Removal Of High Content Manganese From Ground Water With Manganese Oxide-coated Filter

High content of manganese is widely presented in ground water which needs a technique to remove manganese with instant and steady effect. Filter maturation period is quite long during the process of biological removal of manganese and the removal efficiency is not steady. On the basis of exploring the mechanisms of biological removal of manganese from ground water, chemical method was used to coat manganese oxides on filter and the structure of this manganese oxides filter was the same as the biogenic ones. After adsorbing manganese from ground water, chemical oxide agent was used to regenerate saturated manganese oxides. Further more, a new technique named"chemical manganese oxides-coated filter + chlorine dioxide oxides regeneration"was developed.1. The influences of inoculation on filter maturation were studied. Results showed the formation of manganese oxides active layer was the key factor for filter maturation, and the importance of manganese oxides in biological removal of manganese was revealed. (1) Maturation period of filter was 70 days when inoculated but it could not reach maturation when no inoculum was added during this period. (2) Under inoculation circumstances, manganese sands would reach maturation in 20 days because of its higher adsorption ability, but quartz sands need more than 30 days. (3)Adding chlorine dioxide could accelerate the formation of manganese oxides for no inoculation filter. When the dosage of chlorine dioxide was 0.5mg/L, the manganese concentration in outflow was under 0.05mg/L in 30 h; when 1 mg/L chlorine dioxide was added, it would attain the same removal efficiency in 10 h.2. Sterilize the biological manganese removal filter(BMRF) to obtain the biological manganese oxidation filter(BMOF)with no bacteria. The comparison experiment revealed another key process in biological removal of manganese, i.e. the catalytic oxidation of microorganisms regenerated the manganese sorption ability. (1)The removal efficiency of manganese decreased 20~35% in BMOF when the velocity of filtration varied, but in BMRF the value recovered up to 90% after a short decrease. (2)The removal efficiency of manganese in BMOF decreased to 55.9% when the concentration of manganese in original water increased, but the average removal efficiency in BMRF attained 93.2%. (3)The optimal pH range for manganese removal in BMOF was between 6-7 while in BMRF the pH value was between 5-9. The manganese removal process in BMOF could be simulated by Yoon-Nelson model.3. Manganese oxides were made by chemical method, and electron microscopy analysis indicated they had the same Birnessite structure with biogenic manganese oxides. XRD analysis showed this kind of manganese oxides belonged to amorphous form. The load capacity of biological and chemical synthesized manganese oxides was 4.56 mgMn/g filter and 4.62mgMn/g filter respectively, and the intensity of load in latter oxides was much better when they were used in acid, alkaline and neutral environment.4. Adsorption isotherms and kinetic model of SMOF were established by static adsorption study, and the saturation adsorption capacity was 0.32 mgMn/g filter indicated manganese oxides have significant adsorption ability. Thermodynamics results showed the adsorption process was spontaneous. Adsorption process fitted pseudo-second order model.5. Influencing factor research of adsorbing manganese with SMOF indicated the optimal pH was higher than 5, and the manganese concentration in outflow was in linear correlation with the concentration in inflow. Hardness and Fe2+ in water disturbed manganese removal. When hardness of water increased from 100mg/L to 600mg/L, removal efficiency of manganese decreased from 83% to 55%; when Fe2+ concentration in water increased from 0.5mg/L to 3mg/L,removal efficiency of manganese decreased from 82% to 63%.6. Dynamic experiment of removal manganese by SMOF indicated the removal efficiency decreased with the increase of original manganese concentration and the filter rate. The saturated SMOF could be treated with chlorine dioxide to regenerate its adsorption ability. When chlorine dioxide was added in 2mg/L, the capacity of removal manganese could be fully recovered in 10 min. Regenerating everyday would bring about steady removal efficiency. The dynamic process of SMOF fitted Yoon-Nelson model, but the capacity of adsorption was lower than BMOF.7. New technique for removal manganese from ground water was proposed, i.e."chemical manganese oxides-coated filter + chlorine dioxide oxides regeneration". Results showed removal efficiency maintained stable when manganese concentration varied from 1-4mg/L and filter rate changed from 8-15m/h, but manganese concentration in inflow had more influence on outflow quality compared to filter rate. This new technique doesn't need to experience a maturation period.