There's garbage in your greens. That fresh cucumber in your salad or your dose of green leafy veggies could well have been grown using raw sewage discharge.
As water scarcity mounts, farmers in the semi-urban areas are increasingly using sewage or waste water to grow veggies, cereals and fodder. The big concern is a large part of the sewage discharge from the urban centres is untreated, thereby triggering contamination risks on health and environmental issues.
“The area under waste water irrigation is on the rise in India at an estimated one million hectares,” said Mr Avinash Chand Tyagi, Secretary-General, International Commission on Irrigation and Drainage (ICID), an inter-governmental body.
“The poor farmers have no other option but to use the free flowing sewage that's available round the year. The cropping intensity is also high as they grow three to four crops,” Mr Tyagi said.
Rich in macro nutrients
Moreover, the sewage water is rich in macro nutrients such as nitrogen and potash and even in micro-nutrients like phosphorous, calcium and magnesium. “It reduces the demand for nitrogen and phosphatic fertilisers by 25-50 per cent and increases the yield by 15-27 per cent,” said, Ms Ravinder Kaur of the Water Technology Centre of the Indian Agriculture Research Institute.
India is the third largest user of waste water in irrigation after China and Mexico. The ICID, in collaboration with the United Nations Environmental Programme, the UN Water Decade Programme, and the International Water Management Institute, is trying to raise awareness on the safe use of waste water.
“Only 37-38 per cent of the sewage is treated in India due to inadequate capacity,” said Mr J. S.Samra, CEO of the National Rainfed Area Authority under the Planning Commission. He suggests the need to treat sewage even in the rural areas, where rising income levels have boosted consumption levels. Safe water use in agriculture is important mainly from the point of food security, livelihood security and environmental safety, Mr Samra added.
“There's mismatch between the waste generated and the waste treated,” Ms Kaur said, stressing the need to devise strategies for promoting use of waste water in agriculture.
High installation and operational costs, coupled with the shortage of skilled labour, are the major limitations for the proper functioning of the installed sewage treatment plants that are energy-intensive.
At present, about 83 per cent of the total water available is consumed by agriculture. With increasing trend in urbanisation and industrialisation and climate change impacting the supplies, the share of water usage in agriculture is likely to come down to around 70 per cent by 2050, says Mr Samra.
The low government investments in waste water treatment and management and the absence of any national guidelines for safe disposal and application in agriculture are some of the biggest challenges, Ms Kaur said. Further, there is no impact assessment of waste water irrigation in terms of soil, groundwater, food quality and health risks, Ms Kaur said stating that “pollutants are spread all over”.