潜流人工湿地对畜禽养殖废水的净化效果

为了提高潜流人工湿地对畜禽养殖废水中污染物的去除效果,该试验通过改变湿地内部结构构建了4个潜流人工湿地单元,选用灰砖块和碎石做湿地填料,冬夏季轮作栽培齿果酸模和大狼把草,考察湿地运行期间对厌氧消化后猪场废水的净化效果。结果表明：湿地单元经过80 d的启动,运行稳定,有植物湿地比无植物对照湿地提前10 d左右进入稳定期。运行期间,各湿地单元对废水中氨氮（ammonia nitrogen,NH4+-N）、总氮（total nitrogen, TN）、总磷（total phosphorus,TP）和化学需氧量（chemical oxygen demand,CODCr）的去除率与气温变化均呈现显著线性正相关。在水力停留时间（hydraulic retention time,HRT）为4 d,进水中CODCr、NH4+-N、TN、TP浓度分别为520、110、120、10 mg/L左右时,4个湿地单元对CODCr、TP的去除率分别在60%和70%以上,对NH4+-N和TN的去除率分别为28%～67%和32%～58%,植物对CODCr及TP去除的贡献分别稳定在10%和4%左右,植物对氮的去除效果受气温影响较大,夏季对NH4+-N和TN去除的贡献分别可达13%和12%。与一般潜流人工湿地比较,改进的波形潜流人工湿地对NH4+-N、TN和CODCr的平均去除率提高均在3%以上,对TP去除效果差异不显著（P＞0.05）。该研究可为构建大规模的潜流人工湿地处理畜禽养殖废水提供理论依据和技术支持。     

表面流人工湿地在滇池湖滨区面源污染控制中的应用研究

在滇池湖滨带核心区退塘还湖措施的基础上,通过对福保村湖滨废弃鱼塘改造,建立了表面流人工湿地系统,对该区域内面源污水处理进行了研究。研究表明,系统年削减人湖污染物COD、TN、TP负荷分别达7840、650和20kg,单位面积削减量分别为4704、390和12kg·hm^-2,削减率分别为28．02％、35．93％和4．86％;系统对污水中COD、NH3-N、TN、TP的去除率分别为15．57％、56．76％、40．37％和35．64％,且除COD外,旱季污染物去除率高于雨季;推流曝气可提高系统对污染物的去除效果,使NH3-N、TN、TP的去除率分别提高约39％、23％和21％,而COD去除率变化不明显。该系统为滇池湖滨区退塘还湖和湖滨生态系统重建提供了重要的技术示范,对滇池富营养化防治工作的开展具有重要意义。     

基于流域降雨强度的氮磷输出系数模型改进及应用

为研究曹娥江流域农业非点源氮磷输出负荷量,将流域降雨及不同营养源产生的氮磷"合成"考虑,提出了产污系数以表征降雨产汇流过程氮磷输出强度,改进了输出系数模型,并探索发现流域年降雨强度与氮磷产污系数之间呈指数正相关,由此构建了基于年降雨强度的农业非点源氮磷输出负荷模型。利用此模型估算了农业污染源氮磷输出负荷量,显示2005-2010年流域总氮(total nitrogen,TN)年输出总量为5456.60~12268.38 t,总磷(total phosphorus,TP)为393.19~820.65 t,年度分布不均,降雨对TN输出总量的贡献率高达54.75%~69.67%。不同农业污染源对TN、TP输出总量的贡献率表明,该流域农业非点源氮磷输出负荷主要来源于人畜,应加强农村生活污水及垃圾、畜禽养殖粪便等治理,进一步控制农田过量施肥,减少耕地氮磷流失。     

Influence of a riparian wetland on nitrate and herbicides exported from an agricultural field

