| Printing and dyeing wastewater belongs to highly concentrated and difficultly degradable organic wastewater, which is difficult to be released up to standard by conventional biological treatment. After analyzing the character of printing and dyeing wastewater and the practical wastewater treatment technology route of a sewage disposal plant in Zhejiang Province, we bring forward the plan through which the technology route of "anaerobic baffled reactor (ABR)-cross flow aerobic sludge reactor (CFASR)" is utilized to treat this kind of wastewater.Long term operation effect of ABR technics system is examined and results show that under the condition that HRT is 11～12 h, the anaerobic influent pH is unregulated, the average influent COD, BOD and SS value are 1076 mg/L,550 mg/L and 404 mg/L respectively, the average effluent COD, BOD and SS value are 621 mg/L,444 mg/L and 183 mg/L respectively, and the average COD, BOD, SS removal rate are 42%,19.2% and 48.6% respectively. Above data indicate that ABR possesses finer removel effect to COD, BOD and SS. The average value of influent B/C is 0.56, and the average value of effluent B/C is 0.68. The elevation of B/C indicates the improvement of biochemical degradability. The average influent VFA is 2.05 mmol/L, the average effluent VFA is 1.77 mmol/L, and the VFA removal rate variation range is-82～55%. The negative VFA removal rate indicates that there exists accumulation of VFA in the reactor and the acidification effect is finer. When COD/SO42- (m/m) is less than 1.0 during the previous 60 days, the SO42- removal rate is high, between 50% and 70%; during 60～90 d, the SO42- removal rate is decreased to 10～40%, which indicates that SRB do not dominate already while methanogens and acid-producing bacteria (AB) do. Through anaerobic reaction treatment by ABR, effluent NH4+-N rises slightly, effluent TN declines slightly compared with influent TN, and TP content in water rises, so the latter aerobic microbes will be beneficial to grow well.According to the processing effect of ABR to printing and dyeing wastewater, the optimal operating parameters of ABR are determined:the startup HRT is controlled at 60～30 h, and the steady operation HRT is at 11～12 h; the startup pH is 7～8, and the steady operation pH is 7～9.5; the startup MLSS is 45 g/L, and the steady operation MLSS is 35～50 g/L; the startup MLVSS is 30 g/L, and the variation range of steady operation MLVSS is 20～35 g/L; the startup volume load is controlled at 2.0～6.0 kgCOD/(m3·d), and the steady operation volume load is 6.0～12.0 kgCOD/(m3·d); the startup sludge load is controlled around 0.1 kgCOD/(kgMLVSS-d), and the steady operation sludge load is 0.2～0.5 kgCOD/(kgMLVSS·d); in the trial process, the upflow velocity is 1.7 m/h, ORP is-400～-500 mV, the alkalinity is 600～1200 mg/L and the temperature is 30～40℃.The operation effect of lab scale aerobic reactor in series with ABR is examined, and results show:effluent COD is less than 100 mg/L, BOD is less than 15 mg/L and ranges of technological parameters are:HRT= 16 h, pH=7.5～8.5, MLSS=1500～4000 mg/L, MLVSS/MLSS is greated than 0.5, the tempersture is 25～36℃, the variation range of the sludge load is 0.2-0.4 kgCOD/(kgMLSS·d), and that of the volume load is 0.8～1.5 kgCOD/(m3·d).The operation effect of pilot scale aerobic reactor in series with ABR is examined, and results show:when HRT= 17 h, the variation range of pilot scale aerobic influent COD is 523～776 mg/L, that of effluent COD is 66～112 mg/L and the average value is 93 mg/L; when HRT is decreased to 14 h, the pilot scale aerobic effluent COD lasts higher than 100 mg/L. Influent BOD is usually 400～500 mg/L, effluent BOD is less than 15 mg/L, and the BOD removal rate is larger than 96%. Ranges of technological parameters are:HRT= 17 h, pH= 7.5-8.5, MLSS=2 000～5 000 mg/L, MLVSS/MLSS is greated than 0.55, the tempersture range is 20～35℃, the variation range of the sludge load is 0.1～0.4 kgCOD/(kgMLSS·d), and that of the volume load is 0.5～0.8 kgCOD/(m3·d).
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