EUI4: Energy Systems Integration in Large-scale Wastewater Treatment

Thermodynamic calculations show that the chemical energy in biodegradable and inert chemical oxygen demand and reduced nitrogen in municipal wastewater is approx. 2kWh per m3. Largescale Waste Water Treatment (WWT) plants can recover between 5 to 15% of this energy through anaerobic digestion. However, since other important parts of the treatment plants are energy intensive (aerobic biological oxidation requires 0.40-0.65 kWh per m3 of water), it follows that most treatment plants are net users of energy. With the advent of new and improved treatment technologies a net-energy-positive wastewater treatment plant is now considered achievable. However, a significant challenge in this area is the presence of very significant fluctuations in the energy demand from a WWT due to diurnal fluctuations in flow rates and concentrations of carbon and nitrogenous pollutants.

An integrated energy system approach provides opportunity to provide decision support on process operation strategies increase/decrease loading to follow electricity tariffs and/or short-term loading response to provide power system flexibility. Thus, there is a need for real-time data analysis and forecasting systems that will inform process control strategies. The benefits of such an approach are cost savings, improved control systems and decision support systems for planning plant upgrades as part of long-term wastewater throughput and/or tightening nutrient discharge limits.

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