Study On The Removal Of Ammonia By Immobilized Nitrobacteria Pellets

Ammonia removal features of nitrobacteria in immobilized pellets and bio-film during the acclimation phase were studied and the effects of surrounding factors on their activity were discussed after the acclimation. Immobilized nitrobacteria were cultivated in the fluidized bed while nitrobacteria in the bio-film grew on the elastic plastic media in the fixed bed. The nitro-bacterial degradability of immobilized nitrobacteria in the treatment of the corn distillery wastewater was also investigated.The experiments mainly focused on the acclimation of nitro-bacteria, the effects of temperature and DO on the nitro-bacterial degradability of the two reactors, the influence of storage conditions on the nitro-bacteria activity recovery, and the nitro-bacterial degradability of immobilized nitrobacteria in the treatment of corn distillery wastewater.The major conclusions were drawn as follows:1) In the continuous experiment, the ammonia oxidizing ability of the pellets increased from 10mgNH4-N/L·h to 23.4 mgNH4-N/L·h after 37 days'acclimation while the nitrification ratio of the fixed bed increased from 2.0 mg mgNH4-N/L·h to 11. 8mg mgNH4-N/L·h.2) The result of PCR experiment showed that the quantity of the ammonia oxidation bacteria increased substantially during the acclimation.3) When DO declined from 4mg/L to 2mg/L, the nitrification ability of two reactors decreased while the nitrification ability of the fluidized bed is far better than that of the fixed bed. DO of 4mg/L enabled both, reactors to reach the maximum nitrification rate of 34.1mgNH4-N/L·h and 11.8mgNH4-N/L·h respectively, while at 2mg/L, the two reactors had lower nitrification rate of 28.4mgNH4-N/L·h and 9.5mgNH4-N/L·h, respectively. Besides, NO2-N accumulation was detected in both reactors.4) When the temperature was decreased, both reactors were affected and the NO2-N accumulated less. Higher temperature tended to cause nitrite accumulation more likely.5) After long-term storage, the immobilized nitrobacteria kept at 4℃showed quick recovery from an inertia status. Its nitro-degrading rate increased from 1. 8mgNH4-N/L·h to 13.8mgNH4-N/L·h after 7 days'acclimation.High nitrogen removal rate and steady operation were obtained when using the immobilized bacteria to treat the corn distillery wastewater. No inhibitive material was found in the wastewater and the organic material in the water had a limited influence on the nitrification rate. At the influent ammonia of 40mg/L, HRT of 2.5h-3.5h, and DO of 4mg/L, the NH4-N concentration in the effluent water was lower than 15mg/L and was able to meet the requirement.