Low-cost iron-asssisted filters for arsenic removal in Shanxi full document, figures, photos,...

WORLD WATER FORUM WATER SHOWCASE

Low-cost iron-assisted

filters for arsenic removal

from groundwater in

Shanxi province, China

RISE Tsinghua

January 2015


ABOUT US

Rural-International Student Exchange (RISE) Tsinghua is a student-based organization with a focus on rural

development projects in China. The organization is located in Beijing, China and draws upon the student body,

bringing together both international and local graduate students from Tsinghua University to work with rural

communities in China to provide local and sustainable solutions.

CONTACT US

Tsinghua University, School of Environment

Beijing, China, 100084

www.rise-thu.org

[email protected]

WATER QUALITY PROJECT DIRECT CONTACT

[email protected]

http://www.rise-thu.org/


Table of Contents ABOUT US .................................................................................................................................................................... i

1. BACKGROUND .....................................................................................................................................................1

2. THE PROBLEM AREA ............................................................................................................................................1

3. PROJECT OBJECTIVES...........................................................................................................................................3

4. LOW-COST IRON-ASSISTED FILTERS CURRENTLY AVAILABLE ..............................................................................3

4.1. The arsenic biosand filter ............................................................................................................................. 3

4.2. SONO filter ................................................................................................................................................... 4

5. PREVIOUS PROJECT IMPLEMENTATION AND PARTNERS ....................................................................................5

5.1. Ningxia ......................................................................................................................................................... 6

5.2. Gansu ........................................................................................................................................................... 7

5.3. Shanxi ........................................................................................................................................................... 8

6. PROBLEMS ENCOUNTERED AND LESSONS LEARNED ....................................................................................... 10

7. PROJECT PLAN FOR PINGYAO, SHANXI ............................................................................................................ 10

8. BASIC TESTING SET-UP ..................................................................................................................................... 11

9. REFERENCES ..................................................................................................................................................... 12


1. BACKGROUND

At the end of 2012, an estimated 280 million people in China were using unsafe drinking water (Xinhua 2014).

One of the major water quality concerns in China is arsenic contamination. Arsenic is carcinogen and excessive

exposure leads to increased risk of cancer of the skin, lungs, bladder, liver and kidney. To avoid this risk, the

World Health Organisation (WHO) recommends arsenic levels in drinking water be lower than 10µg/L. Recent

modelling revealed that around 20 million people could be exposed to water contaminated with levels of arsenic

higher than this recommended limit (Rodriguez-Lado et al. 2013). This problem is particularly serious in northern

China where people are more likely to rely on groundwater. Groundwater extracted from wells can be high in

arsenic, which leaches naturally from the Earth’s crust and can also originate from mining waste or landfill.

Most cases of arsenic poisoning (arsenicosis) in northern China have been found in Shanxi, Xinjiang and Inner

Mongolia (Zhang et al. 2012). Population density is highest in Shanxi and the province has already been the

subject of a study that found children exposed to drinking water with medium (142±106µg/L) to high

(190±183µg/L) concentrations of arsenic tended to have lower IQs than children drinking water with low arsenic

concentration (2±3µg/L) (Wang et al. 2007). The total area of Shanxi at risk of exceeding 10µg/L was estimated

to be 8100km2 in 2012 and spanned 30 counties in the province (Zhang et al. 2012).

Areas of primary concern are Datong and Jinzhong Basins, but heterogeneity of groundwater arsenic

contamination means that only part of the population living in these areas is actually exposed to high arsenic

concentrations (Wang et al. 2007). In other words, not all groundwater wells in this area are contaminated with

arsenic. Shanxi’s unique geography means that wells at a short distance from each other can have markedly

different arsenic concentrations. Therefore, while modelling and randomised testing of wells can give an

indication of high-risk areas, the actual risk of exposure faced by a population can only by determined through

individual testing of the well from which this group of people sources water.

2. THE PROBLEM AREA

RISE has worked in conjunction with students from Taiyuan University of Technology at the request of Shanxi

Department of Environmental Protection to test water samples taken from a village in Pingyao County, which is

located in the Jinzhong Basin area of Shanxi province. Around 20 households in the village were interviewed and

their water was tested for arsenic. The testing for arsenic was conducted using Palintest® Arsenator (portable

arsenic testing equipment). Results of observations, interviews and arsenic testing revealed that the village had

the following characteristics:

1. Average income was low. Pingyao County gains income from being a tourist destination, but this village

is one of the exceptions.

