环境科学  2021, Vol. 42 Issue (10): 4853-4863   PDF    
部分亚硝化-厌氧氨氧化协同反硝化处理生活污水脱氮除碳
秦彦荣1,2,3, 袁忠玲1,2,3, 张明1,2,3, 张民安1,2,3, 刘安迪1,2,3, 付雪1,2,3, 马娟1,2,3, 陈永志1,2,3     
1. 兰州交通大学环境与市政工程学院, 兰州 730070;
2. 甘肃省黄河水环境重点实验室, 兰州 730070;
3. 甘肃省污水处理行业技术中心, 兰州 730070
摘要: 采用SBR-ASBR组合工艺处理实际生活污水,SBR中考察缺氧/好氧时间比及温度对部分亚硝化(partial nitritation,PN)的作用,ASBR中研究COD/NO2--N(C/N)对厌氧氨氧化(anaerobic ammonium oxidation,ANAMMOX)协同反硝化脱氮除碳的影响.①控制温度为25℃,在缺氧/好氧时间比为30 min:30 min,单周期交替3次时,NO2--N积累率(NiAR)于第22 d为98.06%,比亚硝态氮产生速率(SNiPR,以N/VSS计)为0.28g·(g·d)-1,同步硝化反硝化去除的TN和COD分别为12.29 mg·L-1和110.36mg·L-1.②在缺氧/好氧时间比为30 min:30 min下,温度为15℃时,丝状菌大量繁殖,污泥活性和沉降性变差;温度为30℃时,NH4+-N转化为NO2--N比例为86.83%,造成出水NH4+-N浓度过低,不能为厌氧氨氧化提供合适基质浓度;温度为25℃时,出水NH4+-N和NO2--N浓度分别为31.58 mg·L-1和35.04mg·L-1,匹配厌氧氨氧化基质比.③组合工艺脱氮性能良好,出水TN、NH4+-N和COD浓度分别稳定在13.13、4.83和69.96mg·L-1,去除率分别为83.10%、93.64%和75.11%.调节ASBR进水C/N为2.5、2.0和1.5时,C/N为2.0时厌氧氨氧化协同反硝化脱氮除碳性能最佳,出水NH4+-N、NO2--N、NO3--N和COD分别为0.09、0.25、1.04和32.73mg·L-1.
关键词: 间歇曝气      温度      部分亚硝化      厌氧氨氧化(ANAMMOX)      反硝化      C/N     
Partial Nitritation and Anaerobic Ammonia Oxidation Synergistic Denitrification to Remove Nitrogen and Carbon from Domestic Sewage
QIN Yan-rong1,2,3 , YUAN Zhong-ling1,2,3 , ZHANG Ming1,2,3 , ZHANG Min-an1,2,3 , LIU An-di1,2,3 , FU Xue1,2,3 , MA Juan1,2,3 , CHEN Yong-zhi1,2,3     
1. School of Environment and Municipal Engineering, Lanzhou Jiaotong University, Lanzhou 730070, China;
2. Key Laboratory of Yellow River Water Environment in Gansu Province, Lanzhou 730070, China;
3. Technical Center of Sewage Treatment Industry in Gansu, Lanzhou 730070, China
Abstract: A sequencing batch reactor-anaerobic sequencing batch reactor(SBR-ASBR) process was used to treat domestic sewage. In the SBR, the effects of the anoxic/aerobic time ratio and temperature on the realization of partial nitritation(PN) were investigated. In the ASBR, the effects of different COD/NO2--N(C/N) ratios on the removal of nitrogen and carbon using anaerobic ammonia oxidation(ANAMMOX) and denitrification were studied. The results illustrated that: ① After three single cycles and on the 22nd day, the NO2--N accumulation rate(NiAR) was 98.06%, and the nitrate nitrogen generation rate(SNiPR, calculated as N/VSS) was 0.28g·(g·d)-1, and simultaneous nitrification and denitrification removal the TN and COD were 12.29 and 110.36mg·L-1, respectively(temperature=25℃, anoxic/aerobic time ratio=30 min: 30 min). ② At an anoxic/aerobic time ratio of 30 min: 30 min, the filamentous sludge bulked, the sludge activity decreased, and sludge settleability was poor at 15℃. Furthermore, the conversion rate of NH4+-N to NO2--N was 86.83%, indicating that the effluent NH4+-N concentration was too low to provide suitable matrix concentrations for ANAMMOX at 30℃. The effluent concentrations of NH4+-N and NO2--N were 31.58 mg·L-1 and 35.04mg·L-1, respectively, matching the ratio of the ANAMMOX substrate at 25℃. ③ The SBR-ASBR combined process showed good denitrification performance; the effluent TN, NH4+-N, and COD concentrations were stable at 13.13, 4.83, and 69.96mg·L-1, respectively, and the removal rates were 83.10%, 93.64%, and 75.11%, respectively. When the influent C/N of the ASBR was 2.5, 2.0, and 1.5, respectively, anaerobic ammonia oxidation and denitrification showed the best performance with respect to nitrogen and carbon removal with a C/N of 2.0. The effluent NH4+-N, NO2--N, NO3--N, and COD were 0.09, 0.25, 1.04, and 32.73 mg·L-1, respectively.
Key words: intermittent aeration      temperature      partial nitritation      anaerobic ammonium oxidation(ANAMMOX)      denitrification      C/N     

