Interactive effects of nitrogen and phosphorus loadings on nutrient removal from simulated wastewater using Schoenoplectus validus in wetland microcosms

The concentrations of nutrients (N and P) in the wastewater and loading rate to the constructed wetlands may influence the nutrient removal from the secondary-treated municipal wastewater using wetland plants. Three loading rates of N (low 5.7, medium 34.3 and high 103 mg N d(-1)) and two of P (low 3.4 and high 17.1 mg P d(-1)) were studied in simulated secondary-treated municipal wastewater using Schoenoplectus validus (Vahl) A. L?ve & D. L?ve in the vertical free surface-flow wetland microcosms. After 70-d growth, there were significant interactive effects of N and P on the total, above-ground and root biomass. The below-ground biomass (rhizome and root) was negatively affected by the high N treatment. The tissue concentrations of N increased with an increase in N additions and decreased with an increase in P applications, whereas the tissue concentrations of P increased with an increase in P additions and decreased with an increase in N applications at the low P treatment, but increased at the high P treatment. Significant interactive effects of N and P loadings were found for the removal efficiencies of NH(4) and P, but not that of NO(x). The plant uptake, substrate storage and other losses (e.g. denitrification and formation of organic film) had similar contribution to N removal when N loading was relatively low. The P storage by substrate was the main contribution to P removal when P loading was high, but plant uptake was the major factor responsible for P removal when P loading was low and N loading was high. The high nutrient availability and optimum ratio of N:P are required to stimulate growth of S. validus, resulting in preferential allocation of resources to the above-ground tissues and enhancing the nutrient removal efficiencies, but the high N concentration in wastewater may hamper the growth of S. validus in constructed wetlands.     

复合型人工湿地脱氮效能及其水力负荷影响规律

复合型人工湿地越来越多地被应用在面源污染管理中。不同类型的人工湿地对氮素的去除机理和去除性能是不同的。氮素在湿地生态系统中的去除受多种因素的影响和制约,不同的研究中氮素的去除效率变化较大。通过对韩国西部一复合型人工湿地中氮素的去除能力研究,分析了氮素的去除效率以及水力负荷对去除性能的影响,进而分析了人工湿地去除氮素的主要机理。结果表明,氨氮（NH＋4-N）、硝酸盐氮（NO-3-N）、凯式氮（TKN）和总氮（TN）的平均去除效率分别为13%、29%、35.3和26%。其中有机氮的去除是该复合型人工湿地中氮素去除的主要原因。水力负荷和先行干期天数对氮素的去除能力有一定影响。较长的先行干期天数和较低水力负荷可以提高氮素的去除效率。     

碳氮比对人工湿地污水处理效果的影响

采用表面流人工湿地系统静态小试装置,考察了低、中、高3组不同进水COD/N(2,5,10)对系统中氮、磷及COD去除效果的影响。结果表明:进水C/N的变化对COD的去除率影响不大,平均去除率达到94.6%。TN的去除率随着COD/N的增大而逐渐升高,在C/N=5时达到63.8%,继续提高COD/N,TN的去除率变化不大。NH4+-N去除率随着COD/N的增加而降低。随着碳源的增加,释磷菌能够从进水中获得充足的碳源,从而可以比较充分地释磷,因此,磷的去除率随COD/N的增加而提高。     

Transport and attenuation of dissolved glyphosate and AMPA in a stormwater wetland

Glyphosate is an herbicide used widely and increasingly since the early 1990s in production of many crops and in urban areas. However, knowledge on the transport of glyphosate and its degradation to aminomethylphosphonic acid (AMPA) in ecosystems receiving urban or agricultural runoff is lacking. Here we show that transport and attenuation of runoff-associated glyphosate and AMPA in a stormwater wetland differ and largely vary over time. Dissolved concentrations and loads of glyphosate and AMPA in a wetland receiving runoff from a vineyard catchment were assessed during three consecutive seasons of glyphosate use (March to June 2009, 2010 and 2011). The load removal of glyphosate and AMPA by the wetland gradually varied yearly from 75% to 99%. However, glyphosate and AMPA were not detected in the wetland sediment, which emphasises that sorption on the wetland vegetation, which increased over time, and biodegradation were prevailing attenuation processes. The relative load of AMPA as a percentage of total glyphosate increased in the wetland and ranged from 0% to 100%, which indicates the variability of glyphosate degradation via the AMPA pathway. Our results demonstrate that transport and degradation of glyphosate in stormwater wetlands can largely change over time, mainly depending on the characteristics of the runoff event and the wetland vegetation. We anticipate our results to be a starting point for considering degradation products of runoff-associated pesticides during their transfer in wetlands, in particular when using stormwater wetlands as a management practice targeting pesticide attenuation.     

