-
人工湿地对污水中的氮、磷污染物有很好的去除效果,而且具有投资成本低、维护管理方便和不产生二次污染等优点[1],在农村生活污水处理领域具有广阔的应用前景。目前,人工湿地在农村生活污水中的应用以潜流式为主,包括水平流人工湿地(horizontal flow constructed wetland,HFCWs)和垂直流人工湿地(vertical flow constructed wetland,VFCWs),设计时通常参考国家环保部发布的《人工湿地污水处理工程技术规范》(HJ 2005—2010)。该规范主要适用于城镇污水厂出水深度处理,HFCWs与VFCWs水力负荷建议取值为0.015~0.5 m3∙(m2∙d)−1和0.2~0.8 m3∙(m2∙d)−1;针对农村水质水量变化大、地区之间差别大的情况,参数取值的适宜性尚需探讨。
长三角平原地区人口密度高、环境负荷大、土地资源紧缺,且位于太湖流域,环境敏感性高,近年来对农村生活污水治理与达标排放的要求越来越严格,处理工艺也因此由最初的单纯厌氧池或单纯人工湿地系统慢慢演变为生物处理+人工湿地组合工艺。在生物处理+人工湿地组合工艺中,生物处理被认为担任去除有机污染物、悬浮物和脱氮除磷的主要角色,普遍采用在市政污水处理效果较好的A2O (anaerobic-anoxic-oxic)工艺。污水经生物处理后,可降低后续人工湿地单元的进水浓度,在进一步去除氮磷、稳定出水水质的同时,减少湿地的占地面积[2]。农村生活污水的水量和水质受季节、时段的影响变化大[3],设施进水碳氮比低、运行过程中溶解氧控制调整难[4-7],这些因素均将增加A2O和人工湿地在处理农村生活污水中充分硝化和高效脱氮除磷方面的难度,从而影响设施效果的发挥。
本研究以嘉兴海宁的农村生活污水处理设施为研究对象,实地抽检了11个乡镇内28座A2O与VFCWs组合工艺(A2O+VFCWs)设施和46座A2O与HFCWs组合工艺(A2O+HFCWs)设施,运用统计学方法比较了2种组合工艺处理农村生活污水的出水稳定性及稳定达标率,分析了A2O单元和人工湿地单元对污染物去除的各自贡献率,剖析了2种组合工艺的设计与运行问题,旨在为组合工艺今后脱氮除磷的性能提升提供参考。
A2O与人工湿地组合工艺处理长三角平原地区农村生活污水的效果
Performance of A2O combined with constructed wetland on treating rural domestic sewage in plain areas of Yangtze River delta region, China
-
摘要: 对嘉兴海宁的28座A2O+水平流人工湿地(horizontal flow constructed wetland,HFCWs)和46座A2O+垂直流人工湿地(vertical flow constructed wetland,VFCWs)进行采样,测试了进出水COD、NH3-N、TN、TP和SS,评价了出水稳定性及稳定达标率,比较研究了2种组合工艺对农村生活污水的处理效果及设计和运行问题。结果表明:A2O+VFCWs的出水稳定达标率高于A2O+HFCWs;A2O+VFCWs的出水水质稳定性在冬季较好,但在夏季较差。A2O+VFCWs组合工艺对COD、NH3-N、TN和TP的平均去除率,在冬季为(82.0±18.5)%、(94.8±8.8)%、(49.3±16.8)%和(50.9±16.8)%,在夏季为(72.5±13.2)%、(80.0±16.9)%、(30.0±17.8)%和(30.7±18.9)%,对污染物去除起主要作用的单元是VFCWs。而A2O+HFCWs组合工艺,对COD、NH3-N、TN和TP的平均去除率在冬季为(59.3±21.4)%、(79.1±19.9)%、(42.3±17.3)%和(25.0±10.2)%,在夏季为(62.2±18.0)%、(58.1±30.8)%、(40.6±20.0)%和(28.9±15.7)%,对污染物去除起主要作用的单元是A2O。A2O+VFCWs的A2O单元对TN和TP的平均去除率,在冬季为(20.7±16.3)%和(15.6±10.2)%,在夏季为(20.4±11.9)%和(12.6±13.9)%,而A2O+HFCWs的A2O单元对TN和TP的平均去除率,在冬季为(33.2±16.3)%和(25.0±10.2)%,在夏季为(31.3±24.1)%和(21.9±17.4)%,2种组合工艺中的A2O单元去除效果均不理想,可能与进水碳氮比太低,且排泥少有关。A2O+VFCWs的 A2O单元对各污染物去除率明显低于A2O+HFCWs,主要原因是有效容积偏小且溶解氧控制不够。A2O+VFCWs的VFCWs单元对COD、NH3-N、TN和TP的平均去除率,在冬季为(58.8±25.4)%、(61.4±24.4)%、(22.7±8.5)%和(27.4±21.2)%,比HFCWs分别高出16.0%、36.9%、1.3%和9.5%,在夏季为(59.9±25.0)%、(71.6±26.5)%、(38.3±32.8)%和(39.2±32.9)%,比HFCWs高出28.8%、52.6%、10.5%和5.0%,这主要得益于VFCWs较低的设计水力负荷和较低的出水口位置。综合上述结果,建议该县级市从结构和运行2方面着手进行提升改造。