A New Combination Technology Of Oxidation- Flocculation-mechanical Membrane For Refractory Phenol-formaldehyde Resin Wastewater Treatment

Through investigating process of phenol-formaldehyde resin production and analysis of water quality, we mastered the source, distribution, composition and emissions rules of the wastewater, found that phenol-formaldehyde resin wastewater have high concentrations of organic matter, low pH, strong corrosivity and strong biological toxicity and knew the wastewater have plagued industry development for long time because of its difficult biodegradability biodegrade, high treatment cost and poor effect. In order to make the effluent quality meet the requirements for direct access into the biochemical pool, the O3/H2O2/MgO process based on advanced catalytic oxidation process was applied for its high phenol and formaldehyde removal efficiency. Also, the combination of flocculation and mechanical membrane filtration method was used for the absolute removal of turbidity and SS. The O3/H2O2/MgO-flocculation-mechanical membrane filtration method showed the advantages of easy to operate, stable operation and high efficiency. Moreover, it can significantly reduce the wastewater toxicity and improve its biodegradability, providing possibility for the subsequent biochemical treatment.The phenol-formaldehyde resin wastewater collected from Jinan Shengquan Co., LTD was used as the researched object in the paper. The effects of the combination process O3/H2O2/MgO-flocculation-mechanical membrane filtration method on the wastewater treatments were studied. Optimum parameters were explored and good operating effects were obtained. The main research contents and conclusions were as follows:(1)With the problems of complicated operation process, time-consuming and low accuracy of determination results for national standard method of determination of concentrated phenol and formaldehyde in industrial wastewater, the derivatization-extraction-capillary gas chromatography analysis method was established for the synchronous determination of high concentration phenol and formaldehyde in phenol-formaldehyde resin wastewater by studying derivatization, extraction and determination conditions as well as its feasibility analysis. The optimized conditions were a derivatization agent of DNPH, derivatization temperature of 65℃, derivating agent volume of 25 ml, derivatization time of 20 min, extracting agent of chloroform, and ultrasonic time of 5 min. The linear equations, correlation coefficients and linear ranges were as follows:phenol y=9.5845p+302.98,0.99979,50.0-1.00×104mg/L; formaldehyde y= 33.934p-174.1,0.99952,2.0～5.00×103mg/L.The standard addition recovery tests were conducted respectively using different concentrations of formaldehyde and phenol solution. It showed the method had the relative standard deviation (RSD) of 0.920%×2.80% and the recovery rate of 92.0%～103%. Compared with the national standard methods, derivatization-extraction-capillary gas chromatography analysis method is more convenient, fast, and easy to operate and has high accuracy and precision. It can provide a new method for the determination of concentrated formaldehyde and phenol in industrial wastewater.(2) With the problems of containing high concentrations of phenol and formaldehyde for phenol-formaldehyde resin wastewater, the O3/MgO/H2O2 technology based on CAOP was applied to oxidize such wastewater. The powdered MgO nanocrystals as highly efficient catalyst were prepared by calcination method. I systematically studied the effects of reaction time, original pH value, dosage of H2O2, dose of MgO and concentration of O3 on oxidation efficiency of phenol-formaldehyde resin wastewater including phenol, formaldehyde, BOD as well as COD removal efficiency and obtained the optimal parameters. The oxidation mechanism in O3/MgO/H2O2 process was explored by observing the changing trends of phenol and formaldehyde removal efficiency before and after adding free radical scavenging agent in O3/MgO/H2O2 process. The optimum parameters were:reaction time of 120 min, original pH of 8.0, H2O2 dosage of 5 g/L, MgO dose of 6 g/Land O3 concentration of 0.25 g/L. Under the optimal conditions, the O3/MgO/H2O2 had the best removal effects to catalytic oxidize the phenol-formaldehyde resin wastewater, where the phenol removal rate was 91.8% and the formaldehyde removal rate was 85.2%. BOD and COD removal rate were 33.3% and 72.8%, respectively, and B/C increased from 0.160 to 0.360. Free radical oxidation was the main oxidation mechanism.(3)With the problems of containing concentrated colloid and SS in such wastewater, the jar test was applied for the effluent of the O3/MgO/H2O2 oxidation process. The effects of water pH, concentrations of polyaluminium chloride (PAC) and cationic polyacrylamide (CPAM) on coagulation efficiency were systematically investigated including turbidity, SS, BOD, COD, phenol and formaldehyde removal efficiency. The experimental results showed that:① When pH was in the range of 5.0 and 8.0, it had little influence on removal effects. pH of the phenol-formaldehyde resin wastewater after the O3/MgO/H2O2 was 6.5, which was in the optimum coagulation pH range and thus there is no need to adjust the water pH.② When 3 g/L of PAC and 30 mg/L of CPAM were added, it achieved the best coagulation effects, in which the turbidity removal rate of wastewater was 86.0%, SS removal efficiency was 75.4%, BOD and COD removal rate were 67.2% and 87.2% respectively, phenol and formaldehyde removal rates were 98.3% and 96.4%, respectively.(4) In order to further remove the residual turbidity and SS in the effluent, membrane filtration was adopted for advanced treatment of phenol-formaldehyde resin wastewater. To solve the existence problems for membrane products, such as complex preparation process, high price, easy to be polluted and hard to be cleaned, four different new type mechanical membranes were prepared by computer automatic winding method. Intercept performances of single-stage mechanical membranes and multi-stage mechanical membranes for the water from the outlet of the jar tester were studied. Results showed that: ① The multi-stage membrane module can successfully intercept particles with different size ranges. Compared with the single-stage membranes, the water quality of the multi-stage membranes from the same outlet was nearly the same, but had longer cleaning cycle. ② The mechanical membrane can be easily recycled by reverse flushing with clean water, after which flux recovery efficiency of each membrane can reach more than 90.0%.③After the four-stage membrane filtration, Turbidity was reduced to 1.80 NTU, SS was not detected, concentration of phenol and formaldehyde were reduced to 28.0 mg/L and 43.0 mg/L, respectively from the initial 4.79×103 mg/L and 2.66×103 mg/L. BOD and COD were reduced to 745 mg/L and 2.03×103 mg/L, respectively. B/C was increased to 0.364. Results showed that the effluent after treatment by O3/MgO/H2O2-coagulation-mechanical membrane filtration was suitable for the subsequent biochemical treatment process.