Evaluation of the giant reed (Arundo donax) in horizontal subsurface flow wetlands for the treatment of dairy processing factory wastewater

Two emergent macrophytes, Arundo donax and Phragmites australis, were established in experimental horizontal subsurface flow (HSSF), gravel-based constructed wetlands (CWs) and challenged by treated dairy processing factory wastewater with a median electrical conductivity of 8.9 mS cm(-1). The hydraulic loading rate was tested at 3.75 cm day(-1). In general, the plants grew well during the 7-month study period, with no obvious signs of salt stress. The major water quality parameters monitored (biological oxygen demand (BOD), suspended solids (SS) and total nitrogen (TN) but not total phosphorus) were generally improved after the effluent had passed through the CWs. There was no significance different in removal efficiencies between the planted beds and unplanted gravel beds (p?>?0.007), nor was there any significant difference in removal efficiencies between the A. donax and P. australis beds for most parameters. BOD, SS and TN removal in the A. donax and P. australis CWs was 69, 95 and 26 % and 62, 97 and 26 %, respectively. Bacterial removal was observed but only to levels that would allow reuse of the effluent for use on non-food crops under Victorian state regulations. As expected, the A. donax CWs produced considerably more biomass (37?±?7.2 kg wet weight) than the P. australis CWs (11?±?1.4 kg wet weight). This standing crop equates to approximately 179 and 68 tonnes ha(-1) year(-1) biomass (dry weight) for A. donax and P. australis, respectively (assuming a 250-day growing season and single-cut harvest). The performance similarity of the A. donax and P. australis planted CWs indicates that either may be used in HSSF wetlands treating dairy factory wastewater, although the planting of A. donax provides additional opportunities for secondary income streams through utilisation of the biomass produced.     

不同基质复合垂直流人工湿地对富营养化景观水的净化效果

研究了两套不同基质复合垂直流人工湿地小试装置在不同季节对富营养化景观水的净化效果,分析了温度变化对污染物去除效果的影响,考察了微生物的硝化强度和反硝化强度以及基质理化性质对植物生长状况的影响,并探讨了氮、磷的去除途径.结果表明:不同基质复合垂直流人工湿地随季节变化对浊度、COD和磷的去除效果差异不明显;温度降低对脱氮效果影响显著,对磷的去除影响不大.沸石-页岩湿地硝化强度和反硝化强度优于砾石湿地.采用沸石作为基质可以提高系统对氮的去除效率,促进湿地植物的生长.对氮、磷去除途径的分析表明:微生物的硝化反硝化作用以及基质对磷的吸附沉淀作用是复合垂直流人工湿地去除氮、磷的主要途径;植物吸收分别占湿地TN、TP去除量的16%和35%左右,也是个重要途径.     

Comparative impacts of forest harvest and acid precipitation on soil and streamwater acidity

Annual H+ budgets were calculated for a catchment with a 65-year-old spruce-fir forest, and for an adjacent catchment at three years after a whole-tree harvest. In the harvested catchment sinks for H+ due to weathering and mineralization reactions were 85% greater, and sources of H+ due to biomass uptake were 60% greater than in the undisturbed catchment. There was an overall net consumption of 550 eq H+ ha(-1) year(-1) at year 3 after harvest compared to a net generation of 520 eq H+ ha(-1) year(-1) for the 65-year-old forest. Soil pH increased by 0.2-0.4 units soon after harvest, but there was little change in pH of streamwater from the harvested watershed. The whole-tree harvest resulted in a total production of about 30,000 eq H+ ha(-1) due to biomass removal. In contrast, wet and dry deposition at rates measured in this study could add more than 50,000 eq H+ ha(-1) in the 65-year period before the next harvest. Reducing the intensity of harvest may lessen long-term impacts of these sources of H+ on acidification of soils and streams.     

