ARSENIC POLLUTION IN GROUND WATER IN ANDHRA PRADESH

Patancheru industrial development area is about 40km away from Hyderabad, Andhra Pradesh and is situated on Hyderabad Bombay highway. About 320 industries manufacturing pesticides, chemicals, pharmaceutical products and steel are located in this area. A Common Effluent Treatment Plant (CETP) is installed by about 110 industries that bring their effluents in tankers for treatment purpose. After treating these effluents, wastewater is discharged in a water stream called Peddavagu, which meets the main stream Nakkavagu flowing through Patancheru area. This Nakkavagu finally meets the river Manjira that is one of the main source of drinking water for Hyderabad City.

The trace metals like arsenic present in the soil form complexes with the organic acids such as fumic acid which help these pollutants to migrate faster through the soil and contaminate the aquifers. The decomposition rate of organic matter is very high in India as being a tropical country.

Geochemical map showing the distribution of arsenic in water in Patancheru and Bolaram industrial development areas are prepared. The distribution map clearly shows the arsenic pollution in surface and ground water. The values of arsenic in stream water near Common Effluent Treatment Plant are as high as 40,000ppb. It clearly indicates that the source of arsenic is not from natural rocks but from the industrial effluents brought by different industries to CETP for treatment. Water samples from Peddavagu and Nakkavagu streams are showing high arsenic concentration of upto 5,000ppb. Ground water samples from some of the villages i.e. Bandalguda, Muthangi, Patelgudem etc are having high concentration of arsenic. In some of the wells the arsenic concentration was found to be 750ppb while the permissible limit is only 50ppb. Distribution of arsenic in soil is given in Figure 4. Most of the soil samples are not having high concentration of arsenic except one sample at the confluence of Pamlavagu and Nakkavagu streams. As the soil is normally not contaminated in the area, it is evident that the source of arsenic is not from the surrounding rocks, which are granite.

Arsenic present in the Peddavagu, which is released by Common Effluent Treatment Plant, migrates vertically and horizontally and contaminates the ground water in the wells of adjoining villages which is indicated by the high values of arsenic in well water. The studies reveal that arsenic is released by the industries in CETP through tankers. This arsenic is passed on to the water stream Peddavagu after so called treatment which takes care of COD, BOD and TDS and can not reduce the toxic metals present in the effluents. As CETP was trusting the industries that they will be checking the effluents before bringing to CETP and was not having any facilities with them to check the effluents for heavy metals, all the metals were passed on to the water stream. Patancheru is having 3-10meters of alluvial soil and arsenic was transported to the ground water. Once the aquifer is contaminated, it is very difficult, if not impossible to clean it. The well water in some of the villages is not suitable for drinking or agriculture purpose due to high concentration of arsenic and some other toxic metals.

It is recommended to carry out detailed environmental geochemical studies in the study area to monitor arsenic and other toxic metals in soil and water. Speciation studies should also be carried out because all the valance states of arsenic are not toxic in nature and it is essential to find out whether arsenic is present in the form of As⁺³ or As⁺⁵.

Studies carried out in Bolaram industrial area also show high concentrations of arsenic in surface and ground water. Almost all the wells in the area are contaminated with arsenic as is evident. This area also needs to be monitored for arsenic contamination due to anthropogenic sources.