Simultaneous carbon, nitrogen and phosphorous removal from municipal wastewater in a circulating fluidized bed bioreactor

In this study, the performance of the liquid-solid circulating fluidized bed bioreactor (LSCFBBR) with anoxic and aerobic beds and employing lava rock as a carrier media for the simultaneous removal of carbon, nitrogen and phosphorus from municipal wastewater at an empty bed contact time (EBCT) of 2.4 hrs was discussed. The LSCFBBR was operated without and with bioparticle recirculation between the anoxic and aerobic bed for 260 and 110 days respectively. Without particle recirculation, the LSCFBBR was able to achieve carbon (C), total nitrogen (N) and phosphorous (P) removal efficiencies of 94%, 80% and 65% respectively, whereas with bioparticle recirculation, 91%, 78% and 85% removals of C, N and P were achieved. The LSCFBBR was operated at long sludge retention time (SRT) of 45 - 50 days, and achieved a sludge yield of 0.12 - 0.135 g VSS. g COD^-1. The effect of superficial liquid velocity on biomass detachment without and with bioparticle recirculation was investigated. A dynamic stress study of the LSCFBBR was carried out at varying feed flow rate to determine response to shock loadings.