Study On Nitrogen Removal Of Aquaculture Wastewater

In recent decades, as China's rapid development of aquaculture, the problems of environmental pollution caused by factors such as excrement and uneaten food is increasing prominently. Nitrogen compounds, especially ammonia nitrogen and nitrite nitrogen, are not only likely to cause eutrophication, but also harmful for aquaculture organisms themselves. Therefore, to develop a highly efficient and economic method of denitrification becomes the focus of the work.In order to solve these problems and remove the ammonia nitrogen, nitrite nitrogen and nitrate nitrogen of the closed recirculating aquaculture factory wastewater effictively, we have isolated indigenous ammonia-oxidizing bacteria and aerobic denitrifying bacteria one stain each from the local breeding ponds. Identified by 16S rDNA sequence,it is showed that the similarity between the srain AOB-1 and nitrosomonas eutropha [AY123795] is 100% while the the similarity between the srain DB-1 and two typical strains of Pseudomonas stutzeri [A1501] are 100% and 97%. And then, the ammonia oxidation capacity of the strain AOB-1 and the nitrite reduction capacity of the stain DB-1 were studied. Subsequently, immobilized nitrogen cycling bacteria technology, short-cut nitrification and denitrification technology, simultaneous nitrification and denitrification technology were coupled together to treat aquaculture wastewater with simulated water treatment system which was designed and manufactured by ourselves. Eventually,"the pure immobilized nitrogen cycling bacteria simultaneous short-cut nitrification and denitrification technology"(INCBSSND) were formed.Experimental results show that by using modified membrane filtered suspended balls of ammonia-oxidizing bacteria and of denitrifying bacteria to treat the simulated aquaculture wastewater and the wastewater of the closed recirculating aquaculture factory respectively with the technology of INCBSSND, the average ammonia-nitrogen removal rates reached about 80% and 30%, the average total nitrogen removal rates were 35% and 20%, but the removal rates of nitrite results were poor, so lots of work need to do still. And when we ran the systerm, we controled the value of hydraulic retention time to be 12h, maintained the value of dissolved oxygen to be 1.5 to 3.0 mg / l, and kept the water temperature to be about 28℃.