Study On Biological Manganese Removal In The Groundwater And Its Effecting Factors

According to the manganese concentration of the groundwater in the majority areas in China, by the aid of model experiment in the lab, the character and mechanics of the biological manganese removal in the groundwater was studied. And the time needed for the cultivation of the biological filter was discussed, so were its affecting factors. The factors of filtering velocity,pH,temperature,manganese concentration and Fe²⁺ concentration were studied to evaluate their effect for biological manganese removal, so was bacteria inoculation method. The water quality of the raw water : the concentration of Mn²⁺ was in the range of 0.5 mg/L to 1.0 mg/L, the concentration of Fe²⁺ was 0.1mg/L, pH was in the range of 6.5 to 7.0, dissolved oxygen concentration was in the range of 5 mg/L to 6mg/L, temperature was in the range of 14℃to 28℃, the filter operated at the filtration rate of 2～8m/h. Under this operation conditions, the time needed for the cultivation of biological manganese removal was 55 days and manganese can be removed efficiently. But a novel inoculating approach of grafting mature filter material into filter bed, which is easier to handle than selective culture media, was employed in this research. However, this approach was not suitable to the filter material of quartz sand with weak adsorption capacity.The affecting factors such as filtration speed, temperature, pH and manganese concentration were analyzed. The test results showed that the maximum manganese concentration is 3 mg/L; the needed thickness of the filter bed removing manganese increases once the filtration speed becomes fast, so the choosing of filtration speed is related to the manganese concentration of original water and the thickness of filter bed; the most optimal environment temperature is 20℃; the manganese removal rate is influenced by pH, the manganese which was less than 1.0mg/L can be removed efficiency in the range of pH 6.0—7.5; with the increasing of the pH, the manganese removal rate increases, the optimal pH is 6.0—7.5.The affect of Fe²⁺ concentration for biological manganese removal is very obviously. The manganese can not be efficiently removed when there was not Fe²⁺ in the original water after the filter candle was mature. But when the original included a little Fe²⁺, the manganese concentration in the yielding water was reduced little by little. So, the article thought that the activity of microorganism was related to Fe²⁺.