Researchs And Applications Of Improved Activated Sludge Technology To Remove Emerging Contaminants In Wastewater

The continuous industrial development and the use of various products and pharmaceuticals by humans in recent years have resulted in the generation of emerging contaminants(ECs).ECs are generally divided into various categories,such as pharmaceutical and personal care products(PPCPs),endocrine disrupting chemicals(EDCs),flame retardants,pesticides,and antibiotic resistance genes(ARGs).ECs are structurally stable and are often difficult to degrade naturally in the short-term.The potential hazards and impacts of these ECs on the ecosystem and human health have been gaining attention.Currently,many physicochemical methods have been developed for the removal of emerging pollutants.However,these methods are costly and may cause secondary pollution.Additionally,these methods do not efficiently remove ECs.As a widely used sewage treatment technology,the conventional activated sludge process(CAS)can remove most of the organic matter in the sewage.However,for the combined pollution of organic matter and heavy metals,or the combined pollution of highly toxic antibiotics,the removal efficiency of ECs is very low,and most of the ECs are not removed from the treated wastewater.Therefore,it’s necessary to improve activated sludge technology to effectively remove ECs from sewage.There are usually three typical pollution forms of ECs in the environment: persistent ECs pollution,organic and heavy metal compound pollution,and highly toxic antibiotic compound pollution.This research focuses on three typical pollution forms of ECs,using sequencing batch activated sludge reactor(SBR),bioaugmentation activated sludge technology,cell surface display technology and aerobic granular sludge technology are used to enhance the performance of activated sludge to explore the treatment performance and ECs removal capacity of improved activated sludge technology for different polluted forms of sewage.The main findings are as follows:Perfluorooctane sulfonic acid(PFOS)is an emerging pollutant of flame retardants and a typical stubborn organic pollutant.The existence of perfluorooctane sulfonate(PFOS)in large quantities in the mixed municipal wastewater threatens biosafety.However,the fate of stubborn PFOS in a sequencing batch reactor(SBR)system and its influence on this system have not yet been revealed.In this study,the fate and behavior of PFOS in an SBR processing system were investigated.Mass balance analyses revealed that PFOS removal was mainly through adsorption.After the reactors were run for 20 days,the PFOS(100 mg/L)removal rate was only 28%.Under the influence of PFOS,the removal rates of chemical oxygen demand(COD)and ammonia nitrogen dropped rapidly to 23% and 35%,respectively,and the accumulation of nitrite and nitrate was reduced.Compared with the control group,PFOS stimulates microorganisms to secrete more soluble microbial products(SMP)and extracellular polymeric substances(EPS).The adsorption of PFOS and EPS causes sludge bulking and decreases settling.The richness and diversity of microorganisms decreased significantly,affecting the system’s removal of COD and ammonia nitrogen.Therefore,the SBR system is not suitable for treating wastewater containing stubborn organics.It is necessary to remove stubborn organics through pretreatment to reduce their impact on the SBR system.Textile wastewater is a compound polluted wastewater of organic matter and heavy metals,and it usually contains ECs such as toxic dyes and Cr(VI).Aeromonas hydrophila LZ-MG14 was isolated and characterized to develop an effective bioaugmentation strategy for the bioremediation of malachite green(MG)and Cr(VI)from textile wastewater.Strain LZ-MG14 removed 96.8% of MG(200 mg/L)and 93.71% of Cr(VI)(0.5 mmol/L)within 12 h with a significant increase in biomass.The mechanism underlying MG mineralization by LZ-MG14 involved N-demethylation and decomposition of conjugated structure,while that underlying Cr(VI)removal was reduction.LZ-MG14 bioaugmentation in a membrane bioreactor(MBR)significantly enhanced the efficiency of MG degradation and Cr(VI)removal in textile wastewater.Additionally,LZ-MG14 successfully colonized the activated sludge and shaped the effective microbiota for MG degradation and Cr(VI)removal.This research provides a potential method for the treatment of wastewater polluted by organic matter and heavy metals.Pharmaceutical wastewater is usually complex and highly toxic,mostly containing a variety of emerging antibiotics pollutants.The conventional activated sludge technology is unsatisfactory in the treatment of pharmaceutical wastewater owing to the impact of antibiotic toxicity.In this study,a novel whole-cell biocatalyst that can accelerate the degradation of antibiotics was developed by displaying β-lactamase on the cell surface of Aspergillus niger.The biocatalyst showed high enzyme activity(6.53??U/g dry weight)and stable performance.Cefamezin(80.45%),amoxicillin,and ampicillin were completely degraded by the biocatalyst A.niger-Bla within 1?h owing to the effect of β-lactamase on the β-lactam ring.A.niger mycelial pellets were used as biological carriers to construct aerobic granular sludge(AGS),which was used to treat actual pharmaceutical wastewater containing β-lactam antibiotics.The A.niger-Bla system significantly improves the removal of antibiotics(>60%)and the overall performance of the reactor.The modified A.niger-Bla AGS reduces the impact of antibiotics and maintain the richness and diversity of AGS microbial community,thus improving the system’s overall performance and maintaining the stability of AGS.This technology provides a novel idea for the treatment of wastewater containing compound antibiotics.This study shows that for different types of ECs-containing wastewater,improved activated sludge technology can effectively remediate ECs-containing wastewater and remove ECs in the wastewater.