部分亚硝化-厌氧氨氧化(partial nitritation-anaerobic ammonium oxidation, PN/A)作为一种新型深度脱氮工艺具有效率高、能耗低和污泥产率低等优点, 受到广泛关注[1~3]. PN/A工艺是指部分亚硝化(PN)和厌氧氨氧化(ANAMMOX)反应分别在两个反应器中进行.在SBR反应器中, 氨氧化菌(AOB)将原水中约50%~60%的NH4+-N转化为NO2--N, 然后将其出水进入ASBR反应器, 在厌氧氨氧化菌(AnAOB)的作用下, 把NH4+-N和NO2--N转化为N2, 其化学反应式如下[4]:

近年来, PN/A工艺在高温条件下, 成功应用于养殖业废水[5]、消化上清液[6]和垃圾渗滤液[7]等高NH4+-N(>500mg·L-1)和低C/N(< 0.5)废水处理中, 但该工艺在处理城市生活污水方面研究非常局限[8].城市生活污水由于NH4+-N浓度低, 低NH4+-N条件下难以控制游离氨(FA)和游离亚硝酸(FNA)等不利因素易导致NOB富集, 使PN段出水硝酸盐增加, 难以为ANAMMOX提供稳定NO2--N[9]; 另外城市生活污水水温受季节性影响较大[10], NOB相比AOB对温度敏感性更强, AnAOB活性随温度下降减幅明显, 因此常低温下如何抑制NOB并提高AnAOB活性是PN/A工艺稳定运行的关键[11].陈亚等[12]的研究表明部分亚硝化的稳定运行对ANAMMOX影响较大; Miao等[13]的研究在(30±1)℃成功启动部分亚硝化系统; Yuan等[14]的研究采用进水NH4+-N浓度为50mg·L-1时, 一体式部分硝化厌氧氨氧化(single-stage of partial nitrification and anaerobic ammonium oxidation, SPN/A)工艺耦合反硝化工艺脱氮效果较好, TN去除率为83.50%.

以上研究均在温度较高条件下进行或采用模拟废水, 在处理实际城市生活污水时, 由于SPN/A工艺启动时间长、运行不稳定、微生物关系复杂和前端需特设除碳装置以避免对系统的冲击[15], 而PN/A工艺很好地解决了亚硝化和ANAMMOX污泥龄之间的矛盾[16], 利于控制运行参数, 具有可靠性高、启动时间短和脱氮效率高的优点[17], 另外可利用PN段出水中带入少量污泥和COD使异养菌进行反硝化产生CO2, 这为ANAMMOX协同反硝化脱氮除碳提供可能[18].因此, 本试验以城市生活污水为处理对象, 考察在常低温条件下缺氧/好氧时间比、交替次数、温度和C/N等因素对PN/A工艺部分亚硝化稳定实现和ANAMMOX协同反硝化同步脱氮除碳的影响, 以期为该工艺的实际应用提供理论参考.

1 材料与方法 1.1 试验装置

PN/A工艺如图 1所示, SBR由有机玻璃所制, 直径15 cm, 高40 cm, 有效容积5 L, 侧壁设取样口, 配有搅拌装置, 通过PLC控制器检测pH、ORP及调节温度, 利用时间继电器实现间歇曝气; ASBR主体材质同SBR, 有效容积5 L, 顶部设通气口, 反应产生气体由水封瓶收集后排出, 另设缓冲瓶调节pH, 外壁由锡纸包裹避光.

图 1 PN/A工艺装置示意 Fig. 1 Schematic diagram of PN/A process device

1.2 接种污泥

SBR接种污泥来自实验室稳定短程硝化污泥, MLSS为3 450 mg·L-1, MLVSS/MLSS(f值)为0.59, SV30为42%; ASBR接种污泥来自稳定运行的厌氧氨氧化反应器, MLSS为3 321 mg·L-1, VSS为2 514 mg·L-1, 脱氮性能良好.

1.3 试验进水水质及检测方法

试验用水来自兰州交通大学家属区实际生活污水, SBR水质指标如表 1, 前置SBR反应器实现稳定部分亚硝化后通过加入NaNO2调节ASBR进水C/N, 具体进水水质见表 2.

表 1 SBR进水水质/mg·L-1 Table 1 Qualities of influent in the SBR/mg·L-1

表 2 ASBR进水水质(均值) Table 2 Average quantities of influent in the ASBR

水样经0.45 μm孔径定性滤纸过滤后根据APHA标准方法[19]测定, COD: 快速消解分光光度法; NH4+-N: 纳氏试剂分光光度法; NO2--N: N-(1-萘基)-乙二胺分光光度法; NO3--N: 麝香草酚分光光度法; MLSS和VSS: 重量法; SV30和SVI: 30 min沉降法; 温度、pH和DO: 便携式测定仪.

1.4 运行策略

SBR采用间歇运行, 1 d运行6个周期, 单周期240 min, 即进水5 min→反应180 min→沉淀30 min→排水5 min→闲置20 min, 调节曝气量为100 L·h-1, 排水比为75%.采用2种工况, 工况Ⅰ在25℃下, 采用缺氧/好氧时间比为30 min∶60 min、45 min∶45 min、30 min∶30 min, 分别交替2、2、3次; 工况Ⅱ采用缺氧/好氧时间比为30 min∶30 min交替3次, 调整温度分别为15、25和30℃. ASBR采用间歇运行, HRT为24 h, 排水比为70%, 控制温度为25℃, 调整C/N为2.5、2.0及1.5, 运行80 d.

