Water Pollution Related Studies


A need to monitor the water quality of the river Ganga continuously by establishing Automatic Water Quality Monitoring Station (AWQMS) was recognized. Accordingly, five AWQMS have been designated and set up on river Ganga from Kannouj to Garden Reach. The Central Pollution Control has taken up this work as a development project.

Automatic Water Quality Monitoring of River Ganga 1992-95: ADSORBS/30/1997-98.



The majority of organic halogens are the chemical compounds of anthropogenic origin. Some of the organic halogens are having bioaccumulation characteristics and may induce acute toxicity by being mutagenic, carcinogenic and teratogenic.

Adsorbable Organic Halogens (AOX) Analyzer

Some major sources of organic halogens (OX) in the environment are pulp & paper industries, paints & varnishes, textile units, halogenated pesticide/insecticide industries, potable water treatment, PVC plastic industries, tanneries etc. The analysis of organic halogen may be performed individually by GC or HPLC, but their individual analysis is not only time consuming but also cost prohibitive. Therefore, increasing need has been realised for analysis of organic halogens as summary parameter. It is realized that the introduction of summary parameter will be useful tool for measurement of organic halogen load in the environmental samples. Central Pollution Control Board (CPCB) has, therefore, taken up the project to adopt the German Standard Procedure for AOX analysis (DIN Standard) to Indian condition and to develop the capability for estimation of AOX in different types of environmental samples. CPCB involved three more laboratories for carrying out the studies and the data generated by participating laboratories is compiled, processed for repeatability, reproducibility and spike recovery studies.


Adsorbable Organic Halogens (AOX): LATS/14/1999-2000.



A participatory research project was initiated during 1993-94 involving CPCB and four other laboratories viz. NEERI, Nagpur; ITRC, Lucknow; Jadavpur University, Calcutta and Pesticides Association of India (M/s Gharda Chemicals, Thane). The following are the objectives of the project:

- Standardization of method for pesticides analysis including concentration, clean-up of sample and recovery studies in water;

- Testing the method with synthetic and real samples and preparation of standard manual for pesticides analysis; and

- Inter-laboratory analytical quality assurance for pesticides analysis.

During phase-I of the project, recovery studies of four organo-chlorinated pesticides viz. DDT, BHC, Endosulfan and Cypermethrin have been undertaken in synthetic and field samples. The results indicated recovery of more than 90% for Cypermethrin, 60-78% for PP'DDT, 80-90% for BHC and 90% for Endosulfan.

In phase-II of the project, recovery studies of organo-phosphorus pesticides viz. Monocrotophos, Dimethoate, Anilophos and Chloropyriphos have been undertaken. The average recovery on zero day was 97.22% for Dimethoate; 95.11% for Chloropyriphos; 91.05% for Anilophos and 73.87% for Monocrotophos pesticides in distilled water. In river water, the recovery was 90.77% ; 88.27% 87.50% and 68.19% respectively for these pesticides. In sewage, the recovery was 87.31%; 81.72%; 82.98% and 57.01% for Dimethoate, Chloropyriphos, Anilophos and Monocrotophos pesticides respectively. The data related to repeatability and recovery studies in pesticide standard solution and field samples have been compiled in the report.


Pesticides Analysis in Environmental Samples (Under Publication).



Central Pollution Control Board has developed a Water Testing Kit to assess the water quality of rivers, lakes and other water bodies including ground water and drinking water. This kit is an inexpensive, portable micro-laboratory equipped with apparatus and chemicals needed for testing water samples. This kit is addressed to NGOs, students, and public at large. The main aim to develop this kit was to create mass awareness and to promote public participation for prevention and control of water pollution. Using this kit one can perform physical (5), chemical (13) and biological (3) parameters.

