Accept refuse: A lesson in wastewater management

There is a new technology available now to reuse domestic and industrial refuse. This could just be the solution to India’s increasing water problem.
Constructed wetland at ICRISAT's Patancheru campus. Constructed wetland at ICRISAT's Patancheru campus.

The demand, supply, availability and access of water resources do not always match. Going by the UN estimates, by the year 2022, India is expected to surpass China's population to become the most populous country in the world. As the population increases, the demand for freshwater goes up; with increased usage, the quantum of waste produced increases as well. Changes in land-use patterns, climatic variabilities and diminished efficiency to use resources only strain the available reserves further.

The last 50 years have witnessed the rapid dwindling of per capita availability of freshwater resources--from 3,000 cubic metres to 1,123 cubic metres. The Central Water Commission pegs the overall demand for water in India at 1,180 billion cubic metres in 2050.

Over 60 percent of agriculture and 85 percent of the country’s drinking water supply are groundwater-driven. With groundwater getting depleted, wastewater—from both industries and households—if treated well, can play a crucial role in taking care of a portion of the country’s water needs. 

In his book Self-reliance in water, urban environmentalist Indukanth Ragade mentions that though the quality of grey water generated at homes and industries are not comparable, both can be recycled and reused. “The nomenclature needs to be changed. Stop calling it wastewater. Used water is a more appropriate word,” he asserts.

The central government has laid down strict zero-discharge norms for industries to ensure maximum recovery of reusable water and minimise discharge of pollutants into the environment.

Wastewater being used to irrigate agricultural fields in Karnataka. (Source: IWMI)Using municipal or industrial wastewater for irrigating fields is not new in India. Given that fresh water is a luxury in most parts of India, it is only natural that the farmers are drawn towards wastewater. The International Water Management Institute (IWMI) has documented cases where wastewater has been auctioned for agricultural use in Gujarat.

Constructing wetlands to treat wastewater is a proven technology in the West. Wetlands are of two types--the ones which allow water to flow over the surface (free flow) and those which treat them underground (sub-surface). A series of physico-chemical and biological reactions of plants and micro-organisms like algae and bacteria to help recycle nutrients in wastewater form the core of the constructed wetland treatment technology.

Photosynthesis by algae helps improve the dissolved oxygen content of the water. Vascular plants like typha and canna absorb nutrients from the water, incorporating them into the plant tissue. By doing so, they also provide a substratum for micro-organisms to thrive on. Once this system settle, diffuse, break down and uptake the nutrient, the water exiting the system is stripped off most of its organic and inorganic load.

India-EU collaboration for waste

In one of the largest scientific collaborations between the European Union and India, the Water4Crops project--launched simultaneously in both places in 2012--aims to work out ways to biotechnologically treat and divert industrial and municipal wastewater for agricultural reuse. Agricultural universities and research institutions, along with agri-business industrial partners from the EU and India are involved in developing efficient models for biotechnological wastewater treatment and improved usage of recycled water. The Indian component is funded by the Department of Biotechnology (DBT) under the Union Ministry of Science and Technology.

“Most European countries thrive on surface water which is available in plenty. Recycled water is mainly for watering lawns, gardening and the likes. India is both water and nutrient scarce. As recycled grey water remains relatively nutrient-rich, it gives us the survival advantage and not just a scenic one,” remarks Dr Suhas P. Wani, director, The International Crops Research Institute for the Semi-Arid Tropics (ICRISAT) development centre and scientific coordinator for the Indian component of the Water4Crops project.

Schematics of the constructed wetland. (Source: Water4Crops)The scientific planning process took into account the quality of incoming wastewater and pollutant profiles so as to come up with appropriate designs to remove specific contaminants and make wastewater irrigation friendly. “The aim is to demonstrate technologies that ensure safe water for agriculture. Only when people see something functioning well will they be motivated to set up treatment systems on their own,” adds Wani.

