Study On The Treatment Of Fluorescent Whitening Agent Wastewater

Fluorescent whitening agent wastewater is a typical industrial wastewater which contains large amount of organic substance and salt. Due to its high toxicity and non-biodegradability, the wastewater could severely damage the ecological environment, industrial and agricultural production, and human health if discharged directly or without proper treatment. In this research, we studied the pretreatment, biological treatment and advanced treatment methods of fluorescent whitening agent wastewater, so as to provide some reference for treating fluorescent whitening agent wastewatei and others with similar nature. The removal of high concentration of chloride ion in wastewater was also researched.Fenton's reagent oxidization, ozone oxidization and aerate ferric-carbon micro-electrolysis methods were adopted in pretreatment experiment. Factors affecting treatment efficiency of the three were examined. The results are as following. For Fenton's reagent oxidization, under the optimal conditions where H2O2 dosage was 0.13mol/L, H2O2 to Fe(Ⅱ) molar ratio was 20, pH was 5.0, and the reaction time was 1.0h, the CODCr removal rate reached to 39.9% and the BOD5/CODCr to 0.51. For ozone oxidization the optimal conditions were:reaction time of 70min(the ozone dosage of 2.51 g/L), pH at 9.2, under which the CODCr removal rate reached to 36.7% BOD5/CODCr to 0.47. For aerate ferric-carbon micro-electrolysis method the CODCr removal rate could reach to 57.1% the BOD5/CODCr to 0.45 under the optimal conditions of:iron to carbon weight ratio of 1.0, reaction time for 2.0h, and pH at 2.5. Comparatively the aerate ferric-carbon micro-electrolysis method had the highest CODCr removal rate and the lowest cost of wastewater treatment, suggesting the promising potential for the treatment of fluorescent whitening agent wastewater.After aerate ferric-carbon micro-electrolysis, the wastewater was treated using hydrolysis acidification and biological contact oxidation process. The startup and stability for the bioreactors were examined. Results indicated that, when the HRT of hydrolysis acidification was 30h, temperature was about 38℃, the HRT of biological contact oxidation process was 15h, temperature was about 30℃, the concentration of CODCr could reduced to 1200～1300mg/L and 500mg/L, respectively.In ozone oxidization experiment of biological treatment effluent, the CODCr concentration could be lowered to 346.9mg/L and the chromaticity be lowered to 0 when the quantity of ozone was 2.15g/L.Through the analysis of effluent quality, we concluded that the combined technology of aerate ferric-carbon micro-electrolysis, hydrolysis acidification, biological contact oxidation and ozone oxidization could treat the fluorescent whitening agent wastewater effectively. The CODCr was less than 100mg/L, the suspended solids lowered to 25.9mg/L, the turbidity lowered to 2.4 NTU and the chromaticity lowered to 0 in the effluent, which could meet the first grade of national integrated wastewater discharge standard (GB8978-1996).The extraction experiment about high concentration of chloride ion in water using trioctylamine was performed. Factors associated with chloride ion removal rate following pH, dilution ratio, oil-water ratio, oscillation time, holding time, initial chloride ion concentration and extracted series were studied. The results showed that when the pH was 0.5, dilution ratio was 1.0, oil-water ratio was 0.4, oscillation time was 1min, holding time was 30min, treatment efficiency reached to the best. Chloride ion removal rate could be greater than 90% under the best factor levels when the initial chloride ion concentration was 500mg/L. The removal efficiency decreased with the initial chloride ion concentration while increased with the extracted series. When the chloride ion concentration was 50000mg/L in water, the removal rate reached to more than 80% by third degrees cross extraction. Using 5% NaOH to the organic phase after extraction to re-extract, when the volume ratio of water phase to organic phase was 2.0, it could achieve a better effect of the anti-extraction, and extraction agents could be re-used. As the results showed, aerate ferric-carbon micro-electrolysis method, hydrolysis acidification, aerobic biological treatment and ozone oxidization combined technology could treat the fluorescent whitening agent wastewater effectively, the effluent could reach to the first grade of national integrated wastewater discharge standard (GB8978-1996). And the chloride ion in the effluent could be removed by second degrees cross extraction if necessary.