Water Testing Kit developed by CPCB

In the present study, an attempt was made to evaluate the performance of the Water Testing Kit developed by CPCB as well as to compare the results obtained in field condition using river and ground water samples with standard laboratory methods. It is observed that the parameters like pH, Dissolved O2, Total Alkalinity, Total Hardness, Calcium, Magnesium and Chloride are showing good or moderately accurate results whereas, other parameters like Fluoride, Nitrate, Ammonia, Phosphate and T. Iron are showing less accuracy. It is found that most of the titrimetric parameters are showing positive values, whereas colorimetric estimations showed in both positive and negative values. It may be inferred that the WTK developed by Central Pollution Control Board, Delhi would be able to generate good or moderately accurate data for titrimetric parameters and less accurate for colorimetric parameters. It is to mention that United Nations Children Fund (UNICEF), New Delhi validated this WTK during 1998 and it was assessed as good performance testing kit out of 15 kits validated by the organisation. The CPCB's Water Testing Kit (WTK) was highly appreciated by Her Excellency Khunying Dr. Suthawan Sathirathai, President, Good Governance for Social Development and Environment Institute (GSEI), Thailand and shown keen interest in Transfer of Technology for Commercial production of WTK in Thailand. The water testing kit has also been appreciated by Thai Resources and Environmental Management Institute (TREMI) and Ministry of Natural Resources and Environment, Bangkok as an economical, community friendly, technological innovation useful even in electricity deficient rural areas.


Manual for Water Testing Kit.
Information Brochure for Water Testing Kit (WTK) - Developed by CPCB.



Excessive fluoride in drinking water is of most important concern due to wide spread of health symptoms found in not only in many states of India but also other developing and developed countries. Under the sponsorship of the United Nations Children Fund (UNICEF), New Delhi, Central Pollution Control Board (CPCB) has developed a small testing kit for fluoride determination in water samples in field as well as in laboratory conditions.

Fluoride Testing Kit developped by CPCB

A set of 500 Fluoride Testing kits were distributed to UNICEF for onward distribution to community circles in various parts of the country for monitoring fluoride levels in drinking water. This is a small portable kit equipped with required glassware, plastic ware, reagents, and colour chart and user manual. The method of estimation is based colorimetric principle using SPADNS [Sodium 2- (para - sulfophenylazo) -1,8 - dihydroxy - 3,6 - naphthalene sulfonate] and a Zirconium-dye lake reagents. The Kit is useful to the civic authorities and public at large for monitoring the fluoride levels of drinking water and other water sources.


Manual for Fluoride Testing Kit.


The study objectively analyzes the state of water quality (in terms of DO-BOD) in the Kanpur stretch of river Ganga and assesses the non-point sources and their impact by employing water quality modeling. The Enhanced Stream Water Quality Model (QUAL2E) of USEPA has been used for the study. A stretch of 31-kilometer (starting from a few kilometers upstream of Kanpur) was covered and on the spot water quality sampling and analysis was carried out at various locations to generate the required database for model calibration/validation. The data on various point load discharges were collected in terms of flow and water quality characteristics. Initially the model predicted a better water quality than the quality observed. This mismatch was attributed to the undefined non-point sources of waste discharges. Efforts to calibrate the model estimated the non-point sources in terms of BOD load as about 15700 kg/day and high Sediment Oxygen Demand (SOD). It was observed during field survey that the pollution from non-point sources (e.g. small drains, solid waste disposal etc.) was wide spread along the river and unless non-point sources are controlled, the desired water quality levels are difficult to achieve.


The Water Quality studies / monitoring programme involves collection, comparison and interpretation of analytical data, which leads to decision - making. The correctness of decision or action depends largely upon reliable analytical results. If the errors of the analytical results are high, the manpower material and money spent on any monitoring programme or study would be futile and further leads to wrong decision and improper action plans. Since the success and usefulness of all these information systems derived from analysis results, depend on the quality of input data, it is essential to ensure that adequate comparability and accuracy of analytical results are maintained.

AQC Sample Preparation at CPCB Laboratories

Keeping this fact in view, Central Pollution Control Board (CPCB) started regular and organized Analytical Quality Control (AQC) programme with the laboratories of SPCB, PCC and laboratories recognized under Environment (Protection) Act, 1986 from 1991 onwards as a continuous project activity with the following objectives.

- To assess the status of analytical facilities and skillness of the participating laboratories.

- To identify the serious constraints (random & systematic) in the working environment of laboratories.

- To provide necessary assistance and guidance to the concerned laboratories to overcome the difficulties in the analytical methods.

- To validate the Water Quality Monitoring data.

- To promote the scientific/analytical competence of the participating laboratories to the level of excellence for better output.

- To improve the internal and external quality control of the laboratories of Central and State Pollution Control Boards and also others in an organized manner.

