Effects of sponge pore-size on the performance of a down-flow hanging sponge reactor in post-treatment of effluent from an anaerobic reactor treating domestic wastewater

The effects of sponge pore-size (SPS) in a down-flow hanging sponge reactor were evaluated, in terms of removing organic and nitrogen substances from anaerobic reactor effluent. Five down-flow hanging sponge reactors with SPSs of 0.56, 0.63, 0.83,1.25 and 1.92 mm were constructed and all operated at a hydraulic retention time of 1 h, being continuously fed effluent from an up-flow anaerobic sludge blanket reactor for the treatment of domestic wastewater. The evaluation was conducted over 170-d experimentation under ambient conditions. The results indicate that SPS has a significant influence on the removal of organics and nitrogen from wastewater; however, increasing the SPS from 0.83 to 1.92 mm greatly reduced the accumulation of sludge on the sponge cell matrix, lowering the effective volume of the sponge, which subsequently affected the removal performance of the reactors. The average sludge accumulation for the 0.56 mm SPS was 46 g suspended solids L-1 sponge, exhibiting better performance compared to the other SPSs. (C) 2018 Chinese Institute of Environmental Engineering, Taiwan. Production and hosting by Elsevier B.V.