1.5 计算方法

NH4+-N去除率(ARE)、NO2--N积累率(NiAR)、比氨氮氧化速率(SAOR)、比亚硝态氮产生速率(SNiPR)和比硝态氮产生速率(SNaPR)等计算参考文献[20]的公式.ASBR内各级反应脱氮贡献率计算参考文献[21]的公式.

ASBR内各级反应脱氮贡献率计算:

(1)
(2)
(3)
(4)

式中, A、PN、PD和D分别为: ANAMMOX、部分硝化-ANAMMOX、部分反硝化-ANAMMOX和反硝化反应的脱氮贡献率, %; abc分别为: NH4+-N消耗量、NO2--N消耗量和NO3--N产生量, mg·L-1.

1.6 物料衡算分析

通过物料衡算可得不同间歇模式下SBR部分亚硝化过程中的氮损失(ΔTN, mg·L-1)、碳损失(ΔCOD, mg·L-1)和同步硝化反硝化碳氮比例(ΔCOD/ΔTN)[22]:

(5)
(6)
(7)

式中, cn(TN)incn(TN)eff分别为第n周期进、出水TN浓度, cn-1(TN)eff为第n-1周期出水TN浓度, 单位均为mg·L-1; cn(COD)incn(COD)eff分别为第n周期进、出水COD浓度, cn-1(COD)eff为第n-1周期出水COD浓度, 单位均为mg·L-1; w为排水比.

2 结果与讨论 2.1 缺氧/好氧时间比对实现部分亚硝化的影响 2.1.1 缺氧/好氧时间比下NH4+-N及SAOR变化特征

图 2, 缺氧/好氧时间比为30 min∶60 min(A模式)、45 min∶45 min(B模式)和30 min∶30 min(C模式)中, 进水NH4+-N浓度均维持在49.47~101.22mg·L-1, ARE分别于第42、39及25周期达到稳定, 出水NH4+-N浓度分别为15.85、34.26和38.35mg·L-1, ARE分别为72.55%、54.46%和58.52%, 3种模式均能实现较稳定的部分亚硝化.C模式NO2--N积累高效稳定, 原因为试验接种污泥为短程硝化污泥, A、B模式相比, 好氧段时间减少不利于NH4+-N的去除, 缺氧段时间增加使NO2--N被还原量增加, 相对延长了NO2--N高效积累的时间, 故B模式较A模式所需时间长; A、C模式相比, 可能停曝频率变大有利于筛选出氨氧化速率较快的AOB及相对减少NOB的数量, 缩短C模式稳定部分亚硝化实现的时间.从SAOR来看, AOB生物量的提高表明交替缺氧/好氧环境下有利于AOB提高自身产率系数来加快生长繁殖[23], SAOR分别在45、36和16周期时达到稳定, 其中C模式增长幅度较快, 反应结束时SAOR分别为0.30、0.31和0.43g·(g·d)-1.与刘宏等[24]的研究相比, 本试验通过低曝气频率方式实现稳定部分亚硝化的时间更短, 节省能耗.

(a)30 min∶60 min(A模式), (b)45 min∶45 min(B模式), (c)30 min∶30 min(C模式) 图 2 缺氧/好氧时间比下NH4+-N和SAOR变化特征 Fig. 2 Characteristics of changes in NH4+-N and SAOR under different anoxic/aerobic time ratios

2.1.2 缺氧/好氧时间比下NO2--N积累及SNaPR、SNiPR变化特征

图 3, 3种模式进水NO2--N浓度均在1mg·L-1以下, 出水NO2--N浓度和NiAR均呈上升趋势, NiAR分别于第39、38和22周期稳定至97.87%、94.01%和98.06%, 出水NO2--N浓度分别增至24.00、19.82和25.92mg·L-1; SNiPR分别稳定至0.16、0.18和0.28g·(g·d)-1; 出水NO3--N浓度均随NOB减少而降低, 反应结束时SNaPR分别为0.001、0.007和0.002g·(g·d)-1, 出水NO3--N浓度分别降至0.22、1.00和0.20mg·L-1.

(a)30 min∶60 min(A模式), (b)45 min∶45 min(B模式), (c)30 min∶30 min(C模式) 图 3 缺氧/好氧时间比下NO2--N积累及SNaPR和SNiPR变化特征 Fig. 3 NO2--N accumulation and changes in SNaPR and SNiPR under different anoxic/aerobic time ratios

张立成等[25]的研究认为NiAR在50%以上便实现了部分亚硝化, 刘宏[26]的研究采用交替好氧/缺氧模式第39周期才实现NO2--N稳定积累, 由于NOB为优势菌种, 采用交替好氧/缺氧模式, 在有机碳源充足的情况下, 好氧段产生的NO2--N短时间内易被氧化为NO3--N, 较交替缺氧/好氧模式更不易控制; 若先进行缺氧反应, 因为AOB“饱食饥饿”特性使其更易富集, 张杰等[27]的研究采用停曝比为1∶1并协同其它控制条件的方式实现了部分亚硝化稳定运行, 阶段末NiAR为85.20%.相比连续曝气, 间歇曝气具有碱度投加量少、效率高及避免碳源不足等优点.但匹配ANAMMOX的部分亚硝化并非NO2--N浓度越高越好, 否则需外加铵盐或引入新鲜污水调节基质浓度及比值, 导致处理成本增加、系统崩溃.本试验中C模式实现稳定部分亚硝化最快, 利于降低成本.

