A Study On The Treatment Characteristics Of Enriched Pollutants By Deep Treatment Process For The Printing And Dyeing Wastewater Recycling Process

In recent years,the high wastewater discharge of textile printing and dyeing industry aggravates the difficulty of water environment treatment.In order to protect the water environment,printing and dyeing wastewater discharge standards were further improved.At the same time,printing and dyeing discharge wastewater volume had also been strictly limited,printing and dyeing wastewater recycling was paied attention increasingly.However,it is serious affected that the stability of wastewater treatment system and the quality of printing and dyeing products by the concentration of pollutants in the recycling process.Based on this,a pilot equipment with treatment scale of 5m³/d had been applied experiment on the recycling process for allocated printing and dyeing wastewater.Through combination process of coagulation,hydrolysis acidizing,activated sludge with different deep process which include air floatation,ozone air floatation and ozone air floatation-bypass membrane,characteristics of pollutant enrichment in the recycling process of printing and dyeing wastewater were studied.The operating parameters were regulated according to the characteristics of pollutant enrichment in order to control the pollutant enrichment and improve the effluent quality,and the printing and dyeing wastewater could be recycled.The main research results were summarized as follows:（1）Air floatation as a deep treatment process,The recycling of wastewater lasted for 40 cycles and ended with the breakdown of the biochemical system.During the cycle,organic matter represented by COD,chroma,ammonia nitrogen and total phosphorus and inorganic matter represented by TDS,conductivity and 7kind of typical ions showed different growth trends.The enrichment of organics and inorganics makes the character of activated sludge in aerobic tank deteriorate and the biochemical system tends to collapse.（2）Ozone induced flotation as a deep treatment process,the collapse rate of the biochemical system slowed down,and the recycling of wastewater lasted for 100cycles.The accumulation of organic matter in the circulation was controlled:The COD,ammonia nitrogen,total phosphorus of effluent in ozone induced flotation respectively stabled in 80,0.9,0.45 mg/L,but only reached the standard of printing and dyeing wastewater discharge.Inorganic matter still showed enrichment trend,and the enrichment rate was slightly higher than that in the first test stage.The concentration of COD and chromaticity reduced and the concentration of ammonia nitrogen,total phosphorus,SO₄^2-and Cl^-was increased.The high salinity environment in the aerobic pool significantly reduced the concentration of activated sludge,and the average rate of decline was about 22.28mg/（L·d）（a cycle per day）,which is about half of the first stage.（3）Ozone induced flotation-bypass membrane as a deep treatment process,the wastewater recycling system had been in stable operation for 180 cycles and the sludge concentration maintained above 2200mg/L,and the biochemical system was in a relatively stable state.When the mixture ratio of ozone induced flotation effluent and RO effluent was 6:1,the enrichment phenomenon of inorganic salts and organic compounds controlled,but the effluent conductivity of the system cannot reach the reuse standard of printing and dyeing wastewater.When adjustin the mixing ratio to3:1,the organic and inorganic salt content of wastewater greatly reduced,the system effluent met the recycling standard of printing and dyeing wastewater:COD,chroma,electrical conductivity,total iron,total Mn water were 30mg/L,12 times,2450μs/cm,0.1mg/L,0.018mg/L and the recycling rate reached 72%.