Study On Quick Start-up Of Anammox Process And Characteristics Of Bacterial Community

Anaerobic ammonium oxidation (Anammox) is an efficient and cost-effective biological nitrogen removal process. Due to its high removal efficiency, low sludge production rate, no need of external organic carbon source and dissolved oxygen, it gains extensive attention. Anammox process can deal with high-ammonia wastewater, and it is especially suitable for treatment of wastewater with low carbon/total nitrogen. Recently, Anammox combined process has been developed and widely used in treating high-nitrogen wastewater. However, as the generation time of anammox bacteria needs two weeks, the cultivation of Anammox bacteria requires a very long period, which becomes the bottleneck of Anammox process and limits its intrudustrial applications. To solve such problems, this study explores and improves quick start-up strategy of Anammox. Main research achievements were as follows:(1) Selecting the activated sludge with aboriginal Anammox bacteria as seed sludge can improve the performance of Anammox process and shorten the start-up period. In the experiment, three kinds of seed sludges, randomly selected from different wastewater treatment processes, were inoculated in three parallel reactors. The results showed that only the seed sludge which contained aboriginal Anammox bacteria could successfully started up Anammox process, and it merely took3months to realize this process, which was shorter than the usual start-up period of4months or longer.(2) MBR is suitable for quick start-up of Anammox. It successfully started up Anammox process from the activated sludge in2months since it could realize complete biomass retention and keep the activated sludge with good settling property stay in the reactor. The maximum removal rates of ammonia and nitrite were159.8mgNL-1d-1and185.4mgNL/-d-1, and the specific anammox activity was0.35g (NH4+-N+NO2--N)(gVSS·d)-1. During the Anammox start-up process, membrane fouling rate of sludge conversion stage was higher than that of sludge adaption stage and activity improving stage.Compared to SBR, MBR could save as much as41.6%on time usage of Anammox start-up process. Phylogenetic analysis showed that, after the successful start-up with the same seed sludge, Anammox bacteria species in MBR and SBR were significantly different. MBR had4species while SBR had only2species.(3) Non-woven ring carrier fixed bed reactor can accelerate the start-up process of Anammox and realize long-term operation. In the fixed bed reactor, Anammox activity occurred on39d. The nitrogen removal efficiency was increased by gradually increasing the influent nitrogen loading. The reactor gained a maximum nitrogen removal efficiency on367d, whose total nitrogen loading and removal efficency were10.25kgNm-3d-1and90.19%. During the long-term operation, Anammox activity was inhibited due to nitrite accumulation or pH increase, however, the performance of the reactor could be restored when total nitrogen loading rate and pH were timely adjusted.(4) Anammox sludge stored for long-term period at its optimal temperature can quickly start up Anammox process. Although Anammox activity decreased to29.2%of that before the storage after6-month storage with low nutrition (addition of NH4+-N and NCV-N was both13.6g/(kg MLSS-d)) at37℃, Anammox process successfully started up within2months by inoculating such sludge. One possibility was that the influence of dead non-target bacteria on the start-up process was avoided by adopting this strategy, and consequently, the period of sludge conversion stage was curtailed.(5) Preparation of magnetic entrapped Anammox balls could realize joint embedding of Anammox bacteria and magnetic particles. Keeping the powder to a certain level (0.5-1.5g/(20ml Anammox sludge X20ml PVA-SA)) can increased the Anammox activity. When the amount was0.5g/(20ml Anammox sludge X20ml PVA-SA), the maximum of the balls activity was gained, and nitrogen removal rates of NH4+/-N and NO2--N increased by56.05%and50.03%. Low-frequency ultrasound with appropriate parameters can also improve the activity of the magnetic entrapped Anammox balls. Then the balls with the same content of magnetic powder were placed in KQ5200DE numerical control ultrasonic instrument (35℃,50w). The Anammox activity was enhanced when the ultrasound duration was kept at the range of0-10min, and increased the most by95.45%when the ultrasonic duration was10min.