Opportunities to improve energy use in urban wastewater treatment: a European-scale analysis

Abstract

Wastewater treatment is an essential public service that has a major impact on energy use in the urban water cycle, thus receiving increasing attention in context of the Water-Energy Nexus. Understanding the current energy use for wastewater is an essential step to design reliable policies promoting a more efficient use of resources. This paper develops a pan European estimation of electricity use for the treatment of wastewater, based on a dataset of wastewater treatment plants (WWTPs) across the continent. Prediction of electricity use has been performed using a statistical model that accounts for economies of scale. Different scenarios of improvements of energy use efficiency have been investigated to understand the possible reductions in electricity consumption at the continental scale. The overall WWTP electricity use in Europe (only plants with no less than 2000 population equivalent (PE) have been considered) was estimated at 24 747 GWh yr −1 , about the 0.8% of the electricity consumption in the EU-28. Small plants (less than 50 000 PE) represent almost 90% of the total number of plants, but process only 31% of the PE and require 42% of electricity use. Plants from mid to very large size (more than 50 000 PE), being only 10% of the plants, process about 70% of the PE with 58% of the total electricity use. If all plants that use more than the current average were shifted to the average value, the saving would be slightly more than 5500 GWh yr −1 . With highly stringent targets of efficiency improvement, saving of about 13 500 GWh yr −1 could be expected. Further considerations on the emerging role of WWTPs as energy and material producer are finally discussed.

Operation and Performance of Austrian Wastewater and Sewage Sludge Treatment as a Basis for Resource Optimization

“…While conventional wastewater treatment with the activated sludge system (mechanical, biological and chemical) was well established by the end of the 1990s [1], new issues have risen to the center of attention in the 21st century. The reduction of energy consumption [2,3], stricter effluent quality requirements for carbon and nutrients [4], the recovery of resources [5,6], wastewater reuse [7,8] and the removal of contaminants of emerging concern [9] and of antibiotic resistant genes [10,11] are only some of the new challenges to be addressed. This multitude of new tasks will in some cases not support themselves economically and might have negative side effects on the environment due to higher energy and/or material demands [12].…”

A critical review of resource recovery from municipal wastewater treatment plants – market supply potentials, technologies and bottlenecks

“…135 The European research project Powerstep is currently elaborating designs for energyneutral and energy-positive WWTPs through six different case studies. 136 The recovery of methane to generate electricity can usually offset 25-50% of a WWTP's energy needs, assuming that conventional treatment technology is used. 40 If thermal energy recovery from effluent is applied along with chemical energy recovery, carbon neutrality or better can be achieved.…”

Modelling to Lower Energy Consumption in a Large WWTP in China While Optimising Nitrogen Removal

“…Furthermore, in practice, the energy demand is inversely proportional to the treatment capacity of the plant, for capacities below approximately 38,000 m 3 /d or 190,000 PE-for 200 L/(PE•d) [1]. This is also observed in Europe, where plants smaller than 50,000 PE represent almost 90% of the total number of plants, but process only 31% of the PE and require 42% of the electricity use [6].…”

“…Therefore, in optimisation studies, these are usually the first consumers to pay attention to. It is estimated that WWTPs represent about 1-3% of the overall energy use of country [5]; in Europe, the overall electricity use of WWTPs > 2000 PE, is about 0.8% of t total electricity consumption in the EU-28 [6]. Furthermore, in practice, the ener demand is inversely proportional to the treatment capacity of the plant, for capacit below approximately 38,000 m 3 /d or 190,000 PE-for 200 L/(PE•d) [1].…”