Life cycle costs of advanced treatment techniques for wastewater reuse and resource recovery from sewage sludge

Abstract

Water treated in advanced wastewater treatment plants (WWTPs) could be reused as potable water to address water shortages. Furthermore, sludge from WWTPs can be used to recover nutrients, energy and chemicals. Thus, the role of WWTPs could change from traditional pollution control facilities to sources of freshwater and other valuable resources. However, the economic viability of advanced wastewater and sludge treatment methods aimed at production of potable water and recovery of other resources is currently unknown. To address this gap and inform their future development, this paper considers life cycle costs of the following four wastewater treatment methods: granular activated carbon, nanofiltration, solar photo-Fenton and ozonation. For recovery of resources from sludge, the following options are examined: agricultural application of anaerobically-digested and composted sludge, incineration, pyrolysis and wet air oxidation. Ozonation has the lowest life cycle costs, averaging £112 per 1000 m3 of water treated, followed by nanofiltration at £134. Solar photo-Fenton is the most expensive option with £238/1000 m3. These costs are significantly lower than water desalination and could be competitive in the future with conventional potable water production. For resource recovery from sludge, anaerobic digestion, pyrolysis and wet air oxidation can operate at a profit with the negative overall life cycle costs (-£65, -£291 and -£26/1000 kg dry matter, respectively) if all their recovered products are fully utilised. The next best option is composting with the total life cycle costs of £35/1000 kg dry matter. Incineration is the least preferred alternative with the cost of nearly £54/1000 kg dry matter. Advanced wastewater and sludge treatment would increase the costs of conventional wastewater treatment by 1.5–2.1 times.