2.1.3 缺氧/好氧时间比下ΔTN及ΔCOD

图 4, 由式(5)~(7)可得不同模式氮损失(ΔTN)、碳损失(ΔCOD)和ΔCOD/ΔTN, 忽略内源反硝化与细胞同化作用, 则ΔTN为同步硝化反硝化作用消耗TN. 3种模式下初始ΔTN和ΔCOD分别为1.69、2.43、3.32mg·L-1和42.70、34.39、36.38mg·L-1, 周期末ΔTN和ΔCOD分别稳定至23.60、14.50、12.29mg·L-1和138.54、104.17、110.36mg·L-1, ΔCOD/ΔTN稳定至5.87、7.18和8.98.可见3种模式下均发生了氮损失, 主要原因为[28, 29]: ①反应器存在局部环境DO分布不均; ②活性污泥絮体由于氧传递受限, DO浓度从表面至内部降低; ③存在好氧反硝化菌和异养硝化菌, 为同步硝化反硝化提供了有利条件.A模式下发生同步硝化反硝化所需碳源最多, 但B模式下消耗碳源最少, 可能因为A模式下好氧段相对较长, 使其积累的NO2--N被氧化为NO3--N, 为缺氧段反硝化提供充足的基质, 导致ΔCOD最大, C模式下交替次数的上升有利于COD的去除, 故好氧段的长短和交替次数决定有机碳源的消耗量, 好氧段越长发生同步硝化反硝化所消耗有机碳源越多, 其ΔTN也最大[30]. ΔCOD/ΔTN可作为该模式的理论依据, 以寻求在相对较少的ΔTN下获得较大的ΔCOD, 避免ASBR中COD过高对ANAMMOX产生不利影响.

图 4 缺氧/好氧时间比下ΔTN及ΔCOD变化特征 Fig. 4 Characteristics of changes in ΔTN and ΔCOD under different anoxic/aerobic time ratios

2.2 间歇曝气模式下温度对部分亚硝化及污泥性能的影响 2.2.1 不同温度下NH4+-N及SAOR变化特征

保持缺氧/好氧时间比为30 min∶30 min, 如图 5, 15、25和30℃时, 出水NH4+-N浓度、ARE和SAOR分别为47.50mg·L-1、45.63%、0.38g·(g·d)-1、31.58mg·L-1、60.27%、0.47g·(g·d)-1和4.12mg·L-1、95.35%、0.81g·(g·d)-1.可见一定范围内, 温度越高SAOR越大, ARE越高, 主要因为高温有利于AOB的繁殖, 但高温下系统易失稳转向短程硝化, 不能为ANAMMOX提供合适的基质浓度[31]. 30℃时部分亚硝化系统已失稳转化为短程硝化.

图 5 不同温度下NH4+-N及SAOR变化特征 Fig. 5 Characteristics of NH4+-N and SAOR changes at different temperatures

2.2.2 不同温度下NO2--N积累及SNaPR、SNiPR和污泥性能变化特征

图 6, 15℃时, NiAR波动较大, 出水NO2--N浓度、NiAR和SNiPR分别低至14.05mg·L-1、34.99%和0.12g·(g·d)-1, 而NO3--N浓度和SNaPR居高不下, 可见低温下难以实现部分亚硝化.从15℃上升至30℃, NO2--N浓度、NiAR和SNiPR均明显增大, 说明温度上升有利于NO2--N的积累, 这与Jia等[32]的研究结果相同.Paredes等[33]的研究发现当温度高于15℃, AOB活性及繁殖速率大于NOB, 25℃以上时这一趋势更加明显, 这与本试验的结果一致.如图 7, f和SVI是影响NO2--N稳定积累的重要参数. 3种温度下初始f和SVI(mL·g-1)分别为0.42、0.48、0.45和48.73、65.53、58.06, 各f和SVI值均先上升, 达到稳定分别需36、15和29 d.结束时f和SVI(mL·g-1)分别为0.61、0.79、0.81和126.88、93.17、89.98, 30℃下f增速最快, 15℃下SVI在36 d达到最大值130.46 mL·g-1, 低温环境AOB活性降低, 丝状菌大量繁殖导致污泥膨胀, 伴随污泥上浮现象.而25℃和30℃下SVI稳定在90 mL·g-1左右, 污泥活性和沉降性较好, 说明污泥性能随温度上升而提高.从耗能角度看25℃更适宜匹配ANAMMOX.

图 6 不同温度下NO2--N积累及SNaPR、SNiPR变化特征 Fig. 6 NO2--N accumulation and SNaPR, SNiPR change characteristics at different temperatures

图 7 不同温度下SBR污泥性能变化特征 Fig. 7 Characteristics of SBR sludge performance changes at different temperatures

2.3 SBR-ASBR组合工艺处理实际生活污水效果

图 8, 组合工艺进水TN、NH4+-N和COD浓度均值分别为77.68、75.96和281.07mg·L-1, 出水TN、NH4+-N和COD浓度稳定在13.13、4.83和69.96mg·L-1, 去除率分别为83.10%、93.64%和75.11%, 脱氮效果较好.普遍认为匹配ANAMMOX的基质比NO2--N/NH4+-N在1∶1左右即可[34], 但本试验出水NH4+-N有剩余, 且发现在SBR出水COD均值为113.05mg·L-1下, 组合工艺出水NO3--N稳定在7.46mg·L-1, 说明ASBR中反硝化作用微弱, 导致除碳效果不理想, 有研究表明有机物浓度在150mg·L-1以下AnAOB可以和反硝化菌共存[35], 且有机物对AnAOB具有双向作用[36], 是否在较低有机物浓度下NO2--N的量决定了ANAMMOX协同反硝化脱氮除碳的进程, 故通过投加亚硝酸钠调节C/N对两者协同性能作近一步考察.

