Study On Pretreatment And Advanced Treatment Technology Of Neopentyl Glycol Production Wastewater

The production wastewater of neopentyl glycol in a chemical factory from Zibo Shandong province was characterized by high COD_Cr and high content of formaldehyde. Its strong biological disincentives leaded to low efficiency of biochemical treatment after pretreatment of dilution. The measure of dilution did not conform to the environmental protection policy. And the quality of effluent after biochemical treatment did not meet the demand of stricter standard of wastwater discharge. In this paper, the best pretreatment and deep-treatment technology have been researched according to the wastewater quality characteristics and the existing treatment process. The efficient and economical pretreatment and deep-treatment technology were selected to make the wastewater reach the new discharging standard.Four technologies were investigated in the preprocessing part. The results of experiment showed as follows:（1） The results of alkaline hydrogen peroxide pretreatment indicated that 34.65% of COD_Cr and 71.48% of formaldehyde were reduced, when NaOH of 2g/L, H2O2 of 10 mL/L, reaction time for 60 min, temperature of 35℃. The cost of the method was about 14.47 Yuan/m3.（2） At the conditions of pH value of 11, 10%Ca（OH）2 of 30 mL/L, temperature of 70℃, reaction time for 50 min,the removal rate of COD_Cr and formaldehyde were respectively 31.68% and 97.84%by the lime catalysis, which cost 5.15 Yuan/m3.（3） The removal rate of COD_Cr and formaldehyde were respectively 43.62% and 96.31% at higher cost of 25.06Yuan/m3,when the conditions were attained to the pH value of 3, the mole ratio H2O2 and Fe2+ of 4:1, H2O2 of 20 mL/L, ferrous sulfate of 13.62 g/L, reaction time of 60 min for the Fenton oxidation.（4） The removal rate of COD_Cr and formaldehyde were only28.37% and 62.33%, under the optimum conditions of electrochemical oxidation. The removal rate of COD_Cr and formaldehyde would be elevated to 40.56% and 75.72%after the PAFC flocculation of 10g/L. The cost of the method was about 17.94 Yuan/m3.It concluded that the lime catalysis method was superior to other methods, contrastingthe degradation performance and cost. The content of formaldehyde was reduced to41.47 mg/L, and the BOD5/COD_Cr of sewage was increased form 0.10 to 0.49, which means the sewage was more bio-available to microorganisms.Taking degradation performance and cost in consideration between the chlorine dioxide oxidation and O3/H2O2 oxidation, the research conclusions of advanced treatment were as follows: The removal rate of COD_Cr was 54.28% by using the chlorine dioxide oxidation under the optimum conditions of ClO2 of 20 mg/L, reaction time of 40 min, temperature of 30 ℃, pH value of 7⁸. The removal rate of COD_Cr was43.83% by using the O3/H2O2 oxidation, when pH value of 10, ozone flow of 5 g/h,reaction time of 50 min, H2O2 of 40 mmol/L. The concentration of COD_Cr was degraded to the demand of discharging standard with both the two methods. The chlorine dioxide oxidation was chose to be the optimum treatment because of the better degradation effect and lower cost, which can reduce the cost about 69.75% compared with the O3/H2O2 oxidation.In the practical application, the lime pretreatment process and the chlorine dioxide oxidation advanced treatment process were added. It was conclusive that the improved wastewater treatment process could effectively deal with the sewage of neopentyl glycol with the stable operation and excellent ability to resist impact load. The indexes of effluent could satisfy the requirements of the latest wastewater discharge standard.In addition, the sewage treatment facilities were analyzed in the economic.