Performance evaluation and microbial community structure of mesh rotating biological reactor treating sewage

Abstract

The fundamental properties and performance of sewage treatment by a mesh rotating biological reactor (MRBR) were investigated. MRBR is an improved type of rotating biological contactor (RBC) reactor. Municipal wastewater treatment with a MRBR exhibited 67 % soluble chemical oxygen demand (sCOD) removal at the surface area loading rate of 22 g sCOD·m−2·day−1, and an average of 41 % ammonium nitrogen removal at a ammonium nitrogen surface area loading rate of 3.5 g-N·m−2·day−1. During a continuous experiment, there was no increase in nitrate nitrogen or nitrite nitrogen corresponding to a decrease in ammonium nitrogen, so simultaneous nitrification and denitrification was occurring in the MRBR. The volumetric oxygen transfer coefficient (KLa) of MRBR was 49.0 d−1 at a rotational speed of 5.0 rpm, comparable to the KLa of other RBCs even with the use of only one mesh disk. The biomass in the MRBR was 18,000 g TVS·m−3, which is the first report of the sludge concentration on the MRBR mesh disks. The high sewage treatment performance of the MRBR was attributed to the fundamental properties of the reactor, such as KLa and sludge amount. Microbial community analysis revealed that the MRBR attached biomass harbored a broad range and high abundance of nitrifying and denitrifying bacteria, indicating the development of an optimal microbial community related to the relatively high simultaneous nitrification and denitrification ratio.