Agricultural Drainage Water Research Articles

DIFFERENT POLLUTANT MONITORING IN QARUN LAKE

The presence of pollutants in the lakes considers the most common problem facing consumers. So, the aim of this study was to monitor the physiochemical, bacteriological properties of Qarun lake. It is a closed saline lake in the northern part of El-Fayoum Depression (Middle Egypt) at the margin of the Great Western Desert. During the 20th century, lake water salinity has increased strongly as a result of high evaporation rate. Also fish productivity decreased strongly. It receives agricultural and domestic non-treated drainage waters, which are also used for aquaculture in Qarun area. The study aimed to know the state of the lake and monitored the effect of agricultural drainages and domestic on the concentration of pollutants. The Physiochemical, bacteriological and some heavy metals monitored during the summer of 2017 to compare it with the previous results of the lake. The study proved that the lake suffering pollution by heavy metals as Cd (0.0034mg/l), Zn (1.091mg/l) at Al-Bats drain, NH3 (0.58 mg/l),PO4-3(1.38mg/l),COD (292mg/l) and BOD (71mg/l) at Al-Wadi drain. Therefore, it is necessary to put an environmental policy to control this pollution.

ECONOMICAL AND ENVIRONMENTAL IMPACTS FOR RE-USE OF AGRICULTURAL DRAINAGE WATER IRRIGATION OF AGRICULTURE ABSTRACT FOR A SAMPLE OF FARMERS IN GIZA GOVERNORATE

The study aimed to study the economic and environmental effects of the re-use of agricultural drainage water. The study found that despite the decline in net revenues, for the productivity and economic crops studied, it should be noted that the re-use of water resources, in general, and water drainage in particular. The study indicates that the intensification of the use of water and bring Egypt's largest hydro unit returns while experiencing Egypt where shortages water resources and their limitations. In spite of the economic benefits of re-use of agricultural drainage water, but there are a number of negative impacts on agricultural and human environment due to the use of this water in agriculture, which requires him to improve water quality and further chemical analyzes to mitigate these effects, as well as work on activating the role of Agricultural Extension agricultural cooperation to increase awareness by methods dealing with irrigation water and avoid risks resulting from it.

Water quality analysis and model simulation for the second largest polluted lake in Egypt

This study investigated the spatial variation in the water quality parameters of Burullus Lake using multivariate analysis and MIKE21 model. The lake was classified into zone-1 at north-east (Z1), zone-2 at south-east (Z2), zone-3 at north-middle (Z3), zone-4 at south-middle (Z4), zone-5 at north-west (Z5), zone-6 at south-west (Z6), and zone-7 at west (Z7). The obtained parameters were temperature 21.5±5.0 ºC, pH 8.2±0.6, dissolved oxygen (DO) 5.9±1.0 mg/L, biological oxygen demand (BOD) 23.9±5.7 mg/L, NH3-N 2.5±0.3 mg/L, NO2-N 1.9±0.3 mg/L, NO3-N 1.2±0.3 mg/L, PO4-P 1.9±0.3 mg/L, SiO4 3.2±0.1 mg/L, Chlorophyll-a (Chl-a) 88.2±10.8 µg/L, and salinity 3.2±1.0 g/L. Principal component analysis showed that agricultural drainage water was the key factor influencing the water quality characteristics of Burullus Lake. Water quality index (WQI) varied between “Bad” to “Medium”, suggesting that the lake wasn’t suitable for irrigation and fish growth; however, it was appropriate for some aquatic life. A MIKE21 model was developed to provide a recommendation scenario that could be used to enhance the water quality of Burullus Lake. By improving the water quality of precise drains (namely drains 7 and 8), the WQI at Z4 and Z6 modified from “Bad” to “Medium”. The period required to achieve this self-purification was 5 months.

