October 20, 2014

Systematic Planning for Wastewater Reuse in Agriculture

Priyanie Amerasinghe, International Water Management Institute Priyanka Nanayakkara, University of California, Los Angeles

Across villages and cities in India (and around the globe), water plays an undeniably vital role in human survival and resilience. In today’s world, wastewater could possibly be playing an even bigger role, particularly in agriculture development, although this is not well documented due to its informal nature. Urban return flow, or wastewater, constitutes 70-80% of the water supply in India, a staggering figure that asks us to delve deeper into the issues surrounding wastewater treatment. The challenges associated with wastewater management are explored in the report Urban Wastewater and Agricultural Reuse Challenges in India by Amerasinghe, Bhardwaj, Scott, Jella and Marshall; a few key insights are discussed below.

Inefficient and inadequate wastewater treatment in India

Two main issues regarding wastewater in India have to do with its treatment. The first is simply that current treatment capacities are inadequate. According to the authors, “wastewater generation is around 60-70% over the established treatment capacity, which varies from city to city.” This means that the majority of the generated wastewater cannot be treated even if all the treatment facilities were to run smoothly and efficiently, which is not always the case. The second issue is that not all treatment systems are operating at full capacity, due to the low level of connectivity to the sewage network systems, and/or other priorities and availability of funds of the respective municipalities.

This apparent lack in wastewater treatment does not come without consequences. Vast amounts of untreated wastewater can enter rivers, thus leading to aquatic pollution. This is evidenced by rivers with high biochemical oxygen demand (BOD) levels. BOD levels indicate the amount of organic pollution in a water sample. As examples, the report points to (among others) the Amalkhardi River (State of Gujarat), which at one point had a BOD level of 714 mg/L, and the Ghaggar River (State of Punjab), which at one point had a BOD level of 626 mg/L.  Water quality standards for India prescribe BOD levels for different uses, and in general state approximately 2-3 mg/L as being safe for human use. Polluted water sources seem to have especially negative impacts on the health of residents in cities with heavy industry, such as Ahmedabad and Kanpur, where “visible ulceration, callous tissue formation, heavy skin irritations and dark fingernails” were observed in those who came into contact with this water.

Women planting paddy rice in India. Photos courtesy of Kimberley Gibson.

Women planting paddy rice in India. Photos courtesy of Kimberley Gibson.

Potential uses for treated wastewater in agriculture

Though untreated wastewater can have several detrimental effects on human health, treated wastewater may have an immense potential to benefit agriculture. The report cites evidence that wastewater-irrigable land “can be estimated to be around 1.1 million hectares.” At farm level, using treated wastewater can contribute to higher incomes. During a summer season in Delhi, farmers who used treated wastewater to grow okra had a net income of more than double that of farmers who used groundwater to grow okra because their yields were much higher and they also spent less on fertilizer.

Hence, it is imperative that we continue the study of treatment systems of different types (from low-cost to networked systems) to gain a better understanding of the use of treated wastewater in crop production. As mentioned above, the report discusses the income benefits of treated wastewater usage for farmers, but it also notes that it is important that “a more holistic economic analysis to capture the net benefits to the households and social benefits to the communities” is conducted. Conversely, there is also a need to understand the potential negative externalities and health impacts on farmers and consumers. One main impediment to continued research could be the lack of systematic data on the different discharges.” Therefore, it is important to develop systematic methods for collecting, recording, and analyzing data on wastewater generation and management at a national level to have insights into alternative uses of treated wastewater and also promote safe use of wastewater for agriculture.

As an important first step, the authors present “a data collection and collation template for assessing the wastewater generation and use within the country.” Needless to say, investing time and resources into understanding wastewater management will be necessary in the years to come as India continues to grow and develop.

Priyanie Amerasinghe is a senior researcher at the International Water Management Institute’s Hyderabad office, India. She is a public and environmental health specialist and researches on urban/peri-urban agriculture and related policy issues. Priyanka Nanayakkara is a candidate for a degree in Applied Mathematics at the University of California, Los Angeles and is a blogger in her leisure time.

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  • V. Balasubramanian
    October 20, 2014 at 4:16pm

    Wastewater is a significant source of nutrients as well as pathogens and heavy metals that could cause health risks to users. After treatment, both nutrients and water can be safely used to enrich soils and produce higher yields. In farmers practicing peri-urban and urban agriculture just outside many cities use treated or partially treated wastewater for vegetable production on a sustainable manner, the health risks of such practices for farmers and consumers need to be analyzed and prevented.