The AQC exercise is conducted routinely by Central Pollution Control Board for improving the analytical capability of the concerned laboratories besides enhancing integrity of the data. The acceptable limits for various parameters are arrived using "youden 2 sample plot" method. The data are processed using a software called "PROLAB" developed by Dr. S.Uhlig, Professor in Statistics, German for various applications using ISO, DIN, Q- method/ Huber estimator, Youden, Z- scores and other Robust statistical methods. This software has been procured by GTZ and offered to CPCB under the Quality Assurance programme.

In general, the performance of the laboratories for various parameters in the decreasing order of magnitude is as follows:

Chloride, Total Hardness, Calcium, Boron, Potassium, Total Dissolved solids, Conductivity, Chemical Oxygen Demand, Sodium, Ammonical Nitrogen, Chromium, Magnesium, Fluoride, Sulphate, Total Kjeldahl Nitrogen, Nitrate-N, Biochemical Oxygen Demand, Fixed Dissolved solids, Total Suspended Solids, Phosphate-P.



CPCB is conducting AQC exercises covering various physico-chemical parameters. In the AQC exercises, bacterial parameters like Total Coliform and Faecal Coliform are not yet included because of constraints in preparation of bacterial AQC samples and their preservation and despatch under ice-cold condition. To overcome these problems it was decided to prepare lyophilized bacterial samples in solid form like the one developed for BODSEED in collaboration with Centre for Biochemical Technology (CBT), CSIR, Delhi. The main objectives of the project are:

- To introduce the bacteriological parameters like Total Coliform and Faecal Coliform in AQC scheme;

- To improve the analytical efficiency of concerned laboratories with reference to bacteriological parameters; and,

- To get accurate and reliable data on total coliform and Faecal coliform.
The microbial samples developed were tested in CPCB laboratory to assess the precision and accuracy of the test results. It is planned to introduce Bacterial samples in AQC Inter-laboratory Proficiency Testing (PT) programme during the forthcoming exercises.



Biochemical Oxygen Demand (BOD) is the most important and commonly used parameter in monitoring of water and wastewater. While conducting BOD test, domestic sewage is added as seeding material, a source of microbial population, to decompose the organic waste. The microbial seeds being used in different laboratories at different time are not of uniform nature. Moreover, the microbial community varies from season to season at any place. There are variations in microbial diversity in terms of species and number, which lead to variations in the results of BOD estimation. To overcome these problems associated with use of conventional sewage seed, a standard mixture of microbial cultures has been developed in collaboration with Centre for Biochemical Technology, CSIR, Delhi. This culture is named as BODSEED, which is used as an alternative to conventional sewage, to get reproducible and comparable data in BOD determination. Moreover, the BODSEED is inexpensive, convenient and safe to handle as compared to conventional sewage seed. The developed "BODSEED" has been tested and validated along with conventional sewage-seed for BOD determinations using various synthetic and industrial samples involving seven more laboratories besides Central Pollution Control Board.

BOD Seed developed by CPCB in
Collaboration with Centre for Bio-chemical Technology

The findings of the study revealed that use of BODSEED yields better performance when compare to conventional sewage-seed, which can be replaced by BODSEED, a microbial mixture for BOD determinations. The developed "BODSEED' had been patented and the technology transferred for commercial production.


Testing and Validation of "BODSEED" (A Microbial Mixture), An Alternative to Conventional Sewage Seed in BOD Determination: LATS/11/1998-99.



The project entitled 'Validity of BOD determination at Higher Temperature as against standard condition of 20 0C for 5 days was taken up to evolve incubation condition which will be realised for Indian aquatic environment and also comparable to standard condition of 20 0C for 5 days. The Project involved analysis of about 12,000 samples in 12 laboratories in various sample matrices. The findings of the project recommended incubation condition of 27 0C for 3 days for tropical countries like India. The Bureau of Indian Standards (BIS) has approved the methodology for adoption of test at 27 0C and 3 days incubation for India and published as Indian Standard ("Methods of Sampling and test (physical and Chemical) for Water and Wastewater" Part 44 Biochemical Oxygen Demand (BOD) - IS: 3025 (Part 44): 1993.


