Study On Denitrification Performance Of An Intermittently Aerated Sequencing Batch Reactor For Treating High-ammonium Wastewater In A Thermal Power Plant

Although the denitrification ammonia plant wastewater from the thermal power plant has a small amount of water,the concentration of ammonia nitrogen is very high Even if it is mixed with other renewable wastewater from the power plant,ammonia nitrogen in the mixed wastewater will be high and the chemical oxygen demand to total nitrogen(COD/TN)ratio will be low,which became the key factor affecting the discharge of ammonia nitrogen and total nitrogen in the power plant effluent Compared with the traditional denitrification process,intermittent aerated sequencing batch reactors(IASBR)are more likely to form short-cut nitrification and denitrification,thereby saving the energy consumption of aeration during operation,and greatly reducing the carbon source and alkalinity addition.In this study,IASBR was used to treat high ammonia nitrogen wastewater from thermal power plants.The three COD/TN were studied under four working conditions(working condition 1,COD/TN was 2.5;condition 2,COD/TN was 3.0;and condition 3 and 4,COD/TN 3.5),two operating modes(working condition 1?3,intermittent aeration mode 1,working conditions 4,mode 2)on the effect of denitrification,achieved the following resultsThe denitrification effect of IASBR is greatly affected by the COD/TN.The total nitrogen volume load was 0.30?0.37 kg·(m3·d)-1,and the influent ammonia nitrogen concentration was(300±20)mg·L-1.When the influent COD/TN is 2.5,the denitrification efficiency is 32%?70%;when the COD/TN is 3.0,the denitrification efficiency is 60%?85%;the COD/TN is increased to 3.5,the denitrification efficiency is as high as 95%,the effluent total nitrogen in the stationary phase is less than 15 mg·L-1Short-cut nitrification and denitrification are the basic characteristics of nitrogen removal from IASBR.According to the water quality of the typical cycle in different working conditions,the aerobic first-stage dissolved oxygen was 0.5?0.9 mg·L-1,the aerobic 2-stage dissolved oxygen was 1.0?4.5 mg·L-1,pH 7.1?8.8,and the reactor gradually realized short-cut nitrification and denitrification.The short-cut nitrification during the reaction of working condition 1(35 d)and working condition 2(98 d)is mainly in the aerobic stage 1.The accumulation rate of NO2--N is respectively about 56.1%and 62.5%.Nitrite oxidizing bacteria(NOB)still had greater activity in the aerobic stage 2 with low free ammonia(FA)concentration;The NO3--N concentration was low during the whole period in condition 3(133 d)and condition 4(158 d),and the accumulation rate of NO2--N during the reaction was as high as 95%.The accumulated NO2--N was directly involved in the denitrification reaction.After material balance,denitrification COD accounts for up to 70%in Working Conditions 3 and 4.Therefore,IASBR uses the extra carbon source for denitrification more efficientlyIntermittent aeration mode has a great influence on sludge characteristics and effluent quality.The aerobic time of intermittent aeration mode 2 was extended from 120 min in mode 1 to 138 min,the proportion of Nitrosomonas in the total bacterial population increased from 0.62%at 134 d(pattern 1)to 2.34%at 177 d(pattern 2),and the ammonia nitrogen removal capacity and stability of the reactor was stronger.The flocculation form of sludge in Working Condition 4 was improved compared to Working Condition 3,and SV30 was reduced from 91%at 134 d to 80%at 168 d(mode 2).