Novel Technology Of Low-carbon Wastewater Treatment Based On Solid Carbon Denitrification

Based on traditional biological nitrogen removal theory, enough organic carbon source is essential for biological denitrification, but urban sewage of low carbon source is becoming more evident, especially in the south of China. For low carbon source wastewater, TN has become the main target to meet the discharge standards of the urban sewage treatment. According to the comprehensive analysis of the low-carbon wastewater treatment technologies and the biological treatment characteristics, the enhanced biological nitrification-solid carbon source denitrification sewage treatment technology has been constructed in previous study, this paper developed a combined process of Sequencing Batch Biofilm Reactor and Solid Carbon Denitrification Biofilter(SBBR-SCDNBF). In the treatment of low-carbon source wastewater which COD concentration is less than 200 mg/L, and COD/TN is between 1.7 ~2.7, this dissertation has studied the influence of the different cycle time, aeration rate and temperature on the enhanced biological nitrification effect of SBBR, compared with SBR. Mine while, this dissertation has studied the nitrogen removal efficiency of the SCDNBF and the treatment effect of SBBR-SCDNBF system. The results show that:(1)Considering the factors of effluent ammonia nitrogen concentration, ammonia loading rate and energy saving, when the operation conditions of SBBR were SRT 20 d, water filling ratio 0.4, temperature 23~26℃, the best cycle time and aeration rate of SBBR were 3h and 4.0m3/(h·m3) respectively. At this running mode, the effluent NH3-N, NO3-N and TN concentrations were 0.85mg/L, 19.7mg/L, 25.0mg/L respectively, and the NO3-N account for 78.8% of the TN, achieving a stable and efficient nitrification under short cycle time, low dissolved oxygen(0.88mg/L) conditions. Under the same operating conditions, the nitrification effect and the nitrogen removal effect of SBBR is 1.64 times and 1.30 times of SBR, respectively. Even at the temperature of 10 ℃, effluent NH3-N standardized rate(A level, 8mg/L) of SBBR is still up to 93.3%, showing superior resistance to low temperature.(2)The SCDNBF achieved start-up in 15 day, and the effluent TN concentration was below 4mg/L, denitrification rate was 90%, with no excessive COD during the stable operation. The performance fluctuation caused by backwash can be avoided through appropriate control. When the temperature is 23~26 ℃ and influent TN concentration is around 30 mg /L, HRT should be longer than 0.5h to meet the TN discharge standard of A level, longer than 1h to achieve B level, and longer than 1.5h to keep the effluent TN concentration less than 10mg/L. Even at the temperature of 10 ℃, effluent TN standardized rate(B level, 20mg/L) of SBBR is still up to 66.7%, and HRT can be appropriately prolonged to 1.5h to keep the TN removal meet the discharge standard steadily.(3)When the influent COD, TN and NH3-N concentrations were 93~140mg/L, 40~45mg/L, 33~37mg/L respectively, and the operation conditions of SBBR were SRT 20 d, water filling ratio 0.4, cycle time 3h, aeration rate 4.0m3/(h·m3), the HRT of SCDNBF was 1h, the SBBR-SCDNBF effluent COD, TN and NH3-N concentrations were 23mg/L, 4.25mg/L, 0.95mg/L respectively, all were below the first level A criteria specified in Discharge Standard of Pollutants for Municipal Wastewater Treatment Plant(GB18918-2002). The nitrogen removal efficiency of SBBR-SCDNBF system could exceed 90%, achieving excellent biological nitrogen removal effect of low carbon source wastewater, and with no secondary pollution to the water.