Pretreatment And Utilization As Resources Of Alkali Weight-decrement Wastewater From An Enterprise In Zhejiang

As a kind of polyester processing methods, alkaline weight-decrement processbrings many excellent properties to polyester but also beget wastewater with highCOD, strong alkaline,poor biodegradability and high concentration of terephthalicacid(TA).with the development of alkaline weight-decrement processing,environmental problems caused by alkaline weight-decrement wastewater growincreasingly serious. the treatment idea that directly mix alkaline weight-decrementwastewater and other wastewater for integrated processing not only difficult to makeemissions meet environmental requirements,but also cause sharply increasedprocessing costs for the target of "treating waste".thus environmental benifits andeconomic statistics cannot be taken into account at the same time. This paper mainlystudied coagulation-sedimentation method aimed at removal of terephthalic acid saltsand acid precipitation method aimed at recovery of TA. impact of various factors ontreatment effect is discussed.powdered activated carbon that can be used inwastewater treatment is prepared from TA-containing residue;problems duringrecycling process caused by small particle size of TA are overcomed and preliminarydesign for the The wastewater treatment project has been done.（1）Processing effects using different coagulant alone on alkaline weight-decrement wastewater of are discussed, settlement mixed coagulation treatment isstudied to improve poor effect using only coagulant in alkaline weight-decre-ment wastewater treatment. Various factor’s effect on processing with joined pr-ecipitation agent and coagulant are analysised such as temperature and pH,con-sidering orthogonal experiment’s results and actual engineering conditions, bestprocess conditions is given.experimental results show that treatment with comb-ination of a reasonable amount of precipitation agent and coagulant, COD re-moval rate of wastewater is about75%, approximately98%TA are removed.（2）The influence of pH on treating alkali-decrement wastewater using acidprecipitation is discussed.improvement from PAM reaction time and product’sdehydration has been stuied as well as ways to improve the purity of the recuperated TA. Results show that reaction is almost complete wile pH is less than3. TheTA content in the wastewater was reduced from14800mg/L to102.3mg/L.Total CODremoval rate is up to77%.PAM made small precipitates larger particles forflocculation, thereby improving the dehydration of particulate matter, make it easierfor settlement, while significantly reducing the acid reaction time required. Accordingto the analysis of infrared, HPLC as qualitative and quantitative analysis, acid valueof the recuperated TA is667.7,and it has a purity of92.2%.（3）Traditional disposal way of sanitary landfill and incineration for TAcontainingresidue from coagulation-sedimentation process would cause not only waste ofresources,but also secondary pollution, experimental coagulation residue is used asraw material of activated carbon and620°C is the best carbonization temperatureanalyzed, on which condition only80min would it take for carbonization.activatedcarbon made from the residue can adsorb Congo red, Rhodamine b,Methyl blue andOrange IV(four common dyes)well, Methylene blue adsorption capacity of thisactivated carbon is13.5mL/0.1g.（4）After coagulation or acid treatment,the biodegradability of alkaline weight-decrement wastewater turns good and the COD is reduced considerably, diff-iculty of subsequent processing is also reduced.Considering result of orthogonalexperiment and enterprise’s requirement,suitable processing method is chosen a-nd preliminary design for the project is done.