Published on September 7, 2016
1. Fresh water scarcity and need for wastewater treatment ICRISAT-IDC Wastewater Team Introduction Increasing population growth rate, depleting fresh water resources, finite available land and food scarcity. The map below shows that India will become water stressed by 2025. Key Dilemmas Lack of fresh water resulted in wastewater use in peri-urban and rural areas for agriculture. Urgent need to recycle low quality wastewater for agricultural use. Wastewater treatment plants in Indian urban cities have low treatment capacities resulting in partially treated wastewater. Estimated wastewater generation i.e. class I and class II towns is 38254 MLD. Treatment capacity in class I and class II cities is 11787 MLD. Huge gap between wastewater generation and treatment. Rural parts of India lack efficient wastewater treatment plants. Past and current wastewater treatment status in India shown in Figure below. Wastewater a valuable resource Nutrient rich wastewater generated from peri-urban and rural areas is perennial and nutrient rich containing nitrogen, phosphorus, coliforms and heavy metals-lead, cadmium, chromium and zinc. Untreated wastewater usage for irrigation pose health hazards. Need for low cost, less energy intensive and minimal maintenance systems for wastewater re-use in agriculture. Need to develop constructed wetlands (CWs) as decentralized wastewater treatment systems for improving wastewater quality and sanitation in rural India. What are Constructed wetlands? Human-made engineered systems as low cost, effective in excessive nutrient reduction similar to a natural wetland and requiring minimal maintenance. 0 2 4 6 8 10 12 14 16 1988-1992 1993-1997 1998-2002 2008-2012 Wastewaterquantity (BMC) Wastewater generation Treated muncipal wastewater Not treated muncipal wastewater discharged 11553 233.7 35558 269.6 0 5000 10000 15000 20000 25000 30000 35000 40000 Class I cities Class II cities Wastewater(millionlitresperday(MLD) Treatment capacity MLD Sewage generation MLD What makes constructed wetlands effective? Physical filtration of nutrients due to coarse sand and gravel media. Adsorption of nutrients/contaminants to surface of sand and gravel media. Microbes present in the wastewater responsible for nutrient transformations. Wetland plants reduce excessive nutrients through its uptake in the above-ground biomass (leaves, stems and branches) and below ground part (roots).