Development of a horizontal subsurface flow modular constructed wetland for urban runoff treatment

Constructed wetlands (CWs) are well recognized as having low construction and maintenance cost and low energy requirement. However, CW design has been mainly based on rule-of-thumb approaches. In this study, the efficiency of a modular horizontal subsurface flow (HSSF) CW using four different design schemes was investigated. Based on the results, the four systems have attained more than 90% removal of total suspended solids and more than 50% removal efficiency for total phosphorus, PO(4)-P and Zn. The planted system achieved higher pollutant removal rates than the unplanted system. In terms of media, bottom ash was more effective than woodchip in reducing the pollutants. Considering the flow length, optimum removal efficiency was achieved after passing the sedimentation tank and vertical media layer; with respect to depth, more pollutants were removed in the upper sand layer than in the lower gravel layer. This study recommended a surface area of 0.25 to 0.8% of catchment area for planted CW and 0.26 to 0.9% for unplanted CW using the 7.5 to 10 mm design rainfall.     

Influence of design, physico-chemical and environmental parameters on pharmaceuticals and fragrances removal by constructed wetlands

The ability of several mesocosm-scale and full-scale constructed wetlands (CWs) to remove pharmaceuticals and personal care products (PPCPs) from urban wastewater was assessed. The results of three previous works were considered as a whole to find common patterns in PPCP removal. The experiment took place outdoors under winter and summer conditions. The mesocosm-scale CWs differed in some design parameters, namely the presence of plants, the vegetal species chosen (Typha angustifolia versus Phragmites australis), the flow configuration (surface flow versus subsurface flow), the primary treatment (sedimentation tank versus HUSB), the feeding regime (batch flow versus continuous saturation) and the presence of gravel bed. The full-scale CWs consisted of a combination of various subsystems (ponds, surface flow CWs and subsurface flow CWs). The studied PPCPs were ketoprofen, naproxen, ibuprofen, diclofenac, salicylic acid, carbamazepine, caffeine, methyl dihydrojasmonate, galaxolide and tonalide. The performance of the evaluated treatment systems was compound dependent and varied as a function of the CW-configuration. In addition, PPCP removal efficiencies were lower during winter. The presence of plants favoured naproxen, ibuprofen, diclofenac, salicylic acid, caffeine, methyl dihydrojasmonate, galaxolide and tonalide removal. Significant positive correlations were observed between the removal of most PPCPs and temperature or redox potential. Accordingly, microbiological pathways appear to be the most likely degradation route for the target PPCPs in the CWs studied.     

Influence of surface layer on hydrology and biology of gravel bed vertical flow constructed wetlands.

In France, gravel vertical flow constructed wetlands (gVFCWs) were adapted to treat raw wastewater, which led to important accumulations of matter in filters (organic and mineral). To prevent clogging, large gravel sizes were employed (O 2-6 mm). The aim of this paper was to present the influences of matter accumulation on the hydraulic and biological behaviour of the system. A one-year survey of accumulated matter content and potential respiration activities was completed in three gVFCWs (operating for 3, 4 and 8 years). Cores were sampled into filters. Results showed a vertical stratification of accumulated matter and respiration rates. Dry accumulated matter quantities ranged from 20 kg m(-2) (3 and 4 years operating) to 80 kg m(-2) in the oldest plant (8 years). Potential respiration was larger in the oldest plant (75g O2m(-2)h(-1)) than in the most recent one (15g O2m(-2)h(-1)). Accumulated matter seemed to play a role both on the water retention (enhancing initial percolation time by 5 times) and biological profile (enhancing microfauna's diversity). Contrary to what is generally proposed in the literature, accumulated matter in French gVFCWs seemed to provide better treatment efficiency without leading to surface clogging compared to systems using sand.     

