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Potential research topics on the Biosand Filter (BSF) and other Water, Sanitation and Hygiene issues, according to the

field experience of CAWST and its network of project implementing organizations Updated: April 2014

Please contact CAWST (tngai@cawst.org) if you decide to research a topic on this list. Please also keep us updated on your research status and findings. We want to share your findings with all of our project partners worldwide. We can also provide technical support or advice.

Summary list of topics 1. Biosand filter (BSF) diffuser basin construction 2. Biosand filter longevity 3. Built-in safe storage for the BSF 4. Side wall channeling in a BSF 5. Suitable sources of sand for use in a BSF 6. Organic contamination of the fine sand media 7. Sand preparation for the BSF 8. Alternative media for gravel in BSF 9. Ripening time for the BSF after installation or cleaning 10. When is the BSF filtered water safe to drink? 11. Acceptable influent water sources for the BSF 12. Chlorinated tap water as a water source for the BSF 13. Variable raw water quality on BSF performance 14. Low nutrient raw (influent) water for the BSF 15. Biolayer characterization 16. Microbes living in the lower part of the sand layer 17. Bacterial regrowth in BSF filtered water 18. Removal of inorganic contaminants from BSF 19. Removal of organic contaminants from BSF 20. Metal leaching from sand

21. Flow control of BSF 22. Dosing volume and frequent for the biosand filter 23. Multi-stage BSF 24. Troubleshooting odour problem of the BSF 25. Troubleshooting turbidity problem of the BSF 26. Negative microbial removal efficiency of the BSF 27. User practice impact on BSF effectiveness 28. BSF in cold climates 29. Impact of raw water quality on Kanchan Arsenic Filter (KAF) 30. Enhancing zero valent iron for arsenic removal of KAF 31. Effect of iron nails washing on KAF performance 32. Evaluation of field test kit performance 33. Measurement of training effectiveness 34. Determinant of training effectiveness 35. Evaluation of education materials 36. Retention of knowledge post-training 37. Quantifying outcomes and impacts of household water treatment

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Number Research Topic Objectives Methodology/Descriptions Importance*

1 Biosand filter (BSF) diffuser basin construction

Design a diffuser basin that is low cost and easily manufactured locally

The concrete biosand filter originally designed to use a diffuser plate to break the force of incoming water, to protect the biofilm layer beneath, and to distribute the water evenly. However, recent field experiences found that many plates are either broken or improperly placed, reducing filter performance.

This research will design a low cost diffuser basin that can be easily manufactured or constructed locally.

The diffuser basin should fit inside the concrete BSF version 10. Since many BSF projects tend to start with a small pilot of 10-20 filters, the

diffuser basin construction should be low cost even for small production volume.

Moderate

2 Biosand filter longevity

Determine the durability of the concrete BSF filter body, the diffuser basin, and of the filtration media

In some BSF projects, the concrete filter body cracks and breaks within 1 to 2 years, while in some other projects, the filter body continues to be functional after 10 or more years. What is the realistic long-term longevity of the filter body?

What is the realistic long-term longevity of the diffuser plate, diffuser basin, and the filtration media?

What causes pre-mature breakage of the filter body? How to extend filter durability?

Low

3 Built-in safe storage for the biosand filter

Redesign the construction of the concrete BSF to incorporate a built-in safe storage container

The current design of the concrete biosand filter does not contain a safe storage container for the filtered water. Some households use dirty containers to collect the filtered water, or use containers without lids. This can recontaminate the filtered water.

The research will redesign the construction of the concrete BSF to incorporate a built-in safe storage container

The ideal container should be low-cost, has a lid, is slightly elevated above the ground, and has a tap to withdraw water. The container should also allow easy dosing of disinfectant such as chlorine, to provide a multi-barrier approach to water treatment.

Low

4 Side wall channelling in a BSF

Investigate the potential for short-circuiting of water in the fine sand layer through side wall channelling in a BSF

Does the water go evenly through the sand media without channelling along the sidewalls?

Is there a minimum width or diameter that the BSF should meet? Does the side wall friction factor make a difference? What are the differences between the plastic and cement filter boxes in

relation to side wall channelling?

Low

* Importance according to project implementing organizations

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5 Suitable sources of sand for use in a BSF

Evaluate the suitability and effectiveness of various sources of fine sand to be used in a BSF

There are many different types of sand, including river sand, ocean beach sand, volcanic sand, sand from crushed rock and sand from mining waste.

Evaluate different sources of sand media in the biosand filter to determine 1) suitability as a filter media, 2) effectiveness, 3) biolayer ripening, and 4) different sand preparation requirements.