Phosphorus retention in surface-flow constructed wetlands targeting agricultural drainage water

Surface-flow constructed wetlands (CWs) are potential cost-efficient solutions to mitigate phosphorus (P) loads from agricultural areas to surface waters. Hydraulic and phosphorus loading rates (HLR and PLR) are critical parameters that regulate P retention in these systems. The present study aimed to assess P retention from agricultural drainage discharge by three new CWs in Denmark during three years. The CWs presented different geologies, and received event-driven drainage discharge. The relations of HLR, PLR, dominant P forms, and iron (Fe) inputs to P retention were also investigated. The drainage discharge varied seasonally and average annual HLR ranged from 17 to 60 m yr−1 for the three CWs. PLR varied concomitantly to HLR with average annual PLR from 2.8 to 13.5 g m−2 yr−1, where specific total P (TP) retention followed its variations. Specific TP retention responded differently to HLR and PLR in the CWs, depending on the dominant P forms at the inlet water. The CWs worked as P sinks and presented similar or higher retentions than other Nordic CWs with similar loads. PLR explained most of the variation in specific TP retention (52–72%), whereas HLR only explained 20–34%. Specific TP retention responded more promptly to PLR when the inlet water was dominated by particulate P (PP), since it is more easily retained than dissolved P. TP retention efficiency varied more irregularly and the annual retention ranged from 24 to 66%. It presented weak correlations to HLR and PLR, and depended on the dominant P forms and major retention mechanisms, as well as P biogeochemical stability. Thus, increasing TP retention efficiency occurred under higher stability of sediment bound P, as supported by higher total Fe:PP molar ratios at the inlet water. The supply of P sorbents by drainage discharge, soil redox conditions and Fe:P molar ratios are considered key parameters controlling the biogeochemical stability of P, and thus the long-term P retention performance in CWs.

Long-Term Monitoring of a Surface Flow Constructed Wetland Treating Agricultural Drainage Water in Northern Italy

Agricultural drainage water that has seeped into tile drainage systems can cause nitrogen and phosphorus pollution of the surface water bodies. Constructed wetlands (CWs) can help mitigate the effects of agricultural non-point sources of pollution and remove different pollutants from tile drainage water. In this study, hydrological and water quality data of a Northern Italian CW that has been treating agricultural drainage water since 2000 were considered to assess its ability to mitigate nitrogen and phosphorus pollution. The effects of such long-term operation on the nutrients and heavy metals that eventually accumulate in CW plants and sediments were also analysed. Since 2003, the CW has received different inflows with different nutrient loads due to several operation modes. However, on average, the outflow load has been 50% lower than the inflow one; thus, it can be said that the system has proved itself to be a viable option for tile drainage water treatment. It was found that the concentration of nitrogen and phosphorus in the plant tissues varied, whereas the nitrogen content of the soil increased more than 2.5 times. Heavy metals were found accumulated in the plant root systems and uniformly distributed throughout a 60 cm soil profile at levels suitable for private and public green areas, according to the Italian law

Corn Straw as a Solid Carbon Source for the Treatment of Agricultural Drainage Water in Horizontal Subsurface Flow Constructed Wetlands

Agricultural drainage water with a low C/N ratio restricts the nitrogen and phosphorus removal efficiencies of constructed wetlands. Thus, there is a need to add external carbon sources to drive the nitrogen and phosphorus removal. In this study, the effects of the addition of corn straw pretreated with different methods (acid treatment, alkali treatment, and comminution) on treating agricultural drainage water with a low C/N ratio were investigated in constructed wetlands. The results showed that soaking the corn straw in an alkaline solution was the most suitable pretreatment method according to the release rule of chemical oxygen demand (COD) and the dissolution of total nitrogen (TN) and total phosphorus (TP). The average removal efficiency of TN and TP in constructed wetlands increased respectively by 37.2% and 30.5% after adding corn straw, and by 17.1% and 11.7% after adding sodium acetate when the hydraulic retention time (HRT) was 3 days. As an external carbon source, straw was cheap, renewable, and available. In contrast, the sodium acetate demanded high costs in a long-term operation. Therefore, corn straw had a great advantage in treatment effect and cost, which improved the treatment efficiency of agricultural drainage water using a byproduct of agricultural production as a slow-release carbon source.

