Experimental Research On Medium Density Fibreboard Wastewater Treatment By Combination Of Coagulation And Fenton Reagent Oxidation

Medium density fibreboard (MDF) wastewater is one kind of refractory industry wastewater has complicated components.The combined coagulation-Fenton oxidation process was adopted for the pre-treatment of MDF wastewater which was originated from a wood company of Jiangsu (COD_Cr about 6000³0000mg/L;BOD₅/COD_Cr (B/C) ratio 0.2⁰.3).In consideration of the coagulation effect and the request of the Fenton oxidation process. Polyferric Sulfate(PFS) was choosen as the best inorganic coagulant compared to the others, so it was chosen as the coagulant for the MDF wastewater. The main condition were investigated, based on it, the research of combination of organic coagulant PAM and inorganic coagulant PFS has been studied, The optimal operation parameters of coagulation were determined as follows: the initial pH value, PFS dosage of 1.8g/L(the COD_Cr of MDF effluents is 10110mg/L), high speed agitation of 300 r/min with 30s, PAM dosage of 10mg/L,low speed agitation of 60r/min with 90s and precipitation time of 120min.After coagulation, 60.8% COD_Cr and 87% SS removal were achieved;The pH value was 4.15;The Fe²⁺ concentration of the water was 130.88mg/L;The zeta potential increased from -13.3mv to -3.7mv and the suspended particles of 1-100μm were nearly removed.In order to further improve the biodegradability and reduce the organic load of MDF wastewater, Fenton oxidation process was selected for the sequencing treatment of the effluent. Optimum conditions of Fenton oxidation process for treating the effluent of coagulation were determined as: initial pH of the wastewater treated by coagulation,use the Fe²⁺ contained in the effluent which has been treated by coagulation(the concentration of Fe²⁺ is about 120¹80mg/L), the nFe²⁺/nH₂O₂ is 0.05,reacting for 40mins,pH was then adjusted to 8⁸.5. 62.5% COD_Cr has been removed during the Fenton oxidation period.The combination of coagulation and Fenton oxidation was taken into consideration,and the COD_Cr removal was 80.5%,it has achieved a good effection. The cost performance of this process has been considered, the PFS dosage has been changed into 0.75g/L, and change the nFe²⁺/nH₂O₂ into 0.3, under this condition, the continuos running was evaluate, and the COD_Cr removal efficiency was 66%,the price of treat the effluent is 3.1 yuan per ton. A GC-MS research was taken,the result shows that after coagulation,many organics was removed,but some organics which has a annulate structure were reserved and parts of those annulations was turned into linear chain organics after Fenton oxidation.The experiment verified the combined coagulation-Fenton oxidation process was effective for pre-treatment of MDF wastewater.