Experimental Study On The Effect Of Coal Activated Sludge Process On Wastewater Treatment And Sludge Combustion Characteristics

In the process of wastewater treatment,On the one hand,it is necessary to improve the effect of wastewater discharge.On the other hand,it is necessary to solve by-product sludge of wastewater treatment.Aerobic granular sludge has obvious advantages over traditional activated sludge in improving the effect of wastewater treatment.Incineration is a method of treating sludge.In order to achieve incineration requirements,it is necessary to add combustion aid such as coal and others before incineration in order to increase heating value.Therefore,this study assumed that using coal as a carrier to acclimate activated sludge to form coal activated sludge.While improving the effect of wastewater treatment,the heating value of the sludge is improved to improve the combustion performance of the sludge.This study examined the effects of aeration time,coal adding dosage,and coal particle size on the effect of wastewater treatment.The heating value and combustion characteristics of common sludge and coal sludge were discussed.The main conclusions are as follows:(1)During the sludge acclimation stage,under the aeration time of 4 h and 6 h respectively,after about 30 days of acclimation of the activated sludge.The wastewater treatment effect under aeration for 6 h was generally better than that under aeration for 4 h,but the difference was not significant.Therefore,from the perspective of saving operating costs,the aeration time for the subsequent experiments in this study was 4 h.(2)The test results of the effect of the coal adding dosage on the wastewater treatment results showed that the effect of the coal adding dosage on the manually formulated wastewater and actual wastewater on pollutants were basically the same.The coal adding dosages were 0 g/L,0.2 g/L,0.4 g/L,0.6 g/L,0.8 g/L,1 g/L,respectively.Coal activated sludge had better removal of pollutants,and the optimal coal adding dosage was 0.4 g/L.For the actual wastewater,the average removal rates of COD for the ordinary activated sludge system and coal activated sludge system of 0.4 g/L coal adding dosage were 90.88% and 93.99%,and the average removal rates of ammonia nitrogen were 71.04 % and 97.88%,respectively.The average removal rates of total nitrogen were 53.19 % and 60.21 %,and the average removal rates of total phosphorus were 90.98 % and 96.61%,respectively.(3)For the ordinary activated sludge system and coal activated sludge system of 0.4 g/L coal adding dosage,the results of the sampling test every 30 minutes in a nitrification cycle with aeration time of 4 h showed that the COD,ammonia nitrogen,total nitrogen and total phosphorus pollution indicators in the coal activated sludge system decreased more rapidly compared with the common ordinary sludge system.(4)The effect of the coal particle size on manually formulated wastewater and actual wastewater showed that in the case of coal particle size of 60-80 mesh,80-100 mesh,100-120 mesh,120-140 mesh,and more than 140 mesh,the overall treatment effect of coal activated sludge on various pollution indicators gradually increased with the decrease of particle size.When the particle size of coal was reduced to 100-120 mesh,the treatment effect started to be stable.Therefore,under the conditions of this experiment,it is more appropriate to select coal with a particle size of 100-120 mesh.(5)The study on the heating value and combustion characteristics of ordinary sludge and coal sludge showed that with the increase of coal adding dosage,the heating value of the sludge and the critical moisture content of the combustion gradually increased.When the coal adding dosage was 0 g/L,0.2 g/L,0.4 g/L,0.6 g/L,0.8 g/L,1 g/L,the heating value were 15890.448 kJ/kg,18798.644 kJ/kg,19184.962 kJ/kg,20218.451 kJ/kg,20509.895 kJ/kg,20622.710 kJ/kg,respectively.The critical moisture content for combustion were 67.03%,71.51%,72.02%,73.29%,73.62%,73.75%,respectively.In terms of combustion characteristics,the maximum lost weight of coal sludge was greater than that of ordinary sludge and the maximum burnout temperature was not much different.At different stages of the combustion process,with the change of the coal adding dosage,the change trend of the incineration weight loss of the coal sludge incineration and incineration of the traditional sludge mix with coal before incineration in the literature was consistent.The overall incineration of coal sludge was better than ordinary sludge.(6)According to the experimental results of the wastewater treatment experiment in the coal activated sludge system and the combustion characteristics of coal sludge,the coal activated sludge system with coal as the carrier can improve the wastewater treatment effect and improve the sludge combustion characteristic.This provided new ideas and new methods for wastewater treatment and sludge treatment.