Effect Of Reactor Type On Denitrification Performance Of Food Waste As Denitrifying Carbon Source

The insufficient organic matter in the sewage is an important problem for urban sewage treatment,and it is often necessary to add external carbon source to solve the problem.The acid liquor rich in volatile fatty acid(VFAs)can be produced by anaerobic fermentation of food waste,and the acid liquor can be used as external carbon source for denitrification,which combines the food waste treatment and nitrogen removal in the municipal sewage treatment plant.In this paper,the nitrogen removal efficiency in upflow reactor,fixed bed reactor(combined packing)and fluidized bed reactor(polyurethane filler)was studied by using food waste as external carbon source.The main achievements are as follows:(1)The denitrification performance of food waste in upflow reactor was investigated.Using the treated food waste as the external carbon source,with the decrease of hydraulic retention time(hrt),the indexes of effluent increased gradually.When HRT=0.5 h,the TN concentration was 4.87 ±3.48 mg/L,the removal rate was 84.5±11.3%,the COD concentration was 35.8±9.2 mg/L,and the concentration of polysaccharide was 3.42 ±0.87 mg/L,the protein concentration was 13.16±2.21 mg/L.With the operation of the reactor,the sludge in the reactor gradually changed from floc to particle,and the average diameter of sludge reached about 2 mm.The data show that the denitrification potential of food waste as carbon source in upflow reactor is good,and the granulation of sludge can be achieved.(2)The denitrification performance of food waste in fixed bed reactor was studied.Mature granular sludge was cultured in the upflow reactor and inoculated into the fixed-bed reactor.It was determined by batch experiments that C/N was 5 and HRT was 1 h at the start-up of the reactor.When the HRT decreased to 0.5 h,the TN of the R1 and R2 reactors was 7.31±2.58 mg/L and 5.29±1.49 mg/L,respectively,followed by the increase of C/N to 6,and the TN of the R1 and R2 reactors decreased to 5.58±1.27 mg/L,4.25±0.96 mg/L,the removal rate was 81.61±4.08%,86.33±3.21%.It can be concluded that HRT has a great influence on the utilization of organic matter in the reactor.The sludge concentration on the two reactor packings was first decreased and then increased.In the R2 reactor,the concentration of the packed sludge was 2.6 g/g,1.95 g/g,2.45 g/g,respectively.It can be seen that the higher the HRT and C/N,the higher the sludge concentration.(3)The denitrification performance of food waste in fluidized bed reactor was investigated.The R1 reactor was successfully started for 5 d,the average effluent TN concentration was 5.63±4.83 mg/L in first stage,the R2 reactor required 9 d to start successfully,and the average effluent TN concentration was 8.31±7.56 mg/L.The results show that the reactor with high filling rate starts faster and the effluent quality is better.When the filling rate is the same as the surface area different,HRT=1h,the TN concentration of the R1 and R2 reactors is 6.67±4.05 mg/L and 5.75±3.22 mg/L,respectively.The larger the surface area,the better the effluent quality.The sludge concentrations on the three-stage packing were R1:4850 mg/L,6880 mg/L,9380 mg/L,R2:3930 mg/L,6950 mg/L,and 10830 mg/L,respectively.It can be concluded that the higher the filling rate,the higher the sludge concentration on the packing;the larger the surface area,the higher the sludge concentration on the packing.In this study,the water quality of food waste as denitrification carbon source was different in three groups of reactors,and the water quality of reactor effluent was mainly affected by HRT,filling rate and C/N,and different reactor types had influence on sludge concentration and sludge morphology in the reactor.Through the research on the effect of denitrification of food waste in different reactors,it has laid a certain foundation for the practical application of food waste.