Agrochemicals are a major source of nonpoint pollution. Forested corridors along stream channels (riparian zones) are thought to be potential sites for removal of agricultural contaminants from ground and surface waters. First-order riparian wetlands are reputed to be especially effective at groundwater remediation. The study site is a fairly typical (for eastern Maryland) small, first-order stream in an agricultural watershed. Preferential flow supplies most of the stream water within the riparian headwater wetland. This upstream area also contains the highest average stream N and pesticide loads in the entire first-order riparian system. Zones of active groundwater emergence onto the surface display high concentrations of nitrate throughout the soil profile and in the exfiltrating water, whereas inactive areas (where there is no visible upwelling) show rapid attenuation of nitrate with decreasing depths. Atrazine degradation products appear to penetrate more readily through the most active upwelling zones, and there is a correlation between zones of high nitrate and high atrazine metabolite levels. Deethylatrazine/atrazine ratios (DAR) seem to indicate that stream flow is dominated by ground water and that much of the ground water may have reached the stream via preferential flow. Remediative processes appear to be very complex, heterogeneous, and variable in these systems, so additional research is needed before effective formulation and application of riparian zone initiatives and guidelines can be accomplished.     

亚热带典型农业小流域井水水质季节 变化与空间分布特征

井水是亚热带农业区域农民的饮用水源,其水质状况直接影响到当地农民的身体健康。本文选取亚热带典型农业小流域中井水铵态氮(NH4+-N)、硝态氮(NO3--N)、总氮(TN)和总磷(TP)为研究对象,采用地统计学方法,分析其季节变化和空间分布特征。结果表明,研究区农户井水中NH4+-N、NO3--N、TN和TP含量在全年4个季节的平均值分别为0.05~0.10 mg(N)·L-1、3.0~4.9 mg(N)·L-1、3.4~5.1 mg(N)·L-1和0.03~0.17 mg(P)·L-1,超标率分别为2.3%、10.4%、9.5%和7.9%。在季节动态变化上,NH4+-N在全年变化不显著(P0.05),这主要与土壤的吸附有关;而NO3--N、TN和TP均在夏季达到最高,春季最低,并且两个季节之间的变化具有显著性(P0.05),这主要与农业施肥活动和降水条件有关。在空间变异性上,NH4+-N、NO3--N、TN和TP含量在各季节的块金值与基台值的比值都为0,并且各变量在各季节的变程各不相同,说明这4个变量在各季节分别在不同尺度范围内表现出较强的空间自相关性。在空间分布上,NH4+-N、NO3--N、TN和TP含量都具有斑块状分布,而斑块的位置、大小和形状各不相同。NO3--N和TN在全年的空间分布与研究区地形和土地利用方式有关,在东南部和西南部地势较低的水稻种植区含量较高,而在北部地势较高的林地含量较低。而NH4+-N和TP的空间变异系数高于NO3--N和TN,这主要是由于NH4+-N易被土壤吸附,而磷素在土壤中易被固定,迁移较困难,导致NH4+-N和TP在不同地方的含量差异比较大。地形、水文气候条件、土壤类型、土地利用方式和农业施肥等是造成亚热带农业区域井水水质季节动态变化和空间分布格局差异的主要因素。     

利用有机覆盖物处理的人工湿地外排焦化废水研究

[目的]为进一步降低污染物浓度,提高钢铁企业水资源循环利用率。[方法]采用水平潜流人工湿地处理外排焦化废水,通过监测分析进出水中浊度、化学需氧量(COD),总氮(TN)和总磷(TP)含量,探讨冬季人工湿地植物层不添加及添加有机覆盖物对钢铁企业外排焦化废水净化水平的影响。[结果]在低温季节,水力停留时间为5d时,不添加有机覆盖物人工湿地对外排焦化废水浊度,COD,TN和TP的平均去除率分别为68.55%,14.94%,14.20%和71.26%;添加有机覆盖物人工湿地对外排焦化废水浊度、COD,TN和TP的平均去除率分别为72.54%,21.62%,20.50%和71.88%;有机覆盖膜的保温作用使得COD去除率升幅达44.68%,TN去除率升幅达44.45%。[结论]在植物层添加有机覆盖物作为保温材料,可以提高人工湿地在低温条件下的净化效率。     

