Study On The Treatment Of Saline Wastewater By Sulfate Reduction And Ammonia Oxidation Combined With Anaerobic Ammonium Oxidation Proces

Seawater-based wastewater is generated from many industries(e.g.seafood processing,mariculture wastewater,seawater toilet flushing wastewater,textiles,and leather industry),containing large amounts of nitrogen and salts.However,seawater-based wastewater was difficult to treat by non-halophilic bacteria,as salinity above 1%(w/v)may cause cell plasmolysis and even death owing to increased osmotic pressure.Besides,sulfate is abundant in seawater-based wastewater,sulfide was readily produced through the anaerobic sulfate reduction process.Sulfide caused odor and corrosion hazards to the aquatic environment,which could damage plant and animal health.Therefore,an effective strategy should be developed to treat seawater-based wastewater before it is discharged into the surroundings.In this work,the sulfate reduction ammonium oxidation(SRAO)process was first operated by merely inoculating MAB-based sludge in a sequencing batch reactor(SBR),and the nitrogen removal of MAB-based consortia was investigated in seawater-based wastewater.The main findings are as follows:The SRAO process was investigated to treat seawater-based wastewater under different influent nitrogen to sulfate(N/S)ratios,the nitrogen removal was affected in the SRAO process under different influent N/S ratios.Under the optimum influent N/S ratio of 1.7,the best total nitrogen removal efficiency and sulfate conversion efficiency reached 100% and 62.94%,respectively.At the genus level,the uc＿SBR1031 was proved to be the main functional genus SRAO bacteria,responsible for the SRAO process.The relative abundance of uc＿SBR1031 increased to 47.62% from 11.58% when N/S ratios increased to 1.7 from 0.5.Accordingly,the relative abundance of Candidatus Scalindua decreased to 2.32% from 10.69%.The microbial community composition remained relatively stable at N/S ratios of 1.5-1.7.The mechanism of the SRAO process was identified by the typical operating cycle and energy metabolism pathway.Nitrite was generated from the SRAO process,supplying an ideal substance for MAB to operate the anammox process,which can cooperate to improve nitrogen removal.This indicated that the application of anammox process was expanded by SRAO process.Remarkably,a stronger impact on nitrogen removal was observed on the SRAO process due to the higher concentration of sulfate than nitrite in seawater-based wastewater.The nitrogen removal of MAB-based consortia was investigated by the SRAO process under different influent salinity.Nitrogen removal was changed correspondingly in treating seawater-based wastewater by the SRAO process under different influent salinity.The nitrogen removal efficiency showed an upward trend when the salinity gradually decreased from 35 g/L to 7 g/L.Under the optimum influent salinity of 7 g/L,the nitrogen removal efficiency was 97.35%,and the corresponding sulfate consumption concentration was 100.21 mg/L.