Energy savings with a biochemical oxygen demand (BOD)- and pH-based intermittent aeration control system using a BOD biosensor for swine wastewater treatment

Intermittently aerated activated sludge processes save energy by minimizing the total aeration time per day without deteriorating effluent water quality. Swine wastewater contains high, often widely fluctuating concentrations of biochemical oxygen demand (BOD) and nitrogen. BOD-based aeration control would therefore be a useful method to reduce the energy demands of aeration, but requires a reliable BOD sensor for swine wastewater. In this study we developed a novel approach for BOD- and pH-based intermittent aeration control (BAC) using a BOD biosensor based on exoelectrogenic bacteria and tested it at four swine wastewater treatment plants. This BAC system reduced aeration energy in the plants by 15–36% compared to fixed aeration cycle operations while maintaining low concentrations of BOD and total nitrogen in the effluent. The energy saved per wastewater volume was 477–1012 kWh/m3/yr, equivalent to a reduction of 2.2–7.0 t-CO2/m3/yr in greenhouse gas emissions. The biosensor was equipped with an internet connection to allow for remote monitoring of water quality data with a smartphone, saving labour in the operational management of the plants. Aquabacterium and the aerobic denitrifier Thauera were detected as the predominant genera in the activated sludge. [Display omitted] •A fully automatic and practical BOD biosensor was developed for swine WWTPs.•The BAC system minimizes the total aeration duration per day using the biosensor.•The system saves energy for aeration without deterioration of effluent quality.•This is the first case of utilising BOD as a parameter of aeration control.