Sewage features:

Printing and dyeing industry wastewater discharging volume is big,and contains high concentration pollutants.It’s mainly from dyeing and finishing section,includes desizing,boiling,bleaching,mercerizing,dyeing,calico printing and finishing wastewater.Pollutants mainly are dirt,salt,oil and lipid in textile fibers,and processing project additional dyes,slurry,surfactants,additives,acid and alkali,etc.It’s main features are large volume and complex composition,high organic matter content,COD is 800-2000mg/l,B/C ratio is low,and biodegradability is bad,high alkaline,chroma and temperature,water quality and yield fluctuate greatly,containing large amount of additives and surfactant.

Massive dyes using causes high chroma.Chroma removal is a difficult problem of  printing and dyeing wastewater.Using air floatation as decoloring pretreatment.According to the water featrues,it ususlly adopts aerobic biological treatment as the main process at home.Because the wastewater contains refractory organic matter such as dyes,additives,etc,its biodegradability is bad,adding hydrolysis acidification device before aerobic biological process to improve biodegradability and increase removing efficiency.Biological treatment unit can choose biological fluidized bed,contact oxidation,surface aeration,etc.Combined with practice experience,company summarized a set of effective process:"floatation pool + hydrolysis acidificationl pool + biological contact oxidation pool".The effluent achieved the printing and dyeing industry first-level effluent quality standard of comprehensive wastewater discharge standard,COD_cr≤100mg/l,BOD₅≤20mg/l,NH₃-N≤15mg/l.