Study On Advanced Treatment Of The Straw Pulp Washing And Bleaching Effluent

The shortage and pollution of water has become a serious problem in the world. In order to solve this problem, advanced treatment and recycling of sewage are indispensable except economy.Because of complex component, high load of pollutant and large sewage capacity, the washing and bleaching effluent of straw pulp has become the focus in pollution controlling. Now sewage treatment projects in most mills just include the first and second treatment phases, a majority of chromogenic lignin ramifications are difficult to be decolored. The effluent with deep color and COD_Cr content, can't meet the new and strict dischargable standard. So it's imperative to further reduce COD_Cr and chroma, improve effluent quality and study advanced treatment methods of the washing and bleaching effluent.This study adopts Fe/Cu micro-electrolysis-Fenton and flocculation together to treat this waste water. The main contents include: Firstly, select a most suitable flocculation from several ones and discuss the optimal conditions; and secondly, study the influence of micro-electrolysis-Fenton and flocculation on Fe/C and Fe/C by static experiments, obtain the experiment conditions and parameter. Carry out continuous dynamic experiments to treat waste water in excellent conditions. The results reveal: Al₂(SO₄)₃ is superiority compared with Al₂(SO₄)₃, PAC and FeCl₃,. The suitable condition of Al₂(SO₄)₃ is that input dosage is 900 mg/L, pH=7, reaction time is 16 minutes, speed grads is 23s-1. After flocculation selected, it is necessary to adjust the agitate intensity and reaction time in order to obtain better results.The suitable condition of advanced treatment by Fe/C micro-electrolysis-Fenton is: Fe/C=2, input dosage is 1.4 mL/L, the input pH is 3.The suitable condition of Fe/Cu micro-electrolysis is: Fe/Cu=300, pH=7, the H2O2 dosage is 1.4 mL/L. Fe/Cu can stand longer time and long period of change filling than Fe/C, so micro-electrolysis has a better result.The suitable condition of continuous dynamic experiments is: pH=7, Fe/Cu=300, the time of micro-electrolysis is 90 min, dosage of H2O2 is 1.4 mL/L, Al₂(SO₄)₃ dosage is 500 mg/L.The removal rate of COD_Cr becomes lower and lower with prolonging treating time. The former 48 h, COD_Cr removal rate can reach to 70%, and final removal rate of COD_Cr and chroma is 85.7% and 98% separately, the output water is nicer. Fe/Cu micro-electrolysis-Fenton and flocculation together to treat the washing and bleaching effluent is economic and feasibly with smaller land occupancy, lower invest and the run cost. Because of lower input dosage and avoiding agglomeration, contrasted active carbon, Cu has excellent future.