energy densityEnvironmental benefits Lower sludge volume

Other benefitsCurrent promotional activity H,M,LEvaluation




2020 basecase Klein 2005

Basecase energy use Water Environment Federation 2009New Measure energy savings Proposal (Zhou 2009)

Lifetime Author's EstimateFeasible applications EPA 2008

Costs Proposal (Zhou 2009)Key non energy factors Proposal (Zhou 2009)Principal contacts


Wastewater treatmentUtilities

Electricity

Retrofit3595

Activated sludge wastewater treatment plant without digestion1

2,0000

17

Activated sludge wastewater treatment plant with CASCADE bioreactor1400

0

12Field test

201220

Low80%

8630

7.36

780000Full

2600001300

0

322073.0

31%

SignificantSomewhatSignificant

NoneLow

No large scale results

MediumLarge field demonstration

Fair

56

Units NotesSolar dish/engine for energy storage

WW-JW7

Using solar energy to offset the peak energy demand of a wastewater plant

Market Information:

Industries NAICS 22132End-use(s) UtilitiesEnergy types Electricity

Market segment Retrofit2020 basecase GWh 3595 Estimate from thesis Slaa 2011Reference technology

Description Wastewater treatment plant 4 MGDThroughput or annual operating hours MGD 4

Electricity use kWh 8,000Fuel use MBtu 0

Primary Energy use MBtu 68New Measure Information:

Description Wastewater treatment plant 4 MGD with 1 MW Solar power generationElectricity use kWh 6000

Fuel use MBtu 0Primary Energy use MBtu 51Current status Commercialized

Date of commercialization 2010Estimated average measure lifetime Years 25 thepowerdish.comSavings Information:



Penetration rate LowFeasible applications % 25%Other key assumptions for savings

Electricity savings potential in 2020 GWh 225Fuel savings potential in 2020 TBtu 0

Primary energy savings potential in 2020 TBtu 1.92Cost Effectiveness

Investment cost $ 9000000Type of cost FullChange in annual costs (O&M/other benefits) $ 87600Cost of conserved energy (electricity) $/kWh 4500Cost of conserved energy (fuel) $/Mbtu 0

Cost of conserved energy (primary energy) $/Mbtu 28915Simple payback period Years 102.7

Internal rate of return % N/AKey non energy factors

Productivity benefits NoneProduct quality benefits NoneEnvironmental benefits Significant No greenhouse gase emissions

Other benefits Somewhat Low maintenance costs, peak shavingCurrent promotional activity H,M,L LowEvaluation

Major market barriers Not yet profitable

Likelihood of success H,M,L MediumRecommended next steps Reduce costs

Data quality assessment E,G,F,P FairSources:


Basecase energy use Water Environment Federation 2009New Measure energy savings Proposal (Loge 2009)

Lifetime thepowerdish.comFeasible applications thepowerdish.com

Costs Proposal (Loge 2009)Key non energy factors Proposal (Loge 2009)Principal contacts


Wastewater treatment

57

Units NotesVanadium Redox Flow Batteries

WW-JW8

Using new battery technology to store and mitigate energy use of wastewater treatment plants

Market Information:

Industries NAICS 22132End-use(s) UtilitiesEnergy types Electricity

Market segment Retrofit2020 basecase GWh 3595 Estimate from thesis Slaa 2011Reference technology

Description Wastewater treatment plantThroughput or annual operating hours MGD 1

Electricity use kWh 2,000Fuel use MBtu 0

Primary Energy use MBtu 17New Measure Information:

Description Wastewater treatment plant with VRFB systemElectricity use kWh 1500

Fuel use MBtu 0Primary Energy use MBtu 13Current status Commercialized

Date of commercialization 2010Estimated average measure lifetime Years 11Savings Information:



Penetration rate LowFeasible applications % 10% Estimated installations with digested gas & fuel cells


Electricity savings potential in 2020 GWh 90Fuel savings potential in 2020 TBtu 0

Primary energy savings potential in 2020 TBtu 0.77Cost Effectiveness

Investment cost $ 2500000Type of cost FullChange in annual costs (O&M/other benefits) $ 125000Cost of conserved energy (electricity) $/kWh 5000Cost of conserved energy (fuel) $/Mbtu 0

Cost of conserved energy (primary energy) $/Mbtu 47102Simple payback period Years 20.0

Internal rate of return % -11%Key non energy factors

Productivity benefits NoneProduct quality benefits NoneEnvironmental benefits Somewhat Might enable grid integration renewables

Other benefits Significant Demand response, load managementCurrent promotional activity H,M,L MediumEvaluation

Major market barriers Costs

Likelihood of success H,M,L MediumRecommended next steps Diversification

Data quality assessment E,G,F,P FairSources:


Basecase energy use Water Environment Federation 2009New Measure energy savings Proposal (Toca 2009)

Lifetime Blanc 2009Feasible applications EPA 2008

Costs Proposal (Toca 2009)Key non energy factors Proposal (Toca 2009)Principal contacts


Wastewater treatment

58

APPENDIX D: ENERGY USE DUTCH WASTEWATER SECTOR

1993 1998 2003 2008

Electricity GWh 427 511 550 583

Cogeneration GWh 100 140 149 170

Total electricity GWh 527 629 682 721

GJ 1,897,200 2,264,400 2,455,200 2,595,600

Natural gas use 1000 m3 10935 29563 32703 30193

GJ 424,278 1,147,044 1,268,876 1,171,488

Share aeration

total electricity % 68 63 62 60

Total WW

influent million m3

1839 2145 1757 1928

electricity kWh m-3

0.28657 0.29324 0.38816 0.37396

gas (m3 m

-3) 0.006 0.014 0.019 0.016

Year

Wastewater sector The Netherlands

Documents

University of Groningen Emerging energy-efficient ... · The eight emerging technologies were estimated to have the potential to save close to 1300 GWh, mainly due to the software