土石坝沥青混凝土心墙酸性砂砾石料的适用性研究

以双桥土石坝沥青混凝土心墙为例,系统地进行了酸性砂砾石料的沥青混凝土配合比试验,包括了添加和不添加抗剥落剂的水稳定及拉伸、抗压、弯曲、渗透和三轴性能对比试验。经系统地进行配合比和酸性砂砾石料适用性试验研究,推荐该工程心墙的沥青混凝土配合比为粗骨料采用50%破碎砂砾石料和50%天然砂砾石料,细骨料采用50%破碎砂砾石料和50%天然河砂,水泥用作填料又兼做提高沥青与骨料黏附力的措施。结果表明,添加与不添加抗剥落剂的酸性砂砾石料沥青混凝土的性能没有明显差别。     

堵塞对湿地内水流流态及污水处理效果的影响

通过在污水中加入氯化钠示踪剂,研究人工湿地及其对照系统内水力停留时间的分布(HRTD),探讨潜流人工湿地和垂直流人工湿地中植物在堵塞前后对水流流态的影响,探讨堵塞对上述两种人工湿地水流流态的影响。结果表明:对于潜流人工湿地(SFCW),堵塞前湿地植物缩短了水力停留时间(HRT),堵塞后延长了HRT;对于垂直流人工湿地(VFCW),堵塞前湿地植物对水流流态无明显影响,堵塞后延长了湿地内的HRT。堵塞对湿地内水流流态影响明显,潜流和垂直流湿地由于堵塞其HRT分别延长了12.3%,22.6%。堵塞后湿地对污水的净化能力都要强于堵塞前,但是湿地的污水处理量减小,堵塞严重时湿地丧失其污水净化功能。     

天然砾石骨料对心墙沥青混凝土力学性能影响分析

为了探明天然砾石与人工破碎岩石作为粗骨料对心墙沥青混凝土性能的影响。在相同的基础配合比条件下,以两种不同的矿料配制沥青混凝土试件进行试验,进行了马歇尔稳定度、小梁弯曲及静三轴试验。试验结果表明:天然砾石骨料的抗变形能力优于人工破碎岩石,力学性能差别不明显。因此,天然砾石骨料可以在心墙沥青混凝土中直接应用。     

Slag columns for upgrading phosphorus removal from constructed wetland effluents.

The current best option to upgrade constructed wetlands (CWs) for phosphorus (P) retention, in terms of efficiency, cost and simplicity, consists in using media having a strong P affinity. The media can be used either in the planted beds or in a filtration system downstream of the beds. The use of slag filters was shown to be efficient for removing P from wastewater as it represented a slow release source of calcium and hydroxide, favouring the formation of hydroxyapatite. Our study aimed at maximising the P retention capacity of slag filters located at the outlet of CWs since electric arc furnace slag has been shown to inhibit the growth of macrophytes when used in the filtration matrix. Bench-scale columns (Vtot = 6.2 L) filled with various combinations of filter media (slag, granite, limestone) of different sizes (2-5, 5-10, 10-20 mm) were fed on-site during four months with a CW effluent (in mg/L: 30 COD, 30 TSS, 10 Pt). Results showed that the best media combination enabling the maximum o-PO4 retention (more than 80% removal without clogging) consisted in a series of a ternary mix column (slag 5-10 mm, granite 2-5 mm, limestone 5-10 mm) followed by a slag column (slag 5-10 mm). Pilot scale columns (Vtot = 300 L), filled with the best media combination, were installed at the outlet of a 28 m2 CW. These columns showed more than 75% removal efficiency during one year and were designed to be easily replaced each year.     

级配不连续碎砾石粗细颗粒区分粒径比较分析

粗细颗粒区分粒径是级配不连续碎砾石细粒含量判别法判定渗透变形类型重要指标 ,目前通常使用的有定值法的2mm和颗粒级配曲线中平缓段最小粒径(平均粒径),为进一步验证这2个典型方法和量值的符合性、适宜性 ,统计了26个工程121个试样的渗透变形试验结果进行比较.结果表明 :2种方法和量值的渗透变形类型判断结果与试验结果符合率较高 ,分别为85 .5% 和84 .6% ,均可作为粗细颗粒区分粒径 ,但若和级配连续碎砾石渗透变形类型判断综合考虑 ,推荐2mm作为级配不连续碎砾石粗细颗粒区分粒径.     

