Treatment Of Xanthogenate Wastewater By Membrane Bioreactor (MBR)

Waste water of pharmacy beneficiation plant contains high concentrations of xanthenes compounds; it could make a great deal of harm if we do not deal with emissions. Study shows that:a large number of wastewater containing xanthenes will have an important role in animals'embryo with teratogenic effects. In addition, the xanthenes also have a poisoning effect to nervous system and liver and other organs of human. Under slightly acidic conditions, carbon disulfide (CS2) will be produced. Nervous system will have the diseases under the condition of CS2 enter into the brain; if entering the blood, it will also have adverse effects on the hematopoietic system. Therefore, it is extremely important to find a reasonable and efficient method treatment of xanthenes wastewater immediately.At present, all kinds of method of treatments xanthenes wastewater mainly contains adsorption, decomposition, coagulation, chemical precipitation, biological and chemical, oxidation and other methods. Although these treatment technologies are mature, there are a variety of drawbacks which bring unsatisfactory treatment results. In view of this status quo, it is the first time to dispose high concentrations of xanthenes wastewater by membrane bioreactor (MBR). In this study, we obtain an excellent result.In the sludge acclimation phase, the color of sludge turned to gray brown. The concentration of sludge turns from 6640mg/L at the time of inoculation final to 9130mg/L. In addition, MLVSS/MLSS reached 0.75 in the late domestication. In the early running phase, biologic facies of mixture in reactor mainly included large number of metazoan, such as Brachionus and Vorticella. In the late domestication, as a result of toxicity of xanthenes and the pH value of water was more than 8, both the Brachionus and Vorticella disappeared. After 33d of sludge acclimation, the sludge load and load capacity rosed to 2.17kgCOD/(m3-d) and 0.238 kgCOD/(kgMLSS-d), respectively. At this time, the system stabilized. Xanthenes removal efficiency was more than 90%; COD removal efficiency was more than 80%. In allusion to the condition of too much inert material in the water and parts of activated sludge broke up, we operated a series of experiment to optimize the operating conditions. Finally, the best operating conditions were 0.5g/L of anhydrous sodium acetate added into wastewater as additional carbon source, HRT kept to 24h, reaction temperature maintained at 30℃. In the steady state, the water quality was good, the average effluent of COD was 91.88mg/L, COD removal efficiency was more than 94%; average of the xanthenes concentration in the water was 1.5mg/L, xanthenes removal efficiency was more than 99.7%. Since then, we used this stable MBR to treat producing pharmaceutical wastewater from Tieling xanthenes beneficiation plant. An average of the COD value of the effluent water was 77.02mg/L, the removal rate was more than 94.5%, and in average was 95.71%. In the period of water quality monitoring, all of the effluent COD values were lower than the national-level industrial wastewater discharge standards. An average of xanthenes concentration in the effluent water was 0.859mg/L, removal efficiency was more than 99.8%, and in average was 99.86%. However, due to xanthenes concentration failed to meet water emission standards, whose name is "Liaoning Province Integrated Wastewater Discharge Standard.", still needed follow-up.In virtue of easier decomposition in acidic conditions, in this study at first we used 0.1mol/L HCl to change water pH, and then used hydrogen peroxide as oxidant under acidic conditions to deal with the effluent water from the MBR system. The experimental results were as follows:the best operating conditions is pH value is 4 or so, the concentration of H2O2 is 5mg/L, and oxidation time is 40min. After this treatment, water met the emission standards entirely. At this moment, xanthenes concentration in the effluent water is 0.04mg/L.In addition, membrane fouling phenomenon only deteriorated in the period of late sludge acclimation when reactor operated continuous of 128d. Through the conditions experiments, when the HRT were extended to 24h, membrane fouling can greatly reduced.