CHENNAI: For the past two years, a pilot unit at a sugar factory in Krishna, AP, has been exploring ways to improve the quality of industrial wastewater used for agricultural purposes. After several tests, J D Sophia and her team tasted sweet success as they found a natural way to treat wastewater and also increase the crop yield quality.
In a bid to improve quality of industrial wastewater and its potential reuse, India had launched a project Water4Crops, in association with the European Union. The project was executed by a consortium of partners, including research and academic institutions, industries and NGOs.
The three-member team from the M S Swaminathan Research Foundation (MSSRF) in Chennai, led by principal scientist Sophia, decided to work on a project to treat industrial waste from sugarcane factories and distilleries.
“For every kg of sugarcane, 10 litres of wastewater are produced. They are let into water bodies, canals or streams untreated, or used for irrigation. Both ways, it affects agriculture, aquaculture and in turn our health,” said Sophia, whose team worked at the KCP Sugar and Industrial Cooperation Ltd in Krishna since August 2014.
The wastage of water was enormous, considering that according to the 2012 World Bank data, only about one-third of the cultivated lands in the country are irrigated. The integrated agro-aqua farming system designed by the team involved a sequential treatment process. The wastewater undergoes bacterial and algal treatment and biochar (fine-grained charcoal used for soil amendment).
Even halophytes, known for salinity reduction property, help in treatment when planted in constructed wetland. The constructed wetland system itself is segregated into five chambers. The first and fourth chambers are filled with 40-60 mm gravel, while the second and fifth chambers have 20-40 mm gravel. The third chamber, the largest, is filled with a combination of gravel, sand and soil as its filtering medium.
Since the flow of water also plays an important role in the removal of pollutants, the process will involve a hybridised vertical and horizontal sub-surface flow. In distilleries, a sequential integrated system is used for treatment that combined bacterial and phytoremediation processes to not only improve the quality of distillery effluents, but also to demonstrate its reuse potential, the scientists said.
They said the pH levels of the original effluents (acidic in distillery and alkaline in sugar unit) have been brought to neutral after the treatment. “The sequence itself is considered an innovation since bio-treatment is not used in isolation here. Any change in the sequence will not produce the same results,” the scientist explained.
According to Sophia, the productivity of the crops fed with treated water from the sugarcane factory was either on a par or even better than those fed with freshwater.