Effect of physico-chemical pretreatment on the removal efficiency of horizontal subsurface-flow constructed wetlands

In this study, we tested the effect of a physico-chemical pretreatment on contaminant removal efficiency in two experimental horizontal subsurface-flow constructed wetlands (SSF CWs). One SSF CW was fed with settled urban wastewater, whereas the other with the same wastewater after it had undergone a physico-chemical pretreatment. The SSF CWs were operated with three different hydraulic retention times. During the experiments the effluent concentrations of COD, ammonia N and sulfate were very similar, and, therefore, the physico-chemical pretreatment did not improve the quality of the effluents. COD removal efficiency (as percentage or mass surface removal rate) was slightly greater in the SSF CW fed with pretreated wastewater. Ammonia N removal efficiency was, in general, similar in both SSF CWs and very high (80-90%). At the end of the experiments it was observed that in the SSF CW fed with settled wastewater the hydraulic conductivity decreased by a 20%.     

Nitrogen,Phosphorus, Carbon,and Suspended Solids Loads from Forest Clear-Cutting and Site Preparation: Long-Term Paired Catchment Studies from Eastern Finland

The long-term impacts of current forest management methods on surface water quality in Fennoscandia are largely unexplored. We studied the long-term effects of clear-cutting and site preparation on runoff and the export of total nitrogen (total N), total organic nitrogen (TON), ammonium (NH₄-N), nitrate (NO₃-N), total phosphorus (total P), phosphate (PO₄-P), total organic carbon, and suspended solids (SS) in three paired-catchments in Eastern Finland. Clear-cutting and soil preparation were carried out on 34 % (C34), 11 % (C11), and 8 % (C8) of the area of the treated catchments and wide buffer zones were left along the streams. Clear-cutting and soil preparation increased annual runoff and total N, TON, NO₃-N, PO₄-P, and SS loads, except for SS, only in C34. Runoff increased by 16 % and the annual exports of total N, TON, NO₃-N, and PO₄-P by 18, 12, 270, and 12 %, respectively, during the 14-year period after clear-cutting. SS export increased by 291 % in C34, 134 % in C11, and 16 % in C8 during the 14, 6, and 11-year periods after clear-cutting. In the C11 catchment, NO₃-N export decreased by 12 %. The results indicate that while current forest management practices can increase the export of N, P and SS from boreal catchments for many years (>10 years), the increases are only significant when the area of clear cutting exceeds 30 % of catchment area.     

8种植物床人工湿地脱氮除磷的研究

分别以水葫芦、西洋芹、空心菜、水芹、混合种(黄菖蒲、千屈菜、再力花)、千屈菜、再力花、黄菖蒲等植物床构建潜流人工湿地,研究其对生活污水氮、磷的净化功能及其去除率与水力停留时间(HRT)的变化规律。结果表明,各种植物床对TN、TP的去除率随HRT的延长而增加,不同植物床的脱氮除磷效果是不同的。千屈菜植物床对TN的去除效果最好,HRT为3d时,TN去除率为56%;HRT为6d时,TN去除率达77%。再力花植物床对TP的去除效果最好,HRT为3d时,TP去除率达78%;HRT为6d时,TP去除率达96%。其他植物床也有较好的脱氮除磷效果。各种植物床处理后出水TN、TP均较低,HRT为3d时,出水TN均低于《城镇污水处理厂污染物排放标准》(GB 18918—2002)一级A标准规定的限值(15mg/L),出水TP均低于GB 18918—2002二级标准规定的限值(3mg/L);7种植物床构建的潜流人工湿地(水葫芦的数据丢失)对TN、TP的去除均满足一级反应动力学方程,且相关性显著。     

