Preparation Of Composite Modified Quartz Sand And Research On Effect And Mechanism Of Composite Modified Biological Sand Filter In Secondary Effluent Of WWTPs

Biological sand filter is an advanced treatment process which integrates biological interception,biological filtration and biological treatment.Current studies focus on ordinary quartz sand modification to improve the pollutant purification effect,however,single modification method which focus on specific source water cannot meet the new demand and new discharge standard of wasterwater treatment under growing complexity of source water.In view of this problem,this paper put forward a compound modified quartz sand modification method,develops a biological sand filtration process based on compound modified quartz sand filter material,and discusses the removal mechanism of various pollutants by this new biological sand filtration process.The results of this study are as follows:(1)Preparation and morphological characterization of compound modified quartz sandBased on the glass corrosion process and coating modification method,the composite modification technology suitable for ordinary quartz sand(OQS)was developed,including primary modification sand,such as surface reconstruction sand(SMS);and secondary modified sand,such as hydrophilic(IMS),hydrophobic(OMS),cationic(CMS)and amino modified sand(AMS).Surface morphology analysis showed that surface morphology and Zeta potential of quartz sand were changed.The specific area and surface roughness of SMS were changed greatly;The contact angles of IMS and OMS decreased and increased,respectively;The surface of cationic and amino-modified quartz sand were covered with corresponding functional groups.CMS had the strongest adsorption capacity,while OQS of which had the weakest adsorption capacity.(2)Microbial affinity analysis of compound modified quartz sandMicrobial affinity analysis showed that,compared with OQS,the microstructure of the modified quartz sand surface was complex.The specific surface area was increased,the microbial attachment equilibrium time was shortened and the adhesion stability was enhanced.After modification,there was a great increase in the surface positive electricity,specific surface area,hydrophobicity and adsorption capacity of close-attached extracellular polymer(TB-EPS).Comparative study on static and dynamic bio-film hanging showed the better effect of AMS than CMS,shorter start time of AMS which can fasten the growth rate of microbial,greater covered biomass of CMS.(3)Effect of compound modified biological sand filter on removal of conventional pollutants and Ph ACsCompared with O-BSF,CM-BSF and IM-BSF among composite modified biological sand filters had the best effect on SS removal which up to 76.12%and72.23%,respectively.There was no great difference of each filter on COD removal,which was mainly by bio-degradation effect.AM-BSF had the highest NH₃-N and TN removal rate,which were 88.87%and 54.13%,respectively,mainly by aerobic nitrification/anoxic denitrification effect of biofilm.The removal efficiency of 12 Ph ACs from secondary effluent of wastewater treatment plant by O-BSF,SM-BSF,IM-BSF,OM-BSF,CM-BSF and AM-BSF showed that the removal rates of macrolides,quinolones,analgesics,antihypertensive drugs and tetracycline were 20%?50%,8%?33%,20%?47%,12%?33%and 28%?51%,respectively;CM-BSF had better removal effects on macrolides,analgesics and antihypertensive drugs,while OM-BSF had better removal effects on quinolones and tetracyclines.(4)Study on the mechanism of removal of conventional pollutants(including organic pollutants,nitrogen and phosphorus)and Ph ACs by compound modified biological sand filterMiseq high-throughput sequencing and other techniques were used to identify the types,quantities and functional characteristics of functional flora,the results indicated:The AOB abundance sequence of six groups of quartz sand coated biological samples were OMS>CMS>IMS>AMS>SMS>OQS;NOB abundance sequencce were OQS>SMS>OMS>CMS>AMS>IMS;Denitrifying bacterial abundance were IMS>AMS>CMS>SMS>OMS>OQS;Phosphorus removal bacteria abundance were OQS>OMS>AMS>CMS>IMS>SMS,the distribution of functional bacteria in each sample corresponds to its removal of pollutants.Tetracycline,for example,based on the 2 x 6 groups of quartz sand(coated and uncoated)sequencing batch type experimental data,we built a kinetic reduction model of the tetracycline,we found six groups of coated quartz sand to reduce tetracycline,the earlier stage accorded with zero order reaction,the later stage accorded with first order reaction.By 24h continuous experiments,the contribution ratio of different approaches to the total removal rate was quantified.The microbial community structure and diversity of the composite modified quartz sand coated surface were studied to identify the type and quantity of the microflora,so as to explore the mapping relationship between dominant bacteria and Ph ACs removal.