Biological Nitrogen Removal From Petrochemical Wastewater Using Swim-Bed Biofilm Reactor And Anaerobic Ammonium Oxidation

Biological nitrogen removal from petrochemical wastewater is investigated in this dissertation in order to resolve the problem of low NH₄⁺-N removal efficiency and no TN removal in the present petrochemical wastewater treatment processes. Firstly simultaneous nitrification and denitrification(SND) is studied in the aerobic swim-bed biofilm reactor. The mechanism and the cause of SND are discussed and the influence factors such as the ratio of C0D/NH₄⁺-N(C/N ratio), dissolved oxygen(DO), hydraulic retention time(HRT) on simultaneous nitrification and denitrification are investigated. Then the anoxic/oxic swim-bed biofilm reactor is used to treat petrochemical wastewater with the problem of low NH₄⁺-N and TN removal efficiency using the aerobic swim-bed biofilm reactor. The kinetic characteristic in the anoxic/oxic swim-bed biofilm reactor is analysized and the influence of internal recycle ratio and influent loads on nitrogen removal is discussed. Finally anaerobic ammonium oxidation (ANAMMOX) process is used to remove nitrogen from petrochemical secondary effluent, which has high concentrateon of NH₄⁺-N and NO₃^--N and can not meet the discharge standard. The conclusions are as follows.The swim-bed biofilm technology has several advantages such as easy biofilm cultivation, rapid start-up, good mass-transfer, high removal efficiency and low energy consumption. The biofringe(?) carrier can "swim" in the balance position when aeration intensity and ratio of air and wastewater are 100 m³/m²Â·h and 10:1. The comparison experiment between biofringe(?) carrier and combination carrier shows that the former has better ability. The biofilm can be cultivated within five days. When the initial COD concentration is 600 mg/L, the COD concentration at the end of 5 h is 50 mg/L, and the removal efficiencies is more than 90%.Simultaneous nitrification and denitrification can occur in the oxic swim-bed biofilm reactor when treating petrochemical wastewater. When pH, T, DO concentration, the hydraulic retention time, the influent COD concentration and NH₄⁺-N concentration are 7.0-8.0, 20℃, 4.0 mg/L, 26.1 h, 500 mg/L mg/L, and 30 mg/L, the effluent COD concentration is less than 150 mg/L, and COD removal efficiency and COD removal loads are more than 70% and about 1.4 kg/m³Â·d respectively. Nitrification efficiency and TN removal efficiency are 40.6-50.1% and 31.2-45.7% respectively. There is no NO₂^--N in the effluent and most NO_x^- -N produced by nitrification is transferred to denitrogen gas.The reason why SND can occur in the oxic swim-bed biofilm reactor is that there exists different micro-environment inside the biofilm on the biofringe(?) carrier. Since the thickenss of the biofilm is more than 900 μ m, there exist DO concentration grads inside the biofilm with the restriction of DO diffusion. There exists DO in the outer section of the biofilm and...