Energy benchmarking in wastewater treatment plants: the importance of site operation and layout

Abstract

Energy benchmarking is a powerful tool in the optimization of wastewater treatment plants (WWTPs) in helping to reduce costs and greenhouse gas emissions. Traditionally, energy benchmarking methods focused solely on reporting electricity consumption, however, recent developments in this area have led to the inclusion of other types of energy, including electrical, manual, chemical and mechanical consumptions that can be expressed in kWh/m3. In this study, two full-scale WWTPs were benchmarked, both incorporated preliminary, secondary (oxidation ditch) and tertiary treatment processes, Site 1 also had an additional primary treatment step. The results indicated that Site 1 required 2.32 kWh/m3 against 0.98 kWh/m3 for Site 2. Aeration presented the highest energy consumption for both sites with 2.08 kWh/m3 required for Site 1 and 0.91 kWh/m3 in Site 2. The mechanical energy represented the second biggest consumption for Site 1 (9%, 0.212 kWh/m3) and chemical input was significant in Site 2 (4.1%, 0.026 kWh/m3). The analysis of the results indicated that Site 2 could be optimized by constructing a primary settling tank that would reduce the biochemical oxygen demand, total suspended solids and NH4 loads to the oxidation ditch by 55%, 75% and 12%, respectively, and at the same time reduce the aeration requirements by 49%. This study demonstrated that the effectiveness of the energy benchmarking exercise in identifying the highest energy-consuming assets, nevertheless it points out the need to develop a holistic overview of the WWTP and the need to include parameters such as effluent quality, site operation and plant layout to allow adequate benchmarking.

Enhancing the Energy Efficiency of Wastewater Treatment Plants through Co-digestion and Fuel Cell Systems

“…Data referred to the UK WWTPS (Table 1), are two values derived by the analysis of two sites (Belloir et al, 2015). This work showed how sites with similar energy consumption rate and similar shares, can require different optimization approaches.…”

“…The Directive mandates the protection of the environment from pollution coming from industries and sectors having a high organic load (Jonasson, 2007). Belloir et al mentioned that WWT industry is the fourth largest energy intensive segment in UK, with an annual consumption of 7703 GWh/y, accounting for 1% of annual GHG emissions (Belloir et al, 2015).…”

“…In WWTPs, not only electrical energy is consumed but also chemical (fuel) energy, labor energy and thermal energy. On the other hand, as discussed by Belloir et al (2015), the largest portion of the overall annual primary energy consumption is electrical.…”

“…The UK environment agency has released a report called "Transforming wastewater treatment to reduce carbon emissions," outlining five key strategies: "Source control, Least-carbon end-of-pipe/process addition, Greater operational efficiencies, Redeveloping existing treatment processes and Renewable energy generation" (Sadler et al, 2009;Belloir et al, 2015).…”

A Novel Check-List Strategy to Evaluate the Potential of Operational Improvements in Wastewater Treatment Plants

“…For these reasons, WWTPs are the subject of many research projects aimed to improve the quality of discharged water [3], to improve the value of secondary products [4], and to reduce the energy consumption of the wastewater treatment process [5]. In order to implement the obtained knowledge in practice, it is necessary to constantly evaluate best available technologies for WWTP (e.g., Reference [6,7]). Optimizing the current equipment is one of the ways to adapt current technologies to new requirements, streamline their operation, or save costs.…”