The use of wastewater for irrigation in agricultural lands is a common practice across the globe. But a study by Indian researchers has found that it can also affect the quality of soil and groundwater, and consequently, human health. 

The researchers studied soil and groundwater samples from farms irrigated by tannery effluents in and around Kanpur city in Uttar Pradesh and found that they were contaminated with heavy metals such as chromium, nickel, cadmium, lead and zinc. They found that many small scale units released their effluent directly into water bodies without any pretreatment.

Kanpur is called the ‘leather city’ as some of the largest tanneries in India are situated there. The study revealed that the use of tannery effluent irrigation for crop production has led to the built up of chromium in the soil. This is 28 to 30 times higher than chromium found in soils irrigated with groundwater. In addition, tannery effluents were found to have more chemical and biochemical oxygen demands (COD and BOD) and higher carbonate, chloride and calcium levels than the permissible limits prescribed by the Bureau of Indian Standards (BIS). 

The researchers have prepared a geo-accumulation index for soil in the area. They found that soil samples were ‘heavily’ to ‘extremely’ polluted with chromium, ‘moderately’ polluted with cadmium and ‘unpolluted’ to ‘moderately’ polluted with copper, nickel, zinc, lead and arsenic. 

In a paper published in the scientific journal, Bulletin of Environmental Contamination and Toxicology, researchers have noted that the amount of chromium in many groundwater samples was found to be much higher than the standards set by the United States Environment Protection Agency. A member of the research team, M.L. Dotaniya says that about 40 percent of the total chromium used in the tannery industry was found to be released into the environment. 

The researchers have recommended that “the government should take initiatives to strictly monitor the effluent treatment plants regularly and enforce regulations before the release of tannery effluent into the environment. They said that it is also necessary to spread awareness among the people on the impact of tannery effluents on soil-plant-human systems through government and non-government organizations in the tannery effluent irrigated areas.”

The study was conducted by scientists from the Bhopal-based Indian Institute of Soil Science under the Indian Council of Agricultural Research (ICAR). The research team included V.D. Meena, S. Rajendran, J.K. Saha, S. Kundu, A.K. Patra and M. VassandaCoumar. 

(India Science Wire)