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Aiming for treating decentralized domestic wastewater in rural China, this study evaluates the effects of ceramsite size and structure, and water recirculation parameters, upon the performance of recirculating biofilter (RBF). RBF shows stable capability of chemical oxygen demand (COD) remediation and ammonia nitrification. In addition, the microbial flora and structures of the various layers in the system are analyzed via high-throughput sequencing in order to study the microbial diversity. The results indicate that while the ceramic particle size has no significant influence on the COD remediation capacity, the ceramics with smaller particle sizes exhibit better ammonia nitrogen (NH 4 +-N) removal ability, with a first-order linear relationship between the influent ammonia nitrogen load and the effluent NH 4 +-N concentration in RBF (R2 > 0.64). An increased hydraulic load and intermittent operation are shown to deteriorate the water quality with respect to NH 4 +-N, while an increased recirculation ratio increases the removal rate of NH 4 +-N from the effluent. Further, the water distribution time has a stronger effect upon the NH 4 +-N concentration in the effluent than does the recirculation ratio. Moreover, the microbial structure of the multi-layer recirculating trickle biofilter varies significantly during the process. The results indicate that a high recirculation ratio, long water distribution time, and multi-layer structure will be beneficial for improving the pollutant treatment capacity of RBF. • Ceramics with smaller sizes exhibit better ammonia nitrogen removal ability. • Influent NH 4 +-N load first-order linear related effluent NH 4 +-N concentration. • Water distribution time strongly effects the effluent NH 4 +-N concentration. • Multi-layer structure effectively differentiated microbial community structure. [ABSTRACT FROM AUTHOR]

The drying and utilization of potato pulp have become a bottleneck problem of the potato starch industry. In this study, the process of pectinase and cellulase-assisted fermentation was assessed regarding their effects on the microbial composition and drying of potato pulp. Enzyme-assisted fermentation increased the levels of organic acids, specifically lactic acid, acetic acid, and citric acid. Enzyme-assisted fermentation promoted the growth of Lactobacillus plantarum , which inhibited the growth of bacterial and fungi. Scanning electron microscopy and light microscopy showed that pectinase-assisted fermentation degraded cell walls, altering the microstructure and colloidal properties of potato pulp. Reduction in the water holding capacity and viscosity by pectinase-assisted fermentation improved the drying properties. Texture profile analysis also revealed higher hardness and lower cohesiveness values of potato pulp. Quick drying analysis indicated that pectinase-assisted fermentation could facilitate rapid drying of potato pulp. Based on these findings we could develop more efficient methods for drying and utilization of potato pulp. • Enzyme-assisted fermentation could improve the antimicrobial activity. • Pectinase-assisted fermentation could change the colloidal like system of potato pulp. • Pectinase-assisted fermentation made the rapid drying of potato pulp possible. [ABSTRACT FROM AUTHOR]