不同C／N下人工湿地的脱氮效果及其强化措施

以人工湿地为研究对象,分析了不同C／N下人工湿地的脱氮效果。结果表明,C／N为10时,TN、NO2-N和COD平均去除率分别为（75．36±10．55）％、（86．34±9．23）％和（67．60±4．10）％,都显著高于其他2组系统（P=0．006、0．001、0〈0．01）;随着C／N的增加,NO3-N去除率呈现出上升的趋势;NH4-N刚好相反,C／N为1时,明显要高于其他2种情况（P=0〈0．05）,平均去除率为（65．42-1-14．31）％。针对C／N为1时人工湿地脱氮效率较低（51．294-14．48）％的情况,对系统进水采取了添加一定量好氧反硝化细菌固定化小球并曝气12h的强化实验措施。结果发现,强化实验条件下TN、NOr-N和N03-N去除率均提高了10％以上,且都要明显高于非强化实验条件（P：0．003、0、0〈0．01）,同时NH4-N和COD去除率没有明显差异,研究结果表明,从微生物角度对系统进水进行前处理有助于提高人工湿地脱氮效率。     

2种人工湿地的水力停留时间及净化效果

以复合垂直流人工湿地(IVCW)和水平潜流人工湿地(HSCW)为研究对象,研究了2种湿地运行的季节性最佳水力停留时间(HRT)参数,并监测了2种湿地在最佳HRT参数下运行时对污水的净化效果。结果显示:(1)在IVCW中,最佳HRT在春、秋季为8～10 h;夏季为6 h;冬季为12 h。在HSCW中,最佳HRT在春、秋季为10～12 h;夏季为6～8h;冬季为24～36 h。(2)2种湿地对COD的去除率均无显著的季节性差异;湿地进水中NH4+-N/TN比值与TN去除率显著负相关;不同季节下IVCW对TN的去除效果均高于HSCW。(3)水温对TN、TP去除率的影响在IVCW中比HSCW中的明显;水温高时,2种湿地中的TN去除率较高,IVCW中的TP去除率也较高,但HSCW中的TP去除率则较低,它们间均未达到显著的相关性。     

Effects of macrophytes and external carbon sources on nitrate removal from groundwater in constructed wetlands

Several microcosm wetlands unplanted and planted with five macrophytes (Phragmites australis, Commelina communis, Penniserum purpureum, Ipomoea aquatica, and Pistia stratiotes) were employed to remove nitrate from groundwater at a concentration of 21-47 mg NO3-N/l. In the absence of external carbon, nitrate removal rates ranged from 0.63 to 1.26 g NO3-N/m2/day for planted wetlands. Planted wetlands exhibited significantly greater nitrate removal than unplanted wetlands (P<0.01), indicating that macrophytes are essential to efficient nitrate removal. Additionally, a wetland planted with Penniserum showed consistently higher nitrate removal than those planted with the other four macrophytes, suggesting that macrophytes present species-specific nitrate removal efficiency possibly depending on their ability to produce carbon for denitrification. Although adding external carbon to the influent improved nitrate removal, a significant fraction of the added carbon was lost via microbial oxidation in the wetlands. Planting a wetland with macrophytes with high productivity may be an economic way for removing nitrate from groundwater. According to the harvest result, 4-11% of nitrogen removed by the planted wetland was due to vegetation uptake, and 89-96% was due to denitrification.     

复合改性海泡石同步处理废水中的氮磷

采用盐热和稀土掺杂制备复合改性海泡石,研究了复合改性海泡石对废水中N、P的吸附特征和去除效果。结果表明,与海泡石原矿粉比较,复合改性海泡石的脱氮除磷能力分别提高49.71%和90.14%;复合改性海泡石对N、P的吸附可以用Langmuir吸附模型描述,获得的最大吸附量分别为1.165和1.121 mg/g;修正的Elovich模型能较好地描述复合改性海泡石吸附N、P的动力学过程;用NaOH溶液可以再生吸附材料,获得较好的脱氮除磷效果,再生次数以2次为宜;用复合改性海泡石处理污水处理站的二级生化出水,最终出水的pH、N和P含量均达到《城镇污水处理厂污染物排放标准》的要求。     

