Study On Ozone Oxidation Combined With Sulfur Autotrophic Denitrification For Treatment Of Nitrogen Contaminants In Leachate Tail Water

Most of landfill leachate treatment processes is predominated by MBR units,while TN in the leachate effluents usually is above 200 mg/L,including nitrate and refractory organic nitrogen,which cannot meet the standards<pollution control standard for the landfill site of municipal solid waste>?GB 16889-2008?.It's the critical point for the further disposal of leachate effluents with low carbon and high nitrate.The potential treatment process for the N in leachate effluents such as the biological,physicochemical technologies and advanced oxidation technology were analyzed based on characteristics of leachate and the standard.The leachate effluents should be further disposal by the combination of the advanced treatment process and denitrification process with the additive of varies electron donors.Organic nitrogen should be converted into NO₃^-by the advanced treatment process firstly,and then denitrification process could be followed,with the introduction of electron donors.The selection of electron donor is important for the denitrification process.In this paper,the organic nitrogen and nitrate remaining in the tail water after leachate treatment by MBR were discussed.Advanced ozone oxidation was used to convert the organic nitrogen which was not removed into nitrate nitrogen,and then sodium thiosulfate was used as the electron donor for the deep denitrification through biological method to provides a technical choice for the deep removal of nitrogen in leachate tail water.The main conclusions are as follows:?1?Sulfur autotrophic denitrification with sodium thiosulfate as electron donor has obvious effect on the removal of nitrate from MBR tail water.Under the optimum conditions of HRT=3 h,S/N=4,pH=8,and the ambient temperature of 30°C,the nitrate concentration is 150 mg/L.The removal rate of nitrate in the MBR tail water of nitrate nitrogen is 100%.There is no accumulation of NH₄⁺-N and NO₂^--N during the whole operation,and the operation is stable.?2?The optimal pretreatment condition of Ozone pretreatment of landfill leachate MBR tail water is pH=8,and the dosage of ozone is 60mg/min.Under these conditions,the refractory organic nitrogen in MBR tail water can be effectively converted into nitrate.The nitrate nitrogen of MBR tail water increased from 50.4 mg/L to 85.8 mg/L,TN was 100.6 mg/L,organic nitrogen concentration was 50.2 mg/L,and conversion rate of organic nitrogen to nitrate nitrogen was 70%.?3?The combination of ozone pretreatment and sulphur autotrophic denitrification biological treatment can make the TN of the landfill leachate MBR discharge to the standard.After ozone treatment,the total nitrogen concentration was 99.6 mg/L and the nitrate nitrogen concentration was 82.9mg/L.After O₃ pretreatment and sulfur autotrophic denitrification biological treatment,the TN of the original MBR tail water can be reduced from 99.6mg/L to 18.0 mg/L,which can meet<pollution control standard for the landfill site of municipal solid waste>?GB 16889-2008?witch TN is required less than 40 mg/L.?4?Environmental effects of ozone pretreatment combined with sulphur autotrophic denitrification biological treatment.The removal rate of nitrate nitrogen is 100%,and the removal rate of total nitrogen is 82%.The emission of TN meets national standards and will not cause damage to the environment.Sulfate accumulation occurred during the reaction,and the sulfate concentration increased from 1183 mg/L to 1758 mg/L.The sulfur autotrophic denitrification system produces N₂,O₂,CO₂,CH₄,H₂S,NH₃ and N₂O,and the daily production amounts are 1.19 g,0.20 g,0.13 g,0.00016g,3.22×10^-77 g,6.25×10^-66 g and 0.0017 g,respectively.After this treatment,the water color and turbidity of the treated water are obviously improved.