基于输出系数模型的水库汇水区农业面源污染负荷估算

面源污染是导致环境恶化的主要原因之一,由其所引起的水体富营养化现象,已严重威胁着水环境生态安全。该文以长春市水源地新立城水库汇水区为研究对象,选用输出系数模型对其农业非点源污染负荷进行估算,得到结果如下:1)汇水区内农业非点源污染总氮、总磷负荷量分别为2 822.485、471.123 t/a,且二者空间分布较一致;2)总氮负荷量的贡献率大小顺序为:土地利用畜禽养殖农村人口,总磷的污染负荷贡献率大小为:畜禽养殖土地利用农村人口;3)选取水库2004-2013年水质监测数据计算营养盐输出负荷,与模型估算的输出负荷进行对比,得到模型模拟具有较高精度,系数选取合理可靠,可信度高,可在研究区范围内进行推广,能够为长春市水源地综合整治及水利规划提供了数据支撑及科学依据。     

A comparison of the effects of sediments and standard elutriates on phosphorus kinetics in lakewater

Average rates of atmospheric deposition of total phosphorus (TP) and total nitrogen (TN) to Narrow Lake, located on sedimentary bedrock in the boreal forest of central Alberta, were 20 and 424 mg m^?2 yr^?1, respectively, between 1983–1986. There were no significant differences (P > 0.05) in deposition rates between sites on Narrow Lake, on the lake shore, and on land 18 km away. Deposition of TP, but not TN, followed a distinct pattern during the open-water season; TP was highest just after ice-off (May) and decreased throughout the remainder of the open-water season. Deposition during the winter accounted for only 4 and 12% of the annual TP and TN loads, respectively. Dry fallout contributed 50 and 33% of atmospheric deposition of TP and TN, respectively. In both dry and wet fallout, dissolved P (< 0.45 μm) and organic N were the predominant fractions of TP and TN, respectively. During July 1986, unusually heavy rainfalls caused an increase in TP, but not TN, concentrations in the epilimnion of Narrow Lake. Wet fallout accounted for only 9% of the observed increase of epilimnetic TP; the rest was from surface runoff from the drainage basin. The design of sampling programs to measure atmospheric deposition of nutrients to lakes is discussed.     

漓江流域氮磷排放对水肥管理和下垫面属性变化的响应

为分析漓江流域农业面源污染氮磷排放及其主要影响因素,该研究在多年野外监测试验的基础上,运用SWAT(soil and water assessment tool)模型模拟水肥管理和下垫面属性对青狮潭灌区会仙试区氮磷排放的影响。研究中根据会仙试区径流量、总氮及总磷月排放监测数据校准和验证模型,进而采用情景模拟方法,分析稻田化肥施用量(氮肥和磷肥)、灌溉水量、湿地面积和蓄水容积以及岩溶发育程度等变化对试区径流及氮磷排放的影响。结果表明:1)校准期和验证期径流、总氮和总磷排放模拟值与实测值的决定系数和纳什系数分别在0.70和0.63以上,说明SWAT模型在会仙试区径流、总氮和总磷排放模拟上具有较好的适用性。2)针对不同水肥管理水平,化肥施入量和灌溉水量减少30%时,试区出水口多年平均总氮、总磷排放量分别下降11.45%和8.98%、7.79%和5.81%,化肥施用量减少对总氮、总磷排放的削减效果优于降低灌溉水量的削减效果。3)湿地面积或蓄水容量的增加和减少会相应降低和增大试区总氮、总磷排放量,若将湿地面积和蓄水容量均扩大50%,出水口总氮、总磷排放量可削减12.40%和10.44%;同时改变湿地面积和蓄水容量对试区总氮、总磷排放量的影响,超过单独改变其中一个属性影响的叠加。4)岩溶发育程度参数对子流域出水口氮磷排放影响各异,土壤厚度和土壤容重降低可减少试区径流量和氮磷排放量,而土壤有效含水量和饱和渗透系数则表现出相反的作用。该研究显示合理控制化肥施用量,防止湿地面积萎缩和蓄水能力退化,改善和保持岩溶区土壤结构,有助于削减漓江流域岩溶灌区氮磷污染的排放,为当地农业措施优化和水土管理方法提供指导。     