Assessing nitrogen and phosphorus removal potential of five plant species in floating treatment wetlands receiving simulated nursery runoff

The feasibility of using floating treatment wetlands (FTWs) to treat runoff typical of commercial nurseries was investigated using two 8-week trials with replicated mesocosms. Plants were supported by Beemat rafts. Five monoculture treatments of Agrostis alba (red top), Canna × generalis ‘Firebird’ (canna lily), Carex stricta (tussock sedge), Iris ensata ‘Rising Sun’ (Japanese water iris), Panicum virgatum (switchgrass), two mixed species treatments, and an unplanted control were assessed. These plant species are used for ornamental, wetland, and biofuel purposes. Nitrogen (N) and phosphorus (P) removals were evaluated after a 7-day hydraulic retention time (HRT). N removal (sum of ammonium-N, nitrate-N, and nitrite-N) from FTW treatments ranged from 0.255 to 0.738 g·m^?2·d^?1 (38.9 to 82.4% removal) and 0.147 to 0.656 g·m^?2·d^?1 (12.9 to 59.6% removal) for trials 1 and 2, respectively. P removal (phosphate-P) ranged from 0.052 to 0.128 g·m^?2·d^?1 (26.1 to 64.7% removal) for trial 1, and 0.074 to 0.194 g·m^?2·d^?1 (26.8 to 63.2% removal) for trial 2. Panicum virgatum removed more N and P than any other FTW treatment and the control in both trials. Results show that species selection and timing of FTW harvest impact the rate and mass of nutrient remediation. FTWs can effectively remove N and P from runoff from commercial nurseries.

     

生活污水不同进水C/N比负荷对垂直潜流式人工湿地排放温室气体的影响

人工湿地处理的生活污水含氮量或者有机物含量很高时,可能会造成人工湿地在处理污水的过程中排放大量温室气体。研究了垂直潜流式人工湿地在人工合成的生活污水不同污染物进水C/N负荷条件下污水处理效果和温室气体(CO2和CH4)的排放量,利用现场测量和碳平衡模型估算分析了可以达到最佳污水净化效果和最少温室气体排放量的污染物进水C/N负荷条件。结果显示,在进水C/N负荷为C/N=6∶1~9∶1时可以得到最佳的污染物去除率。温室气体CH4排放量较CO2排放量可以忽略不计,而在进水C/N负荷为C/N=3∶1~6∶1时可以实现最少的温室气体排放。综上所述,最优的进水C/N负荷确定为C/N=6∶1,此时人工湿地可以得到较高的污染物去除率而排放较少的温室气体。     

Influence of earthworm Eisenia fetida on removal efficiency of N and P in vertical flow constructed wetland

This study investigates biomass, density, photosynthetic activity, and accumulation of nitrogen (N) and phosphorus (P) in three wetland plants (Canna indica, Typha augustifolia, and Phragmites austrail) in response to the introduction of the earthworm Eisenia fetida into a constructed wetland. The removal efficiency of N and P in constructed wetlands were also investigated. Results showed that the photosynthetic rate (P _n), transpiration rate (T _r), and stomatal conductance (S _cond) of C. indica and P. austrail were (p?<?0.05) significantly higher when earthworms were present. The addition of E. fetida increased the N uptake value by above-ground of C. indica, T. augustifolia, and P. australis by 185, 216, and 108 %, respectively; and its P uptake value increased by 300, 355, and 211 %, respectively. Earthworms could enhance photosynthetic activity, density, and biomass of wetland plants in constructed wetland, resulting in the higher N and P uptake. The addition of E. fetida into constructed wetland increased the removal efficiency of TN and TP by 10 and 7 %, respectively. The addition of earthworms into vertical flow constructed wetland increased the removal efficiency of TN and TP, which was related to higher photosynthetic activity and N and P uptake. The addition of earthworms into vertical flow constructed wetland and plant harvests could be the significantly sustainable N and P removal strategy.     

