| Short nitrification and denitrification is a new biological nitrogen removal technology. It reduces energy consumption and operating costs, improves the utilization of resources. The key of the process is inhibit the activity of nitrite oxidizing bacteria (NOB), and achieve long-term stability of partial nitrification.In this study, the ammonia oxidizing bacteria (AOB) were immobilized by polyvinyl alcohol and sodium alginate. The effects of initial free ammonia (FA), pH, DO, organic matter, temperature on the stability of partial nitrification were investigated. The results showed that ammonia oxidizing bacteria predominated in the embedded pellets at25～30℃. Rising temperature would widen the gap between their growth rate, which was conducive to the elimination of NOB. DO should be controlled at4.0-5.5mg/L, it not only met the needs of bacterial growth, but also avoided excessive aeration. Otherwise it would increase the friction between the carriers, resulting in the reduction of theirs useful life. The pH of8-9was suitable for the embedded pellets, the higher ammonia oxidation rate under this pH condition. The embedded pellets were strongly resistant to nitrogen loading rate, and also withstood the influence of organic matter to ammonia oxidizing bacteria. The activity of AOB was inhibited when initial FA concentration was over6.5mg/L. After enriched ammonia oxidizing bacteria sludge had been embedded, the ammonia removal efficiency decreased about7.5%. Nitrite accumulation rate could be maintained at more than80.0%, ammonia removal efficiency was up to99.9%. In addition, anoxic zone was formed inside the embedded pellets while ensuring partial nitrification process. Denitrification could be achieved in the anoxic zone, because AOB made nitrite as the sole electron acceptor, and organic matter, ammonia or hydrogen as an electron donor to achieve denitrification, improving ammonia removal efficiency of the system.On the basis of a small trial, pilot study on synthetic ammonia industrial wastewater treatment using immobilized microbial technology. Pilot study optimal process parameters: aeration rate and reflux ratio respectively were9～11m3/h and4:1. Ammonia loading rate was up to0.24kgNH4+-N/(m3·d), the maximum ammonia removal efficiency was91.7%, total nitrogen removal rate was75.0%, COD average removal rate was80.9%. The effluent concentration was lower than Synthetic Ammonia Industrial Water Pollutant Discharge Standard GB (13458-2001). The results show that immobilized microbial technology can be successfully applied to synthetic ammonia industrial wastewater treatment, and achieves a good effect on nitrogen removal. |
