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我国城镇污水处理厂出水执行《城镇污水处理厂污染物排放标准》(GB 18918-2002)一级A标准,出水中有机物、氮磷含量不仅高于地表水环境标准Ⅴ类水,也远高于水体富营养化氮磷标准。污水厂排放入河水质呈现微污染状态,长此以往造成河流水体向富营养化发展[1-2]。原位生态净化技术是在微污染水源地(如水库、湖泊、河流等地)就地采取措施处理水体污染物,不需要将微污染水进行转移,达到净化水质的目的,具有省时、高效、对环境影响小的优点[3-4]。常见原位生态净化技术有水生植物修复、人工浮岛、微生物修复和近自然河岸带等,其中人工浮岛利用挺水植物去除水体中污染物且适用范围广,但由于植物自身和季节变化的影响,其对污染物去除能力有限;生态河床由基质生物膜与水生植物构成,可有效去除水体中氮、磷等物质,提升河流自净能力,但温度变化对其净化能力影响较大;生态滤坝具有良好的过滤性能,能够有效去除SS,对COD等污染物去除效果不明显,易受渗流量变化影响[5-8]。
单一原位生态净化技术去污能力有限,并不能满足河流水质的净化要求,而通过不同类型技术组合应用,能够有效改善水质,提高净化能力[9-10]。FANG等[11]通过底泥疏浚措施,并组合水生植物修复带、人工浮岛等技术,构建集成生态工程净化富营养化河水,监测结果表明,COD、TP和TN去除量从40.32、2.49和33.69 t·a−1提升至74.36、3.75和58.28 t·a−1,明显改善河流水质,并增强河流去除污染物能力。SZKLAREK等[12]选择物理沉淀、石灰石吸附和水生植物,设计沉淀区、生化反应区和生物过滤区,构建沉淀-生物过滤系统,应用于小城市河流雨水净化,运行2个水文年后,该系统对TSS、TP、
${\rm{PO}}_4^{3-} $ 、TN、${\rm{NH}}_4^{+} $ -N、${\rm NO}_3^- $ 和Cl−去除率分别为61.4%、37.3%、30.4%、46.1%、2.8%、44.8%和64%。目前,虽然国内广泛地将原位生态净化技术组合应用于河流治理中,但对于如何在低温条件下提高原位生态组合技术净化效果的研究相对较少。为此,在自然河道中组合人工浮岛、生态河床和生态滤坝3项技术,以污水厂二级出水作为进水水源,在控制实验河段进水流量的基础上,利用基质内电解,增强微生物脱氮效果和植物耐寒生长特性,开展现场实验研究,分析改善措施对冬季原位生态组合技术净化效果的影响,并为冬季河流微污染水体的治理提供参考。
冬季原位生态组合技术改善二级出水净化效果分析
Analysis of improving secondary effluent purification by in situ ecological combination technique in winter
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摘要: 为改善冬季低温条件河流原位生态组合技术对微污染水净化效果,将某硬质纳污河道改造为实验河道。通过进水流量控制、铁炭填料内电解和耐寒植物3种优化措施,考察人工浮岛、生态河床和生态滤坝组合技术对污水处理厂二级出水净化情况。结果表明,在改善措施完成后,组合技术对COD的去除效果由14.3%提高至19%,NH4+-N和TN的去除效果由7.8%和13%提高至15.5%和22.8%,TP去除效果由6.3%提高至12.9%。铁炭内电解增加了脱氮微生物种属和丰度,使微生物活性由0.22 mg·g−1增加至0.3 mg·g−1,硝化/反硝化强度由0.97 mg·(kg·h)−1/2.69 mg·(kg·h)−1增加至1.26 mg·(kg·h)−1/3.11 mg·(kg·h)−1,显著改善组合技术的脱氮效果。此外,沿水流方向布置耐寒挺水植物-浮水植物-沉水植物,进水TP中55%~86.9%的颗粒态磷得到去除。这对提升寒冷地区受污染河流治理效果具有参考价值。Abstract: In order to improve the purification of micro-polluted river water by in-situ ecological combined technique under low temperature conditions in winter, hard sewage river was transformed into an experimental river. The purification of secondary effluent by the combined techniques of artificial floating island, ecological river bed and ecological filter dam was investigated by three optimization measures: influent flow control, iron-carbon filler internal electrolysis and cold-tolerant