Greywater reuse in residential schools in Madhya Pradesh, India—A case study of cost–benefit analysis

Greywater treatment and reuse systems were constructed in residential schools (Schools) in Madhya Pradesh, India and treated greywater was used for toilet flushing and irrigating the food crops.Cost–benefit analysis was undertaken for greywater reuse by considering internal and external costs and benefits. The internal costs consist of construction of a greywater reuse system as well as the operation and maintenance costs. The construction cost (material and labour costs) equalled Indian Rupee (INR) 50,300 (1 USD = 42.5 INR) and operation and maintenance cost is INR 5725 per year. Internal benefits were estimated to be INR 30,000 per year due to the reduction in tankered water. Appropriate valuation methodologies were applied to monetize external benefits such as savings on water infrastructure, reuse of pollutants such as nitrogen, phosphorus and potassium (equivalent to market cost of chemical fertilizer). Monetary values of external benefits and costs in terms of environmental and health benefits were derived by using scientific references. The environmental and health benefits were estimated as INR 44,000 and INR 793,380 respectively.In summary, the internal and external benefits of greywater reuse are substantially higher than the internal and external costs.