A^2/O工艺用于污水处理厂升级改造的适宜性探讨

Discussion on Suitability of A^2/O Process for Upgrading of Wastewater Treatment Plant

以国内普遍采用的A^2/O工艺为背景,通过与UCT工艺的模拟对比,揭示A^2/O在脱氮上略逊UCT,而在除磷方面明显落后于UCT。倒置A^2/O虽能避免回流污泥中的硝酸盐氮对厌氧释磷的影响,但却以牺牲生物除磷为代价。进言之,UCT较A^2/O可聚集更多反硝化除磷菌(DPB),这将最大化同步脱氮除磷作用,同时亦可节省曝气量。但是,UCT在生物除磷上的优越性会导致出水SS的高含磷量(5%~6%),所以,较高的出水SS(10 mg/L)肯定会产生较高的出水总磷(TP)。降低出水SS(5 mg/L)并辅助外加碳源或侧流磷沉淀,UCT工艺出水水质不仅可以满足国家一级A标准,甚至还能达到更为严格的北京地方排放标准的A标准。厌氧单元上清液侧流磷沉淀与外加碳源具有异曲同工之处,可以将化学除磷宏量效果好、生物除磷微量效果佳之特点发挥至极致,不仅避免了外加碳源,亦可实现磷回收。

On the background of the A^2/O process widely applied in China, comparative simula- tions between UCT and A^2/O demonstrate that A^2/O is a little bit inferior to UCT in N removal but falls behind UCT in P removal. Although the inverted A^2/O process can avoid the effect of nitrate in return sludge on anaerobic release of phosphate, this action will completely damage P removal. Moreover, UCT over A^2/O can accumulate more DPB in the system, which would enhance simultaneous N ＆ P removal and also save aeration. However, the good behavior of UCT in P removal can result in a higher P content （5% -6% ） in effluent SS （10 rag/L）, which will definitely cause a higher TP concentration in effluent. Lowering SS （5 rag/L） in effluent, associated with external carbon addition or phosphate precipitation in side stream, would meet the need of the state effluent discharge standards A and even reach the strict local standards of Beijing A. Phosphate precipitation in side stream and external carbon addition have different approaches but equally satisfactory results, which can apply chemical ＆ biological P removals to the utmost, and also avoid adding external carbon and realize phosphate recovery.