Abstract: Samples from 28 A2O combined with horizontal flow constructed wetlands (A2O-HFCWs) and 46 A2O combined with vertical flow constructed wetlands (A2O-VFCWs) in Haining County, Jiaxing City were collected, chemical oxygen demand (COD), ammonia nitrogen (NH3-N), total nitrogen (TN), total phosphorus (TP) and suspended solids (SS) in the influent and effluent were determined. Then the stability of effluent quality and compliance rate were evaluated, the comparisons between these two processes on the performance of rural domestic sewage treatment, and the problems of design and operation, were conducted. The results showed that: The compliance rates of A2O-VFCWs were higher than those of A2O-HFCWs.The effluent stability of A2O-VFCWs was good in winter, but poor in summer. The average removal rates of COD, NH3-N, TN and TP by A2O+VFCWs were (82.0±18.5)%, (94.8±8.8)%, (49.3±16.8)%, and (50.9±16.8)% in winter, respectively, while they were (72.5±13.2)%, (80.0±16.9)%, (30.0±17.8)%, and (30.7±18.9) % in summer, respectively. The main unit being responsible for pollutants removal was VFCWs. For A2O+HFCWs, the average removal rates of COD, NH3-N, TN and TP by A2O+VFCWs were (59.3±21.4)%, (79.1±19.9)%, (42.3±17.3)% and (25.0±10.2)% in winter, respectively,, while they were (62.2±18.0)%, (58.1±30.8)%, (40.6±20.0)% and (28.9±15.7)% in summer, respectively. The main unit being responsible for pollutants removal was A2O. The average TN and TP removal rates of A2O unit in A2O+VFCWs were (20.7±16.3)% and (15.6±10.2)% in winter, (20.4±11.9)% and (12.6±13.9)% in summer, respectively, which were significantly lower than those of A2O unit in A2O+HFCWs: (33.2±16.3)% and (25.0±10.2)% in winter, (31.3±24.1)% and (21.9±17.4)% in summer, respectively, The reason was the small effective volume and insufficient dissolved oxygen control. The removal efficiencies of A2O unit in these two combined processes were not ideal, which may be related to the low ratio of carbon to nitrogen and insufficient sludge discharge. The average removal rates of COD, NH3-N, TN and TP of VFCWs unit in A2O+VFCWs were (58.8±25.4)%, (61.4±24.4)%, (22.7±8.5)%, and (27.4±21.2)% in winter, which were 16.0%, 36.9%, 1.3%, and 9.5% higher than those of HFCWs, respectively; they were (59.9±25.0)%, (71.6±26.5)%, (38.3±32.8)%, and (39.2±32.9)% in summer, which were 28.8%, 52.6%, 10.5%, and 5.0% higher than those of HFCWs, respectively. The main reasons were the lower design hydraulic load and lower outlet level of VFCWs. To sum up, the county-level city was suggested to improve the performance of A2O or constructed wetland by upgrading structure of the units and optimizing operation strategies.