Validity of BOD Determination at Higher Temperature as Against Standard Condition of 20oC for 5 days: LATS/4/1987-88.



Biochemical Oxygen Demand (BOD) is the most important and commonly used parameter in water quality monitoring and designing of effluent treatment plant. The test takes considerable time say 3 days at 27 0C or 5 days at 20 0C, as well as consumes lot of energy. To overcome these constraints, attempts have been made to carry out the test in short time through the technique using BIO-SENSOR probes. This technique involves selection of suitable microbial composition for using Bio-sensor so as to degrade the wide range of wastes. In this endeavour, CPCB is attempting in collaboration with Centre for Biochemical Technology (CBT), CSIR, Delhi to develop BIO-SENSOR for BOD test. The project is in progress.


The water quality monitoring and management is usually performed only on the basis of limited number of physico-chemical variables. This approach has several inherent drawbacks and limitations.

The Netherlands Government under its International Cooperation Programme on Environment with the Government of India agreed to include the development of integrated water quality monitoring method as one of the project, which can overcome the drawbacks & limitations of physico-chemical approach of water quality monitoring & management. This project was executed as a joint venture of the National Institute of Public Health & Environmental Protection (RIVM), Bilthoven, the Netherlands, and the Central Pollution Control Board, Delhi, India. The results of this were analysed for redundancy & information content with respect to pollution gradients using advanced statistical programme in computer (principle component analysis & clustering).

- During the project an easily comprehensive yardstick methodology for integrated water quality evaluation was developed involving experts from RIVM and CPCB and discussed in an international workshop.

- Draft manual for carrying out bio-monitoring was prepared. The finalized methodologies were then validated & tested for one year on different rivers in India. On the basis of results of the validation programme, the manual has been revised and finalized.

Bio-monitoring of Water Quality

- Water Quality Criteria has been developed based on diversity and Saprobity score of benthic macro-invertebrates based on bio-monitoring studies.


Bio-monitoring of Water Quality at Sultanpur Lake, Delhi

Photo 7a

- The bio-monitoring methodology as standardized in association with Dutch Experts has been used for bio-assessment of raw water at drinking water sources, canals of yamuna basin, lakes, rivers and their tributaries and other water bodies.

- The transformation of biological water quality information of a water body in the form of a colour map to indicate various water quality classes in terms of clean, slight pollution, moderate pollution, heavy pollution and severe pollution of a water body have been employed. Bio maps of Yamuna River and tributaries in respect of their pollution load have been prepared.

- The studies on Bio-mapping of Rivers of Meghalaya State have been undertaken in collaboration with Meghalaya State Pollution Control Board. The data is under compilation and processing.

- The water quality management in problem areas is complex task due to several ongoing environment management problems in highly polluted areas. On the basis of various environmental problems, 24 problem areas have been identified in the country in collaboration with the concerned State Pollution Control Boards/Pollution Control Committees in Union Territories. The pollution control measures had already been initiated through time bound action plans to mitigate the environmental problems and ensuring improvement in environmental quality of problem areas. The bio-monitoring of environmental components of problem areas will provide information about the state of ecological environment of surface water bodies in vicinity of problem areas, as well as extent of deterioration/improvement taken place as a result of implementation of pollution control measures.

- The bio-monitoring methodology has been employed for monitoring of Damodar River in collaboration with the Zoological Survey of India (ZSI), Calcutta and the Central Pollution Control Board, Zonal Office at Calcutta.

- Biomonitoring study has been carried out in the lakes and reservoirs in and around Delhi using the bio-monitoring methodology. The physico-chemical, heavy metal and pesticide contents in the water were analysed. The water bodies are lying under moderately and severely polluted category. Bioaccumulation of heavy metals and pesticides were also carried out. Recommendations to preserve the lakes and reservoirs have been presented in the report.


Specifications for Instruments/Equipments Required for Biomonitoring of Inland Surface Waters: LATS/7/1991-92.
Manual on Integrated Water Quality Evaluation; Indo-Dutch Project Report 802023003, January 1994.
Bio-monitoring of Water - CPCB Newsletter, 1995.
Bio-mapping of Rivers - CPCB Newsletter, 1999.
Water Quality Status of Lakes and Reservoirs in Delhi: ADSORBS/37/2000-01.
Bio-monitoring of Water Quality in Problem Areas - CPCB Newsletter, 2001.


