Performance Of A Novel Two-stage Powdered Activated Carbon And Dynamic Membrane Filtration(PAC-DMF) Process For Wastewater Treatment

Currently,biological wastewater treatment technologies?such as conventional activated sludge processes?have several disadvantages,including high energy consumption and carbon emissions,which are mainly caused by aeration and the large-scale footprint,and low resource and energy recovery,due to the mineralization of organic matter and the conversion and elimination of nutrients?nitrogen and phosphorus?with low environmental capacities.Thus,it is urgent to develop new paradigms for simultaneous wastewater treatment and resource utilization using physicochemical processes rather than conventional biological means.Based on this,the researchers developed various new treatment methods to reduce energy consumption,achieve net production capacity,recover nutrients such as nitrogen and phosphorus.Meanwhile,it is proposed that the concentration of organic matter in sewage will be used as a pre-treatment step to improve energy recovery.For this reason,a novel two-stage powdered activated carbon-dynamic membrane filtration?PAC-DMF?system was constructed for domestic sewage treatment.In this thesis,coagulation batch test was used to compare the COD removal rate of domestic sewage and the trend of medicament load with adding four commonly coagulants including poly aluminum chloride?PACl?,ferric chloride,aluminum sulfate and poly aluminum ferrous chloride under different dosage conditions.And diatomite and powdered activated carbon?PAC?with strong adsorption capacity were selected as composite coagulants in order to increase the retention of dissolved organics in domestic sewage,and PAC1+PAC was selected as most suitable coagulant.The dynamic membrane filtration batch test is based on previous coagulation experiment with a constant flux?50-60 L/m²·h?and low TMP?less than 15 kPa?operating conditions to select the dynamic membrane pre-coating agent,and the changes of TMP,flux and effluent turbidity of the coagulation dynamic membrane were investigated by adding PAC,PACl and PAC+PACl respectively.The PAC was selected as the best pre-coating agent.The dynamic membrane filtration test used three kinds of membrane substrates,namely nylon mesh,steel wire mesh and non-woven fabrics,to investigate the flux of clear water membranes and the retention capacity of organic matter.After a series of pre-experimental tests,nylon meshes of 300 mesh and 500mesh were selected for testing.A novel two-stage powdered activated carbon-dynamic membrane filtration?PAC-DMF?system was developed using PAC as a carrier to enhance DM formation and organic pollutant retention.The particle size and dosage of PAC,strategy for operating the continuous reactor in the first stage,and selection of the PAC particle size in the second stage were investigated.The effluent from the first stage was found to have a stable water quality,with turbidity in the range of 50-70 NTU.Efficient retention of organic materials was also achieved with a retention rate of 74%-82%,and the COD content in the concentrate was above 3000 mg/L in the cycle filtration experiment.In the second stage,further enhancement of water quality and organics retention were observed,as evidenced by the low effluent COD?<70 mg/L?and turbidity?5-20 NTU?.Meanwhile,the effluent that was rich in nitrogen and phosphorus was suitable for agricultural irrigation or gardening.In the methanogenic potential analysis test,organics could be effectively enriched into the concentrate after single cycle operation,the COD of the concentrated liquid on the first reactor was about 3500 mg/L before sieving and1700 mg/L after sieving,and on the second reactor was about 1100 mg/L.The concentrate of the first stage reactor could be a substrate for anaerobic digestion achieved good performance of gas production.The biochemical methane potential of the concentrated liquid was 195 m LCH₄/gCOD before sieving,215 mLCH₄/gCOD after sieving and 271 m LCH₄/gCOD after sieving and sedimentation.The results indicated that the developed two-stage PAC-DMF system could be a highly promising alternative to the conventional wastewater treatment process.