Towards an Energy Self-Sufficient Resource Recovery Facility by Improving Energy and Economic Balance of a Municipal WWTP with Chemically Enhanced Primary Treatment

Abstract

The recent trend of turning wastewater treatment plants (WWTPs) into energy self-sufficient resource recovery facilities has led to a constant search for solutions that fit into that concept. One of them is chemically enhanced primary treatment (CEPT), which provides an opportunity to increase biogas production and to significantly reduce the amount of sludge for final disposal. Laboratory, pilot, and full-scale trials were conducted for the coagulation and sedimentation of primary sludge (PS) with iron sulphate (PIX). Energy and economic balance calculations were conducted based on the obtained results. Experimental trials indicated that CEPT contributed to an increase in biogas production by 21% and to a decrease in sludge volume for final disposal by 12% weight. Furthermore, the application of CEPT may lead to a decreased energy demand for aeration by 8%. The removal of nitrogen in an autotrophic manner in the side stream leads to a further reduction in energy consumption in WWTP (up to 20%). In consequence, the modeling results showed that it would be possible to increase the energy self-sufficiency for WWTP up to 93% if CEPT is applied or even higher (up to 96%) if, additionally, nitrogen removal in the side stream is implemented. It was concluded that CEPT would reduce the operating cost by over 650,000 EUR/year for WWTP at 1,000,000 people equivalent, with a municipal wastewater input of 105,000 m3/d.

Energy Self-Sufficiency Aiming for Sustainable Wastewater Systems: Are All Options Being Explored?

“…For example, optimizing economies of scale (pumps as large as feasible), increasing the levels of automation of key processes (aeration), or providing specialized training to operators [11,25,34]. Additionally, by implementing processes with lower energy demand, like those based on anaerobic processes for secondary treatment [7,35].…”

Current Situation and Prospect in Urban Sewage Treatment Plants

“…In addition, CEPT not only has an excellent organic matter capture rate, but also has advantages in organic matter retention. Budych-Gorzna et al [24] studied the coagulation and sedimentation of primary sludge by using ferric sulfate and carried it out on-site. Experiments showed that the COD removal rate reaches 70 %.…”

Hydropower Potential for Energy Recovery in Wastewater Systems. Assessment Methodology and Practical Application

“…For example, optimizing economies of scale (pumps as large as feasible), increasing the levels of automation of key processes (aeration), or providing specialized training to operators (Avilés et al, 2019;Longo et al, 2018;Nakkasunchi et al, 2021). Additionally, by implementing processes with lower energy demand, like those based on anaerobic processes for secondary treatment (Musabandesu & Loge, 2021;Budych-Gorzna et al, 2021). ▪ Second, by the implementation of renewable energy generation technologies (Diaz-Elsayed et al, 2019;Gandiglio et al, 2017;Maktabifard et al, 2018), aiming for energy neutrality or self-sufficiency.…”