Bio-monitoring can be done by measuring the change in structural and/or functional components of an eco-system due to adverse effect caused by environmental change such as pollution. Several bio-monitoring methods have been developed all over the world for the measurement of water quality. Each method has got its own advantages and limitations. The method developed by the Central Board in collaboration with Dutch scientists for measurement of water quality using biological parameters rely on benthic community structure. In the situation where river-beds are sandy or concrete structures, properly established biological communities are very rare, and thus, bio-monitoring can not be done properly. To overcome this problem, use of artificial substratum is considered as best option in western countries.


Artificial Substratum (Iron Cage) developed by CPCB for Bio-monitoring

Artificial substratum is an iron cage containing glass marbles, submerged at a number of places in the water body. The cages are retrieved after 4 to 6 weeks and the macro-invertebrates, which are colonized on the marble substrata are collected. The number of species of benthic macro-invertebrates are identified and scored for the evaluation of water quality.

Bio-monitoring through Artificial Substratum at Wazirabad Water Works, Delhi

Two methods have been adopted for the evaluation of water quality i.e. Diversity Index and Saprobity Index. The Diversity Index is the ratio of the total number of runs (when the next macro-invertebrate is different from last one a new run starts) and the total number of organisms encountered. High diversity of benthic macro-invertebrates always supports a good quality of water.


Application of Artificial Substratum for Bio-assessment of water bodies: LATS/13/1998-99.


More than 10 lakhs people took bath during the solar eclipse of August 1999 at Brahm Sarovar, Kurukshetra. Water quality study was carried out before, during and after solar eclipse mass bathing to assess the changes in the water quality due to mass bathing. It was deduced from the study that there were slight change in the values of conductivity, total alkalinity and considerable variation in bacteriological parameters due to mass bathing. Residues of Organo-chlorine pesticides were observed in some raw water samples. Recommendations for maintaining water quality during mass bathing have been provided in the report.


Mass Bathing during Solar Eclipse at Brahm Sarovar, Kurukshetra (Haryana)


Water Quality Assessment during Solar Eclipse, Mass Bathing at Brahm Sarovar, Kurukshetra (Haryana): ADSORBS/31/1999-2000.


The sewage treatment plant (installed capacity 80 MLD) was commissioned in 1994 at village Dinapur, Varanasi. The treatment plant receives approximately 100 MLD sewage. The treated sewage is partly used for irrigation purpose and rest is discharged into River Ganga. The total irrigation area is approximately 9 sq. km. covering villages Dinapur, Kamoli, Kutwan, Chirai gaon, Raghunathpur, small Yadav and Harijan Basti.

It was observed that because of improper functioning of STP and over loading of sewage inflow, the treatment is inadequate and it overflows to nearby fields at Sewage Treatment Plant. The public complaints were received frequently from the villagers of the nearby areas around Dinapur sewage treatment plant at Varanasi.

To assess the impact of treated sewage on ground water quality, ground water was monitored at 20 locations selected in the villages around Dinapur STP with five control points approximately at 3.5 Km. radial distances from STP, where the effect seems to be minimum. The ground water quality was monitored for a year at regular interval.

The major observation indicated serious Bacteriological contamination in the open wells in the villages on both sides of the treated sewage flowing channel. Higher concentrations of Hardness, Calcium, Magnesium, Alkalinity, Total Dissolved Solids (TDS), Chlorides, Sulphates, Sodium, Phosphates and Heavy Metals; like Cr+6 and Fe were observed in the ground water in comparison to the quality of control points, the values were above the permissible limit for drinking water norms.

The level of ground water in the open wells up to 1 Km. on both sides of the treated sewage channel have been increased by about 4 to 5 meters against the wells situated at 3 to 4 Km. away from the channel. The level of ground water in the open wells near STP channel was observed at only 1.5 m depth from top due to the influence of treated sewage to the ground water, thus poor villagers were deprived of drinking water source.

Due to uncontrolled irrigation and poor maintenance of irrigation channel and minors, water-logging occur, which aggravates the problem of infiltration.


Status Report of Dinapur Sewage Treatment Plant and Surroundings : PROBES/83/2001-02.


