Simultaneous C and N Removal in a Hybrid CAST Reactor

Cyclic Activated Sludge Technology (CAST) is one of the variations of SBR processes. In this experiment, suspended media were introduced into the CAST reactor to increase the quantity of microorganism and micro anoxic environment. Simultaneous carbon and nitrogen removal performance of the hybrid CAST reactor was investigated. The experiment results demonstrated that more than 96% COD and 98% TN removal were achieved when the influent COD was 4686-5781 mg/L and TN was 180 mg/L, the removal rate of COD and TN reached to 3.05-3.77 kgCOD/(m3.d) and 0.12 kgTN/(m3.d) respectively. Nitrogen track studies indicated that TN was mainly removed though SND mechanism with nitrite as the intermittent product. The occurrence of SND during the aeration period was resulted from the existence of micro anoxic environment in the suspended carriers of the reactor.