图 8 SBR-ASBR组合工艺处理生活污水效果 Fig. 8 Treatment effect of the SBR-ASBR combined process on domestic sewage

2.4 厌氧氨氧化协同反硝化脱氮除碳性能优化 2.4.1 不同C/N下ASBR氮素和COD变化特征

ASBR进水来自SBR出水, 其进水COD和NO2--N分别稳定在113.05和37.48mg·L-1左右, 投加NaNO2调整ASBR进水C/N分别为2.5、2.0和1.5.如图 9, C/N为3.0是SBR-ASBR组合工艺处理实际生活污水ASBR段效果, C/N从3.0降至2.0时, ARE和COD去除率均呈上升趋势, C/N降至1.5时, ARE下降, 而COD去除率保持稳定.C/N的变化对NO2--N的去除影响较小, 其去除率接近100%.C/N从3.0降低到1.5过程中, 出水NO3--N浓度由7.29mg·L-1降至0.22mg·L-1.

图 9 不同C/N下ASBR氮素和COD变化特征 Fig. 9 Variation characteristics of nitrogen and COD during anaerobic ammoxidation under different C/N

C/N为3.0时, 试验初期菌体处于内源呼吸期, AnAOB对基质需求迫切, 增加的NO2--N使AnAOB得到相对充足的电子受体, 但NO2--N量不足使AnAOB难以继续与剩余NH4+-N进行ANAMMOX, 异养菌反应微弱, 对COD去除率不高[37]; C/N为2.0时, 微过量的NO2--N为ANAMMOX和异养反硝化菌提供充足基质, 反硝化菌为AnAOB解除了氧毒[38], 促进ANAMMOX和反硝化反应, 出水NH4+-N、NO3--N、COD浓度减幅明显; C/N为1.5时, ANAMMOX取决于NH4+-N的量, 剩余NO2--N和ANAMMOX生成的NO3--N为反硝化菌提供充足的基质, 使脱氮性能变差.

C/N降低过程中, NO2--N浓度逐渐增大, 以ANAMMOX为主协同反硝化脱氮除碳作用逐渐增强; C/N < 2.0时, AnAOB竞争优势减弱, 系统内以反硝化为主, 协同性能下降.可见C/N是决定ANAMMOX协同反硝化的重要因素[39], 马艳红等[40]的研究发现适当的COD浓度可以增强ANAMMOX协同反硝化的效果; 王凡等[41]的研究处理模拟废水在C/N为0.4时AnAOB和反硝化菌协同能力最强.本试验C/N为2.0时系统协同性能最佳, 出水NH4+-N、NO2--N、NO3--N和COD分别为0.09、0.25、1.04和32.73mg·L-1.

2.4.2 不同C/N下脱氮贡献率和化学计量比变化特征

图 10, 整个过程中, 全程反硝化脱氮占比逐渐增大.C/N为3.0系统脱氮贡献主要由ANAMMOX、部分反硝化和全程反硝化提供, ANAMMOX平均脱氮贡献率达89.64%, 部分反硝化-ANAMMOX和全程反硝化平均脱氮贡献率共计7.03%, NO2--N不足使系统部分反硝化-ANAMMOX占比较全程反硝化大, 另外系统内存在少量氮循环菌属参与其它脱氮途径; C/N为2.5 ANAMMOX脱氮贡献率相对稳定, 部分亚硝化和部分反硝化脱氮贡献率降低, 全程反硝化脱氮贡献率增至10.30%; C/N为2.0 ANAMMOX平均脱氮贡献率降至77.98%, 而全程反硝化增至21.16%, 可见C/N由3.0降至2.0过程中, 系统ANAMMOX协同反硝化作用增至最大, 脱氮性能上升; C/N降至1.5后, ANAMMOX平均脱氮贡献率降至49.72%, 反硝化菌逐渐占据优势, 这与Zhang等[42]的研究结果一致.

a.ΔNO3--N/ΔNH4+-N理论值0.26, b.ΔNO2--N/ΔNH4+-N理论值1.32 图 10 不同C/N下脱氮贡献率和化学计量比变化特征 Fig. 10 Variation characteristics of nitrogen removal contribution ratio and stoichiometric ratio under different C/N

C/N为3.0和2.5时, ΔNO2--N/ΔNH4+-N和ΔNO3--N/ΔNH4+-N分别在其理论值附近波动, 且均值略低于理论值, 因为在ANAMMOX为主反应的前提下, 硝化、反硝化等氮循环菌属少量协同脱氮, 且ASBR中存在少量的AOB和DO易造成实际比值低于理论值[43]; C/N为2.0, 微过量的NO2--N促进了反硝化菌繁殖, NH4+-N浓度相对不足, 造成ΔNO2--N/ΔNH4+-N高于理论值, 反硝化脱氮贡献率增大, 造成ΔNO3--N/ΔNH4+-N进一步偏低, C/N为1.5时这一趋势更加明显, 不利于AnAOB协同其它菌属脱氮.

目前多探究ANAMMOX协同反硝化进水有机物的阈值, 有关COD对ANAMMOX系统微生物的影响尚无确切定论[44, 45], 且添加COD易造成反硝化菌大量繁殖, 不易控制, 本试验在ASBR进水COD均值为113.05mg·L-1下, 发现NO2--N的量决定了ANAMMOX协同反硝化脱氮除碳的程度.