Hydraulic behaviour and removal efficiencies of two H-SSF constructed wetlands for wastewater reuse with different operational life

This work focuses on the performance evaluation of two full-scale horizontal suburface flow constructed wetlands (H-SSF CWs) working in parallel, which have an almost equal surface area (about 2,000 m2) but with different operational lives: 8 and 3 years. Both H-SSF CWs, located in Southern Italy (Sicily), are used for tertiary treatment of the effluent of a conventional wastewater treatment plant. This study evaluates and compares H-SSF CW efficiency both in terms of water quality improvement (removal percentage) and achievement of Italian wastewater discharge and irrigation reuse limits. The mean removal percentage, for the overall operational life, of TSS, COD and BOD (80%, 63%, 58% obtained for H-SSF1 and 67%, 38%, 41% for H-SSF2), confirm the high reliability of CWs for wastewater treatment. However, despite the satisfactory removal of microbial indicators (the mean E. coli removal was up to 2.5 log unit for both beds), CWs didn't achieve the Italian limits for wastewater reuse. Information on hydraulic properties of the CWs were extracted from breakthrough curves of a non-reactive tracer (NaCl). By comparing the nominal (tau(n)) and actual residence time (tau), hydraulic behaviour was revealed.     

南水北调中线工程漕河段岭东料场骨料碱活性研究

详细介绍了南水北调中线京石段应急供水工程漕河段岭东料场天然砂砾石骨料碱-硅酸反应活性的研究结果.岩相法检测显示卵石样品主要由石英、钠长石及白云石和少量云母类矿物组成,砂样品主要由石英、钠长石等矿物组成,重要的碱活性物质玉髓主要出现在白云岩裂隙和硅质灰岩的基质中;"砂浆棒快速法"检测结果显示砂、小石、中石样品14 d的膨胀率均不超过0.1%,为非碱-硅酸反应活性骨料,但卵石样品仍具有一定的碱活性,且后期膨胀率一直持续增长.综合"岩相法"和"砂浆棒快速法"的试验结果,认为漕河岭东料场的砂砾石骨料在工程中使用时必须采取有效的抑制措施.碱-硅酸反应抑制试验结果表明在混凝土中掺加20%～25%的粉煤灰抑制碱-硅酸反应是有效的.岭东料场的白云岩为不具有潜在碱-碳酸盐反应活性骨料.研究结果为漕河工程的料场选定及混凝土的配制提供了技术支持,为保证工程质量奠定了基础.     

Optimal maintenance of constructed wetlands using an environmental decision support system.

Constructed wetlands (CWs) are artificial wastewater treatment systems appropriate for small communities because of their affordability, operability and reliability. These qualities are true whenever CWs are designed and constructed properly, and as long as the necessary operation and maintenance procedures are carried out correctly. Experience shows that the operation and maintenance procedures, and the frequencies with which these procedures are carried out, differ from one CW to another. With this in mind, and along with a projected increase in CWs in Catalonia, the Catalan Water Agency (Agència Catalana de l'Aigua) has developed an Environmental Decision Support System (EDSS) which proposes guidelines for monitoring and maintenance, according to the characteristics of each CW. This EDSS was developed following a methodology based on five steps: (i) problem analysis; (ii) collecting data and knowledge acquisition; (iii) model selection; (iv) model implementation and (v) validation. This paper describes the methodology followed to build the decision support system and presents some examples of the information provided by this EDSS.     