Can organics/salts associated with the sand be tolerated or eliminated?

Moderate

6 Organic contamination of the fine sand media

Evaluate whether organic contamination of the fine sand media may cause an increase in bacteria in the BSF effluent

CAWST recommends choosing sand media from clean sources such as crushed rocks, and avoid (if possible) sand from river banks because of potential animal/human contamination.

Does organic contamination of the fine sand media act as a source of food for bacteria to grow/live in the fine sand layer? For how long and to what extent? If so, how should the sand media be prepared to prevent or reduce this?

High

7 Sand preparation for the biosand filter (BSF)

Compare and evaluate the best method to prepare fine sand media to maximize microbial removal performance of a BSF

Using the same sand source and same raw water, evaluate whether sand preparation has an effect on filter start-up microbial removal efficiency.

Understand what is/are the best sand preparation technique(s). Compare the performance of BSFs with sand media that is i) washed with

water, ii) washed with dilute chlorine, iii) soaked in strong chlorine, iv) placed under strong sunlight for a day, v) cooked to high temperature in a kiln or oven.

High

8 Alternative media for gravel in BSF

Investigate the possibility of alternative media to replace gravel in a BSF

Due to geological reasons, it is very difficult to find gravel or stones in certain countries, such as Bangladesh. Most of the country is situated on a delta. The ground is composed of primary sand and clay.

The lack of gravel is an issue in the construction of BSF. Gravel is needed to make the filter body and needed as the underlying drainage media.

Brick chips have been suggested as an alternative. Does it work?

Low

9 Ripening time for the BSF after installation or cleaning

Investigate how to quicken the establishment of the biolayer in the BSF

The biolayer takes some time to be developed after new BSF installation. The biolayer is disturbed and partially damaged during filter cleaning. How long does it take to ripen and re-establish the biolayer? Plot microbial removal over time after BSF installation and cleaning. What influences the rate of re-establishment? Is it related to raw water

quality, usage level, temperature?

High

10 When is the BSF filtered water safe to drink?

Investigate when is the BSF filtered water safe to drink

Because time is needed for the biofilm to ripen or re-establish after installation or cleaning, when is the filtered water safe to drink?

High

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11 Acceptable influent water sources for the BSF

Compile latest knowledge on acceptable range of influent water for the BSF

There have been a number of studies on the performance of the BSF under different water quality conditions.

What water sources, measured in terms of water quality parameters, are suitable for treatment in the BSF?

Moderate

12 Chlorinated tap water as a water source for the BSF

Determine the applicability and performance of BSF when chlorinated tap water is used

Even though chlorinated water can kill the biolayer in the BSF, the BSF may provide protection from other contaminants such as protozoa (Giardia lamblia and Cryptosporidium) through physical straining.

Is using chlorinated water as the raw water supply for the filter totally unsuitable?

Low

13 Variable raw water quality on BSF performance

Investigate how the BSF microbial removal performance is affected by variation in influent water quality

Many of the BSFs in use today are fed with surface water such as lakes, ponds, rivers, and canals. The water quality can change significantly day-to-day, especially after rainfall.

How does the variation in raw water quality affect the BSF microbial removal performance?

Plot the raw water microbial count versus effluent microbial count over time to assess if clear trends can be found.

Moderate

14 Low nutrient raw (influent) water for the BSF

Determine the applicability and performance of BSF when low nutrient raw water is used

Proper ripening (or development) of the biolayer in a BSF is essential for bacteria and virus removal.

What type of nutrients is essential to the development of the biolayer? How to measure the nutrient level?

Do low nutrient raw water sources such as deep wells and rainwater affect or delay the development of the biolayer and reduce the effectiveness of the filter?

Low

15 Biolayer characterization

Characterize the biolayer to evaluate how to enhance biolayer activities and removal efficiency

What is in the biolayer? What are the constituents? What is the best water to use to form a good biolayer? Photograph the biofilm development and label the relevant organisms.

Moderate

16 Microbes living in the lower part of the sand layer

Investigate how to eliminate pathogens living in the lower part of the sand layer

Do pathogens live in the fine sand layer of the BSF? What is their distribution profile from top to bottom of the sand layer? What do they need for survival? Aerobic or anaerobic? Organic matter as

food? How can they be eliminated to ensure that they are not flushed out together

with the filtered water, such that the filtered water is safe?

Low

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17 Bacterial regrowth in BSF filtered water

Determine how the filtered water from a BSF should be stored to prevent/reduce re-contamination

Do bacteria or other contaminants in the storage water increase or decrease over time?

