Study On Quick Start-up And Operation Of One-stage Autotrophic Nitrogen Removal

As a novel and promising biological nitrogen removal process, completely autotrophic nitrogen removal over nitrite(CANON) has attracted extensive studies in recent years. But relatively long and unstable start-up still hindered its wildly application. In this research, the effect of different ways of sludge inoculation to the start-up was studied, which was hoped to provide theoretical guidance and technical assistance to the practical application of CANON process.In the study, several CANON processes were started using synchrono us or asynchronous inoculation of nitritation sludge and anammox sludge. The nitrogen removal performance, evaluation of autotrophic nitrogen removal and variations of main functional microbial communities in every start period were analyzed. The effect of low temperature on performance of CANON was also investigated. At last, this process was evaluated from the view of economic efficiency.One CANON was started using synchronous inoculation way and four others were started using different asynchronous inoculation ways respectively. One-stage autotrophic nitrogen removal system was established in five CANON reactors, by adjusting the DO, p H, reflux flow velocity condition, etc. And all those five autotrophic nitrogen removal systems were successful by the analysis of the stoichiometric ratios. All four start-up using asynchronous inoculation(anammox sludge were inoculated after 5d, 10 d, 15 d and 19 d of nitritation period, separately) took shorter time than the one using synchronous way, considering the start-up time of four reactors was 48 d,46d,41 d,41d,respectively. There was obvious positive correlation between the start-up time and duration of the partial nitritation period, and the duration of partial nitritation period more than 15 d could significantly accelerate the start-up time of CANON for 7 days. FISH result also proved that aerobic ammonium oxidizing bacteria(AOB) and anammox bacteria(An AOB) were the dominated communities, otherwise the main undesirable nitrite oxidizing bacteria(NOB) was successfully suppressed.Decrease the operation temperature from 31 ℃ to the room temperature(11-21℃), the autotrophic nitrogen removal system deteriorated seriously. The ammonia removal rate decreased from 80% to 23.3%, and total nitrogen removal rate also dropped from 0.44 to 0.05 kg/(m3·d). The two representative stoichiometric ratios, ΔNO3-/ΔNH4+ and ΔTN/ΔNH4+, changed to 0.74 and 0.20, respectively, which were far from their theoretical values. After the 36 days of operation under relatively high temperature(19-23℃), this system was hardly recovered to its initial performance. High activity of NOB and low activity of An AOB were responsible for this deterioration.