Efficiencies of anaerobic hybrid and UASB reactors to alleviate the adverse effect of elevated salinity in wastewater

BACKGROUND Untreated high-strength salinity wastewaters pose a serious threat to the environment. Anaerobic treatment is an effective process with double advantages of waste stabilization and energy production. However, high organic compound and sodium toxicity in high-salinity wastewaters adversely affect the performance of anaerobic treatment. In this study, anaerobic hybrid (AH) and upflow anaerobic sludge blanket (UASB) reactors were investigated for their efficiencies to alleviate the negative effects of high-salinity wastewater. RESULTS Double increases in the NaCl concentration drastically deteriorated the performances of both reactors. The activities of acetoclastic methanogens (ACM) and hydrogenotrophic methanogens (HTM) in both reactors decreased to 22-28% and 36-40% compared to the previous period, respectively. However, the methanogen population (Methanosarcinales and Methanobacteriales) was not affected negatively. The AH reactor exhibited excellent performance during the recovery and restart periods, which only required 7 days to complete the recovery period. Furthermore, during the restart period, the AH reactor showed high chemical oxygen demand (COD) removal efficiency, methane (CH4) production and yield as approximate to 90%, 2600 mL day(-1) and 0.30 m(3) CH4 kg(-1) CODremoved, respectively. The rate of biomass washout from the AH reactor also was lower compared to the UASB reactor. The concentration of attached biomass in the packed zone of the AH reactor gradually increased indicating the growth of an active microbial biofilm. CONCLUSION The excellent performance of the AH reactor was presumably a result of its packed zone configuration which provided the supporting media to entrap smaller microbial aggregates, reduce biomass washout and support the growth of active biofilm. (c) 2021 Society of Chemical Industry (SCI).

Automated summary

The study found that high-salinity wastewaters significantly deteriorated the performance of reactors, but the AH reactor demonstrated better recovery capability and treatment efficiency.