Treatment Of RO Concentrated Water From Landfill Leachate By Blowing-Catalytic Oxidation Coupled With Aerobic Biotechnology

The RO concentrate of landfill leachate has higher pollutant concentration and lower biodegradability than the original leachate,which makes the treatment difficult.The RO concentrated water produced in China is about 4.56 million tons per year.The existing technology costs are high,and the equipment is easy to be damaged and replaced frequently,which has become a pollution control problem faced by garbage disposal enterprises.Therefore,it is urgent to explore an economic and efficient RO concentrated water treatment technology for landfill leachate.In this study,the normal and emergency process RO concentrated water in a leachate treatment plant in Bishan was taken as the research object.In view of the characteristics of high nitrogen,high humus and high salt in RO concentrated water,based on ammonia stripping with high ammonia nitrogen pretreatment,catalytic oxidation tower can reduce the concentration of humus,Heterotrophic nitrification-aerobic denitrification,HN-AD composite microbial agent has the characteristics of high ammonia nitrogen,high salt,high organic matter and high denitrification,with the help of microbial agent biofilm technology,a combined process of stripping-catalytic oxidation coupling aerobic biotechnology was constructed.The ammonia nitrogen was pretreated by ammonia stripping tower,and the humus content was reduced by catalytic oxidation tower.The carbon source in RO concentrated water was fully utilized for biological nitrogen removal,and then the carbon source was added to further degrade TN and NH₄⁺-N in the effluent of the fully aerobic combined process,and the standard discharge was achieved.The morphology of the catalyst in ozone catalytic oxidation and its action mechanism on humic substances in RO concentrated water were studied,and the optimal operating parameters of ammonia stripping tower,catalytic oxidation tower and all-aerobic combination process at different C/N were obtained.The micro-mechanism of nitrogen removal by C/N under different C/N ratios was investigated by high-throughput sequencing technology.Finally,the optimal parameters of each unit were used in the coupling process to obtain the final effluent of RO concentrated water treatment by blowing-catalytic oxidation coupled aerobic biological technology.Here is the main conclusions:1?Using ammonia stripping tower for RO concentrated water pretreatment,the optimum operating parameters of ammonia stripping tower are:temperature 25?30°C,liquid flow 150ml/min,p H=13,gas-liquid ratio=1000,operating time 6h.Under the optimal operation parameters,the effluent COD,NH₄⁺-N,TN and removal rates of ammonia stripping tower were 7900mg/L,2428mg/L and 2710 mg/L,6.69%,59.53%and 56.92%,respectively.2?The optimal catalyst screened was Ce-AC.From the morphology and structure,the pore structure on the Ce surface was covered by Ce O₂ coating,and the catalyst was uniformly loaded on AC in the form of Ce O₂ fluorite crystal.During the treatment of RO concentrated water,the results of UV and fluorescence showed that humic substances were obviously degraded but not completely mineralized.The calculation results of UV₂₅₄ and FRI further confirmed the degradation of humic substances,and the removal rate was about 67%.FTIR results showed that humic substances were mainly decomposed into carbohydrates and small molecular organics such as organic amines,sulfur and alcohols by the indirect oxidation of·OH generated on the surface of the catalyst.In the catalytic oxidation tower,the effluent of ammonia stripping tower was treated with Ce-AC catalyst.The optimal operating parameters of the catalytic oxidation tower were obtained as follows:temperature 25–30°C,O₃ flow rate 20L/min,O₃ concentration 90mg/L,catalyst dosage 3.33g/L,and reaction time 3h.Under the optimal operation parameters,the COD,NH₄⁺-N,TN and their removal rates in the effluent of catalytic oxidation tower were 3310mg/L,958mg/L,and 1167mg/L,and58.10%,60.54%,and 56.94%,respectively.3?The combined process of aerobic MBBR pretreatment and BCO advanced treatment was used to treat the effluent of catalytic oxidation tower.The optimal operating parameters of the combined process were obtained as follows:temperature25-30°C,C/N=6,aeration rate 40L/min,HRT=24h.Under this condition,the effluent COD,NH₄⁺-N,TN and their removal rates were 1040mg/L,19.28mg/L and 26.01mg/L and 41.57%,73.20%and 76.37%,respectively.The results of high-throughput sequencing showed that with the increase of C/N,the richness and diversity of microorganisms showed an upward trend.Truepera,the most dominant and representative genus under each C/N in the all-aerobic combination process,first increased and then decreased with the increase of C/N,and the highest abundance was35.91%,which was the key to ensure the nitrogen removal in the all-aerobic combination process.4?The RO concentrated water was treated by blowing-catalytic oxidation coupled with total aerobic biological technology.Under the optimal operating parameters obtained by each unit,the final effluent concentrations of COD,NH₄⁺-N and TN in the coupled process were 3105mg/L and 8mg/L,and the total removal rates were 96.34%,99.92%and 99.87%,respectively.TN and NH₄⁺-N met the emission standards of Table2?Domestic Waste Landfill Pollution Control Standard(GB16889-2008)?.The daily cost of per ton water treatment is 69.14 yuan per ton,which is about 30%less than that of traditional RO.