Oryzalin fate and transport in runoff water in Mediterranean vineyards

An experimental study was conducted in a 91.4-ha Mediterranean vineyard catchment in southern France to characterize the fate and transport of oryzalin in runoff water and thus to assess the risk of contamination of surface waters. Oryzalin concentrations in soil were monitored on two fields, one no-till and one tilled from March 1998 to March 2000. Concentrations in solution and on solid phase of runoff water were measured at the outlets of both fields and the catchment. The droughts in the two summer periods reduced the dissipation of oryzalin and increased its field half-life up to 35 days. Consequently, oryzalin was detected throughout the year in runoff water, with maximum dissolved concentrations > 600 microg l(-1) at the field scale. Oryzalin transport essentially occurred in solution. At the no-till field, seasonal losses were 2.29% and 1.89% of the applied amount in 1998 and 1999, respectively. The corresponding values at the tilled field were 1.56% and 0.29%, since tillage reduced total losses by reducing surface runoff. At the catchment scale, oryzalin concentrations were smaller than those at the field scale, due to dilution effects and staggering of application. Large part of the overland flow from the fields reinfiltrated in the ditches before reaching the outlet of the catchment. As a result, seasonal oryzalin losses were <0.2% of the applied amount.     

Enhanced organics and nitrogen removal in batch-operated vertical flow constructed wetlands by combination of intermittent aeration and step feeding strategy

Oxygen and carbon source supply are usually insufficient in subsurface flow constructed wetlands. Simultaneous removal of organic pollutants and nitrogen in five batch-operated vertical flow constructed wetlands under different operating conditions was investigated. Alternate aerobic and anaerobic regions were created well with intermittent aeration. Four-month experiments showed that the wetland-applied intermittent aeration combined with step feeding strategy (reactor E) greatly improved the removal of organics, ammonium nitrogen (NH₄–N), and total nitrogen (TN) simultaneously, which were 97, 96, and 82 %, respectively. It was much better than non-aerated reactors A and B and outperformed intermittently aerated reactor D without step feeding. Continuous aeration (reactor C) significantly enhanced the organics removal and nitrification, but it limited the TN removal (29 %) seriously as a result of low denitrification level, and the high operation cost remained a question. The effect of plants was confirmed in this study, and the monitoring data showed that the plants could grow normally. Intermittent aeration as well as step feeding had no obvious influence on the growth of wetland plants in this study.     

Constructed wetlands treating highway runoff in the central Mediterranean region

Two free water surface (FWS) and two subsurface flow (SSF) pilot-size constructed wetlands treating highway runoff (HRO) were monitored over a period of two years (September 2005-August 2007). One FWS and one SSF were designed with a hydraulic retention time (HRT) of 12h, named FWS12 and SSF12, respectively, with each one capable of treating a maximum HRO of 12.6 m(3) d(-1). The other couple, named FWS24 and SSF24, respectively, was designed with an HRT of 24h, with each receiving a maximum HRO of 6.3 m(3) d(-1). The influent flowed from a highway section with a total surface 2752 m(2) on the island of Crete, Greece, in the heart of the South-Central Mediterranean region. Influent and effluent were monitored for COD, TSS, total N (TN), NO(3)(-) and total P (TP) concentrations. Furthermore, removal efficiencies were examined for heavy metals (Cu, Ni, Pb, Zn) for both years, while polycyclic aromatic compounds (PAHs) were examined for the period between September 2006 and August 2007. The influent had a two-year average COD value of 101 mg l(-1), whereas the mean values for TSS, TN, N-NO(3)(-) and TP were 203, 4.30, 1.25 and 4.17 mg l(-1), respectively. For Cu, Ni, Pb and Zn the respective two-year mean influent concentrations were 56, 114, 49 and 250 microg l(-1). Mean concentration of total PAHs in runoff (summation operator PAHs, 16 compounds) were 12.01 microg l(-1). The performance among the four beds was not significantly different according to ANOVA analysis followed by Tukey test (at p<0.05) for almost all the above physicochemical parameters, suggesting that all systems performed in a similar way. All studied systems, achieved a mean of two-year removal efficiencies of 47% for COD, 89% for TSS, 49% for TN, 58% for N-NO(3)(-), 60% for TP, 47% for Cu, 23% for Ni, 33% for Pb, 61% for Zn and 59% for summation operator PAHs (16 compounds).