Research On Treating And Reusing Of Paper Machine White Water

The pulp and paper industry is a highly energy-consumed and water-dependent industry,and generat large amounts of wastewater.Therefore it is becoming one of focus of environmental problems.The wastewater from the pulp and paper industry can be divided into three types: black liquor,gray water and paper machine white water.The paper machine white water is getting more attention because of its easy treating and recycling.Therefore,there is an urgent demand on the treatment technology for white-water which is practical,reliable and economic to overcome the pressure of wastewater increase and the demand of effluent reuse.In this study,the paper machine white water?3700 white water?was selected as the treatment target.Based on analysis of water quality and comparison of treating schemes,a feasible treatment scheme was selected and optimized,which procided theoretical guidance for practical engineering.The molecular weight distribution and organic matter types of the 3700 white water were analyzed.The 3700 white water COD_cr and SS were 750³500 mg/L and 2000⁷000 mg/L,respectively.The result indicated that most of the organics in paper machine white water were composed by suspended organics,accounting for above 64% of the total organic pollutant and mainly were macromolecular,above 5 kDa accounting for nearly 60%.The result of the GC-MS stated that there was silane material in the 3700 white water.According to these wastewater characteristics,two kinds of proposed schemes were brought forward and investigated.They were coagulation-biological treatment-sand filter process and coagulation-membrane bioreactor process.Based on the treatment efficiency and operation approach,the coagulation-biological treatment-sand filter process was optimal treatment scheme.Then the optimal operating conditions of the process were determined.The suggested operating conditions of coagulation sedimentation pretreatment were: initial pH in the reaction of 7⁸,V?iron mud?: V?white water?= 1:7,PAM dosing quantity of 1.5 mg/L.The optimum running condition of aerator tank was that the temperature was 20²5°C,the hydraulic detention time?HRT?was 24 hours and the organic load rate was 0.6⁰.9 kgCOD_cr/?m³·d?.Based on the exploration of bench sacle test,the united system reaearch has been conducted to form a complete technological process.When the influent COD_cr was 1950²300 mg/L,SS was 2320³020 mg/L,chroma was 250²80 times,conductivity was 5100⁶070 ?s/cm,total hardness is 632.53⁶64.66 mg/L,the water quality of the effluent was stable,and the effluent COD_cr was 65⁸0 mg/L,SS was 7¹0 mg/L,chroma was 15³0 times,conductivity was 5510⁶610 ?s/cm,total hardness was 556.46⁶16.52 mg/L.The cost of employing this process system for 3700 white water?medicament expense and electricity charge?was about 0.638 Yuan/m³.