2. The main water source is a groundwater well. Water from the well is generally piped to the houses but

not treated.

3. Levels of arsenic are high. The Arsenator shows a ‘>>’ symbol for samples with arsenic concentrations of

over 100µg/L. Water used in each household was tested at least twice. Of around 40 tests, only 4


showed under 100µg/L. The drinking water standard for this kind of water supply in China is 50µg/L (the

drinking water standard for large water treatment plants in urban areas of China is 10µg/L). This means

the average arsenic concentration test result for the village was more than 2 times the allowed standard

and more than 10 times the WHO standard.

4. Households are unhappy with the quality of water. Of the households interviewed: (1) 95% said the

water had an odor, which worsened in summer. (2) 100% complained that the water did not taste

pleasant. (3) Many complained about the look of their water and said it contained black debris and/or

black bugs and was yellow looking (see Figure 1). Many households put a net over their tap to remove

the larger debris (see Figure 2).

5. Households show interest in having a low-cost method to reduce arsenic in drinking water. Of the

households interviewed, 95% said they would be willing to use a low-cost filter to remove arsenic. The

majority currently using bottled drinking water but complain about the expense. The minority don’t buy

it because they can’t afford it and instead drink water from the well after boiling. Those interviewed said

only a few households in the village can afford to buy a machine to purify their water as these market

for between 2000-3000yuan. Previous testing carried out by RISE in another village elsewhere revealed

that such water filters do not necessarily reduce arsenic concentration in the water.

From the above points, RISE has concluded that households in the village are highly suited to a project aimed at

disseminating low-cost filters for arsenic removal. Arsenic concentration is well over the allowed standard and

this is a significant health risk. This indicates there is real need for such a project. The residents are dissatisfied

with the quality of their water and generally feel they would prefer not to buy bottled water. This is a major

factor in the success and uptake of low-cost filters for arsenic removal.

Figure 1: Yellow looking water in Pingyao country, Shanxi.


Figure 2: Debris on net attached to water tap in Pingyao county, Shanxi.

3. PROJECT OBJECTIVES

RISE will be working with Shanxi Department of Environmental Protection and students from Taiyuan University

of Technology to test and introduce low-cost iron-assisted filters in this village. Our project has the following

aims:

1. To identify the most appropriate type of low-cost iron-assisted filter for application to this groundwater

source.

2. To teach households in the target village to build and maintain the filter.

3. To provide reliable removal of arsenic to below China’s arsenic standard for groundwater wells (50µg/L)

and preferably below the WHO standard of 10µg/L.

4. To assess the success of the project and extend it to other suitable areas of Shanxi identified as being

affected by arsenic contamination.

4. LOW-COST IRON-ASSISTED FILTERS CURRENTLY AVAILABLE

4.1. The arsenic biosand filter

The biosand filter (BSF) is a low-cost filter made of sand, gravel, a plastic or concrete container, PVC pipes and a

diffuser to break the flow of water flowing into the top. It is based on the principle of slow sand filtration and is


built to encourage the formation of biofilm in the top layer of sand, which is biologically active (Chiew et al.

2009). Turbidity and microorganisms are removed by the sand and biofilm.

The biosand filter has since been modified to include a layer of iron nails in a diffuser basin suspended above the

standing water to make the filter suitable for removing arsenic. This arsenic biosand filter is also known as the

Kanchan Arsenic Filter. In this filter, the nails rust and iron (III) oxides are formed. Fresh iron hydroxides are then

formed which adsorb arsenic in the water and become trapped in the sand (Chiew et al. 2009). This removes

arsenic from the water.

Figure 3: Example of an arsenic biosand filter. Source: Chiew et al. 2009.

4.2. SONO filter

The SONO filter also removes arsenic by corrosion of iron and sand filtration. In this filter, water filtration occurs

across two buckets. The first bucket contains two layers of coarse sand separated by iron material, which is

called composite iron matrix and is made from iron filings. The second bucket contains a layer of coarse sand

and a layer of fine sand separated by a layer of wood charcoal. In each bucket, brick chips are placed in front of

pipe connections to prevent clogging.