3 结论

(1) 当温度为25℃, 缺氧/好氧时间比为30 min∶30 min, 交替次数为3时, 实现高效稳定亚硝积累时间最短, SBR部分亚硝化中ARE、NiAR和出水NO2--N浓度分别为60.27%、99.38%和35.04mg·L-1.

(2) 不同缺氧/好氧时间比下易发生同步硝化反硝化现象, 好氧段的长短决定有机碳源的消耗量, 从而影响同步硝化反硝化氮损失.缺氧/好氧时间比分别为30 min∶60 min、45 min∶45 min和30 min∶30 min时, ΔTN和ΔCOD分别稳定至23.60, 14.50、12.29mg·L-1和138.54、104.17、110.36mg·L-1, 缺氧/好氧时间比为30 min∶30 min下消耗COD较多的同时因同步硝化反硝化发生的氮损失最少.

(3) 组合工艺脱氮性能良好, 出水TN、NH4+-N和COD浓度分别稳定在13.13、4.83和69.96mg·L-1, 去除率分别为83.10%、93.64%和75.11%.ASBR进水COD为113.05mg·L-1下, NO2--N的量决定了ANAMMOX协同反硝化脱氮除碳的效果, 当C/N为2.0协同性能最佳, 出水NH4+-N、NO2--N、NO3--N和COD浓度分别为0.09、0.25、1.04和32.73mg·L-1.