Ground water plays an important role and an essential and vital component of our life support system. The ground water resources are being utilized for drinking, irrigation and industrial purposes. There are exploitation pressure on ground water resources and growing concern of deterioration of ground water, due to unplanned disposal of effluents, sewage and sewerage. The following project studies have been conducted related with ground water quality and pollution aspect.

- During August/September, 1995 severe flood situation was observed in Delhi and nearby areas of Yamuna river basin and water intrusion in ground water table has been reported at various low-lying areas in the city. Inadequate drainage facilities caused mixing of flood water with urban and industrial wastewater, and its percolation led to the risk of groundwater contamination. The ground water quality in flood-affected areas of Delhi has been studied and seventeen samples of groundwater were collected and analysed for 35 parameters immediately after the flood water receded. Deterioration of water quality in terms of physico-chemical parameters has been observed. The concentrations of heavy metals were found within the permissible limits of drinking water standard except iron and manganese. The total coliform was noticed only at few locations and surprisingly the faecal coliforms were not recorded in any of the locations. The pesticides (BHC) exceeded the limits in most of the locations, whereas the other pesticides were within the limits prescribed by WHO for drinking water. The comparison of water quality data of the flood-affected areas between pre and post-monsoon reveals that in general the concentration of cations, anions and pesticides were towards higher side with few exceptions and these exceptions may be due to different nature of solubilities of solutes and their leaching into the groundwater.

- The collaborative study has been conducted by Central Pollution Control Board, Delhi alongwith Central Ground Water Board during February and March, 1998 to assess the ground water quality and its suitability. The extensive field survey have been undertaken, during which 303 ground water samples were collected and analysed from different abstraction structures (Hand pumps, tube wells, dug wells, bore wells etc.) representing various depths and locations in Delhi. The analysis of ground water samples have been undertaken for physico-chemical parameters (including trace metals), bacteriological parameters, organo-chlorinated and organo-phosphorous pesticides and total organic carbon.

- Ground water quality monitoring was carried out at 19 locations in Najafgarh drain basin area, occupying around 832 sq. km in Delhi. The ground water samples were collected at monthly frequency and analyzed for 34 parameters covering physico-chemical parameters including heavy metals and pesticides and also bacteriological analysis of Total and Fecal coliform. The results of monitoring revealed that the ground water quality in this region was highly polluted in respect of dissolved solids, alkalinity, hardness, calcium, Magnesium, Iron, Chromium, sodium, fluoride, nitrate, boron and bacteriological parameters like total and fecal coliform. The concentrations of heavy metals are not significantly high in the ground water. The main sources of ground water contamination are due to the disposal of liquid and solid wastes generated from domestic and industrial origin and also certain extent from agricultural and farm activities.


Groundwater Quality in Problem Areas - A Status Report (Part-I): GWQS/1/1995-96.
Groundwater Quality in Problem Areas - A Status Report (Part-II): GWQS/2/1995-96.
Groundwater Quality in Problem Areas - A Status Report (Part-Ill): GWQS/3/1995-96
Groundwater Quality in Problem Areas - A Status Report (Part-IV): GWQS/4/1995-96.
Groundwater Quality in Ten Towns of Uttar Pradesh: GWQS/5/1995-96.
Groundwater Quality in Problem Areas - A Status Report (Part - V): GWQS/6/1995-96.
Groundwater Quality of Flood Affected Areas of Delhi - 1995: GWQS/7/1995-96.
Groundwater Quality and Pollution Aspects in NCT - Delhi - Collaborative Project Report with Central Ground Water Board, Chandigarh, January 2000.


The arsenic contamination of groundwater in some districts in West Bengal is the cause of concern. The removal of arsenic from ground water is necessary before its human consumption. During the study various techniques and principles for removal of arsenic from ground water and pilot plants erected by different private and Government agencies have been studied. It has been observed that As (V) species can be easily removed as compared to As (III) species and Iron based flocculants and adsorbents are having better capacity than Aluminium based chemicals. Fly ash based candle is also recommended for treating arsenic in drinking water.


A Report on Sources of Arsenic and its Control in West Bengal; IMPACTS/4/2000-01.


