| Wastewater reusing can reduce the wastewater discharge and lower water consumption of paper making. A shoe paperboard plant of Foshan had some problems because of waste water recycling. This topic analyzed the causes of these problems, put forward several countermeasures to solve these problems, and chose appropriate methods to treat this wastewater properly then reused it. The main purpose of this study was not only to provide a solutions for these problems that wastewater reusing leads to in the shoe paperboard plant,but also to provide some reference for wastewater reuseing of other paper mills at the same time.This paper analyzed the water quality changes of whitewater,and found the variation of the accumulation of harmful substances in cycle.Combined with the production situation as wastewater recycling, it provided critical value of the circulating water index:COD was about5700mg/l;SSwas about1100mg/l; the chroma was60times,and the wastewater had be reused for6days. When the wastewater had be reused for13days or so, COD and SS of whitewater in wet end reached a dynamic balance,then the COD was15700mg/l or so,SS was5600mg/l or so,and the chroma was120times or so.In order to eliminate the effects of harmful substances that were accumulated by wastewater cycle, workers had to increase production additives dosage.However, when the cycle was to a certain extent,additives that were increased cound not eliminate the harmful influence on production. The workers had to discharge wastewater and inject fresh water,then wastewater enter into the next reuse cycle.Considering the simple and applicability of the process and the efficiency of the initial investment,this paper chose coagulation precipitate and chemical oxidation as the wastewater treatment process. It investigated the effect of the amount of coagulant dosage and pH on coagulation precipitation. As for chemical oxidation experiment,it investigated the effect of the oxidant species, oxidant dosage, pH and reaction time on its treatment effect. The results showed that:(1) The best operating conditions of coagulation sedimentation were that PAC dosage was120mg/L, PAM dosage was2.5mg/L and pH was9.Under these conditions,the removal of SS was about70%, COD reduced about30%and the removal of chroma was48.35%.(2) The best operating conditions of Fenton oxidation were that H2O2dosage was40ml/L, which was about1.3times of theory dosing quantity, the ratio of the nFe2+/nH2O2was0.1, pH was4and the reaction time was80minute, under these conditions, COD of wastewater reduced about30%and the removal of chroma was42.9%. The best operating conditions of NaClO oxidation were that NaClO dosage was10ml/L, pH was3, oxidation time was45minute, under these conditions,removal of COD was27%and the chroma reduced75.4%. The optimum operating conditions of the KMnO4oxidation were that KMnO4dosage was40mg/l, pH was3, oxidation time was50minute.In KMnO4oxidation experiment, The decolorization effect was not obvious,and the best removal of COD was24.56%.(3) The joint experiment of Coagulation precipitate and chemical oxidation showed that the coagulation precipitate-Fenton oxidation process cound be effectively reduced the COD of wastewater,the removal of COD was above74%, the treated wastewater cound reach the level for reusing.And the decolorization effect of NaClO oxidation coagulation sedimentation process was better than other processes, and it cound reduce chroma of wastewater more than81%. In general, the coagulation precipitate-Fenton oxidation process cound be used for wastewater treating.However, NaCIO oxidation-coagulation sedimentation process should be used when decolorization is needed. |
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