Investigating energy and operation flexibility of membrane bioreactors by using benchmark simulations.

Wastewater volumes are increasing globally as a result of increased population and industrial growth. This, together with increasingly stringent discharge limits, has resulted in a consequent rise in energy demand for wastewater treatment. Activated sludge process has been successfully used for more than a century with various configurations for the removal of organic carbon and nutrients. Compared to conventional activated sludge plants, membrane bioreactors (MBRs) offer a higher treatment efficiency, however, they are energy-intensive. The aim of this study is to investigate the operational and energy flexibility of MBRs by mathematical modeling. Based on a variable electricity price tariff, an appropriate optimization strategy can save 9%--41% of the energy cost without violating exiting discharge standards. The results of dynamic simulation revealed that, under variable energy price structures, hybrid MBRs can provide significant flexibility for reducing energy costs while maintaining satisfactory effluent quality. [ABSTRACT FROM AUTHOR]