Impact of forced aeration on vertical flow treatment wetland performances for combined sewer overflow

IF 3.9 2区环境科学与生态学 Q1 ECOLOGY Ecological Engineering Pub Date : 2024-08-14 DOI:10.1016/j.ecoleng.2024.107359

Daniella Portela , Katharina Tondera , Stéphane Troesch , Pascal Molle

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Abstract

Combined Sewer Overflow Treatment Wetlands (CSO wetlands) are designed to remove pollutants under stochastic events with variable hydraulic loads. Upgrading them with forced aeration promises to increase the effectiveness and resilience of the treatment. We have tested two vertical CSO wetlands with forced aeration (CSOa and CSOb) to understand the effects of aeration on CSO treatment. Both filter beds have 0.95 and 0.80 m of saturated layer. CSOa uses gravel as top filtering layer, while CSOb utilizes sand and an additional transition layer. Tracer tests were conducted in both filters with and without aeration to assess the impact of aeration on hydraulic performance. CSOa operated with four different aeration conditions, with the optimal condition tested on both filters for comparison. Samples were taken for analysis of global parameters and the redox potential was monitored online. In the tracer test, CSOa allowed to observe the mixing impact of aeration, which avoids any preferential path when influent entered the filter. The addition of a sand layer at the surface (CSOb) allows for a more even distribution of water on the top, which limits preferential flows when aeration is off. In both filters, the results showed that aeration increased the residence time and mixing degree (NTIS <3). Testing different aeration strategies revealed the dependence of dissolved pollutant removal on oxygen supply. In CSOa, the median outlet concentration varied from 23 to 6.4 mg.L⁻¹ in TSS, 153 to 32 mg.L⁻¹ total COD (CODt), 124 to 20 mg.L⁻¹ soluble COD (CODs) and 5 to 2.5 mg.L⁻¹ NH₄-N according to aeration strategy. The lower outlet concentrations were always under the highest aeration condition. Under the optimal condition (75 min on/15 min off), median removal of CSOa was 97% TSS, 85% CODt, 78% CODs and 75% NH₄-N. Besides COD and TSS, outlet concentration and removal efficiency did not significantly differ between CSOa and CSOb. Pollutant removal demonstrated a linear correlation with organic surface load. Overall, forced aeration in CSO-TW distinctly affected filter dynamics and improved its performance.

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强制曝气对合流污水溢流垂直流处理湿地性能的影响

合流制污水溢流处理湿地（CSO 湿地）的设计目的是在水力负荷可变的随机事件下清除污染物。采用强制曝气技术对其进行升级，有望提高处理效果和复原能力。我们测试了两个采用强制曝气的垂直 CSO 湿地（CSOa 和 CSOb），以了解曝气对 CSO 处理的影响。两个滤床的饱和层分别为 0.95 米和 0.80 米。CSOa 使用砾石作为顶部过滤层，而 CSOb 则使用沙子和额外的过渡层。为了评估曝气对水力性能的影响，在两个过滤器中分别进行了曝气和不曝气的示踪试验。CSOa 在四种不同的曝气条件下运行，最佳曝气条件在两个过滤器上都进行了测试，以进行比较。取样分析总体参数，并在线监测氧化还原电位。在示踪试验中，CSOa 可以观察到曝气对混合的影响，避免了进水进入过滤器时的任何优先路径。在表面添加砂层（CSOb）可使顶部的水分布更均匀，从而在关闭曝气时限制优先流。结果表明，在这两个过滤器中，曝气都增加了停留时间和混合程度（NTIS <3）。对不同曝气策略的测试表明，溶解污染物的去除取决于氧气供应。在 CSOa 中，根据曝气策略的不同，总悬浮固体（TSS）、总化学需氧量（CODt）、可溶性化学需氧量（CODs）和 NH4-N 的中位出口浓度分别为 23 至 6.4 毫克/升、153 至 32 毫克/升、124 至 20 毫克/升和 5 至 2.5 毫克/升。在最高曝气条件下，出口浓度总是较低。在最佳条件下（开 75 分钟/关 15 分钟），CSOa 的去除率中值为 97%的总悬浮固体、85%的 CODt、78%的 CODs 和 75%的 NH4-N。除了 COD 和 TSS 外，CSOa 和 CSOb 的出口浓度和去除效率也没有显著差异。污染物去除率与有机表面负荷呈线性相关。总之，CSO-TW 中的强制曝气明显影响了过滤器的动态，并改善了其性能。

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来源期刊

Ecological Engineering 环境科学-工程：环境

CiteScore

8.00

自引率

5.30%

发文量

293

审稿时长

57 days

期刊介绍： Ecological engineering has been defined as the design of ecosystems for the mutual benefit of humans and nature. The journal is meant for ecologists who, because of their research interests or occupation, are involved in designing, monitoring, or restoring ecosystems, and can serve as a bridge between ecologists and engineers. Specific topics covered in the journal include: habitat reconstruction; ecotechnology; synthetic ecology; bioengineering; restoration ecology; ecology conservation; ecosystem rehabilitation; stream and river restoration; reclamation ecology; non-renewable resource conservation. Descriptions of specific applications of ecological engineering are acceptable only when situated within context of adding novelty to current research and emphasizing ecosystem restoration. We do not accept purely descriptive reports on ecosystem structures (such as vegetation surveys), purely physical assessment of materials that can be used for ecological restoration, small-model studies carried out in the laboratory or greenhouse with artificial (waste)water or crop studies, or case studies on conventional wastewater treatment and eutrophication that do not offer an ecosystem restoration approach within the paper.