Effects of an electrocoagulation–air flotation–microfiltration pretreatment process on the start-up of a moving bed biofilm reactor: performance and microbial community structure

Abstract

A moving bed biofilm reactor (MBBR) is an efficient water treatment process, widely used in recirculating aquaculture systems. The optimization of relevant parameters to shorten the start-up period and improve the performance of the MBBR is an ongoing research hotspot. In this study, a new aquaculture wastewater pretreatment process, the electrocoagulation–air flotation–microfiltration technology (EC–AF–MF), was constructed, and its effects on the MBBR start-up, performance, and microbial community structure were investigated. The electrocoagulation–air flotation (EC–AF) process significantly increased the particle size of total suspended solids (TSS), thereby enhancing the microscreen drum filter's removal efficiency (RE) for TSS. In addition, EC altered the microbial community and improved the MBBR's RE for TSS, chemical oxygen demand (COD), and total ammonia nitrogen (TAN). Interestingly, the Fe anode produced better results. The REs for TSS, COD, and TAN in the Fe group were 89.27 ± 0.30%, 69.99 ± 1.13%, and 100%, respectively. The Fe anode accelerated not only the biofilm formation and stability but also the start-up of the MBBR. These findings indicate that the EC(Fe anode)–AF–MF process could shorten the start-up period and enhance the performance of the MBBR, providing a reference for the standard treatment of aquaculture wastewater and promoting an ecologically sustainable aquaculture industry.