Operation of a full-scale pumped flow biofilm reactor (PFBR) under two aeration regimes

A novel technology suitable for centralised and decentralised wastewater treatment has been developed, extensively tested at laboratory-scale, and trialled at a number of sites for populations ranging from 15 to 400 population equivalents (PE). The two-reactor-tank pumped flow biofilm reactor (PFBR) is characterised by: (i) its simple construction; (ii) its ease of operation and maintenance; (iii) low operating costs; (iv) low sludge production; and (v) comprising no moving parts or compressors, other than hydraulic pumps. By operating the system in a sequencing batch biofilm reactor (SBBR) mode, the following treatment can be achieved: 5-day biochemical oxygen demand (BOD₅), chemical oxygen demand (COD) and total suspended solids (TSS) reduction; nitrification and denitrification. During a 100-day full-scale plant study treating municipal wastewater and operating at 165 PE and 200 PE (Experiments 1 and 2, respectively), maximum average removals of 94% BOD₅, 86% TSS and 80% ammonium-nitrogen (NH₄-N) were achieved. During the latter part of Experiment 2, effluent concentrations averaged: 14 mg BOD₅/l; 32 mg COD_filtered/l; 14 mg TSS/l; 4.4 mg NH₄-N/l; and 4.0 mg NO₃-N/l (nitrate-nitrogen). The average energy consumption was 0.46–0.63 kWh/m³_treated or 1.25–1.76 kWh/kg BOD_{5 removed}. No maintenance was required during these experiments. The PFBR technology offers a low energy, minimal maintenance technology for the treatment of municipal wastewater.