Decentralized wastewater treatment using ‘pumped flow biofilm reactor’ (PFBR) technology

Clean water resources are imperative for sustainable development. Thus, protection and management of waters receiving wastewater discharges have received significant attention from policy and regulatory bodies. The quality of wastewater effluent must meet regional (e.g. Water Framework Directive), national and local discharge standards. In addition, there is now significant pressure on engineers and operators to reduce energy consumption, sludge production and operation/maintenance issues, particularly at small-scale and decentralized wastewater facilities. Therefore, significant interest has risen in new technologies and operational insights which can (i) minimize operating costs; (ii) simplify and reduce the use of mechanical equipment; (iii) result in low sludge production; and (iv) ease operation/maintenance. This study investigated the performance of a small-scale municipal wastewater facility over 5 months from commissioning. The facility uses a new biofilmbased technology – the pumped flow biofilm reactor. Two experimental periods Phase 1 (28 to 36 days) and Phase 2 (Days 100 to 146) were examined. During Phase 2, removal rates averaged 98% for 5-day biochemical oxygen demand (BOD₅), 93% for total suspended solids, and 94% ammoniacal-nitrogen (NH₄-N). Energy requirements averaged 0.22 kWh.m^-3_treated and 1.74 kWh.kg-BOD₅^-1_removed. Extensive, camera-based studies revealed minimal excess sludge in the reactor tanks and sludge removal was not required during the study period. The use of vertically stacked plastic media to support the biofilm may have limited biofilm sloughing. Sludge yield during steady state operation was estimated at around 0.03 g-SS.g-COD^-1_removed. The study indicates that given careful design and operation, small-scale wastewater treatment systems can be as efficient as much larger, fully manned plants.