How is the recontamination level influenced by temperature, types of storage container, hygiene practices, or water quality? Determine optimal dosing for post-filtration chlorine disinfectant.

Low

18 Removal of inorganic contaminants from BSF

Evaluate the effectiveness of BSF in removing various types of inorganic contaminants such as manganese and fluoride

In some parts of the world, the ground water can be contaminated by heavy metals above the WHO guidelines

To what extent can the BSF remove these contaminants? The use of zero valent iron for pollution control (e.g. underground reactive

barrier) is well known. Can the principle be applied to HWT? What other simple and inexpensive changes can be made to the BSF to

improve removal effectiveness?

High

19 Removal of organic contaminants from BSF

Evaluate the effectiveness of BSF in removing various types of organic contaminants such as pesticides and herbicides

Some surface water sources are contaminated by pesticides and herbicides. To what extent can the BSF remove these contaminants? The use of zero valent iron for pollution control (e.g. underground reactive

barrier) is well known. Can the principle be applied to HWT? What other simple and inexpensive changes can be made to the BSF to

improve removal effectiveness?

High

20 Metal leaching from sand

Investigate the potential of leaching of the heavy metal previously adsorbed on sand surface

BSF is able to remove some heavy metal from the raw water because heavy metal can be adsorbed on the sand. E.g. iron oxide naturally found on sand surface can adsorb arsenic.

If raw water source is changed, e.g. switching from high pH ground water to low pH rainwater, will metal leach?

Low

21 Flow control of the biosand filter

Compare the performance of BSF in which the flow rate is controlled by the sand conductivity versus by a mechanical flow control device

In a regular BSF, the flow rate is determined by the sand size and hydraulic conductivity.

An alternative is to restrict the flow by a mechanical flow controlling device, such as an orifice at the outlet tube.

What are the effects of using a flow control device versus the flow controlled by the hydraulic conductivity of the sand media?

How do the two options compare in terms of removal effectiveness, sand media sizing, and residence time in the filter?

Low

22 Dosing volume and frequent for the biosand filter

Determine the range of dosing volume and frequency to a BSF that can still provide adequate microbial removal effectiveness

Find out what is the minimum and maximum use that the BSF can tolerate while still providing adequate removal effectiveness.

What is the minimum and maximum pause period for effective microbial die off?

Does the frequency of use depend on temperate or water quality? How many people can one BSF reliably serve?

Moderate

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23 Multi-stage biosand filters

Evaluate the potential of enhancing microbial removal of BSF by operating two or more BSFs in series, or by filtering the water twice

Biosand filters operated in series with the water from first filter flowing into the second filter (and then possibly a third filter), or filter the water twice.

How do these configurations affect the removal effectiveness? Would this allow smaller filters, such as 20 litre bucket filters, to be used and

still achieve the same results as a single large biosand filter?

Low

24 Troubleshooting odour problem of BSF

Determine the cause of odour problem of the BSF

Although the occurrence is rare, the BSF can sometimes produce water that has odour problems.

What is causing the odour problem? Is it due to sand sourcing, the type of water filtered, the usage (or lack of) procedure, microbial activities, or other reasons?

How to correct the problem?

High

25 Troubleshooting turbidity problem of BSF

Determine the cause of turbidity problem of the BSF

Although the occurrence is rare, the BSF can sometimes produce water that has higher turbidity than influent water.

In addition, in some parts of northern Ghana, eastern Nepal and southern India, the BSF is unable to reduce the turbidity of the water to less than 5 NTU. The treated water still appears cloudy.

What is causing the turbidity problem? What is that cloudiness? Is it fine clay particles, dissolved colour, charged

particles? How to correct the problem?

High

26 Negative microbial removal efficiency of BSF

Investigate why the BSF effluent occasionally contains higher counts of microbial indicator organisms than influent raw water

Occasionally, when testing BSF treatment performance, the effluent water contains higher counts of microbial indicator organisms than the influent raw water. Several hypotheses have been developed but need to be tested.

Is it because of microbial growth within the filter? If so, how can it be prevented?

Is it because of the plug flow regime of the BSF, the effluent water is actually the raw water from the previous batch? Filter performance should be tested by comparing previous batch raw water with the current filtered water?

Is it because of re-contamination at the pipe, spout, or storage container? Is it because the types of microbial indicator organisms are different in the

raw and effluent water, so that the testing technique is ineffective?

High

27 User practice impact on BSF effectiveness

Investigate the effect of user practice on BSF performance

The technical performance of the BSF can be influenced by many factors, from technology design to manufacturing quality to operation and maintenance.

