Municipal wastewater treatment using a full-scale pumped flow biofilm reactor (PFBR)

A novel wastewater treatment technology, suitable for centralised and decentralised wastewater treatment and known as a pumped flow biofilm reactor (PFBR), has been developed and patented in the National University of Ireland, Galway (NUI Galway). This two-reactor-tank technology has been extensively tested at laboratory-scale and trialled at a number of sites for populations ranging from 15 – 400 population equivalents (PE). Hydraulic pumps are used to cycle the wastewater from one reactor tank to the other. A biofilm process, the system is characterised by: (i) its ease of operation and maintenance; (ii) low operating costs; (iii) low sludge production; and (iv) comprising no moving parts or compressors, other than hydraulic pumps. Aeration is achieved by alternately exposing the biofilm (attached to plastic media modules) in each of the two reactor tanks to atmospheric air, thereby eliminating the need for forced aeration. By operating the system in a sequencing batch reactor (SBR) mode, the following treatment can be achieved: 5-day biological oxygen demand (BOD5), chemical oxygen demand (COD) and suspended solids (SS) reduction; nitrification and denitrification. During an 80-day full-scale plant study operating at 150 PE treating municipal wastewater, average removals of 97 % BOD5, 95 % SS and 81 % ammonium-nitrogen (NH4-N) were achieved. Effluent concentrations averaged: 8 mg BOD5/l; 45 mg COD/l; 5 mg SS/l; 6 mg NH4-N/l; and 5 mg NO3-N/l (nitratenitrogen). The average energy consumption was 16 kWh/day – or about 0.6 kWh/m treated.