Chemical Oxygen Demand (COD) is an important parameter for determining the pollution potential of domestic and industrial wastewater. During the course of its analysis, silver sulphate is added as catalyst while mercuric sulphate is added to overcome the interference from halides. After analysis, the COD waste containing the compounds of silver and mercury are disposed off. Considering the hazardous nature and cost factor, an effort was made to recover silver as metallic silver and mercury as mercuric iodide.

A view of Metallic Silver recovered from COD Waste

During the process the COD waste was treated with dilute HCl to precipitate silver as silver chloride. The silver chloride was dissolved in dilute ammonia and sodium sulfide was added to precipitate silver as silver sulfide. The silver sulfide was mixed with flux material and ignited to 1200 0C to separate silver metal and slag material.

The waste after recovery of silver, contains mercury in its compound form. Potassium iodide can precipitate mercury as mercuric iodide. But excess addition of potassium iodide will dissolve the precipitate. Hence, calculated amount of 10% potassium iodide was added to precipitate all mercury as mercuric iodide.

Photo 12

A view of Mercuric Iodide recovered from COD Waste

As much as 18 grams of silver were recovered from 15 litres of COD wastewater. The recovery percent for both silver and mercury was found more than 95%.


The chemical oxygen demand (COD) is a summary parameter, commonly tested for various effluent samples for estimating total oxygen demand. In this method, toxic and costly heavy metal chemicals like mercuric chloride and silver sulphate are used for removal of chloride interference and to act as catalyst. In order to replace these chemicals with other chemicals of same properties and reaction with a main objective to abate the toxic/costly chemicals and also to develop a cost-effective method for COD estimation, study has been carried out using other compounds such as zinc oxide, copper sulphate, nickel sulphate, titanium oxide for synthetic sample, glucose-glutamic acid mixture with different concentrations of chloride levels and the results are encouraging. Further studies under various permutations and combinations are in progress.


The increasing contamination of aquatic water bodies with pollutants bearing trace metals cause deleterious impact not only on the immediate aquatic ecosystem but also on the well being of human population. Heavy metals are toxic elements with lipophilic affinities and bio-accumulation tendencies in biotic tissue. Bio-accumulation is the process in which chemical substances are concentrated, accumulated and magnified in the body tissue of living organisms either directly from surrounding environment or indirectly through the food chain. In aquatic organisms, trace metals uptake occurs directly from the surrounding water across the permeable body surface, alongwith food and water. The metallic species are accumulated in biotic tissue in critical ranges due to the imbalance of absorption and elimination mechanism in living system.

Fishes, which occupy highest trophic level of food pyramid in aquatic ecosystem are important target of bio-magnification of trace metals and also act as possible bio-transfer route to human beings. With above in view, the project studies on bio-accumulation of trace metals in commonly available species of fishes of river Yamuna have been undertaken with following major objectives.

- To generate information regarding bio-accumulation of critical trace metals in fish tissues of various edible species available in Delhi stretch of river Yamuna.

Photo 13

Fish Catch for Human Consumption

- To establish suitability of various species of fishes and their consumption as food by the public and to suggest mitigation measures to counteract bio-accumulation process.

- To determine suitability of various species of fishes and their consumption as food by the public and to suggest mitigation measure to counteract bio-accumulation process.

The results of the Bio-accumulation studies indicated that there is no significant accumulation of heavy metals traceable from fish muscle tissue. The metals - Lead, Nickel and Zinc have been found in the fish body, but these were within permissible limits. The study suggests the consumption of fish as food is supposed to be safer in respect to critical trace metal accumulation perse.


Kolkata (220 34'N and 880 22'E) is a typical riverine city situated in the lower tidal reaches of Hugli. The city does not yet have any full-fledged sewage treatment plant. A qualitative study of the sewage revealed that the city sewage is mixed with industrial waste owing to the presence of good number of hazardous industries within the city limit. It however, possesses a unique system of utilization of sewage. About 2000 acres of land in the eastern part of the city (Dhapa and Bantala area) developed by dumping of solid wastes, is used for growing sewage irrigated vegetables, which comprises a major part of the city's vegetable supply. The vast wetland here also supports sewage fed fisheries, which supply a considerable quantity of fish to the Kolkata market. The studies on the impact of sewage on vegetables and fish quality are being continued at CPCB Zonal Office - Kolkata.


