Reusing wastewater can ease pressure on burdened centralised water supply systems in urban areas. However, existing systems are not cost-effective.
Researchers from IIT Madras and Germany analysed the issue. Greywater, from domestic and commercial sources, contains lower levels of contamination, making it easier to treat and process. But wastewater with fecal matter, urine and other pathogen-rich contaminants requires more elaborate treatment and is usually done in a centralised system. Existing greywater and wastewater reuse networks show low velocity of flow leading to deposition in sewers. This leads to additional costs in terms of maintenance, and the costs outweigh the benefits. To enhance the economic feasibility of these reuse systems, there was a need for optimization.
There are two possible models. One involving on-site treatment and reuse of grey water and the other, involving decentralized treatment and reuse of treated waste water. The researchers studied the economic feasibility of integrating both models into existing sewerage systems using two test cases: a hypothetical network and a realistic network resembling the network in IIT Madras.
They optimised greywater and wastewater treatment and reuse by examining the factors involved in each model and estimated the total cost of implementing each network, considering factors such as sewer details and velocity of flow in each sewage pipe, water demand and expected population growth.
The team found that the optimal implementation of on-site greywater reuse would significantly reduce the cost of water supply by twenty per cent. And fresh water demand would reduce by more than thirty-six per cent.
The optimisation model outlined by the researchers can ensure that the annual cost of greywater treatment and reuse is viable. Additionally, the cost of centralised fresh water supply will decrease due to decreased local demand.
Engineers and decision makers in public works departments need to examine the practical utility of the research results for the sustainable use of water – a precious resource.
Water 2021, 13, 2004
Ohviya Raja Prakash
TERI School of Advanced Studies, New Delhi