The polyvinyl alcohol (PVA) wastewater was pretreated by the process of flocculation-Fenton oxidation. Raw wastewater was treated by the different flocculants first. The results showed that when the flocculant FeSO4 was used, its effect was better than Fe2(SO4)3 and PAC, the dosage of it was 10g/L, under which COD removal efficiency reached 61.72%. The effects of FeSO4 and H2O2 addition and pH on treatment effect were studied in the follow-up Fenton oxidation. The results showed that when the addition of FeSO4 was 20g/L, the dosage of H2O2 was 250mL/L, pH was 4, the removal efficiency of COD reached over 90%. The experiments of fractionated adding the reagents showed that the removal rate of COD was significantly higher in the situation of fractionated adding FeSO4 required in the flocculation and Fenton oxidation process than one-time added. The removal rate of COD changed little when the H2O2 fractionated addition in the process of Fenton oxidation.

Mid-stage Pulping Wastewater was pretreated in a combined system of microelectrolysis and Fenton oxidation-coagulation . When the aeration was 6L/min, the ratio of iron-carbon mass was 4/1, the addition of iron was 1500mg/L, pH was 4, and reaction time was 30min, the removal rates of COD and chrominance reached 65% and 60% respectively and the concentration of generated Fe2+ reached 157mg/L. Fe2+ generated by micro-electrolysis process was used for the following Fenton oxidation. When the conditions was without additional Fe2+, the addition of H2O2 (concentration is 30%) was 3mL/L, pH was 4, and the reaction time was 15min, the removal rates of COD and chrominance both reached over 80% and the concentration of generated Fe2+ reached 217mg/L. Fe3+ generated by Fenton oxidation was used for following studies of flocculation. The treatment efficiency of three kinds of flocculants PAM, PAC and silicate was compared. The results showed that the effect of PAM was best, the treatment efficiency reached the best when its additon was 0.15mL/L as pH was 7. the removal efficiency of COD reached 41% and the chrominance removal efficiency reached 75%, the final effluent chrominance was 4 and the COD concentration was 45mg/L which was lower than 60mg/L, that met with the first order of effluent standard.