Development Of Nitrifying Bacteria Bio-accelerators And Research Of Accelerating Mechanism On Biological Nitrification

Many municipal Wastewater Treatment Plants?WWTPs?contain industrial wastewater.High concentrations of heavy metals in industrial wastewater will pose inhibitory effects on biological nitrification process,which results in effluent ammonia concentrations exceeding the set standard.The unreasonable effluent will cause economic losses and bring threat to our environment.Therefore,it is of great urgent to develop and optimize bio-accelerators under inhibited-situations.In this study,Cu²⁺ and Cd²⁺ were chosen as inhibitors,bio-accelerators were developed and dosed in parallel SBRs.The effluent NH₄⁺-N,NO₂^--N,and NO₃^--N concentrations,microbial bioactivity,and distribution of heavy metals were investigated,in order to assess variation of bioactivity during inhibitory and recovery periods.Furthermore,the mixture,dosage,and dosing mode of bio-accelerators were optimized.Results showed that,50.00 mg/L Cu²⁺ could inhibit 80.00% nitrification effiency within 4 days,and 25.00 mg/L Cd²⁺ could inhibit 85.00% nitrification effiency within 3 days.Dosing bio-accelerators in recovery period was better than natural recovery process.Dosing biotin,L-aspartic acid,and cytokinin simultaneously was the optimum mixture.Under 50.00 mg/L Cu²⁺and 25.00 mg/L Cd²⁺ inhibition situations,nitrification could recover completely within 8 days and 10 days respectively with dosing those three substances.Amide?NH?and carboxyl?COOH?groups in bio-accelerators could attract heavy metals,and repair membrane loss caused by Cu.Besides,the unique structure in bio-accelerators could help mediate Cd toxicity.In terms of dosage and dosing mode,more bio-accelerators meant higher nitrification recovery efficiency,and 0.048-0.48 ?g/gMLSS exhibited the best recovery efficiency.Dosing bio-accelerators evenly at each cycle was the most effective.High efficiency,simple formula,easy operation,and low cost will make the bio-accelerators promising in practical application.