Wetland saturation with introduced Fe(III) reduces total carbon emissions and promotes the sequestration of DOC

Solutions containing dissolved organic carbon (DOC) from a depressional wetland that receives agricultural drainage water were incubated in pure quartz sands with FeCl3 added as the main electron acceptor. The effects of three factors (the water, DOC, and Fe contents) on the CO2 and CH4 production rates, integrated cumulative C emissions and Fe-OC co-precipitation were studied. The results showed that CO2 production during the DOC mineralization process was facilitated by Fe(III) reduction at the expense of CH4 production. Additionally, the cumulative CO2 emissions determined by integrating the temporal curves of CO2 production were negatively correlated with those of CH4 (r = −0.48, p < 0.01). Extremely large ratios of the CO2:CH4 production rate (13,762 and 44,885 under two soil water conditions: saturation and flood conditions of twice the saturation level) were observed. These ratios were likely caused by simultaneous anaerobic fermentation, microbial respiration, and methanogenesis suppression triggered by iron reduction. The effects of exogenous Fe(III) inputs on total C emissions (as the sum of integrated cumulative CO2 and CH4) were only dependent on soil water conditions during the initial period of the experiment, and flooded conditions increased total C emissions by as much as double. Increased ratios of Fe inputs to C contents were found to proportionally increase the total C emissions (R2 = 0.32, p < 0.01). Under saturated conditions, the co-precipitation of Fe-OC complexes prevented the remainder of the DOC from undergoing mineralization. In terms of DOC, we concluded that wetland saturation with introduced Fe(III) can reduce total C emissions from anaerobic respiration and promote C sequestration.

Influence of Deficit Irrigation Using Saline Water on Yield of Tomato under Two Irrigation Systems

Field experiment was conducted in calcareous soil at Maryout Experimental Station Farm, Desert Research Center, Egypt to investigate the influence of deficit irrigation water using highly saline water on yield and water productivity of tomato (Lycopersicon esculentum, mill., cultivator 888) under drip and gated pipe irrigation systems. The tomato plants were subjected to 3 deficit irrigation depths (100, 75 and 50 % of ETc) throughout 3 growth stages (development, flowering and harvesting) using highly saline water of 9.15 dSm-1 plus control treatment. The tomato plants were irrigated by the full irrigation (100 % ETc) during the whole growth season using slightly saline water of 2.80 dSm-1.The reduction percentage in tomato fruit yield ranged between 9.9 to 41.5 % and 9.1 to 30.9 % at treatment T2100 – D (plants irrigated by the full irrigation: 100% of ETc) using highly saline water throughout the development stage then irrigated by the same water depth using slightly saline water (agricultural drainage water), throughout the other growth stages and treatment T950 – F (plants irrigated by deficit irrigation depth of 50% ETc using highly saline water, 9.15dSm-1. The flowering growth stage of tomatoes was the highest stage influenced to deficit irrigation using highly saline water especially at deficit irrigation of 50 % ETc. The tomato fruit yield under drip irrigation system was significantly higher than that obtained under gated pipe irrigation system. The highest value of crop water productivity (CWP) was obtained at control treatment and the lowest value was obtained at treatment T950-F. The highest and lowest values were 9.5 and 5.56 kg/m3 and 8.23 and 5.69 kg/m3 under drip and gated pipe irrigation systems, respectively. A significant polynomial relationship between tomato fruit yield (Y), kg/m2, and applied irrigation water (AW), m3/m2 was given with R2 0.78. The predicted maximum yields were 18.54 and 11.63 kg/m2 and the corresponding calculated the applied irrigation water were 2.57 and 2.59 m3/m2 under drip and gated pipe irrigation systems, respectively. The crop response factor (Ky) using highly saline water under drip and gated pipe irrigation systems were 1.090 and 0.743, respectively.