The SONO filter has been tested extensively in high arsenic areas of Bangladesh and shows excellent long-term

arsenic removal for many different types of groundwater. It costs around US$50 and can also remove a number

of other chemical and biological contaminants present in contaminated water (Hussam and Munir 2007). We

believe this filter also has potential for application in China and we will be communicating with other NGOs

currently using this method to discuss its construction. The main obstacle to employing this method in the

future is the composite iron matrix, which is produced in Bangladesh through a proprietary process. However, it

has been previously applied to high arsenic areas outside Bangladesh (e.g. Nepal).

Figure 4: The SONO filter. Source: Hussam and Munir 2007.

5. PREVIOUS PROJECT IMPLEMENTATION AND PARTNERS

RISE has previously implemented projects in three northern Chinese provinces using the biosand filter (no nails)

and the arsenic biosand filter (with nails). Partners have included a combination of universities, government and

non-governmental organisations. Support and resources have also been provided by a variety of organisations

such as Palintest, Microsoft and Tsinghua University. The projects conducted by RISE have won a number of

awards including the 2014 Enactus North China District First Prize and the 2014 Tsinghua University Student

Social Practice Gold Prize.


5.1. Ningxia

RISE worked with the local government in Mahuangshan to set up a pilot project of 100 BSFs and deliver

materials for over 1000 BSFs to households relying on water from underground cisterns. The target was to

reduce turbidity and contamination by microorganisms. Results from a follow-up in July 2014 revealed that all

biosand filters reduced turbidity, but that the effectiveness could be affected by construction and use patterns.

Uptake of the filter was very much dependent on support from the local village leader and each household’s

desire to improve their water quality. A selection of the turbidity results are provided in Figure 5.

Figure 5: Graph of turbidity removal rates for a sample of biosand filters in Mahuangshan, Ningxia.

[NOTE 1: HYL = Huang Yang Ling; GJZ = Guang Ji Zhang; XGY = Xia Gao Yao; MHS = Ma Huang Shan; SJS = Song Jia

Shui; SYX = Sha Yao Xian; BJY = Bao Jia Yuan; TPZ = Tang Ping Zhuang; LYP = Li Yuan Pan]

[NOTE 2: Unfiltered = shuijiao water; Filtered = biosand filter (BSF) water]

[NOTE 3: The figures on the x-axis the represent flow rate of the BSF]

0

5

10

15

20

25

30

35

40

Turb

idit

y (

NT

U)

Turbidity Removal in Ningxia

Unfiltered

Filtered


Figure 6: The highest turbidity found during our surveys in Ningxia, 167NTU. Water taken from underground cistern near the road.

Figure 7: Example of biosand filter used in Ningxia project.

5.2. Gansu

RISE currently cooperates with a local volunteer organisation in Lanzhou called Wennuan Shuibei to build

biosand filters in primary schools in the surrounding rural areas.


Figure 8: Making a biosand filter for a primary school in Huining county, Gansu.

5.3. Shanxi

RISE cooperated with students from Taiyuan University of Technology on a project in a county near Taiyuan

(capital of Shanxi) to build arsenic biosand filters and reduce arsenic levels in groundwater.

The arsenic biosand filters used this project used a 75L (75kg water) plastic bucket with 8cm of larger gravel, 4

cm smaller gravel, sand, iron nails (1.5 kg) and raw water (see Figure 4). The total cost of the materials and

transport of materials was 150 yuan (US$24) per filter ($US1 = 6.2RMB).

Figure 9: Example of arsenic biosand filter used previously by RISE in Shanxi province.


Water quality testing of influent and effluent water for these arsenic biosand filters showed positive results.

Arsenic concentrations were tested for source water from 8 different households using water from three

different wells within 2km of each other in a county near Taiyuan City. Influent arsenic concentration ranged

from just above the WHO standard (11μg/L) to well over China’s highest drinking water standard (67μg/L).

Effluent from the arsenic biosand filter was between 2-7 μg/L and under the WHO standard in each case. Testing

for some of the 8 households was carried out within 5 days of the filter having been built. Testing for other

households was carried out between 2-2.5 months after the filter was first built. Iron concentration was also

reduced (see Table 1). In one case, arsenic concentration was tested on the first day after building the filter

(influent: 67μg/L; effluent: 14μg/L) and one day after building the filter ((influent: 67μg/L; effluent: 6μg/L) and

the results revealed that arsenic removal can improve at this early stage. All testing was done with Palintest®

equipment.

