Environ. Sci. Technol. 2005, 39, 4300-4306
Ineffectiveness and Poor Reliability of Arsenic Removal Plants in West Bengal, India M. AMIR HOSSAIN,† MRINAL KUMAR SENGUPTA, SAD AHAMED, MOHAMMAD MAHMUDUR RAHMAN,‡ DEBAPRIYA MONDAL, DILIP LODH, BHASKAR DAS, BISHWAJIT NAYAK, BIMAL K. ROY,§ AMITAVA MUKHERJEE, AND DIPANKAR CHAKRABORTI* School of Environmental Studies, Jadavpur University, Kolkata 700 032, India, and Indian Statistical Institute, Kolkata 700 108, India
In the recent past, arsenic contamination in groundwater has emerged as an epidemic in different Asian countries, such as Bangladesh, India, and China. Arsenic removal plants (ARP) are one possible option to provide arsenic-safe drinking water. This paper evaluates the efficiency of ARP projects in removing arsenic and iron from raw groundwater, on the basis of our 2-year-long study covering 18 ARPs from 11 manufacturers, both from home and abroad, installed in an arsenic affected area of West Bengal, India, known as the Technology Park Project (TP project). Immediately after installation of ARPs on August 29, 2001, the villagers began using filtered water for drinking and cooking, even though our first analysis on September 13, 2001 found that 10 of 13 ARPs failed to remove arsenic below the WHO provisional guideline value (10 µg/L), while six plants could not achieve the Indian Standard value (50 µg/ L). The highest concentration of arsenic in filtered water was observed to be 364 µg/L. Our 2-year study showed that none of the ARPs could maintain arsenic in filtered water below the WHO provisional guideline value and only two could meet the Indian standard value (50 µg/L) throughout. Standard statistical techniques showed that ARPs from the same manufacturers were not equally efficient. Efficiency of the ARPs was evaluated on the basis of point and interval estimates of the proportion of failure. During the study period almost all the ARPs have undergone minor or major modifications to improve their performance, and after our study, 15 (78%) out of 18 ARPs were no longer in use. In this study, we also analyzed urine samples from villagers in the TP project area and found that 82% of the samples contained arsenic above the normal limit.
* Corresponding author phone: +91-33-24146233; Fax: +9133-24146266; e-mail:
[email protected]; website: www.soesju.org. † On leave from the Institute of Statistical Research and Training, University of Dhaka, Dhaka 1000, Bangladesh. ‡ Present address: Centre for Environmental Risk Assessment and Remediation, University of South Australia, Mawson Lakes Campus, SPRI Building, Mawson Lakes, SA 5095, Australia. § Indian Statistical Institute. 4300
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Introduction Before 2000 there were five major incidents of groundwater arsenic contamination in Asian countries: Bangladesh (14), West Bengal, India (5-7), and three sites in China (8). By 2004 new instances emerged from different Asiatic countries (9) with reports of arsenic contamination in the Kurdistan province of western Iran (10) and in Vietnam (11). Our preliminary studies point to further arsenic contamination in India and Bangladesh involving a significant portion of the Ganga-Meghna-Brahmaputra (GMB) plain, an area of 569 749 km2 with a population of over 500 million (9, 12). Since 1997, the governments of Bangladesh and West Bengal, the World Bank, UNICEF, WHO, and other international aid agencies along with national nongovernmental organizations (NGOs) have initiated a two-phase program to combat the arsenic crisis. The first phase was identification of the contaminated tube wells and the second the provision of safe drinking water. Tube wells were painted green or red corresponding to arsenic concentrations below and above 50 µg/L, respectively, utilizing field kits for arsenic testing. The poor reliability and validity of these field kits seriously disrupted the national programs (13, 14). UNICEF stopped using these kits in West Bengal, India, after evaluating them independently, and the South East Asia Regional director of WHO urged the development of a standardized laboratory testing of arsenic (15), but the debate persists (16). The plan to use arsenic removal plants (ARP) posed a scenario of controversy like that of field kit testing, fueled by the keen interest of many national and international companies to supply ARPs and other water treatments. The installation of ARPs based on adsorption, coprecipitation, and ion-exchange