新型生态防洪护面连锁块水力特性的试验研究

通过试验模拟研究了预制混凝土连锁块在洪水期水流中的受力状况、整体稳定性、孔内填充碎石的作用及连锁块阻力参数，综合分析了连锁块结构的力学稳定性和抗冲性；给出了碎石填充的要求及安全度。试验表明：新型生态防洪工程护面连锁块与传统堤防工程的护面形式相比，具有抗高切应力、稳定、透水性好、改善河道生态环境等优点，而且施工方便快捷。     

海岛结构环氧砂浆抗冲磨性能试验研究

以往研究表明，采用海岛结构环氧增韧技术可以提高环氧砂浆的断裂韧性和抗冲磨强度。本文通过正交试验，对不同增韧剂掺量和不同砂胶比环氧砂浆的力学强度和抗冲磨强度进行了试验研究。试验结果表明，当增韧剂掺量小于80％时，环氧砂浆的力学强度和抗冲磨强度均随增韧剂掺量的增大有较大提高；当砂胶比大于700％时，环氧砂浆的力学强度和抗冲磨强度均明显下降。试验还表明，环氧砂浆的抗拉强度和抗冲磨强度正相关。     

Filter media for stormwater treatment and recycling: the influence of hydraulic properties of flow on pollutant removal.

Improved urban water management in Australia is of national importance. Water resources are stretched and urban runoff is a recognized leading cause of degradation of urban waterways. Stormwater recycling is an option that can contribute to easing these problems. Biofilters are effective structural stormwater pollution control measures with the potential for integration into stormwater treatment and recycling systems. However, premature clogging of biofilters is a major problem, with resulting decreased infiltration capacity (and hence the volume of stormwater the system can detain) and increased detention time. This paper presents preliminary findings with respect to the effect of clogging on pollutant removal efficiency in conventional stormwater filter media. A one-dimensional laboratory rig was used to investigate the impact of clogging on pollutant removal efficiency in a conventional biofiltration filter media (gravel over sand). Both the individual gravel layer and the overall multi-filter were highly efficient at removing suspended solids and particulate-associated pollutants. This removal efficiency was consistent, even as the filters became clogged. Removal of dissolved nutrients was more variable, with little reduction in concentrations overall. Although preliminary, these results challenge the concept that increased detention time improves the treatment performance of stormwater filtration systems.     

PVA纤维掺和胶凝砂砾石材料的力学性能研究

随着胶凝砂砾石坝(CSG Dam)的应用,对CSG材料的力学性能研究亦有所增加。为改善CSG材料的强度及破坏变形率等力学性能,选取天然砂砾石为原材料,采取等骨料级配及砂率,通过掺和纤维及选用不同胶凝材料用量、龄期等参数以正交试验方法研究设计配合比,并通过试验及回归方程分析CSG材料力学性能。结果表明:CSG材料掺和PVA纤维能较好地改善原材料的延性,且将试件破坏形态由脆性破坏转化为延性破坏,特别是掺入3%PVA纤维时,试件的抗压及劈拉强度均达到最大值。研究成果可为CSG今后在坝体材料上的推广运用提供科学依据。     

On-site infiltration of road runoff using pervious pavements with subjacent infiltration trenches as source control strategy

The focus in this work was on subsoil infiltration of stormwater from parking lots. With regard to operation, reduced infiltration performance due to clogging and pollutants in seepage, which may contribute to contaminate groundwater, are of interest. The experimental investigation covered a pervious pavement with a subjacent infiltration trench draining an impervious area of 2 ha. In order to consider seasonal effects on the infiltration performance, the hydraulic conductivity was measured tri-monthly during monitoring with a mobile sprinkling unit. To assess natural deposits jointing, road bed, gravel of infiltration trenches and subsoil were analysed prior to commencement of monitoring for heavy metals, polycyclic aromatic and mineral oil type hydrocarbons. Furthermore, from 22 storm events, water samples of rainfall, surface runoff, seepage and ground water were analysed with regard to the above mentioned pollutants. The study showed that the material used for the joints had a major impact on the initial as well as the final infiltration rates. Due to its poor hydraulic conductivity, limestone gravel should not be used as jointing. Furthermore, it is recommended that materials for the infiltration facilities are ensured free of any contaminants prior to construction. Polycyclic aromatic and mineral oil type hydrocarbons were, with the exception of surface runoff, below detection limits. Heavy metal concentrations of groundwater were with the exception of lead (because of high background concentrations), below the permissible limits.     