-
表 1 2种组合工艺的冬季和夏季水质
Table 1. Water quality of the two combined processes in winter and summer
季节 工艺类型 抽检设施/座 沿程水质 NH3-N/(mg∙L−1) TN/(mg∙L−1) TP/(mg∙L−1) COD/(mg∙L−1) SS/(mg∙L−1) 冬季 A2O+HFCWs 16 A2O进水 28.4±14.1 38.4±19.1 2.7±1.2 40.7±29.6 15.4±15.0 A2O出水 13.6±12.2 26.0±12.8 2.3±1.1 30.2±26.3 16.6±23.2 湿地出水 6.8±7.5 20.4±9.1 2.0±0.9 16.1±9.2 9.6±19.0 A2O+VFCWs 8 A2O进水 36.2±27.1 46.6±28.8 3.7±2.8 45.8±44.2 107.4±189.7 A2O出水 31.4±26.9 40.0±24.2 3.2±2.2 44.1±41.5 16.1±24.0 湿地出水 4.0±3.1 33.1±21.4 1.9±0.9 12.8±2.9 13.1±17.3 夏季 A2O+HFCWs 29 A2O进水 45.2±17.3 53.4±18.6 5.1±1.8 144.8±64.3 94.0±44.4 A2O出水 25.1±20.6 41.3±20.0 4.3±1.6 64.7133.8 33.4±16.0 湿地出水 24.0±19.0 35.7±19.3 3.8±1.5 53.0±29.5 27.0±19.4 A2O+VFCWs 21 A2O进水 38.2±27.3 46.6±27.0 4.9±2.9 102.8±84.2 68.9±61.2 A2O出水 32.1±26.2 40.9±36.4 4.3±2.7 99.5±132.9 49.3±43.5 湿地出水 11.3±17.0 36.4±21.5 3.9±2.5 28.0±24.3 17.8±17.6 表 2 2种组合工艺出水在冬夏两季的稳定达标率与偏差系数
Table 2. Stable compliance rates and deviation coefficients of effluents from the two combined processes in winter and summer
季节 工艺名称 稳定达标率/% 偏差系数 NH3-N TP COD SS NH3-N TP COD SS 冬季 A2O+VFCWs 99.9 88.7 100 93.8 −1.02 −1.21 −0.82 −0.77 A2O+HFCWs 97.2 86.5 100 90.8 −1.01 −1.48 −0.75 −0.77 夏季 A2O+VFCWs 89.8 44.5 98.1 85.3 −1.15 1.13 −1.09 −1.12 A2O+HFCWs 66.3 32.3 93.1 58.0 0.28 1.16 −1.27 0.37 -
[1] DRIZO A, FROST C A, GRACE J, et al. Physico-chemical screening of phosphate-removing substrates for use in constructed wetland systems[J]. Water Research, 1999, 33(17): 3595-3602. doi: 10.1016/S0043-1354(99)00082-2 [2] 桂双林, 王顺发, 吴永明, 等. 生物滤塔-人工湿地组合工艺对农村生活污水净化效果研究[J]. 环境工程学报, 2011, 5(10): 2312-2314. [3] 黄锦楼, 陈琴, 许连煌. 人工湿地在应用中存在的问题及解决措施[J]. 环境科学, 2013, 34(1): 401-408. [4] 匡武, 王翔宇, 周其胤, 等. 提高低C/N值农村生活污水中TN的去除效果[J]. 环境工程学报, 2015, 9(9): 4252-4258. doi: 10.12030/j.cjee.20150926 [5] 孟红, 李传松, 周健, 等. C/N值对序批式深床反硝化人工湿地脱氮的影响[J]. 中国给水排水, 2016, 32(13): 1-5. [6] YU G, PENG H, FU Y, et al. Enhanced nitrogen removal of low c/n wastewater in constructed wetlands with co-immobilizing solid carbon source and denitrifying bacteria[J]. Bioresource Technology, 2019, 280: 337-344. doi: 10.1016/j.biortech.2019.02.043 [7] 王宁宁, 赵阳国, 孙文丽, 等. 溶解氧含量对人工湿地去除污染物效果的影响[J]. 中国海洋大学学报(自然科学版), 2018, 48(6): 24-30. [8] 国家环境保护总局. 水和废水监测分析方法[M]. 4版. 北京: 中国环境科学出版社, 2002. [9] NIKU S, SCHROEDER E D, SAMANIEGO F J. Performance of activated sludge processes and reliability-based design[J]. Journal (Water Pollution Control Federation), 1979, 51(12): 2841-2857. [10] 苏魏, 杜鹏飞, 陈吉宁. 城市污水处理厂运行稳定性评估方法初探[J]. 环境污染治理技术与设备, 2005, 6(8): 84-87. [11] 何雪梅, 吴义锋. 统计模型在污水处理厂试运行评价中的应用[J]. 工程与建设, 2006, 20(5): 521-523. doi: 10.3969/j.issn.1673-5781.2006.05.047 [12] 安芳娇, 赵智超, 黄利, 等. HRT对厌氧氨氧化协同异养反硝化脱氮的影响[J]. 环境科学, 2018, 39(9): 4302-4309. [13] 周慧芳, 刘正辉, 李德豪, 等. 一体化OCO工艺脱氮除磷效果优化的ORP调控策略[J]. 环境科学与技术, 2017, 40(6): 61-65. [14] 侯京卫, 范彬, 曲波, 等. 农村生活污水排放特征研究述评[J]. 安徽农业科学, 2012, 40(2): 964-967. doi: 10.3969/j.issn.0517-6611.2012.02.129 [15] 宋小燕, 刘锐, 董宝刚, 等. 