Sugar processing and distillery industries joined hands with the Indian consortium’s research partners to improve their wastewater treatment efficiency while the primary concern for municipalities and panchayats was to manage their liquid waste properly to ensure overall cleanliness and hygiene. Demonstration units now operate across 30 sites; 27 sites are dedicated to showcasing domestic wastewater treatment technology and three are for industrial refuse.

Polluting sugar

The sugar industry is one of the country’s most advanced agro-based industries and is also one of the most polluting. With its high organic and inorganic load, effluents from sugar industries and distilleries, if not properly treated and disposed of, can wreak havoc on both surface and groundwater.

“Close to 3.2 million cubic metres of water is being used on a daily basis by the country’s 550-odd sugar industries,” says principal scientist from the M S Swaminathan Research Foundation (MSSRF), Dr J. D. Sophia. The process also generates 0.6 million cubic metres of effluent daily. Along with Sophia, a team of scientists from the MSSRF has been working for over two years at one of the Water4Crops’ industrial collaborator’s production facility--KCP Sugar in Lakshmipuram, Andhra Pradesh. While the factory has the infrastructure for the primary treatment of raw industrial wastewater, the water is still not fit for direct agricultural use. Farmers have been using this for cultivating sugarcane and paddy during summer months when there is a break in water supply from the Krishna barrage.

Constructing wetlands to treat wastewater

The MSSRF team designed a five-chambered wetland to polish off the primary treated sugar-processing wastewater to ensure its suitability for irrigation. Depending on the incoming water quality, retention time in the wetland is calculated to ensure increased treatment efficiency. Locally-consumed fish varieties such as catla and rohu are reared in the tanks that hold the recycled water which is periodically drained into surrounding fields. Farmers report substantial reduction in fertiliser use as the treated water is rich in nitrates and potassium (the N and K of the common three-component NPK fertilisers) and also an improvement in the weight of both cane and juice.

Effluents from sugar industries wreak havoc on water sources if not treated and disposed off properly. (Source: The Hindu)Due to its higher organic load, the process for treating distillery waste is slightly different. A four-stage sequential treatment process involving bacteria, algae, activated charcoal and planted soil bed has been put in place at KCP’s Vuyyuru distillery to polish anaerobically pre-treated effluents. “The system functions purely because of the sequence. If the algae are placed ahead in the sequence or the bacterial culture is pushed towards the end, the system will collapse,” explains Sophia. 

Tests reveal an 89.7 percent drop in biological oxygen demand (BOD) and a 61 percent reduction in total dissolved solids (TDS), indicating a marked improvement in the water quality. The treated water has been used for cultivating sweet corn in nearby fields.

Seeing is believing

As the quality and pollutant profile are completely different from the industries, the media for filtration (the type and quantity of gravel used) and design specifications differ for treating domestic waste. Care has been was taken to ensure that the systems were low-tech, affordable and simple to ensure long-term sustainability. Artificial wetlands were constructed at one or two sites in a village manned and maintained by local self-help group (SHG) members.

Tests in Telangana’s Kothapally village reveal the system’s satisfactory functioning--chemical oxygen demand (COD) reduction of 65 percent have been observed, indicating a decrease in pollutants along with an 87 percent pathogen-removal efficiency. “Though the objective and the design varied, our singular goal was to demonstrate affordable technology for people to observe and learn. Seeing is believing,” remarks Wani.

Improvement in local village hygiene is open for everyone to see. Representatives from neighbouring panchayats have been visiting demonstration sites, looking to replicate these systems in their villages. Impressed by the results, the DBT has given in-principle approval for the project’s second phase. The government is also keen to make this an integral part of the Swachh Bharat Abhiyan to ensure grey-water recycling spreads far and wide.

“Knowledge gained in labs often gets lost in transit before they reach the farms. It has not happened here so far and we hope to keep it that way,” says Wani. As a critically water-starved nation, we hope so, too.

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