Treating Coking Plant Wastewater With Simultaneous Nitrification And Denitrification Technique

As the discharge of coking plant wastewater arouses great harm to environment, the removal of organic compound and the dinitrication in the coking plant wastewater gained much more attention day by day. In this paper, we choose simultaneous nitrification and denitrification process to treat the coking plant wastewater in order to offer some valuable reference for engineering apply, and study on factors which affect the treatment effect of the system.First we choose orthogonal test to investigate how factors such as DO HRT pH effect on the removal of organic compound and the dinitrication, and then confirm the best techniques conditions for the removal of organic compound. Hie result indicates that: DO is the most affective factor, and under different DO levels, the most difference of COD removal achieves 58;61 % .The other factors are pH>COD load>HRT>compositive error>ammonia load, thus we educe the best condition, HRT =44.1h; DO=3.5-4.0 mg/L; pH=8.The analyze on factors which effect on ammonia shows that: the ratio of ammonia removal can achieve 95% when HRT was no less than 40h, and the concentration of exit ammonia was less than 5mg/L; the nitrification can fully complete, and the quality concentration of total ammonia reduced, which suggested it happened nitrification and denitrification at the same time; the quality and amount of methanol is a key factor which effect denitrification, the ratio of denitrification was low without methanol while high within methanol; pH is a important factor during nitrification process, as the microorganism can only exist in certain pH, the best pH is about 7.5 to 8.5.The study on dynamics of system shows that: when the infall concentration of COD is around 1500mg/L approximately, velocity of organic compound removal is comparatively slow, and the half- velocity constant is 291.18mg/L, the maximal velocity of organic compound removal per cubage filling material is 28.25mg/m~2.h; and when the infall concentration of ammonia is around 300mg/L approximately ,the maximal velocity of ammonia per cubage filling material is 5.7471 mg/m~2.h, the saturated constant of nitritebacterium oxygenation is 2.9954mg/L.The study on microorganism shows that: there are many kinds of microorganism in the biofilm, and a great deal of aerobic microorganism in it can use the organic carbon metabolize COD in the wastewater under aerobic conditions. The anaerobic environment inside made dinitrification microorganisms have suitable metabolizing condition and go on dinitrification with beforehand storaging carbonate.