低温条件IASBR处理养猪沼液脱氮性能研究[J]. 环境科学学报, 2017, 37(3): 1013-1020. [16] 王亚宜, 彭永臻, 王淑莹, 等. 碳源和硝态氮浓度对反硝化聚磷的影响及ORP的变化规律[J]. 环境科学, 2004, 25(4): 54-58. doi: 10.3321/j.issn:0250-3301.2004.04.011 [17] ÁVILA C, MATAMOROS V, REYES-CONTRERAS C, et al. Attenuation of emerging organic contaminants in a hybrid constructed wetland system under different hydraulic loading rates and their associated toxicological effects in wastewater[J]. Science of the Total Environment, 2014, 470-47: 1272-1280. [18] DECEZARO S T, WOLFF D B, PELISSARI C, et al. Influence of hydraulic loading rate and recirculation on oxygen transfer in a vertical flow constructed wetland[J]. Science of the Total Environment, 2019, 668: 988-995. doi: 10.1016/j.scitotenv.2019.03.057 [19] 王鹏, 董仁杰, 吴树彪, 等. 水力负荷对潜流湿地净化效果和氧环境的影响[J]. 水处理技术, 2009, 35(12): 48-52. [20] LU S, GAO X, WU P, et al. Assessment of the treatment of domestic sewage by a vertical-flow artificial wetland at different operating water levels[J]. Journal of Cleaner Production, 2019, 208: 649-655. doi: 10.1016/j.jclepro.2018.10.111 [21] 刘国臣, 王福浩, 梁家成, 等. 不同水位垂直流人工湿地中植物及微生物特征[J]. 中国海洋大学学报(自然科学版), 2019, 49(2): 98-105. [22] 马剑敏, 张永静, 马顷, 等. 曝气对两种人工湿地污水净化效果的影响[J]. 环境工程学报, 2011, 5(2): 315-321. [23] 赵军, 薛宇, 李晓东, 等. 复合人工湿地去除生活污水中的有机物和氮[J]. 环境工程学报, 2013, 7(1): 26-30. [24] 王凯军, 陈世朋, 董娜, 等. 微型复合垂直流人工湿地处理农村灰水试验研究[J]. 中国给水排水, 2008, 24(17): 40-43. doi: 10.3321/j.issn:1000-4602.2008.17.011 [25] 龙翠芬, 郑离妮, 唐晓丹, 等. 农户庭院型人工湿地对农村生活污水的净化效果[J]. 环境工程学报, 2012, 6(8): 2560-2564. [26] 丁怡, 王玮, 王宇晖, 等. 不同进水碳氮比对水平潜流人工湿地脱氮效果的影响[J]. 工业水处理, 2014, 34(10): 29-32. doi: 10.11894/1005-829x.2014.34(10).029 [27] WANG R, ZHAO X, LIU H, et al. Elucidating the impact of influent pollutant loadings on pollutants removal in agricultural waste-based constructed wetlands treating low C/N wastewater[J]. Bioresource Technology, 2019, 273: 529-537. doi: 10.1016/j.biortech.2018.11.044 [28] 夏艳阳, 崔理华, 黄小龙. 污水碳源对复合垂直流-水平流人工湿地脱氮效果的影响[J]. 环境工程学报, 2017, 11(1): 638-644. doi: 10.12030/j.cjee.201509223 [29] 李海波, 杨瑞崧, 李晓东, 等. 水淬渣人工湿地强化除磷作用研究[J]. 环境科学, 2009, 30(8): 2302-2308. doi: 10.3321/j.issn:0250-3301.2009.08.021 [30] 李林锋, 年跃刚, 蒋高明. 植物吸收在人工湿地脱氮除磷中的贡献[J]. 环境科学研究, 2009, 22(3): 337-342. [31] 汤显强, 李金中, 刘学功, 等. 人工湿地填料磷去除效果的影响因素分析[J]. 农业环境科学学报, 2008, 27(2): 748-752. doi: 10.3321/j.issn:1672-2043.2008.02.063 [32] 袁东海, 景丽洁, 高士祥, 等. 几种人工湿地基质净化磷素污染性能的分析[J]. 环境科学, 2005, 26(1): 51-55. doi: 10.3321/j.issn:0250-3301.2005.01.012 [33] ZHENG X, JIN M, ZHOU X, et al. Enhanced removal mechanism of iron carbon micro-electrolysis constructed wetland on C, N, and P in salty permitted effluent of wastewater treatment plant[J]. Science of the Total Environment, 2019, 649: 21-30. doi: 10.1016/j.scitotenv.2018.08.195 [34] GE Z, WEI D, ZHANG J, et al. Natural pyrite to enhance simultaneous long-term nitrogen and phosphorus removal in constructed wetland: Three years of pilot study[J]. Water Research, 2019, 148: 153-161. doi: 10.1016/j.watres.2018.10.037