The Central Pollution Control Board organized the first national workshop on "Development and Use of Reference Materials in India (DUREM-1)", during February 14-16, 1996 at New Delhi to make an assessment of the existing activities and the future needs of the environmental reference materials which have a direct relevance in the implementation of standards and the performance evaluation of the emission/effluent facilities existing in the country. As a follow-up of decisions taken at DUREM-1, 1996, a national task force for reference materials (REMTAF) development and use in India has been formed. The first meeting of the REMTAF was held on September 25, 1996 at CPCB, Delhi. The meeting identified 12 nodal agencies on different areas. The first meeting of the nodal agencies was held on March 3, 1997. The meeting decided preparation of comprehensive proposal by CPCB for development of priority certified reference materials (CRM's) through the nodal agencies.


International Directory of Suppliers and Dealers of Standard Reference Materials For Measurement of Metals and Organics: LATS/8/1991-92
First National Workshop on Development and Use of Environmental References Materials - DUREM-1:LATS/10/1997-98
Second National Workshop on Development and Use of Environmental References Materials: DUREM-2:LATS/12/1998-99.
Proceedings Second National Workshop on Development and Use of Reference Materials, LATS/15/2000-01.


The need for analytical measurements of metals during environmental monitoring is well recognized and accomplished with use of reference material. Standard Reference Materials (SRM's) are well-characterized material used to maintain the quality of measurements. The use of certified reference material (CRM) during routine measurement of trace metals is quite expensive therefore it has become necessary to develop economical and indigenous Certified Reference Material (CRM). Central Pollution Control Board has undertaken project for preparation of Reference Material for toxic metals in industrial effluents under sponsorship of Department of Science & Technology (DST).

The Certified Reference Material for toxic metals like Chromium, Copper and Nickel in Electroplating industrial effluent were selected and the homogeneous samples were distributed to 32 reputed environmental and R&D laboratories in the country for analysis. The analytical data as obtained from 32 laboratories have been compiled, statistically processed and computed in order to certify its use as reference material.

Relevant Publications:

International Directory of Suppliers and Dealers of Standard Reference Materials For Measurement of Metals and Organics: LATS/8/1991-92
First National Workshop on Development and Use of Environmental References Materials - DUREM-1:LATS/10/1997-98
Second National Workshop on Development and Use of Environmental References Materials: DUREM-2:LATS/12/1998-99


Toxicity test method based on Dimensionless Toxicity Factor has been developed by CPCB, which has been recognized and adopted by the Bureau of Indian Standards (BIS) New Delhi and published as "Bio-assay Method for Evaluating Acute Toxicity of Industrial Effluents & Wastewater - Part 2 using Toxicity Factor to Zebra Fish (Brachydanio rerio)" as IS-6582 (Part 2):2000.

A toxicity factor (TF value) has been introduced for evaluation of industrial effluent standards. It is a number on geometrical scale by which the samples need to be diluted for hundred percent survivals of fish. The TF values for tannery, pesticide, pharmaceutical, dye & dye intermediates and textile industries wastewater were 16, 4,4,4 and 1, respectively.

The project is being taken up by CPCB in collaboration with three other laboratories i.e. Gujarat Pollution Control Board, Gandhinagar; National Institute of Occupational Health, Ahmedabad and National Environmental Engineering Research Institute (NEERI), Nagpur to develop toxicity based Minimum National Standards (MINAS) for various industries. The standards are being developed based on Dimensionless Toxicity Factor based standardized method.


Preparation for Toxicity Factor Experimentation

Studies have been undertaken under project for "Development of Toxicity Based Standards for Dye & Dye Intermediate, Bulk Drug and Textile industries". The effluents were collected from various industries in collaboration with Gujarat State Pollution Control Board, Gandhinagar; NEERI, Nagpur; CPCB Zonal Office, Kanpur and National Institute of Occupational Health, Ahmedabad and analyzed for effluent toxicity. The effluent toxicity was measured in terms of toxicity factors.


Dimensionless Toxicity Factor - An approach to Toxicity Testing for Regulatory purpose: LATS/10/1998-99.
Effluent Toxicity Status in Water Polluting Industries, Part-I: Dye & Dye Intermediate, Bulk Drugs and Textile Industries - PROBES/91/2002-2003.

Back to Content