Study On Effects Of Carbon Supplementation Of Raw Wastewater On The Performance Of SFSBR For Anaerobically Digested Swine Manure Treatment

With the rapid development of my country’s livestock and poultry breeding industry,the environmental pollution problems caused by the discharge of livestock and poultry breeding wastewater and feces are becoming increasingly serious.The combined anaerobic-aerobic biological treatment technology is currently the mainstream technology for livestock and poultry farming wastewater treatment.However,during anaerobic digestion,there is a problem that BOD₅and COD,BOD₅and NH₄⁺-N biodegradation and conversion are not synchronized,which make the carbon-to-nitrogen ratio of anaerobic digestion effluent severely unbalanced,resulting in a lack of electronic donors and an imbalance of alkalinity in the subsequent processing system,which seriously affects the processing of subsequent processes effect.In order to realize the efficient denitrification and dephosphorization of anaerobically digested wastewater on the basis of carbon source/alkalinity self-balance,step-fed sequencing batch reactor（SFSBR）running with two-stage anoxic/aerobic（A1-O1-A2-O2）alternate was used to treat anaerobically digested swine manure in this paper,solving the problem of insufficient carbon source in the denitrification process by adding raw swine manure in each anoxic section,investigating the effects of proportion（carbon supplementation proportions of raw swine manure of the three identical SFSBR reactors（R1,R2,R3）were 10%,30%and 50%,respectively）and mode（the quantitative raw swine manure was used for carbon supplementation in the volume ratio of 1:1,1:3 and 3:1 at the start of A1and A2 stages of each cycle of the reactor,respectively,referred to as condition I,II,III）of carbon supplementation of raw wastewater on the SFSBR treatment characteristics and alkalinity balance characteristics.（1）The study of effects of carbon supplementation proportions of raw wastewater on the performance of SFSBR for anaerobically digested swine manure treatment:Increasing carbon supplementation proportion of raw swine manure had basically no effect on the removal effect of COD.The removal effect of three reactors on COD was relatively stable,and the COD concentration of the effluent was maintained at 300-400 mg/L.Increasing carbon supplementation proportion of raw swine manure was beneficial to improve the phosphorus removal performance of the SFSBR system and could significantly improve the removal effect of TP.After stable operation of three reactors,the average removal rates of R1,R2,R3 to TP were 56.7%,68.2%,86.3%,respectively.The greater the carbon supplementation proportion of raw swine manure,the faster the SFSBR system would tend to stabilize.Increasing carbon supplementation proportion of raw swine manure was beneficial to improve the nitrogen removal performance of the system,and could significantly improve the removal effect of NH₄⁺-N and the volume load of TN.After three reactors were stable,the average removal rates of R1,R2,R3 to NH₄⁺-N were 56.7%,68.2%,86.3%,respectively,and the maximum volume load of TN of R1,R2,R3 could reach 0.012,0.055,0.106 kg/（m³·d）,respectively.The denitrification degree and denitrification rate of the SFSBR system in the A2 section both increased with the increase of carbon supplementation proportion of raw swine manure.In system R1,under the condition that carbon supplementation proportion of raw swine manure was 10%,the carbon supply was seriously lacking,and the amount of NO₂^--N in section A2 was almost not reduced.The denitrification degree and denitrification rate of R2 in section A2 were 56.7%and 1.07 mg/（g·h）,respectively.The denitrification degree and denitrification rate of R3 in section A2 were 94.3%and 2.19 mg/（g·h）,respectively,which were 1.7 times and 2.0 times of R2.（2）The study of effects of carbon supplementation modes of raw wastewater on the performance of SFSBR for anaerobically digested swine manure treatment:short-cut nitrification and denitrification was achieved in all three carbon supplementation modes,NAR of three carbon supplementation modes were higher than 90%,and the removal rates of NH₄⁺-N were above 95%.The carbon supplementation mode of raw manure directly affected the denitrification process.The denitrification rates of the reactor in A2 stage under the condition I and II reached 2.19 and 2.15 mg/（g·h）,respectively,which were about 1.6 times as high as that under the condition III.The carbon supplementation mode of raw manure had significant differences between A-stage phosphorus release and O-stage phosphorus uptake under the three conditions.The SFSBR phosphorus removal effect was better under the condition I and III,the effluent concentrations of TP were 7.9 and 6.4mg/L respectively,the efficiencies of TP removal were 84.4%and 87.3%respectively,which were 9.5 and 12.4 percents higher than those of condition II,respectively.With a comprehensive consideration of nitrogen and phosphorus removal,organic matter degradation and carbon source/alkalinity self-balance control,the condition I was the best carbon supplementation mode,the effluent concentrations of COD,NH₄⁺-N and TP were 360,10.6 and 7.9 mg/L respectively,and the removal rates were 74.9%,98.6%and 84.4%respectively.The carbon supplementation mode which the A1/A2 raw wastewater addition ratio was 1:1（condition I）can realize the high-efficiency nitrogen and phosphorus removal of anaerobically digested swine manure on the basis of carbon source/alkalinity self-balance.（3）The study on the characteristics of alkalinity balance in the process of SFSBR for anaerobically digested swine manure treatment:When the carbon supplementation proportions of raw swine manure were 10%and 30%respectively,the changes in alkalinity of the SFSBR system within one operating cycle were less than zero,and the system couldn’t achieve alkalinity self-balance.When the carbon supplementation proportion of raw swine manure was 50%,the change in alkalinity of the SFSBR system within one operating cycle was greater than zero,and the system could achieve alkalinity self-balance.The SFSBR system could achieve alkalinity self-balance under the condition I and II,but couldn’t achieve alkalinity self-balance under the condition III.Under three working conditions,the theoretical alkalinity changes of the SFSBR system within one operating cycle were very close to the measured alkalinity change.The theoretical analysis of alkalinity balance of the SFSBR system matched the alkalinity changes during the actual operation of the system.