| A large amount of chloride ions in high-salt wastewater will increase the osmotic pressure of the surrounding environment of bacteria,bacterial wall separation,and the activity of microorganisms will be inhibited,leading to a decline in the nitrogen removal effect of the wastewater biological treatment system.The salt-tolerant denitrifying bacteria composed of salt-tolerant denitrifiers,salt-tolerant nitrifiers,and common salt-tolerant bacteria have the advantages of wide salt tolerance range,high nitrogen removal efficiency,and strong impact resistance,and can achieve simultaneous nitrification and denitrification.However,the optimal carbon-nitrogen ratio required for denitrification is 15:1,which is much higher than the demand for denitrification reactions of ordinary microorganisms.Cellulose solid carbon sources are rich in pores and stable in carbon release rate,and are good carbon sources and biological carriers.In this study,a composite bacteria agent composed of salt-tolerant denitrifying bacteria,salt-tolerant nitrifying bacteria,common salt-tolerant bacteria,and solid carbon source corn cob was used to synergize the biological nitrogen removal performance of high-salt wastewater.Nitrogen accumulation,optimization of the coupling system startup conditions,the effects of C/N and substrate concentration on the denitrification effect of the system provide theoretical basis and technical support for the stable operation of the coupled system composed of a solid carbon source and a complex bacterial agent.The salinity stage is adopted for domestication.First,the sludge is cultivated at a salinity of 0%.After the effluent indicators are stabilized,the salinity is gradually increased according to a gradient of 1%,2%,and 3%.After 70 days of acclimation of salt-tolerant sludge,the COD concentration in the effluent was stable at 40-60mg/L,and the removal rate reached more than 90%.The effluent concentration reached about 50mg/L;the effluent concentration of NO3--N was stable at 3-5mg/L.During the domestication process,the problem of NO2--N accumulation was serious,reaching 50mg/L.To address the problem of NO2--N accumulation during domestication,two technical solutions were used:adding compound bacteria and increasing the COD concentration of the incoming water.After adding 4 days of compound bacteria,the effluent concentration of NO2--N decreased to 5.17mg/L.After increasing the COD of the incoming water to 100mg/L,the effluent concentration of NO2--N after 9d was stabilized at 8mg/L.The effect of adding the compound bacteria agent is better than increasing the COD concentration of the incoming water.The corn cob was used as the carbon source and the bio-carrier was fixed into the SBR reactor to construct a coupling enhancement system.The four-factor three-level orthogonal test was used to optimize the system’s starting conditions.The optimized result was:C/N:15:1.Initial ammonia nitrogen concentration:130mg/L,dosing amount of immobilized carbon source:15g/L,MLSS:4500mg/L,the system’s nitrogen removal rate can reach95.97%under optimized startup conditions.The analysis of variance showed that C/N（RA’=6.82）had the most significant effect on the nitrogen removal effect;the initial ammonia nitrogen concentration（RB’=4.65）was the second;MLSS（RD’=0.18）had a certain effect on the nitrogen removal effect..The impact of the amount of immobilized carbon source（RC’=0.18）was not significant.A comparative study of the denitrification performance of the coupled enhanced system and the composite bacterial agent enhanced system showed that the addition of a solid carbon source increased the TN removal rate and the NO2--N accumulation decreased by 37.95%.The effects of different aeration times on the denitrification effect of the system were investigated during the stable operation of the coupled system.Under the condition of aeration time of 6h,the effluent concentration of TN was 10.04mg/L,and the removal rate of TN reached 94.93%.When the aeration time is 5h,the TN effluent concentration is 10.5mg/L,and the removal rate of TN reaches 90.51%.The SBR reactor was started under optimized conditions,and the effect of different aeration times on the nitrogen removal effect of the system was investigated.Under the condition of aeration time of 6h in 2#reactor,the TN effluent concentration was 10.04mg/L,and the removal rate of TN reached 92.93%.Under the condition that the aeration time of reactor#1 is 5h,the effluent concentration of TN is 10.5mg/L,and the removal rate of TN reaches 92.51%.It can be seen that the aeration time after stable operation has little effect on the nitrogen removal effect of the system.After the typical cycle of the system,the concentrations of TN,NH4+-N,NO2--N,and NO3--N decreased to 13.13mg/L,3.68mg/L,8.65mg/L,0.83mg/L,NH4+-N and The removal rates of TN are 98.58%and 95.22%,respectively,which meet the comprehensive sewage discharge standards in Liaoning Province.When the coupled system is running stably,keep the C/N of the system unchanged,and the system with lower water concentration reaches stability faster.When the water COD concentration reaches 3900mg/L,the system needs to be sludged and supplemented with bacteria.The effluent quality of the system meets the standard when the operation ability such as agent is reached,and the effluent effect of the low concentration system is better.Although the denitrification effect of high-concentration system and low-concentration system is different,both of them maintain a high denitrification rate,indicating that the effect of COD and NH4+-N concentration on the nitrogen removal effect of the system is relatively small.Change the concentration of COD or NH4+-N in the feedwater to adjust the C/N of the system to 15:1,8:1,5:1,respectively,and examine the effect of C/N on the nitrogen removal effect of the coupled system.After C/N decreased from 15:1 to 8:1,the system reached stability after 5cycles,the nitrogen removal effect decreased to a certain extent,and the removal rate of TN decreased from 84.82%to 80.62%.After C/N decreased from 8:1 to 5:1,the system reached stability after 8 cycles,and the nitrogen removal rate decreased significantly.The removal rate of TN was only 73.22%.Due to insufficient carbon source,the accumulation of NO2--N reached 15-16mg/L. |
