氨氮对生物净化滤柱中铁锰氨氮去除效果的影响

Effects of ammonia on efficiency of iron,manganese and ammonia removal in biological purifying filter

采用培养成熟并稳定运行一段时间的生物除铁除锰除氨氮滤柱,考察进水氨氮浓度变化对铁锰氨氮去除效果的影响。结果表明:进水氨氮从约1.2 mg·L^(-1)逐步提高到约2.0 mg·L^(-1)的过程中,铁、锰和氨氮的去除效果没有受到影响。当进水氨氮超过2 mg·L^(-1)时,进水溶解氧不足,铁的去除效果不受影响;生物除锰受到氨氮升高过程中产生的亚硝氮的抑制,并且与氨氮竞争溶解氧,导致出水锰升高,然而锰氧化菌能够在低溶解氧条件下将锰氧化,出水锰数天后又降到0.05 mg·L^(-1)以下;出水氨氮随进水氨氮的升高而升高。沿程分析发现,进水溶解氧充足时,氨氮和锰的氧化速率没有受到影响;但进水溶解氧不足时,氨氮和锰的氧化速率明显降低;铁的去除速率不受溶解氧的限制。生物净化滤柱可以在较低的溶解氧条件下运行,从而降低能耗。

A biological filter for iron,manganese,and ammonia removal,which was start-up successfully and steady operated for a long time,was used to investigate the influence of the levels of ammonia in the influent on the efficiency of iron,manganese,and ammonia removal. The results showed that when the levels of ammonia gradually increased（ from about 1. 2 mg·L-1to about 2. 0 mg·L-1）,the efficiency of iron,manganese and ammonia removal was not affected. When ammonia in the influent increased to above 2. 0 mg·L-1,the concentration of dissolved oxygen（ DO） in the influent was insufficient to completely oxidize iron,manganese and ammonia,whereas the efficiency of iron removal was not affected. The concentration of manganese in the effluent increased because biological manganese removal is influenced by nitrite,which is generated in the process by which levels of ammonia increased,and manganese competed for DO with ammonia. However,manganese levels decreased to below0. 05 mg·L-1after a few days due to the oxidation of manganese in low DO conditions by manganese oxidizing bacteria. Ammonia in the effluent increased due to the increased levels of ammonia in the influent. Variation in the iron,manganese,and ammonia removal along the filter depth showed that when DO in the influent was sufficient,the oxidation rates of manganese and ammonia were not affected; however,when DO in the influent was insufficient,the oxidation rates of manganese and ammonia decreased obviously. The oxidation rate of iron was not affected by DO. The biological purifying filter could be operated in relatively low DO conditions to reduce energy consumption.