techniques began at the end of 1998 in West Bengal. Over 1900 ARPs have been set up, at an average price of US$1500/unit, in nine arsenic affected districts of West Bengal with comparable installations in Bangladesh. Our preliminary investigations of the efficiency of ARPs in West Bengal also began in late 1998, resulting in the submission of five reports evaluating the efficiency of 513 ARPs in the districts of Nadia, Murshidabad, and North 24Parganas of West Bengal to the Government of West-Bengal, ARP manufacturers, and other concerned NGOs for their information and follow-up action. Our study findings from July 1999 to July 2004 are shown in Table 1 of the Supporting Information. Description of Evaluation Procedures. While our initial studies on ARP effectiveness were underway, the Technology Park Project (TP project) was implemented at Baruipur in the arsenic-affected district of South 24-Parganas (Figure 1) by the All India Institute of Hygiene and Public Health (AIIH&PH), Kolkata, in partnership with a number of NGOs and with the financial support of the India-Canada Environment Facility (ICEF), New Delhi, to demonstrate, monitor and evaluate the currently available technologies for arsenic removal (17). In the TP project, 19 ARPs from 11 different national and international manufacturers were installed. Figure 2 shows a schematic diagram of a typical ARP. Table 1 is a detailed description of the ARPs (17, 18) installed in the TP projects, defining the mechanism of activity, media, price, and the manufacturer’s stated achievement target for arsenic and iron removal. All of the ARPs, except plants 3 and 17, were installed on August 28, 2001, with the filtered water from each made available to the villagers for drinking and cooking as of August 29, 2001. Plants 3 and 17 were installed on August 7, 2002 and May 22, 2002, respectively. Plant 19 was not 10.1021/es048703u CCC: $30.25
2005 American Chemical Society Published on Web 04/07/2005
Trockner and Ionochem listed 300 µg/L as the limiting concentration for iron. No health-based guideline value for drinking water iron is proposed by WHO (19), but taste is usually unacceptable at iron concentrations above 300 µg/L, and this is used as the target for our evaluation. During our 2-year study period (September 13, 2001 to September 8, 2003), most of the ARPs underwent some major or minor changes, including media, design, or site change, resinking, etc. Only three ARPs (plants 4, 5, 15) were consistently in operation. Four ARPs (plants 1, 10, 11, 18) were officially abandoned by the project authority due to poor performance and failure to cope with the problem of silvery colloidal sand rising along with the water and choking the tube well and the filter media of the ARPs, known as sand gushing.
Experimental Methods
FIGURE 1. Map of the study area indicating the location of the arsenic removal plants installed therein.
FIGURE 2. Schematic diagram of a typical arsenic removal plant (Pal-Trockner). installed until the last months of the project and is excluded from our evaluation. Table 2 of the Supporting Information lists the number of samples received for analysis from each ARP and the reasons for missing samples. The stated achievement targets for the ARPs varied widely: Oxide-India (plants 1-3) and Pal-Trockner (plants 13, 14) cited arsenic free water, an impracticable target; RPM marketing (plants 7, 8) claimed an arsenic removal target of below detection limit (BDL), which obviously varies with the analytic method. For these cases, the WHO target for arsenic, e10 µg/L, was assumed (19). The target levels for iron also varied. Oxide India and Adhiacon cited the WHO permissible limit, while Pal-
Study Area. The study area, Technology Park, has an area and population of 8 km2 and 23 963, respectively, and is located in the Baruipur block of the South 24-Parganas district, one of the nine arsenic-affected districts of West Bengal (Figure 1). Of the 4720 families residing in the project area, approximately 45% were below the poverty level. The primary sources of drinking water were, and continue to be, shallow tube wells. We had previously analyzed 856 tube well water samples from the 15 villages in the project area and observed that 46% and 38% of them had arsenic concentrations >10 and >50 µg/L respectively, while 16% of the analyzed tube-wells showed arsenic concentrations above 300 µg/L, the concentration predicting overt arsenical skin lesions (6). Our medical team registered 