Nitrogen Removal And Optimization Of Pre-anoxic A~2/O Process Treating High-Ammonia Nitrogen Wastewater

The modified A2/O process was used to treat high ammonia nitrogen domestic wastewater.The results show that total nitrogen is not up to the standard.In this paper,we find out The reasons for this situation by analysis on the nitrogen removal.Optimizing modified A2/O process and make the evaluation.Results are as follows:First.The bio-denitrification in first anoxic zone and second anoxic zone was an important way for total nitrogen(TN)removal in system.The nitrogen removal efficiency by this way was more than 49%,The nitrogen removal efficiency by first anoxic zone was more 14.86%.Visible the first anoxic zone was very important to nitrogen removal.Second,With the increase of the rate of mixed liquid recycles,the nitrogen removal efficiency was not changed much.And at the same time,we find out that the ammonia removal efficiency was improved.Considering it will cost more electrical energy with the increasing of reflux ratio,Obviously increase of the rate of mixed liquid recycles was not a good measure to make total nitrogen up to the standard.Third,when we inlet by three point,The anoxic zone can get more Carbon source,the effluent concentration of Total nitrogen have had a significant impact.In addition,It suggests that enough carbon source was the key factor of denitrification in anoxic tank.Without considering the external carbon source,we can choose to make a better allocation of carbon source,improve the utilization rate of carbon source,and reduce carbon consumption in denitrification process.But,at the same time,they can have adverse effects on phosphorus removal.Fourth,we fount it can reduction of 25%energy consumption when Aeration rate in different locations of aerobic zone was diminishing,and at the same time,we got a more better effect of denitrification.Moreover,the dissolved oxygen concentration in the end of aerobic zone was about 1.0 mg/L,it would lead to simultaneous nitrification and denitrification.The dissolved oxygen concentration in The anoxic zone was about 0.5mg/L.We can find shortcut nitrification-denitrification in anoxic zone.Compared to the conventional nitrification and denitrification,shortcut nitrification-denitrification and simultaneous nitrification and denitrification need less carbon source,it was why the consumption of COD did not significantly increase but the nitrogen removal effect become obviously better.So,control of dissolved oxygen can got a better effect of nitrogen removal.Fifth,with the increasing of the hypoxia area to make sewage stay a longer time in anoxic zone,the effluent effect of total nitrogen become better.Investigate its reason,with the increasing of the hypoxia area,Aerobic Tank become smaller,The nitration reaction would be affected by those change.and cause the effluent of ammonia increasing.