极浅型潜流人工湿地用于污水处理和风沙土改良的中试研究

[目的]就利用极浅型潜流人工湿地同步处理污水和改良风沙土的可行性进行中试,为后续相关工程的设计、建设和运行提供科学依据。[方法]以污水处理厂初沉池出水为原水,以取自毛乌素沙漠的风沙土为湿地填料,以高羊茅、黑麦草和狗牙根为湿地栽培植物,研究并分析湿地对水中污染物的去除效果和在风沙土的富集特征。[结果]经过15个月的运行,各湿地对污水中COD,TN以及TP的平均去除率分别高于原土68.75%,70.09%和62.74%。运行完毕后,各湿地风沙土较原土有机质、全氮含量显著增加(p0.05),全磷含量虽呈增加趋势但增幅不显著(p0.05),其中风沙土有机质、全氮及全磷含量分别较原土增加了10.64~18.77,8.74~13.98,0.34~0.55倍。[结论]利用极浅型潜流人工湿地同步处理污水和改良风沙土可行。它既能高效净化污水,又可快速提升风沙土的生产力。     

几种挺水植物净化生活污水总氮和总磷效果的研究

研究了石菖蒲、灯心草和蝴蝶花3种不同植被系统、基质为河砂的潜流型人工湿地净化生活污水总氮和总磷的效果,并同无植被系统、相同基质的潜流型人工湿地净化效果进行了比较,结果表明:在较低浓度范围里无植被的人工湿地和3种有植被的人工湿地对污水中总氮有较好的去除作用,随着污水中总氮浓度的增加,虽然无植被的人工湿地和有植被的人工湿地去除总氮的效果均有下降的趋势,但有植被的人工湿地仍然能维持较高的总氮去除水平,无植被的人工湿地总氮去除效果则下降较快。在有植被的人工湿地中,以石菖蒲植被人工湿地氮素净化能力最强,其次为灯心草和蝴蝶花,这与植被自身吸收同化污水中氮素水平以及植物根系微生物作用有关。对于污水中总磷的去除,本研究中由于污水中磷素浓度较低,无植被和有植被的人工湿地对污水中磷素均有很好的去除作用,没有明显差异,但不同的植物体中磷素仍有明显的吸收同化富集现象,其中石菖蒲吸收同化磷素能力最强,其次为蝴蝶花和灯心草,植被在人工湿地系统中对于污水中总氮和总磷的去除起着重要的作用。     

绿狐尾藻湿地对养殖废水中不同污染负荷氮去除效应

为研究绿狐尾藻湿地对不同污染负荷养殖废水氮去除效应和影响因素,该研究在野外建立了9条表面流绿狐尾藻湿地,以低负荷（60 L/d废水+120 L/d清水）、中负荷（120 L/d废水+60 L/d清水/d）和高负荷（180 L/d废水）养殖废水为处理对象,研究了不同污染负荷下绿狐尾藻湿地水体氮素时间变化规律;结合线性混合模型,进一步探究了影响绿狐尾藻湿地氮去除的关键环境因子。结果表明,整个试验期间（2014-07－2015-05）,绿狐尾藻湿地对低、中、高负荷废水铵氮（NH4+-N）和总氮（Total Nitrogen,TN）去除率均较高,其中NH4+-N平均去除率为85.0%～98.6%,TN平均去除率为83.6%～97.1%。线性混合模型分析结果表明,影响绿狐尾藻湿地NH4+-N去除的关键环境因子是水体溶解氧和硝态氮以及底泥NH4+-N含量,其中水体溶解氧对绿狐尾藻湿地NH4+-N去除影响最大。由于绿狐尾藻湿地对不同污染负荷废水NH4+-N和TN去除率均达到80.0%以上,因此绿狐尾藻可作为耐铵植物处理高负荷养殖废水。该研究结果可为绿狐尾藻湿地在规模养殖场的实际应用提供参考。     