水平潜流人工湿地脱氮除磷研究进展

总结了水平潜流人工湿地的脱氮除磷机理,分析了进水水质、植物、基质、温度和水力停留时间这5种影响处理效果的主要因素,从不同角度论述了提高脱氮除磷效果所采取的措施,并探讨了水平潜流人工湿地存在的局限性和发展趋势。     

采用天然砾石骨料的浇筑式沥青混凝土配合比设计及性能研究

在进行沥青混凝土配合比设计时,为保证骨料与沥青的粘附性及心墙的安全可靠性,沥青混凝土骨料多采用碱性岩石破碎的人工碎石,当采用天然砾石骨料配置沥青混凝土时,材料的配合比及水稳定性越来越受到工程界的关注。本文采用广泛分布于新疆的天然砂砾料作为原材料,进行沥青混凝土配合比设计。提出当丁朴荣公式中沥青含量为8.3%～8.6%、填料用量为10%～14%、级配指数0.33或0.34时,采用天然砂砾料配置的沥青混凝土仍具有良好的流动性能,同时也符合沥青混凝土的水稳定性要求。     

Efficacy of constructed wetlands to mitigate non-point source pollution from irrigation tailwaters in the San Joaquin Valley, California, USA.

The efficacy of using constructed wetlands (CWs) to sequester organic carbon and nutrients from irrigation tailwaters was studied in the San Joaquin Valley, California. Two CWs were monitored during the 2004 irrigation season, a new CW (W-1) and 10-year-old CW (W-2). Input/output waters from CW were collected weekly and analyzed for a variety of water quality contaminants. Organic carbon, nutrient and sediment retention efficiencies were evaluated from input/output concentrations. Characteristics of sediment were examined spatially at W-2. Results indicate that W-2 was more efficient at contaminant removal. Average particulate organic carbon retention, was 70+/-13% (mean +/-standard deviation) in W-2 and 48+/-32% in W-1. Chlorophyll-a, a measure of algal biomass, was higher at W-1, especially in input waters. Initially, output concentration of chlorophyll-a increased 15-fold in W-2, however over time, as emergent vegetation established, chlorophyll-a decreased to 35% of input levels. Average total N removal efficiency was 45 +/-18% for W-2 compared to 22 +/-32% in W-1. Total P removal efficiency was 72+/-14% at W-2 compared to 18+/-26% at W-1. CWs were most effective at removing total suspended solids, 84 +/-15% and 97+/-2% for W-1 and W-2, respectively. Results demonstrate that CWs are effective at capturing POC, sediment and nutrients from irrigation tailwaters.     

人工湿地处理四环素类抗生素废水时有机碳源的影响

研究了以葡萄糖和乙酸钠为碳源的条件下,垂直流人工湿地对四环素(TC)、土霉素(OTC)和金霉素(CTC)等3种四环素类抗生素(TCs)的去除效果。结果表明,在试验条件下,乙酸钠与葡萄糖两种碳源均能有效促进人工湿地系统对3种TCs的去除;在相同碳源条件下COD质量浓度越高,TCs的去除率越高,当COD质量浓度大于400mg/L时,对3种TCs的去除率均达到90%以上;垂直流人工湿地对TCs的去除过程包括2个阶段:前2 h为湿地基质吸附作用下的快速去除阶段,2~24 h为缓慢去除阶段。乙酸钠与葡萄糖两种碳源对TCs去除率的提高,主要发生在2h之后的第二个阶段,分析认为发生了微生物共代谢作用,促进了湿地系统对基质吸附富集之后的TCs的进一步降解。