Table 1: Arsenic biosand filter influent and effluent testing results for RISE project in country near Taiyuan city,

Shanxi.

[NOTE 1: All water samples are tested with Palintest portable equipment.]

[NOTE 2: “<<“ means < 0.01 mg / L]

Household Shanxi province results

Before filtering After filtering

Turbidity

(NTU)

As

(g／L)

Fe

(mg／L)

Turbidity As

(g／L)

Fe

(mg／L)

1 (well 1) 5.33 19 -- 0.46 7 --

2 (well 1) 1.54 11 0.27 0.43 2 0.01

3 (well 2) 2.28 24 0.44 0.32 3 0.01

4 (well 3) -- 57 0.31 -- 4 <<

5 (well 3) -- 67 0.25 -- 4 <<

6 (well 3) -- 66 0.25 -- 3 <<

7 (well 2) -- 24 -- -- 4 --

8 (well 3) -- 48 -- -- 5 --


6. PROBLEMS ENCOUNTERED AND LESSONS LEARNED

From our previous projects, we have learnt the following lessons that we take into our coming project in Shanxi.

1. Drinking water contamination can be a sensitive topic and it is best to cooperate with local government

on this issue to avoid conflict.

2. It is important that households are clear on what the filter consists of and what it can achieve. This will

increase the likelihood of long-term uptake. It is also important that they believe their water quality has

problems. This is an issue for arsenic contamination, which is not visible to the naked eye. On-site water

testing can help.

3. Households should be trained in filter construction and maintenance, but construction should also be

overseen to ensure materials are used. The scale of the project should be controlled so that this aim can

be achieved. In particular, this can avoid problems of people only using half the sand provided or not

constructing the filter at all.

4. All stakeholders must be convinced of the effectiveness of the filter. It helps to have portable testing kits

to assure households and volunteers that effluent water quality is better than influent water quality. It is

also necessary to seek the best possible filter for the groundwater source in question. This is why we

hope to test a number of different options in our future Shanxi Project.

5. The filter must be easy to use and must not require extra addition of chemicals and changing of filter

media after the initial construction. It must not require maintenance more than once every two months.

All of the options we are considering fit this criteria.

6. Subsidies must be decided with caution. If the filters are highly subsidised or free, it is possible that

households will not value them or may not perceive a need for them.

7. PROJECT PLAN FOR PINGYAO, SHANXI

March 2015

- Set up five different filters in village of Pingyao region. Four filters are: (1) unmodified biosand filter –

water passed through once; (2) arsenic biosand filter with 5kg Fe-C composite nails in a diffuser above

standing water – water passed through once; (3) arsenic biosand filter with 5kg Fe-C composite nails in a

diffuser above standing water – water passed through twice; (4) modified biosand filter a 3cm layer of

iron nails under then top 5cm layer of sand. The final filter will be the SONO filter. The inclusion of this

filter in the project depends on our communication with NGOs currently using the filter in Nepal and

Bangladesh over the following two months.

May 2015

- Return to Pingyao to collect water samples after two month period. Water testing.

Mid July 2015

- Return to Pingyao to collect water samples after four month period. Water testing

End of July 2015


- Supply materials and build 40 filters in village. Villagers are trained to build and maintain their filter and

are guided during the building process. The cost burden for the households will be determined in

conjunction with our government partner (Shanxi Department of Environmental Protection). Based on

our experience and the experience of other non-government organisations doing similar work, providing

free filters or highly subsidised filters is inadvisable as households do not value the filter and may even

receive materials despite having no intention of constructing or using it. With this in mind, we may set

the cost of the filter at around $30 to cover materials and material transportation.

September

- Return two months are all filters are built. Take samples for arsenic testing from the original filter (6

month testing) and selected other filters. Remind households of maintenance procedure. This involves

the addition of water, light swirling of top layer of sand and disposal of dirty water outside the

household’s yard. Maintenance is necessary every 2-3 months when flow decreases. Maintenance is

simple, but households require reminding of the procedure and of the importance of proper hygiene

and precaution when dealing with the wastewater.

November

- Second follow-up trip. Survey households to determine satisfaction. Identify next appropriate village

using groundwater sampling and opinion surveys.

March 2016

- Commence second project with a similar structure although less initial testing will be necessary.