参考文献
[1] Liu T, Hu S H, Yuan Z G, et al. High-level nitrogen removal by simultaneous partial nitritation, anammox and nitrite/nitrate-dependent anaerobic methane oxidation[J]. Water Research, 2019, 166. DOI:10.1016/j.watres.2019.115057
[2] Wu L N, Yan Z B, Huang S, et al. Rapid start-up and stable maintenance of partial nitrification-anaerobic ammonium oxidation treatment of landfill leachate at low temperatures[J]. Environmental Research, 2020, 191. DOI:10.1016/j.envres.2020.110131
[3] Han X Y, Zhang S J, Yang S H, et al. Full-scale partial nitritation/anammox(PN/A)process for treating sludge dewatering liquor from anaerobic digestion after thermal hydrolysis[J]. Bioresource Technology, 2020, 297. DOI:10.1016/j.biortech.2019.122380
[4] Sui Q W, Di F, Zhang J Y, et al. Advanced nitrogen removal in a fixed-bed anaerobic ammonia oxidation reactor following an anoxic/oxic reactor: nitrogen removal contributions and mechanisms[J]. Bioresource Technology, 2021, 320. DOI:10.1016/j.biortech.2020.124297
[5] Pan Z Z, Dai R Z, Liao J S, et al. Spontaneous formation and mechanism of anaerobic ammonium oxidation(anammox)bacteria in swine wastewater treatment system[J]. International Biodeterioration & Biodegradation, 2020, 154. DOI:10.1016/j.ibiod.2020.105058
[6] Zhou X, Zhang Z Q, Zhang X A, et al. A novel single-stage process integrating simultaneous COD oxidation, partial nitritation-denitritation and anammox(SCONDA)for treating ammonia-rich organic wastewater[J]. Bioresource Technology, 2018, 254: 50-55. DOI:10.1016/j.biortech.2018.01.057
[7] Lin Z Y, Xu F Y, Wang Y M, et al. Autotrophic nitrogen removal by partial nitrification-anammox process in two-stage sequencing batch constructed wetlands for low-strength ammonium wastewater[J]. Journal of Water Process Engineering, 2020, 38. DOI:10.1016/j.jwpe.2020.101625
[8] Deng S Y, Peng Y Z, Zhang L, et al. Advanced nitrogen removal from municipal wastewater via two-stage partial nitrification-simultaneous anammox and denitrification(PN-SAD)process[J]. Bioresource Technology, 2020, 304. DOI:10.1016/j.biortech.2020.122955
[9] 王思萌, 苗圆圆, 彭永臻. 低温投加短程硝化污泥下城市污水SPN/A工艺运行特性[J]. 中国环境科学, 2019, 39(4): 1456-1463.
Wang S M, Miao Y Y, Peng Y Z. Operation characteristics of the SPN/A process for municipal wastewater under low temperature shortcut nitrification sludge[J]. China Environmental Science, 2019, 39(4): 1456-1463. DOI:10.3969/j.issn.1000-6923.2019.04.013
[10] Cao Y S, Van Loosdrecht M C M, Daigger G T. Mainstream partial nitritation-anammox in municipal wastewater treatment: status, bottlenecks, and further studies[J]. Applied Microbiology and Biotechnology, 2017, 101(4): 1365-1383. DOI:10.1007/s00253-016-8058-7
[11] Gao D W, Xiang T. Deammonification process in municipal wastewater treatment: challenges and perspectives[J]. Bioresource Technology, 2021, 320. DOI:10.1016/j.biortech.2020.124420
[12] 陈亚, 印雯, 张星星, 等. 反硝化除磷耦合部分亚硝化-厌氧氨氧化一体式工艺的启动[J]. 环境科学, 2020, 41(5): 2367-2372.
Chen Y, Yin W, Zhang X X, et al. Start-up of an integrated process of denitrifying phosphorus removal coupled with partial nitritation and anaerobic ammonium oxidation[J]. Environmental Science, 2020, 41(5): 2367-2372.
[13] Miao J, Yin Q D, Hori T, et al. Nitrifiers activity and community characteristics under stress conditions in partial nitrification systems treating ammonium-rich wastewater[J]. Journal of Environmental Sciences, 2018, 73: 1-8. DOI:10.1016/j.jes.2017.12.020
[14] Yuan Y, Li X, Li B L. Autotrophic nitrogen removal characteristics of PN-anammox process enhanced by sulfur autotrophic denitrification under mainstream conditions[J]. Bioresource Technology, 2020, 316. DOI:10.1016/j.biortech.2020.123926
[15] Chen Y Z, Zhao Z C, Liu H, et al. Achieving stable two-stage mainstream partial-nitrification/anammox(PN/A)operation via intermittent aeration[J]. Chemosphere, 2020, 245. DOI:10.1016/j.chemosphere.2019.125650
[16] 姜黎安, 隋倩雯, 徐东耀, 等. 部分亚硝化-厌氧氨氧化工艺处理低氨氮废水研究进展[J]. 环境工程, 2019, 37(1): 61-66.
Jiang L A, Sui Q W, Xu D Y, et al. Research progress on treatment of low ammonia nitrogen wastewater by partial nitrification-anammox process[J]. Environmental Engineering, 2019, 37(1): 61-66.
[17] Sharp R, Khunjar W, Daly D, et al. Nitrogen removal from water resource recovery facilities using partial nitrification, denitratation-anaerobic ammonia oxidation(PANDA)[J]. Science of the Total Environment, 2020, 724. DOI:10.1016/j.scitotenv.2020.138283
[18] Yan J, Wang S J, Wu L Y, et al. Long-term ammonia gas biofiltration through simultaneous nitrification, anammox and denitrification process with limited N2O emission and negligible leachate production[J]. Journal of Cleaner Production, 2020, 270. DOI:10.1016/j.jclepro.2020.122406
[19] APHA. Standard methods for the Examination of water and wastewater(21st ed. )[M]. Washington, DC: American Public Health Association, 2005.
[20] 孙洪伟, 吕心涛, 魏雪芬, 等. 游离氨(FA)耦合曝气时间对硝化菌活性的抑制影响[J]. 环境科学, 2016, 37(3): 1075-1081.
Sun H W, Lü X T, Wei X F, et al. Synergetic inhibitory effect of free ammonia and aeration phase length control on the activity of nitrifying bacteria[J]. Environmental Science, 2016, 37(3): 1075-1081.
[21] 曹雁. 厌氧氨氧化与反硝化协同脱氮及微生物特性研究[D]. 广州: 华南理工大学, 2018.
Cao Y. Study on performance and microbial characteristics of co-existence of anammox and denitrification for simultaneous nitrogen removal[D]. Guangzhou: South China University of Technology, 2018.
[22] 刘安迪, 赵凯亮, 刘宏, 等. 不同控制策略下短程硝化启动及运行工况优化[J]. 环境科学, 2019, 40(10): 4569-4577.
Liu A D, Zhao K L, Liu H, et al. Short-cut nitrification start-up and optimization of operating conditions under different control strategies[J]. Environmental Science, 2019, 40(10): 4569-4577.
