Biocarbone Aerated Filters - Ten Years After: Past, Present, and Plenty of Potential

About ten years ago, the first full scale Biocarbone aerated filter went into service in Soissons (France) for a capacity of 40 000 population equivalents. This compact wastewater treatment system combines aerobic biodegradation and filtration in one unit, eliminating the need for clarifiers and achieving high removal rates through fixed biomass. Since, a number of independent investigations have been performed to establish dimensioning criteria and process performance. This article summarises the reports of the US EPA, the Japanese JSWA, and the British WRC, as well as experiences acquired by cities and water authorities. In pilot and demonstration scale, reactor kinetics, sludge production and energy consumption was measured. Most reports agree on removal rates up to 4 kg BOD/m 3 d or nitrification rates around 0.6 kg N/m 3 d. Sludge yields ranged consistently around 0.8 kg SS / kg BOD removed, but oxygen transfer measurements varied from 7 % to 15 %. Full scale experience confirms these values, and operation results from large plants in North America are given. Several examples of using the Biocarbone process for low pollution residuals are demonstrated, including plants in Britain, Denmark and Switzerland. As tertiary installation fed with clarified secondary effluent, final residuals below 1 mg/l N-NH4 and 5 mg/l for SS and BOD can be achieved in a hydraulic detention time around one hour. On settled sewage, two hours detention time results in advanced secondary effluent quality below 5 mg/l N-NH4 and around 10 mg/l for BOD and SS. If an anoxic reactor is added, total nitrogen residuals below 10 mg/l can be achieved in about three and a half hours.