Urban wastewater and agricultural reuse challenges in India

Urban wastewater management has become a challenge in India as infrastructural development and regulations have not kept pace with population growth and urbanization. Annually, more and more people are moving into cities, and the figures are expected to reach about 600 million by 2030 making India more peri-urban than rural. Already, there is enormous pressure on planners to provide utility services, and water supply is a priority, especially where peri-urban water is exported formally or informally to fulfill city requirements. At the same time, the urban return flow (wastewater) also increases, which is usually about 70-80% of the water supply. This study attempted to analyze the current status of wastewater generation, its uses and livelihood benefits especially in agriculture, based on national data and case studies from Ahmedabad, New Delhi, Hyderabad, Kanpur and Kolkata. The challenge of the growing Indian economy is that, in many cities, the wastewater generated is a mixture of domestic and industrial wastewater which makes risk mitigation and reuse recommendations a challenge. Lack of systematic data on the different discharges makes it difficult to estimate the volume and quality of wastewater discharged and the total area under (usually informal) wastewater irrigation. Data from more than 900 Class-I cities and Class-II towns (with the population of each over 1 million and between 0.5 and 1 million, respectively) showed that more wastewater gets collected than eventually treated. In general, wastewater generation is around 60-70% over the established treatment capacity which varies from city to city. Governmental efforts to reduce surface water pollution remain jeopardized by the untreated wastewater fraction as well as by India's estimated 160 million latrines and septic tanks which contribute, according to Centre for Science and Environment (CSE), to 80% of the pollution of the national surface waters. The way forward will have to be built on further investments in treatment capacity for septage collected from on-site sanitation units, and in particular for industries to avoid interference in domestic and industrial waste streams. Reuse could offer business opportunities for cost recovery, while in smaller towns options like riverbank filtration, reed bed technologies and phytoremediation should also be explored to turn the waste stream into a resource. From the data set used for this study, it is evident that over 1.1 million ha could be irrigated if rendered safe for use. The major users of wastewater in the study sites include growers of cereal (like rice), horticultural and fodder crops and aquaculture (mostly in East Calcutta Wetlands [ECW] and also in Delhi), and to a lesser extent floriculturists. In Delhi and Kanpur, treated water was issued by farmers for agricultural production. However, with time the quality of wastewater had deteriorated, especially in Kanpur and it was no longer suitable for crop cultivation. In Hyderabad, although the government did not support the use of partially treated wastewater for irrigation, the farmers used it as it was the only source of water downstream of the city. Industrial pollution was highest at Kanpur and Ahmedabad so that both water quality and crop quality were affected at the heavily polluted sites. Data from the selected sites show that the financial benefits associated with wastewater farming were higher than those associated with freshwater-agriculture for cities where domestic wastewater does not mix with industrial sewage. Also, adverse health and environmental impacts were lower in such cities. The highest gains were reported from the ECW, where sewage farming has been practiced for over a century. However, a more holistic analysis which includes all household expenses like health, food, etc., and considers both direct and indirect costs and benefits would be required to calculate the net benefits. Particular attention is required to assess the effects of hazardous contaminants on water, soil and crops. Health risk assessments from most cities showed that wastewater farmers were more vulnerable than others to certain diseases and environmental hazards. However, site-specific health risk assessments are needed to investigate the short- and long-term health impacts of wastewater, so that effective remedial measures could be adopted. Given the increasing peri-urban character of India, this study showed that wastewater management needs much more attention than it has received so far. This is required from the perspectives of both health and water resources management. With nearly 70% of the population projected to live in cities, and water scarcity being reported from many parts of the country, planners need to have a strategy on how best to utilize the various water resources, including untreated, partially treated and fully treated wastewater, for different productive purposes. Monitoring and data collection are increasing in India but they must be carried out in a systematic manner. Institutionalizing the proposed data collection template which links into an extended AQUASTAT database could help collect uniform data sets for strategic planning.