| Denitrification and phosphorus removal technology has always been a gap in the fields of circulating cooling sewage treatment.This study was based on the latest domestic and international research progress,taking Combined Biological Filter(CBF)and active sand filter as an integrated process for treatment of the circulating cooling sewage.The performance of the process was discussed and operation parameters are optimized both in the pilot test and the engineering application.A survey of 10 gas-fired power plants showed that circulating cooling sewage contained high concentrations of TP,TDS,SS,TN and low carbon,and the circulation ratio and reclaimed water quality were two key factors that affected the circulating cooling wastewater quality.A single-stage CBF was used in the denitrification of circulating cooling water.The start-up was accomplished in 20 days.Operating parameters were as follows: the TN loading rate was 0.45 ~ 0.76 kg/m · d(the influent water flow 300 L/h,TN concentration 35 ~ 60 mg/L,the reactor volume 0.65 m3),the effluent TN concentration was lower than 10 mg/L and TN removal rate between 71.4 ~ 83.3%;SS concentration decreased from 9 ~ 18 mg/L to below 5 mg/L;aeration on the upper part of CBF can remove excess carbon source,keeping the effluent CODCr lower than 20 mg/L;the best C/N ratio was 3.5:1 and the optimum temperature was 35 ℃;TN removal efficiency decreased with the TN loading rate increased.Polyaluminium chloride was added and active sand filter was used to remove phosphorus and the effluent TP was less than 0.2 mg/L.The coefficient was between 3.85 ~ 6.50 and increased with the TP concentration increasing.Combination technology was applied to Beijing Jingxi gas-fired power plant circulating cooling water treatment engineering(10000 t/d).After 40 days of start-up and months of commissioning and test run,the effluent TN,TP and CODCr,SS meet the "Beijing Integrated Water Pollutant Discharge Standard"(DB11307-2013). |
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