节水防污型农田水利系统构建及其效果分析

不合理的农田水肥管理是造成农业面源污染的主要原因之一。为了探寻灌区水稻节水、增产和减污相统一的措施,提出运用由田间、草沟、塘堰湿地和骨干沟"四道防线"组成的系统净化农田排水,并在广西桂林市青狮潭灌区及广西灌溉试验中心站开展了系统的试验研究。通过站内不同水肥处理下对田间节水、水稻增产、氮磷流失减少指标的分析,优选水稻田间最优水肥管理模式,即采用间歇灌溉模式、施氮肥总量不变、适当减少氮肥基肥增加追肥用量;在站外根据现有的水系分布构建"四道防线"系统,分析了各道防线对农田排水的净化效果以及提高净化效果的主要措施。由"四道防线"构成的节水防污型农田水利系统对农田氮磷排放具有良好的净化效果,实现了减少农田面源污染和修复农田水环境的目的。     

多级串联表面流人工湿地净化生活污水效果

农村生活污水已经成为农业面源污染的主要来源之一。为了研究如何在经济发展水平不高的农村建立能有效治理农村生活污水,且建设成本低、运行维护简单的人工湿地系统,该文通过在桂林市青狮潭灌区构建了多级串联的表面流人工湿地系统,研究分析了不同子系统的水质净化效果及相关检测指标浓度的沿程变化规律。研究结果表明,湿地系统对氮磷的去除效率总体呈现出随时间推移逐渐下降的趋势,同时湿地的表面积越大,其对氮磷的去除率越高。研究还发现,该湿地系统对高浓度进水具有快速、稳定的去除效果,而对低浓度进水的营养盐去除则表现得较为平缓和持久。通过对湿地系统沿程氮磷浓度衰减的拟合及回归分析,建立了与湿地系统进口浓度有关的TN、NH4+-N和TP浓度的沿程衰减模型,相关分析表明其最佳的拟合模型均为指数衰减模型。该湿地系统在整个试验时期内均表现出了良好的净化效果,有效地减轻了农村生活污水对外界水环境的破坏,指数衰减模型的建立也为后续湿地设计及排水水质预测提供了理论分析依据。     

Sulphate Mobilization and Pore Water Chemistry in Relation to Groundwater Hydrology and Summer Drought in two Conifer Swamps on the Canadian Shield

Variations in sulphate (SO₄ ^2-) concentration of porewater and net SO₄ ^2- mobilization were related to differences in water level fluctuations during wet and dry summers in two conifer swamps located in catchments which differed in till depth and seasonality of groundwater flow. Sulphate depletion at the surface and in 20 cm porewater coincided with anoxia and occurred mainly during the summer when water levels were near the peat surface and water flow rates were low in both catchments. There was an inverse relationship between net SO₄ ^2- mobilization and water level elevation relative to the peat surface, explaining variation in SO₄ ^2- dynamics between the swamps during summer drought periods. Aeration of peat to 40 cm and a large net SO₄ ^2- mobilization (10–70 mg SO₄ ^2- m^-2 d^-1) occurred during a dry summer in which the water level dropped to 60 cm below the surface in the swamp receiving ephemeral groundwater inputs from shallow tills within the catchment. This resulted in high SO₄ ^2- concentrations in the surface water and porewater (30–50 mg L^-1), and elevated SO₄ ^2- concentrations remained through the fall and winter. In contrast, within the swamp located in the catchment with greater till depth (> 1 m), continuous groundwater inputs maintained surface saturation during the dry summer, and SO₄ ^2- mobilization and concentrations of SO₄ ^2- in the pore water during the following fall did not increase. Susceptibility to large water table drawdown and mobilization of accumulated SO₄ ^2- is influenced by the occurrence of ephemeral vs. continuous groundwater inputs to valley swamps during dry summer periods in the Canadian Shield landscape. This study reveals that extrapolation of results of SO₄ ^2- cycling from one wetland to another requires knowledge of the hydrogeology of the catchment in which the wetlands are located.     