How importance is proper operation and maintenance? How O&M errors are commonly made by the users, and how do they affect

performance? How to avoid/minimize the errors?

Moderate

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28 BSF in cold climates Investigate applicability of the BSF in cold climates

What are the challenges in constructing, installing, operating and maintaining the BSF in cold climates or near freezing temperatures?

For example, would the concrete cure properly and would the biofilm die if the water freezes?

Low

29 Impact of raw water quality on arsenic removal of Kanchan Arsenic Filter

Recommend the operating ranges/limits for optimal operation

The Kanchan Arsenic Filter (KAF) is a modified BSF with an additional tray of rusty iron nails for arsenic removal.

Arsenic removal efficiency is believed to be dependent on the extent of iron rusting, contact time with iron, and available arsenic adsorption sites on iron.

Certain chemicals in the raw water may negatively or positively influence the process of arsenic adsorption and removal. Examples include pH, phosphate, manganese, hardness, alkalinity and silica.

Evaluate what and how raw water quality can influence the arsenic removal effectiveness of KAF.

High

30 Enhancing zero valent iron for arsenic removal of KAF

Compare the effectiveness of various types of zero valent iron for arsenic removal when incorporated in a BSF/KAF

While zero valent iron is known for its ability to adsorb arsenic (and many other contaminants), there are many forms and shapes of zero valent iron, with different properties and reactivity. Examples include different types of iron nails, steel wool and iron particles.

Which of these are more effective for arsenic removal when incorporated in a BSF/KAF?

Which of these are more practical? How can the iron reactivity or longevity be enhanced? Should the iron be mixed with other substances to increase rusting?

High

31 Effect of iron nails washing on KAF performance

Explore the potential of enhancing iron corrosion and arsenic removal in a KAF by washing the iron nails

Iron nails in the KAF may lose their arsenic removal if the adsorption sites are exhausted or rusting is inhibited by coating of mineral deposits.

How to increase rusting and available adsorption sites? Can washing the iron nails help? How to wash the iron nails? With water? With dilute acid (e.g. lemon juice)? How frequently should the nails be washed?

Moderate

32 Evaluation of field test kit performance

Determine the likely range of error in field test kit measurements

Compare and evaluate the reliability of field test kit results with laboratory instrument results.

Parameters may include arsenic, fluoride, pH, phosphate, nitrate, ammonia, chlorine, iron, coliforms, etc.

How much should the field kit results be trusted? Create a summary table and expected error range for each of the field-based

tests, when conducted under actual field conditions.

Low

33 Measurement of training effectiveness

Develop metrics for measuring training effectiveness

How should training in water, sanitation, and hygiene be measured? What indicators can be used to measure training effectiveness? When and how the measurements will be conducted?

Moderate

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34 Determinant of training effectiveness

Investigate the relative importance of different factors in determining the effectiveness of a training workshop

The effectiveness of training workshops to teach water and sanitation knowledge depends on a wide variety of factors, such as the characteristics of the participants, the knowledge of the trainer, the relevance of the training materials, the way the training is conducted, and others.

What is the relative importance of these factors in determining the training effectiveness?

Low

35 Evaluation of educational materials

Develop a protocol to evaluate the effectiveness of education materials

There are many types of educational materials on water, sanitation, and hygiene available. These materials are produced by various organizations, from universities to multi-lateral agencies to governments to NGOs.

How to evaluate which materials are suitable for an organization planning to implement water, sanitation, and hygiene programs?

What should be the criteria or protocol to evaluate the usefulness or effectiveness of education materials?

Moderate

36 Retention of knowledge post-training

Investigate the dilution of training and other methods of knowledge transfer and recommend how to overcome this

One way to spread the use of household water treatment in the developing world is through training and education. Often this training is passed on from organization to organization and from person to person.

How to measure knowledge retention? What is the dilution of knowledge in this process?

How, and how frequently, does the training need reinforcement/refreshing?

High

37 Quantifying outcomes and impacts of HWTS implementation

Develop a common metric to compare the impact of HWTS implementation

Different organizations use different metrics to measure their HWTS implementation impact.

Examples include number of filters distributed, number of filters in operation, number of people reached, number of litres of water treated, number of bottles of chlorine sold, and number of water-borne disease cases adverted.

Some argue that HWTS implementation is considered successful only when it targets children under 5 years whom do not have piped water supply and whom water is the dominant transmission pathway for exposure to diarrhoeagenic agents and whom will be unlikely to get improved water sources in the near future.

What are the strengths and limitations of each of these indicators? How can the different implementation results be compared?

High

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