Pilot scale application of anaerobic baffled reactor for biologically enhanced primary treatment of raw municipal wastewater

A four-cell anaerobic baffled reactor (ABR) was operated for two years treating raw municipal wastewater at ambient water and air temperatures of 12–23 °C and −10 to 35 °C, respectively. The 1000-L pilot reactor operated at a 12-h hydraulic residence time and was located in the Headworks building of the Plum Creek Water Reclamation Authority. The average influent was TSS = 510 ± 400 mg/L, BOD5 = 320 ± 80 mg/L and the average removal of TSS and BOD5 was 83 ± 10% and 47 ± 15%, respectively. The TSS and BOD removal exceeded that of conventional primary clarification, with no wasting of the settled solids over the two-years and stoichiometric production of methane. The estimated energy content of the biogas produced per unit volume of wastewater treated averaged 0.45 kWh/m3. The TSS and total COD removal in the first cell averaged 75 ± 15% and 43 ± 14%, respectively, but methane production was only 20% of the total observed for the full ABR. The performance of the ABR relative to the extent of solids hydrolysis and methane production can be varied by the number of cells and hydraulic residence time. The anaerobic baffled reactor is an energy-positive technology that can be used for biologically enhanced primary treatment of raw municipal wastewater in cold climates. [Display omitted] •A mainstream anaerobic baffled reactor (ABR) was operated for two years at 12–23 °C.•The average removal of TSS and BOD5 was 83 ± 10% and 47 ± 15%, respectively.•Stoichiometric amounts of methane were produced based on ultimate BOD removal.•ABR operation does not require energy, and biogas energy content was 0.45 kWh/m3 flow.•No settled solids were wasted over the two years of operation.