不同类型人工湿地对洞庭湖水质净化效果研究

同等条件下开展了3种不同类型人工湿地（垂直流、潜流和表面流人工之地）对洞庭湖水质净化效果的研究。结果表明:（1）洞庭湖水体中NH₄⁺-N,TN,TP,高锰酸钾指数,BOD₅和COD_Cr的进水浓度与3种不同类型人工湿地出水浓度季节变化规律保持一致,冬季明显高于夏季,洞庭湖进水中NH₄⁺-N,TN,TP,高锰酸钾指数,BOD₅和COD_Cr浓度均高于3种不同类型人工湿地出水浓度,相同时期,3种不同类型人工湿地出水水质NH₄⁺-N,TN,TP,高锰酸钾指数、BOD₅和COD_Cr浓度基本表现为表面流 > 潜流 > 垂直流;（2）3种类型人工湿地对TN,TP,高锰酸钾指数、BOD₅和COD_Cr的去除率依次表现为垂直流 > 潜流 > 表面流,而对NH₄⁺-N的去除率依次表现为垂直流 > 表面流 > 潜流,其中以BOD₅的去除效果最好（去除率最高）,但3种类型人工湿地对BOD₅的去除率差异均不显著（p > 0.05）;（3）3种类型人工湿地植物地上和地下生物量均表现为垂直流 > 潜流 > 表面流,差异均显著（p < 0.05）,垂直流人工湿地植被N含量、P含量、N积累量和P积累量均显著高于潜流和表面流（p < 0.05）;（4）3种不同类型人工湿地植物的N,P积累量分别与生物量、N含量、P含量均呈显著的线性关系（p < 0.01）,人工湿地植物生物量对N,P积累量的影响大于植物体内N,P含量的影响,可以通过生物量来评价人工湿地植物对N,P去除效果。     

浸润线高度对垂直潜流湿地处理效果的影响研究

针对污染物浓度较高的猪场沼液,开展了不同浸润线高度下垂直潜流湿地处理效果的对比研究。试验结果表明：湿地浸润线可改变湿地填料层中的溶解氧分布和水力流态,从而造成了3种类型湿地系统对猪场沼液处理效果的差异;在不同水力负荷下,中浸润线垂直潜流湿地（VSSF-M）对猪场沼液中各项污染物的去除效果均好于低浸润线垂直潜流湿地（VSSF-L）和高浸润线垂直潜流湿地（VSSF-H）;中浸润线垂直潜流湿地利用溶解氧梯度在填料层内实现了好氧区、缺氧区和厌氧区的共存,从而使硝化作用与反硝化作用在同一系统内完成,提高了系统的脱氮能力;中浸润线垂直潜流湿地系统还可适当增大系统的水力停留时间（HRT）,并可优化水力流态,从而进一步改善湿地系统的净化效果。因此,结合处理效果和出水水质的稳定性,中浸润线垂直潜流湿地对浓度较高的猪场沼液具有较高的去除效率。     