107 patients with arsenical skin lesions from 92 affected families in the area. We performed the chemical analysis of both raw and filtered water samples from each of the ARPs in operation through the 2-year study period with weekly samples from September 2001 until August 2002 and biweekly samples from September 2002 until September 2003. Water was initially analyzed for five parameters: arsenic, iron, conductivity, hardness, and pH; when stability was evident, the later samples were analyzed only for arsenic and iron and occasionally for other parameters. Instrumentation. A flow injection hydride generation atomic absorption spectrometer (FI-HG-AAS) and a UV spectrophotometer were used for the arsenic and iron analyses as described in earlier publications (20, 21). TP Project Authority Protocol. The terms of agreement between the TP project authority and our laboratory regarding the collection and analysis of water samples were as follows. (1) Water samples for chemical analysis were collected from each ARP before and after filtration by the project authority according to our prescribed procedure as described in previous publications (12, 22). (2) The TP project authority sent both raw and filtered water as coded (blinded) samples from all ARPs on Wednesday afternoon; analyses were to be carried out on the same day and a report submitted to the TP authority the following day. (3) The TP project authority would independently analyze duplicate aliquots at their laboratory and one or more outside laboratories. The project authority would inform our laboratory immediately of any significant differences. Interlaboratory Comparison. In addition to the TP project protocols, we carried out interlaboratory comparisons for both arsenic and iron on our own. Aliquots of raw water samples from 16 tube wells from the study area were sent to the Intronics Technology Centre (ITC), Dhaka, Bangladesh, and Central Food Laboratory (CFL), Kolkata, India, after analyses for arsenic in our laboratory by the FI-HG-AAS method. Both outside laboratories conducted arsenic analyses by FI-HG-AAS after reduction. No significant differences VOL. 39, NO. 11, 2005 / ENVIRONMENTAL SCIENCE & TECHNOLOGY
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TABLE 1. Description of the ARPs Installed in Technology Park no.
manufacturer
no. of plant s
mechanism of activity
manufacturers’ claim for efficacy of removal media
media capacity based on 2 years base performance with 600 L/h capacity, 4000 L/ day for 0.5 ppm raw water based on 1 ppm, 1000 L/day with periodic media replacement at 6-8 months 600-1000 L/h (requires periodic sludge removal and/or backwash/ cleaning) based on 200 000 L/year with 0.5 ppm per liter intake based on 0.5 ppm, 2000 L/day media recharging at 4-6 months based on 1 ppm, up to 10 000 L (requires periodical sludge removal or backwash) based on 0.5 ppm, 1 440 000 L with 600 L/h 900 000 L based on 1 ppm (requires periodic backwash) 1000 L/h (requires periodical sludge removal and/or cleaning)
1
Oxide India (Catalysts ) Pvt. Ltd., Durgapur, representing B. E. College model
3
adsorbant
activated alumina AS-37
2
Apyron Technologies India (P) Ltd., representing Apyron Technolog ies Inc. USA
2
adsorbant
3
Public Health Engineeri ng Dept (PHED), Govt. of West Bengal
1
adsorption
Aqua Bind (activated alumina mostly in combination with metal oxide) patented red hematite (Fe2O3) lumps + quartz + sand + activated alumina
4
RPM marketing Pvt. Ltd., New Delhi, representing Alcan Chemicals USA School of Fundamental Research (SOFR), Kolkata
2
adsorbant
1
adsorption
AFDWS-2000 (patent pending)
5
activated alumina + AAFS-50, patented aluminum silicate + ferric hydroxide
6
Adhiacon, Kolkata
2
7
Ionocem, Kolkata
1
catalytic precipitation/ electron exchange ion exchange
8
Pal Trockner (P) Ltd. Kolkata (German origin)
2
adsorbant
AdsorpAs (patented)
9
All India Institute of Hygiene & Public Health (AIIH&PH), Kolkata
1
clorinating agent (BP) + ferric alum (calcd dose)
10
W. S. I., USA, represented by Harmonite Impex (Pvt.) Ltd., Kolkata
2
oxidation + coagulation + flocculation/ precipitation/ filtration ion exchange
11
Anir Engineering, collaborat ion with ITP Gmbh, Germany
1
adsorption
a
NA, information is not available.
ferric hydroxide
bucket of resins (BOR) mostly in combination with metal oxide (patented) slurry/granular ferric hydroxide (S/GFH)
price (US$)
As
Fe
1070 + 326 per charge + 4% sales tax
arsenic-free water
permissible limit
1810 + 340 per charge
