Saving Energy Through Use of Biofiltration for Advanced Primary Treatment of Wastewater

Water and wastewater treatment account for substantial energy consumption, statewide and across the country. Conventional wastewater primary treatment uses clarification for solids removal and activated sludge treatment for secondary treatment to remove organics. Biofiltration is an emerging advanced primary-treatment technology that more efficiently and economically removes particulate and soluble material than the conventional primary method of clarification that removes only particulate material. In a biofiltration system, particulate material is removed mainly through filtering, and soluble organic material is removed by using microorganisms to capture and biologically degrade the pollutants. Biofiltration generates energy savings by removing more organic load (when compared with conventional primary treatment), which in turn reduces aeration electricity consumption in the downstream biological treatment and increases digester gas energy production from the diverted organic material. Additional benefits include reduced capital costs and a smaller physical footprint requirement for primary treatment.

Energy savings from biofiltration were demonstrated and quantified at a demonstrationscale biofiltration system at the Linda County Water District Wastewater Treatment Plant, north of Sacramento, California, from July 2018 through March 2020. Throughout the study, the biofilter performed at high levels of total suspended solids, biochemical oxygen demand, and chemical oxygen demand removal. Analysis of 40 sample sets showed total suspended solids, biochemical oxygen demand, and chemical oxygen demand removal rates of 70, 52, and 50 percent, respectively. Biological removal also increased with biofilm development on the filter media. Results showed soluble biochemical oxygen demand and soluble chemical oxygen demand removals of 22 and 25 percent, respectively. The biofilter’s total suspended solids, biochemical oxygen demand, and chemical oxygen demand removal performance was approximately 30 to 50 percent higher than with primary clarification. This report evaluates the feasibility of biofiltration as an advanced primary treatment technology based on treatment performance, hydraulic performance, energy consumption, and performance simulation results.