Copper (Cu(II)) and nickel (Ni(II)) are often encountered in wastewaters. This study investigated the individual toxic effects of long-term addition of Cu(II) and Ni(II) on the biochemical properties of aerobic granules in sequencing batch reactors (SBRs). The biochemical properties of aerobic granules were characterized by extracellular polymeric substances (EPS) content, dehydrogenase activity, microbial community biodiversity, and SBR performance. One SBR was used as a control system, while another two received respective concentration of Cu(II) and Ni(II) equal to 5 mg/L initially and increased to 15 mg/L on day 27. Results showed that the addition of Cu(II) drastically reduced the biomass concentration, bioactivity, and biodiversity of aerobic granules, and certainly deteriorated the treatment performance. The toxic effect of Ni(II) on the biodiversity of aerobic granules was milder and the aerobic granular system elevated the level of Ni(II) toxicity tolerance. Even at a concentration of 15 mg/L, Ni(II) still stimulated the biomass yield and bioactivity of aerobic granules to some extent. The elevated tolerance seemed to be owed to the concentration gradient developed within granules, increased biomass concentration, and promoted EPS production in aerobic granular systems.
BACKGROUND: To elucidate the process and mechanism of Cu(II) biosorption onto aerobic granules, the influence of pH and ionic strength (IS) on the Cu(II) biosorption capacity and biosorption mechanism was studied.
BACKGROUND: To validate the possibility of aerobic granulation at a lower organic loading rate (OLR) than 2 kg COD m −3 day −1 (GS 1) in a sequencing batch reactor (SBR), the formation, structure, and microbial community of granular sludge (GS) were investigated.
The characteristics of tannery wastewater are complex composition, high suspended substance (SS) and heavy sludge load. Adding the functional bacteria agent into the Aerobic system and Sludge digestion tank can improve the biological system activity and reduce sludge discharge. The pilot-scale study results show that: The removal of CODcr and NH3-N was improved after biological synergy. The average removal rate of CODcr was 90.1% and the average removal rate of NH3-N was 97.4%, both of which were higher than the control group. The excess sludge reduction of the system could reach 75.16%, and the effect of sludge reduction was obvious in the experimental group. After biological synergy, the number of bacteria in aerobic pool increased significantly, and the microbial flora migrated in a better direction.
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