Advanced Treatment Of Pulping And Papermaking Wastewater By Persulfate Oxidation Technology

Pulping and papermaking wastewater after secondary biochemical treatment still cannot meet the national discharge standards because of the complex composition.According to GB 3544-2008,the national requirements for discharge standard of papermaking wastewater are increasingly stringent.Therefore,it is necessary to take further treatment of secondary biochemical effluent to make it meet the standard.In this paper,the secondary biochemical effluent of actual pulping and papermaking wastewater was taken as the research object,and the advanced persulfate oxidation technology was applied to the advanced treatment of biochemical effluent.At the same time,the treatment efficiency and mechanism were studied and the effectiveness of the advanced persulfate oxidation technology was verified.The main contents and conclusions are as follows.Firstly,the CODcr,TP,TN,inorganic cation and anion in the actual pulping and papermaking wastewater were characterized,and the configuration method of simulated wastewater was further determined based on the results and the literature.The configuration method was as follows:the concentrations of glucose,p-hydroxyphenylpropionic acid and lactic acid were 0.10 g/L,0.007g/L,and 0.68 mmol/L,respectively.Secondly,different methods were used to activate the persulfate,and the system was optimized by analyzing the influencing factors to the treatment of simulated organic wastewater.The experimental results showed that the removal efficiency of CODcr by five activation systems were compared as follows:heat-Na₂S₂O₈(84.2%)>hv/Fe³⁺-Na₂S₂O₈(79.2%)>hv-Na₂S₂O₈(41.5%)>Fe²⁺-Na₂S₂O₈(32.4%)>ultrasound-Na₂S₂O₈(21.6%).The energy consumption of heat-Na₂S₂O₈system and hv/Fe³⁺-Na₂S₂O₈system were 1 kw·h and 1.5 kw·h,respectively.Through comprehensive comparison,the heat-Na₂S₂O₈system was selected as the optimal activation system.Thirdly,the influences of coexisting inorganic ions were studied.The experimental results showed that the anions had a certain effect on the degradation of CODcr in the simulated organic wastewater,and the order of the influences degree were as follows:Cl^->NO₃^->SO₄^2->H₂PO₄^-.However,the cations had no effect on the degradation of CODcr in the simulated organic wastewater.By comparing the effects of inorganic ions on different systems,on the one hand,the system based on SO₄^·—radical was less affected by anions than the system based on·OH radical.On the other hand,compared with other activation systems,heat activated persulfate system was less affected by anions and cations.Fourthly,the degradation mechanism of the optimal activation system was studied.The experimental results showed that SO₄^·—and·OH radicals exist in the system.Among them,SO₄^·—and·OH radicals both played an important role in the degradation of p-hydroxyphenylpropionic acid and lactic acid.·OH radical played a slightly major role in the degradation of glucose,and SO₄^·—radical played a secondary role.By detecting possible intermediate products of simulated pollutants,the degradation pathways of simulated pollutants were deduced,and these pollutants were mineralized into CO₂and H₂O eventually.Finally,the optimal activation system was applied to the treatment of secondary biochemical effluent from actual pulping and papermaking wastewater.The experimental results showed that both the CODcr and chroma of the actual wastewater met the discharge standards under acidic and neutral conditions,proving the effectiveness of the heat-Na₂S₂O₈system in treating the actual wastewater.By comparing the types of organic matter before and after treatment,the results indicated that the content and species of organic matter were greatly reduced after treatment.