| China's energy structure of “rich coal,poor oil and little gas” determines that China must take coal as the pillar energy.With the development of coal chemical industry,comprehensive,clean and efficient utilization of coal led by coal pyrolysis technology has been paid increasing attention at this stage.The coal pyrolysis process is characterized by high water consumption,large waste water discharge,complex water quality,difficult waste water treatment and recovery.The government also requires coal chemical wastewater to meet “zero emission” requirements,so effective treatment and utilization of coal pyrolysis wastewater is a necessary condition for the flourishing development of the coal chemical industry.This paper shows the water quality characteristics and current treatment technology of coal pyrolysis wastewater.Aiming at the actual engineering biological enrichment tank unit,Polyurethane suspension filler(PU)is selected to replace powdered activated carbon(PAC)in the biochemical treatment of coal pyrolysis wastewater.Chlorella is used as a co-metabolic carbon source to enhance the denitrification process of coal pyrolysis wastewater.The further degradation efficiency of Chlorella on residual refractory organic matters and total nitrogen in the effluent of biological enrichment tank is explored.The feasibility and economy of treating coal pyrolysis wastewater with suspension filler and Chlorella are studied.In the pilot test of comparing the efficiency of treating coal pyrolysis wastewater with suspension filler and activated carbon,COD of blank group,activated carbon group and suspension filler group in effluent are all lower than 200 mg/L after adding filler and running stably.The treatment effect of activated carbon group is better,and the COD removal rate is about 90% after stabilization in the second stage.The treatment effect of blank group and suspension filler group was lower,about 82% and 83% respectively.The removal effect of total phenol is consistent with the degradation trend of COD.The residual amount of ammonia nitrogen in the suspension packing group in the effluent is about 85 mg/L,and the degradation rate is the highest among the three groups.After the reaction,the sludge concentration,EPS and high flux were analyzed,and it was found that the suspension filler can significantly increase the sludge concentration of the mixed liquid,and the species abundance and the number of species increased,reaching a certain degree of biological concentration.After stable operation,when sodium acetate and glucose were added 165 mg/L(COD accounted for about 76.9 mg/L)and 110 mg/L(COD accounted for about 116.93 mg/L)respectively,the nitrite nitrogen removal rates were 96.1% and 97.5% respectively in the Chlorella intensified denitrification pilot experiment.When Chlorella is added to 150 mg/L(COD accounts for about 151 mg/L),the removal rate of nitrite nitrogen is more than 80%,and when Chlorella is added to 165 mg/L(COD accounts for 166.3 mg/L),the removal rate of nitrite nitrogen and total nitrogen can reach more than 95%.Studies have shown that sodium acetate,glucose and Chlorella can be used as organic carbon sources for denitrification and enhanced denitrification in the intermediate links of coal pyrolysis wastewater.Through economic analysis of each carbon source,it can be seen that when glucose is used as an external carbon source,the direct cost is the lowest,followed by Chlorella and sodium acetate.However,in view of the comprehensive treatment effect,Chlorella has the advantages of better treatment effect,easy addition,direct cost and low operation and maintenance cost when used as an intermediate carbon source.Therefore,Chlorella can be used as an intermediate reaction for coal pyrolysis wastewater Carbon source is available for nitrification and denitrification.In the actual project site debugging,the COD of the influent of the on-site biological enrichment tank is between 800 and 1000 mg/L.After the suspension filler is added,the COD effluent gradually decreases from about 300 mg/L to 150?200 mg/L,and the COD degradation rate gradually stabilizes to about 85%.Ammonia nitrogen in the influent of on-site biological enrichment pond is between 150 and 200 mg/L.About 15 days after the first batch of filler was added,the ammonia nitrogen removal rate was 53%.With the stabilization of the system,ammonia nitrogen in the enrichment tank can be effectively converted into nitrate nitrogen and nitrite nitrogen,and nitrite nitrogen is the main nitrogen,when aeration ensures that the outer corridor DO is within the normal range.During the experiment of adding Chlorella to the wastewater actually produced in the onsite bioconcentration pond,the total nitrogen degradation rate gradually increased when the Chlorella group was operated for about 25 days.After 35 days of operation,the degradation rate of total nitrogen was maintained at about 90%,and the remaining amount of total nitrogen was less than 20 mg/L.It proves that Chlorella has a good strengthening effect on the removal of total nitrogen,which is consistent with the conclusion of the laboratory test. |
PDF Full Text Request