Yufei Li

Experimental Study on Simultaneous Nitrification and Denitrification in Municipal Wastewater

The influencing factors of simultaneous nitrification and denitrification (SND) was investigated in this study. The experiment was carried out with synthetic wastewater in Sequencing batch reactor (SBR). Some effect factors and mechanism of SND were studied through continuous running of SBR process. Optimum operation condition of SND was obtained in the experiment, and it was found that the removal efficiency of COD and TN reached 90% and 83%~95% respectively when influent CODCr concentration of 200~300mg/L, NH3-N of 25~35mg/L, TN of 40mg/L with temperature of 18~25, C/N ratio of 12, and DO in the range of 0.5~1.5mg/L. Further more, SND can overcome the phenomena of insufficient alkalinity in wastewater, and that alkalinity yield by denitrification can fill up descend of PH value, which resulted in the degradation of organic and nitrogen compounds via microorganism. Thus, simultaneous nitrification and denitrification can be achieved by SBR process at normal temperature.

Effect of Low-Temperature for the Treatment of Municipal Wastewater in a Full-Scale BAF

The impact of temperature on nitrification in biological aerated filter (BAF), process was studied in order to improve the nitrification performance in municipal wastewater treatment. When the water temperature dropped, the nitrification performance obviously deteriorated. Effects of important process variables such as DO concentration and backwash period to nitrification performance were investigated when the water temperature dropped from 23℃ to 9℃. The study shown that by raising the DO concentration to enhance nitrification performance was not available in low water temperature environment and by extending the backwash period to enhance nitrification was available. The effluent NH4-N concentration reduced from 8mg/L to 6.5mg/L, when the backwash period extended from 48 hours to 65 hours and the the effluent concentration of SS and head loss were all in a permissible range.