[23] Zheng Z M, Huang S, Bian W, et al. Enhanced nitrogen removal of the simultaneous partial nitrification, anammox and denitrification(SNAD)biofilm reactor for treating mainstream wastewater under low dissolved oxygen(DO)concentration[J]. Bioresource Technology, 2019, 283: 213-220. DOI:10.1016/j.biortech.2019.01.148
[24] 刘宏, 南彦斌, 李慧, 等. 间歇曝气模式下曝气量对短程硝化恢复的影响[J]. 环境科学, 2018, 39(2): 865-871.
Liu H, Nan Y B, Li H, et al. Effect of aeration rate on shortcut nitrification recovery in intermittent aeration mode[J]. Environmental Science, 2018, 39(2): 865-871.
[25] 张立成, 党维, 徐浩, 等. SBR快速实现短程硝化及影响因素[J]. 环境工程学报, 2015, 9(5): 2272-2276.
Zhang L C, Dang W, Xu H, et al. Achievement and influencing factors of shortcut nitrification in SBR process[J]. Chinese Journal of Environmental Engineering, 2015, 9(5): 2272-2276.
[26] 刘宏. 间歇曝气SBR完全短程硝化+ASBR厌氧氨氧化脱氮性能研究[D]. 兰州: 兰州交通大学, 2018.
Liu H. Study on nitrogen removal performance using SBR complete shortcut nitrification under intermittent aeration+ASBR Anammox[D]. Lanzhou: Lanzhou Jiaotong University, 2018.
[27] 张杰, 劳会妹, 李冬, 等. 不同停曝比对连续流亚硝化颗粒污泥运行的影响[J]. 环境科学, 2020, 41(11): 5097-5105.
Zhang J, Lao H M, Li D, et al. Effect of different ratios of anaerobic time and aeration time on the operation of a continuous-flow reactor with partial nitrification granules[J]. Environmental Science, 2020, 41(11): 5097-5105.
[28] 杨玉兵. 两段式短程硝化-厌氧氨氧化脱氮性能及其N2O产生途径研究[D]. 北京: 北京工业大学, 2018.
Yang Y B. Two-stage partial nitrification-anaerobic ammonium oxidation denitrification performance and its N2O production pathway[D]. Beijing: Beijing University of Technology, 2018.
[29] 冯亮, 袁春燕, 杨超, 等. 好氧反硝化生物脱氮技术的研究进展[J]. 微生物学通报, 2020, 47(10): 3342-3354.
Feng L, Yuan C Y, Yang C, et al. Research progress in nitrogen removal by aerobic denitrification[J]. Microbiology China, 2020, 47(10): 3342-3354.
[30] 赵智超, 黄剑明, 李健, 等. 间歇曝气连续流反应器同步硝化反硝化除磷[J]. 环境科学, 2019, 40(2): 799-807.
Zhao Z C, Huang J M, Li J, et al. Simultaneous nitrification and denitrifying phosphorus removal in continuous flow reactor with intermittent aeration[J]. Environmental Science, 2019, 40(2): 799-807.
[31] Xu Z Z, Zhang L, Gao X J, et al. Optimization of the intermittent aeration to improve the stability and flexibility of a mainstream hybrid partial nitrification-anammox system[J]. Chemosphere, 2020, 261. DOI:10.1016/j.chemosphere.2020.127670
[32] Jia W L, Chen Y F, Zhang J, et al. Response of greenhouse gas emissions and microbial community dynamics to temperature variation during partial nitrification[J]. Bioresource Technology, 2018, 261: 19-27. DOI:10.1016/j.biortech.2018.03.137
[33] Paredes D, Kuschk P, Mbwette T S A, et al. New aspects of microbial nitrogen transformations in the context of wastewater treatment-a review[J]. Engineering in Life Sciences, 2007, 7(1): 13-25. DOI:10.1002/elsc.200620170
[34] Dong H, Zhang K Y, Han X, et al. Achievement, performance and characteristics of microbial products in a partial nitrification sequencing batch reactor as a pretreatment for anaerobic ammonium oxidation[J]. Chemosphere, 2017, 183: 212-218. DOI:10.1016/j.chemosphere.2017.05.119
[35] 李田, 曹家炜, 谢凤莲, 等. ABR除碳-亚硝化耦合厌氧氨氧化处理城市污水[J]. 环境科学, 2019, 40(3): 1390-1395.
Li T, Cao J W, Xie F L, et al. ABR decarbonization-nitrosation coupled with ANAMMOX to treat municipal wastewater[J]. Environmental Science, 2019, 40(3): 1390-1395.
[36] Li J L, Li J W, Peng Y Z, et al. Insight into the impacts of organics on anammox and their potential linking to system performance of sewage partial nitrification-anammox(PN/A): a critical review[J]. Bioresource Technology, 2020, 300. DOI:10.1016/j.biortech.2019.122655
[37] 安芳娇, 黄剑明, 黄利, 等. 基质比对厌氧氨氧化耦合反硝化脱氮除碳的影响[J]. 环境科学, 2018, 39(11): 5058-5064.
An F J, Huang J M, Huang L, et al. Effect of substrate ratio on removal of nitrogen and carbon using anaerobic ammonium oxidation and denitrification[J]. Environmental Science, 2018, 39(11): 5058-5064.
[38] 童颖. 有机物对厌氧氨氧化双向影响及抑制解除[D]. 沈阳: 沈阳建筑大学, 2014.
Tong Y. Two-way role of organic matter on anammox and inhibition[D]. Shenyang: Shenyang Jianzhu University, 2014.
[39] Wang Z Z, Ji Y, Yan L N, et al. Simultaneous anammox and denitrification process shifted from the anammox process in response to C/N ratios: Performance, sludge granulation, and microbial community[J]. Journal of Bioscience and Bioengineering, 2020, 130(3): 319-326. DOI:10.1016/j.jbiosc.2020.04.007
[40] 马艳红, 赵智超, 安芳娇, 等. 不同COD浓度下低基质厌氧氨氧化的启动特征[J]. 环境科学, 2019, 40(5): 2317-2325.
Ma Y H, Zhao Z C, An F J, et al. Start-up performance of low-substrate anaerobic ammonium oxidation under different COD concentrations[J]. Environmental Science, 2019, 40(5): 2317-2325.
[41] 王凡, 刘凯, 林兴, 等. 不同TOC/NH4+-N对厌氧氨氧化脱氮效能的影响[J]. 环境科学, 2017, 38(8): 3415-3421.
Wang F, Liu K, Lin X, et al. Effect of different TOC to NH4+-N ratios on nitrogen removal efficiency in the ANAMMOX process[J]. Environmental Science, 2017, 38(8): 3415-3421.
[42] Zhang X Y, Liu Y, Li Z R, et al. Impact of COD/N on anammox granular sludge with different biological carriers[J]. Science of the Total Environment, 2020, 728. DOI:10.1016/j.scitotenv.2020.138557
[43] 刘安迪. 部分亚硝化耦合厌氧氨氧化脱氮除碳性能研究[D]. 兰州: 兰州交通大学, 2020.
Liu A D. Experimental study on nitrogen and carbon removal performance of partial nitrification coupled with anaerobic ammonia oxidation[D]. Lanzhou: Lanzhou Jiaotong University, 2019.
[44] Deng L Y, Peng Y Z, Li J W, et al. Enhanced simultaneous nitrogen and phosphorus removal from low COD/TIN domestic wastewater through nitritation-denitritation coupling improved anammox process with an optimal Anaerobic/Oxic/Anoxic strategy[J]. Bioresource Technology, 2021, 322. DOI:10.1016/J.biortech.2020.124526
[45] Pijuan M, Ribera-Guardia A, Balcázar J L, et al. Effect of COD on mainstream anammox: Evaluation of process performance, granule morphology and nitrous oxide production[J]. Science of the Total Environment, 2020, 712. DOI:10.1016/j.scitotenv.2019.136372