Abstract: Aiming at solving the contradiction of sludge retention time (SRT) between nitrification and dephosphorization, and enhancing the simultaneous nitrogen (N) and phosphorus (P) removal efficiency of the low C/N (P) ratio domestic sewage in the traditional A²/O process, an improved A²/O technique with long SRT was developed. The novel process could select and strengthen the activated sludge, and enrich the denitrifying phosphorus accumulating organisms (DPAO) with long SRT effectively. After washing out nitrite oxidizing bacteria (NOB), the reactor ran under the condition of SRT=19.6 d, and sludge concentration (MLSS)=5.5 g·L^-1, hydraulic retention time (HRT)=8.2 h, sludge return ratio (R)=90%, nitrated liquid reflux ratio (r)=250%, dissolved oxygen (DO)=1.5—0.3 mg·L^-1 for the A²/O zone. HRT=4 h, aeration cycle was 1 h, aeration time was 1 min (DO=0.3—0.5 mg·L^-1) and settling time was 59 min for the intermittent aeration zone. Average removal rate of COD, NH₄⁺-N, TP and TN reached 88.71%, 99.2%, 93.77% and 89.52% respectively, nitrosation rate (NO₂^--N/NO_x^--N) was up to 97.2%, and DPAO/PAO ratio in sludge was 95.5%, and the final effluent met the first class level A of the GB 18918—2002 standard. It was found that about 72.96% of COD in sewage was utilized by DPAO for PHA production to accumulate P, 15.75% of COD was consumed by heterotrophic denitrifying bacteria, and about 41.96% and 31.31% of N were wiped off through phosphorus removal and heterotrophic denitrifying. The discharged sludge was mainly composed of the biomass of DPAO and denitrifying bacteria, accounting for 82.74% and 17.24% respectively. The technique could reduce 58.76% of carbon source consumption and 44.6% of sludge discharge comparing to the traditional nitrogen phosphorus removal pathway.

Key words: A²/O, anaerobic, aerobic, waste water, low C/N ratio, denitrifying phosphorus removal, partial nitrification

摘要： 为解决传统A²/O工艺硝化与除磷泥龄(SRT)之间的矛盾,进一步提高低C/N(P)比生活污水同步脱氮除磷效率,采用一种改良A²/O工艺在长SRT条件下处理生活污水.试验结果表明,该工艺可有效筛选和强化反应器内活性污泥,并大量富集长SRT的反硝化除磷菌(DPAO).通过亚硝酸盐氧化菌(NOB)淘洗阶段后,反应器在SRT=19.6d、A²O段污泥浓度(MLSS)=5.5 g·L^-1、水力停留时间(HRT)=8.2 h、污泥回流比(R)=90%、硝化液回流比(r)=250%、溶解氧(DO)=1.5～0.3 mg·L^-1,间歇曝气段HRT=4 h、曝气周期1 h曝气1 min(DO=0.3～0.5 mg·L^-1)、沉淀59 min条件下长期运行,COD、NH₄⁺-N、TP和TN的平均去除率分别为88.71%、99.2%、93.77%和89.52%,出水亚硝化率(NO₂^--N/NO_x^--N)可达97.2%,DPAO占聚磷菌(PAO)比为95.5%.污水中约72.96%的COD被DPAO合成PHA除磷,15.75%的COD由异养反硝化消耗,约41.96%和31.31%的N分别通过反硝化除磷和异养反硝化去除.剩余污泥主要由DPAO和反硝化菌增殖产生,分别占82.74%和17.24%,较传统脱氮除磷途径减少了58.76%的碳源消耗和44.6%的污泥排放.

关键词: A²/O, 厌氧, 需氧, 废水, 低C/N比, 反硝化除磷, 短程硝化