plants. The results showed that, after the improvement measures were completed, the removal efficiencies of COD, NH4+-N, TN and TP increased from 14.3% to 19%, from 7.8% to 15.5%, from 13% to 22.8%, and from 6.3% to 12.9%, respectively. Iron-carbon internal electrolysis elevated the species and abundance of denitrifying microorganisms, the microbial activity was enhanced from 0.22 mg·g−1 to 0.3 mg·g−1, and the nitrification/denitrification intensity was enhanced from 0.97 mg·(kg·h)−1/2.69 mg·(kg·h)−1 to 1.26 mg·(kg·h)−1/3.11 mg·(kg·h)−1, the denitrification effect of the combined technique was significantly improved accordingly. Besides, along the water flow in the river, cold-tolerant emerged plants-floating plants-submerged plants were configured longitudinally, 55%~86.9% of particulate phosphorus in influent TP was removed. This result has reference value for improving the treatment effects of polluted rivers in cold regions.
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表 1 处理单元参数
Table 1. Parameters of the treatment units
处理单元 位置/m 植物、基质配置 规模尺寸 人工浮岛 10~20 美人蕉、千屈菜、黄菖蒲、羊蹄、水芹菜;沸石、炉渣、缓释碳源净水基质=2∶2∶1,阿科蔓生态基 聚乙烯材质床体,覆盖面积15 m2 生态河床Ⅰ 20~60 粉绿狐尾藻,栽种面积为30 m2,密度为80株·m−2;砾石、缓释碳源净水基质=13∶2,铁炭填料占基质总量1%~5% 长40 m,宽2.5~3 m,面积约110 m2,基质层厚度0.15~0.20 m 生态滤坝Ⅰ 60~80 砾石、缓释碳源净水基质=13∶2 顶宽3.8 m,底宽3 m,坝高0.6 m,坝长2.1 m,上游坡为直角,下游坡度1∶2,面积约6.3 m2 生态河床Ⅱ 80~140 菹草、伊乐藻,栽种面积共50 m2,密度为80株·m−2;砾石、缓释碳源净水基质=13∶2,铁炭填料占基质总量1%~5% 长50 m,宽2~3 m,面积约125 m2,基质层厚度0.15~0.20 m 生态滤坝Ⅱ 140~160 砾石、缓释碳源净水基质=13∶2 顶宽3.3 m,底宽2.5 m,坝高0.6 m,坝长3.9 m,上游坡度1∶3,下游坡度1∶2,面积约9.75 m2 注:缓释碳源净水基质是由玉米芯、沸石粉、膨润土、硅藻土、水泥材料制成的圆形颗粒,具有释放碳源、加速微生物挂膜的功能;铁炭由铁粒和炭块在较高温度下烧结而成。 表 2 进水水质参数
Table 2. Water quality parameters of the influent
季节 浊度/NTU DO /(mg·L−1) 温度/℃ pH COD /(mg·L−1) ${\rm{NH}}_4^{+} $ -N /(mg·L−1)TP /(mg·L−1) TN /(mg·L−1) 秋季 4.37~44 3.69~6.45 10~18.7 6.5~7.73 24.08~52.67 0.178~5.59 0.526~0.95 21.96~31.54 冬季 5.1~49.75 4.62~7.2 6.27~10 6.8~7.65 27.09~50.09 0.34~7.69 0.304~0.946 20.2~40.56 表 3 实验河道水力参数
Table 3. Hydraulic parameters of the experimental river
月份 进水流量/(m3·d−1) 水深/m HRT/h 流速/(m·s−1) 10—12 2 400 0.5~0.87 2.8 0.016~0.02 1 800 0.4~0.6 6.9 0.006~0.007 2 400 0.4~0.45 11.2 0.003~0.003 9 -
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