凤眼莲生态修复工程改善滇池水质及湖体氮磷收支平衡

为了研究凤眼莲(Eichhornia crassipes)对滇池草海水体水质改善及湖体氮、磷归趋的影响,于2011-2013年在滇池草海实施了规模化控养凤眼莲生态修复富营养化湖泊水体的试验性工程。生态工程实施期间,监测草海水体总氮(TN)和总磷(TP)浓度及分析湖体TN、TP收支平衡。结果显示,草海水体TN和TP浓度均值分别由工程实施前(2006-2010年)的14.48 mg/L和0.60 mg/L降低至工程实施期间(2011-2013年)的7.09和0.36 mg/L,分别下降了51.04%和40.00%;草海入湖水体TN和TP浓度均值由入湖河口经凤眼莲控养区至出湖口的沿程方向上分别下降了9.74和0.40 mg/L。草海湖体TN、TP收支平衡表明,经出湖口排出和水体库存的TN量占入湖TN量比例较小,凤眼莲的吸收作用是入湖TN量去除的重要途径之一,而大部分入湖TN量(40.31%~59.04%)极可能是通过微生物的硝化反硝化、沉积等作用去除;各种途径支出的TP量高于入湖TP量,其中凤眼莲吸收的TP量为入湖TP量的40.44%~116.56%。因此,规模化控养凤眼莲对草海水质改善发挥了较大作用,凤眼莲的吸收作用既是湖体TN去除的重要途径之一,又是TP去除的主要途径之一。     

Treatment Efiiciencies of Constructed Wetlands for Eutrophic Landscape River Water

The efficiencies of two types of constructed wetlands for the treatment of low-concentration polluted eutrophic landscape river water were studied in the western section of the Qingyuan River at the Minhang campus of Shanghai Jiaotong University. The first wetland was a single-stage system using gravel as a filtration medium, and the second was a three- stage system filled with combinations of gravel, zeolite, and fly ash. Results from parallel operations of the wetlands showed that the three-stage constructed wetland could remove organics, nitrogen, and phosphorus successfully. At the same time, it could also decrease ammoniacal odour in the effluent. Compared to the single-stage constructed wetland, it had better nutrient removal efficiencies with a higher removal of 19.37%-65.27% for total phosphorus （TP） and 21.56%- 62.94% for total nitrogen （TN）, respectively, during the operation period of 14 weeks. In terms of removal of chemical oxygen demand （COD）, turbidity, and blue-green algae, these two wetland systems had equivalent performances. It was also found that in the western section of the test river, in which the two constructed wetlands were located, the water quality was much better than that in the eastern and middle sections without constructed wetland because COD, TN, and TP were all in a relatively lower level and the eutrophication could be prevented completely in the western section.     

Behavior of Pilot-Scale Constructed Wetlands in Removing Nutrients and Sediments Under Varying Environmental Conditions

Water resources are threatened globally and declining water quality is primarily due to stormwater, agricultural, urban, and mining runoffs. Steamboat Creek in Nevada is the largest non point source (NPS) of pollution to the Truckee River. Treatment wetlands are a cost-effective and reliable technique to control NPS pollution, therefore, a large-scale wetland along Steamboat Creek has been proposed as a component of a regional watershed restoration plan. This study used ten parallel pilot-scale wetland mesocosms, and tested the effects of drying and rewetting, hydraulic retention time (HRT), and high nitrogen loading on the efficiency of nutrient and total suspended solids (TSS) removal. Drying and rewetting produced noticeable effects on nutrient retention, but the effect was short-lived. During longer HRT period nutrient removal in manipulated mesocosms with an 8 h HRT were higher than controls with a 4 h HRT. Reducing the HRT from 4 h to 30 min further decreased nutrient interception. During increased influent nitrogen loading (9.5?±?2.4 mg l^?1), manipulated mesocosms functioned as sinks for total nitrogen (TN) with removal efficiency increasing from 45?±?13% to 87?±?9%. The average change in TN concentration was 9.1?±?2.2 mg l^?1. Drying/rewetting and varying HRT influenced total phosphorus (TP) and TSS similarly, and TP removal was associated with TSS removal. Results can help make decisions regarding wetland construction, management, and operation more effective in order to reduce nutrient loads to the Truckee River.