8. BASIC TESTING SET-UP

1. Testing of the best method for arsenic removal requires field testing using the target groundwater. This

is because other water quality parameters can affect arsenic removal (e.g. iron and phosphorus

concentrations) and these are difficult to simulate effectively in a laboratory experiment (Chiew et al.

2009).

2. March: We have decided to test 5 arrangements to determine which is most appropriate for arsenic

removal in this area. Five of the most reliable and prominent households in the village will be selected to

each be responsible for one of these arrangements over a four month period. The filter arrangements

are:

a. unmodified biosand filter – water passed through once. This will act as a control to determine

whether the addition of nails indeed contributes to arsenic removal.

b. arsenic biosand filter with 5kg Fe-C composite nails in a diffuser above standing water – water

passed through once. This is the standard arsenic biosand filter structure and method of use.

c. arsenic biosand filter with 5kg Fe-C composite nails in a diffuser above standing water – water

passed through twice. It has been suggested that more contact time is required to increase the

likelihood of iron oxidation and binding with arsenic in the water. Rust formation benefits from

exposure to both air and humidity. Passing water through twice could provide these conditions.

d. modified biosand filter a 3cm layer of iron nails under then top 5cm layer of sand. Embedding

the iron nails within the sand will increase contact time between the iron and arsenic. However,

it will also limit exposure of the nails to air.


e. SONO filter. The inclusion of this filter in the project depends on our communication with NGOs

currently using the filter in Nepal and Bangladesh over the following two months.

3. The same groundwater source will be used for each filter. We will determine a daily amount of water

that satisfies the needs of the largest household and direct all four households to add this amount of

water to the biosand filter each day. Each week, the four households will take two clean plastic 550ml

mineral water bottles and collect one influent and effluent sample. These can be stored and collected at

the two month period for arsenic and iron testing. For the two households with standard arsenic

biosand filters (nails in diffuser), a sample should also be taken from the standing water. This will assist

in determining the effectiveness of the nails as an arsenic removal method (i.e. if this sample does not

contain less arsenic or more iron than the influent, the nails are not functioning as expected (Chiew et

al. 2009).

4. May: RISE and Taiyuan University of Technology volunteers will return to collect further water samples

at the two month period for testing of influent/effluent iron (Fe), arsenic (As), phosphorus (P), pH,

turbidity, nitrate (NO3-), total bacteria count and alkalinity. Arsenic, turbidity and total bacteria count are

the removal targets. Phosphorus, pH, iron and alkalinity can affect arsenic removal. Nitrate levels may

increase in the effluent and should be tested (Chiew et al. 2009). Other parameters checked in a

previous study of the arsenic biosand filter include conductivity, hardness, NH4+, chlorine (Cl),

manganese (Mn) and sulfur (S). Whether these parameters are tested depends on access to testing

equipment and perceived necessity.

5. Mid July: Another round of similar testing will be conducted four months after filter installation. This will

be used to determine which model is most effective at removing arsenic for this type of groundwater.

6. End of July: The most effective filter will be introduced to the remaining households in the village who

express desire to use it.

9. REFERENCES

1. Chiew, H. et al., 2009, Effect of groundwater iron and phosphate on the efficacy of arsenic removal by

iron-amended biosand filters, Environmental Science and Technology 43 (16), 6295–6300.

2. Hussam, A. and Munir, A., 2007, A simple and effective arsenic filter based on composite iron matrix:

Development and deployment studies for groundwater of Bangladesh. Journal of Environmental Science

and Health Part A 42 (12), 1869-1878.

3. Rodríguez-Lado, L. et al., 2013, Groundwater arsenic contamination throughout China, Science 341

(2013), 866–868.

4. Wang, S. et al., 2007, Arsenic and fluoride exposure in drinking water: Children's IQ and growth in

Shanyin County, Shanxi Province, China, Environmental Health Perspectives 115, 643–647.

5. Xinhua, 2014, Drinking water unsafe for 280m, China Daily, March 14. Available from:

http://www.chinadaily.com.cn/bizchina/greenchina/2014-03/14/content_17348477.htm

6. Zhang, Q. et al., 2013, Predicting the risk of arsenic contaminated groundwater in Shanxi Province,

Northern China, Environmental Pollution 165, 118-123.

http://www.chinadaily.com.cn/bizchina/greenchina/2014-03/14/content_17348477.htm


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