Closed-loop Wastewater Treatment and Resource Recovery

Abstract

Since the early 20th century the primary source of phosphorus (P) has been extraction from phosphate-rich sedimentary rocks. However, phosphate rock is a non-renewable resource which has no substitutes in the environment. Globally approximately 4.6Mt of P/year is collected in WWTPs equating to 2% total world phosphate rock production. P in wastewaters arises from human excrement, food wastes, dishwasher detergents, laundry detergents, industrial and commercial discharges. In order to reduce eutrophication of water bodies in the EU countries, the Urban Waste Water Treatment Directive was introduced which sets obligatory final effluent P discharge targets for WWTPs. The spreading of sewage sludge containing P to land is an inefficient method of recycling P, due to leaching which enhances eutrophication risk to water bodies. A paradigm shift is required to focus not on what must be removed from wastewater, but rather on what can be recovered from wastewater. This paradigm shift encapsulates the need to change the view of P as a waste or a pollutant, but rather as a resource. Using new process technologies P in municipal sewage can be recovered and processed into a P rich fertiliser, such as struvite. The findings of a recently completed PhD research at the University of Surrey (UK) show that large wastewater treatment plants require careful adaptation to ensure the function of P recovery in the form of commercial grade fertiliser.

About the speaker

Dr Devendra Saroj is Senior Lecturer (Associate Professor) in the Department of Civil and Environmental Engineering at the University of Surrey, UK. Prior to joining Surrey, he worked at UNESCO-IHE (Delft, Netherlands) as a Lecturer in Urban Water Infrastructure Department. His recent work includes water/wastewater infrastructure, urbanization and environment, sanitation technologies, decision support in urban water reuse, and adaptation of sewage treatment for resource recovery and environmental protection. He is involved in projects addressing environmental management challenges in developing countries such India and Philippines. He is particularly interested in technology development & innovation for water and sanitation infrastructure applicable to the urbanising areas of both developed and developing countries.