Study On The Treatment Of Kitchen Waste Fermentation Wastewater By Anaerobic-Nitrification-Sulfur Autotrophic Denitrification Combined Process

The anaerobic fermentation treatment of kitchen waste will produce a certain amount of digestive waste liquid,which together with the moisture contained in the kitchen waste itself constitutes the kitchen waste fermentation wastewater,which has the characteristics of low C/N,high NH₄⁺-N and COD concentration,contains difficult-to-biochemical organic matter,rich in oil and protein,and large fluctuations in water quality.When the traditional biological denitrification process is used to treat this type of wastewater,a large amount of electric energy,alkalinity and carbon source are consumed,and the development of a high-efficiency and low-consumption treatment process becomes a top priority.Sulfur autotrophic denitrification is considered a better biological denitrification technology than heterotrophic denitrification because of its economical,environmentally friendly and low sludge yield.It is suitable for the treatment of high-concentration nitrogen and low-C/N wastewater.Processing has huge potential for promotion.In this paper,three processing units,including ABR,fully mixed activated sludge reactor,and sulfur autotrophic denitrification biological filter,are used to construct an anaerobic-nitrification-sulfur autotrophic denitrification combined process to treat actual kitchen waste fermentation wastewater.Through independent experimental research on the treatment performance of each treatment unit and inspection of the combined process for the overall treatment of food waste fermentation wastewater,the main results are as follows:（1）The anaerobic carbon removal unit uses ABR as the anaerobic reactor,and the actual kitchen waste fermentation wastewater is used as the experimental water.The continuous inflow of water for 18 days was successfully started by means of gradually increasing the concentration of influent water through fixed HRT.The single factor experiment obtained the best control parameters:p H is 7.0-8.5,HRT is 24h,and temperature is 30℃.Running continuously for 63 days under the best single factor parameters,the influent COD concentration is 4 483-5 719 mg/L,the volumetric load is4.48-5.71 kg COD/（m³·d）,and the COD removal rate is 62.5%-79.8%.When the volumetric load is 4.84 kg COD/（m3·d）,the COD removal rate can reach 79.8%;The average concentration of TN in the effluent is reduced by 5.29%to 6.09%compared with the influent,and the average concentration of NH₄⁺-N is basically the same;The COD removal ratio of the first compartment along the water flow direction in the ABR is the largest,reaching 46.1%.（2）The nitrification unit adopts a completely mixed activated sludge reactor,and uses the effluent from the anaerobic unit as the experimental feed water.The continuous water intake for 29 days was successfully started by the way of gradually shortening the HRT by fixing the influent concentration,and the optimal HRT was determined to be 5days.The single factor experiment obtained the best control parameters:p H is 7.0～8.5,DO concentration is 3.3 mg/L,and temperature is 25～30℃.Running continuously for 30days under the best single factor parameters,the influent NH₄⁺-N concentration is 1 185-1 234 mg/L,the sludge load is 0.036～0.038 kg NH₄⁺-N/（kg MLSS·d）,and the NH₄⁺-N removal rate is 87.3%-98.9%,The effluent NO₃^--N concentration is 1 073-1 251 mg/L;The influent COD concentration is 1 076-1 856 mg/L,and the COD removal rate is44.5%-68.0%.（3）The sulfur autotrophic denitrification and denitrification unit uses a commercial filter material to construct a sulfur autotrophic denitrification biological filter,and the effluent from the nitrification unit is used as the experimental inlet water.The continuous water intake for 42 days was successfully started by means of gradually increasing the concentration of the influent water through fixed HRT.The single factor experiment obtained the best control parameters:HRT is 24h,the influent p H is 6.5-8.0,and the temperature is 30℃.In addition,the best influent NH₄⁺-N concentration is 20～40 mg/L.COD can form heterotrophic-autotrophic synergistic denitrification to enhance the denitrification effect.When the influent COD is 1000 mg/L,the NO₃^--N removal rate can reach 97.9%,and the contribution of heterotrophic denitrification is about 13%.Running continuously for 30 days under the above optimal parameters,the influent NO₃^--N concentration is 1 063-1 244 mg/L,the volume load is 1.06-1.24 kg NO₃^--N/（m3·d）,and the NO₃^--N removal rate is 90.3%-93.6%;The average concentration of SO₄^2-in the effluent is 4 796 mg/L,and the concentration ratio of SO₄^2-and NO₃^--N removed is 4.4,which is inferred that the sulfur-containing substances in the filter material are mainly S^2-and S^1-;The NO₃^--N removal rate in the filter gradually decreases along the water flow direction,and the NO₃^--N concentration curve shows a concave arc.（4）Under the best parameters of the combined process,using kitchen waste fermentation wastewater as the feed water for continuous operation for 30 days,the removal rates of COD,TN,and NH₄⁺-N are 87.3%-89.5%,82.3%-85.9%,97.1%-100%,respectively,SO₄^2-and NO₃^--N effluent concentrations are 4748-5167 mg/L and 55-100mg/L,respectively.Finally,optimization ideas are discussed according to the treatment effect.