Performance of Iron Plaque of Wetland Plants for Regulating Iron, Manganese, and Phosphorus from Agricultural Drainage Water

Agricultural drainage water continues to impact watersheds and their receiving water bodies. One approach to mitigate this problem is to use surrounding natural wetlands. Our objectives were to determine the effect of iron (Fe)-rich groundwater on phosphorus (P) removal and nutrient absorption by the utilization of the iron plaque on the root surface of Glyceria spiculosa (Fr. Schmidt.) Rosh. The experiment was comprised of two main factors with three regimes: Fe2+ (0, 1, 20, 100, 500 mg·L−1) and P (0.01, 0.1, 0.5 mg·L−1). The deposition and structure of iron plaque was examined through a scanning electron microscope and energy-dispersive X-ray analyzer. Iron could, however, also impose toxic effects on the biota. We therefore provide the scanning electron microscopy (SEM) on iron plaques, showing the essential elements were iron (Fe), oxygen (O), aluminum (Al), manganese (Mn), P, and sulphur (S). Results showed that (1) Iron plaque increased with increasing Fe2+ supply, and P-deficiency promoted its formation; (2) Depending on the amount of iron plaque on roots, nutrient uptake was enhanced at low levels, but at higher levels, it inhibited element accumulation and translocation; (3) The absorption of manganese was particularly affected by iron plague, which also enhanced phosphorus uptake until the external iron concentration exceeded 100 mg·L−1. Therefore, the presence of iron plaque on the root surface would increase the uptake of P, which depends on the concentration of iron-rich groundwater.

Removal of phosphorus from agricultural subsurface drainage water with woodchip and mixed-media bioreactors

Woodchip bioreactors that stimulate denitrification are proposed to reduce nitrogen (N) loads emanating from subsurface agricultural drainage. However, agricultural drainage water contains both N and phosphorus (P), frequently in concentrations exceeding environmental criteria. A mixed-media bioreactor containing woodchips plus reactive media that binds soluble P could concurrently lower both N and P loads in subsurface agricultural drainage. This study evaluated the P concentration and load reductions achieved with woodchip and mixed-media bioreactors in full-scale field installations in the cold, humid climate of Quebec, Canada, during a three-year period. Bioreactors contained either woodchips-only or woodchips plus an activated alumina/gravel mixture (mixed media). Total P, particulate P, soluble P, soluble reactive P, and soluble organic P concentrations and loads for the bioreactor influents and effluents were assessed weekly and also following &gt;10 mm rainfall events. In the first two months of operation, both woodchips-only and mixed-media bioreactors released P but became either a negligible source or net sink for P retention within the first year of operation. While the mixed-media bioreactor had 9% lower total P concentration and about 19 times greater reduction in total P load than woodchips-only bioreactors during the study period, the total P concentration was not reduced to the critical environmental threshold level of 0.03 mg L⁻¹ with either bioreactor type. Both configurations were effective at reducing the soluble P fraction, especially the soluble reactive P species that are bioavailable and thus contribute directly to eutrophication. A woodchips-only bioreactor can adsorb P from subsurface agricultural drainage; however, a woodchips bioreactor containing the activated alumina/gravel mixture has greater P sorption capacity and should be considered as part of an integrated system for concurrent N and P removal from subsurface agricultural drainage.

Optimization of External Carbon Addition for Biological Selenium Removal from Agricultural Drainage Water

Optimization of External Carbon Addition for Biological Selenium Removal from Agricultural Drainage Water

Carbon Quality of Four-Year-Old Woodchips in a Denitrification Bed Treating Agricultural Drainage Water

Abstract. A denitrification bed is a system that can reduce the nitrate concentration in subsurface drainage water. There is a need to investigate the carbon quality of old woodchips to gain a better understanding of the effect of age on woodchip properties. The objectives of this study were to characterize the carbon quality and carbon to nitrogen (C/N) ratio of aged woodchips and to examine the suitability of a denitrification bed for a replicated experiment. To achieve these goals, we excavated four-year-old woodchips along the length of a 106.4 m long denitrification bed near Willmar, Minnesota, and analyzed them for particle size, C/N ratio, and carbon quality. Particle size analysis showed similarities from 12.5 to 106.4 m along the bed. We found a mean C/N ratio ranging from 58.4 ±3.17 to 153.4 ±9.57 (smallest at the inlet). The mean lignocellulose index (LCI, a measure of carbon quality) of the four-year-old woodchips ranged from 0.47 to 0.57 (highest at the inlet). The woodchip particle sizes, C/N ratios, and LCI from 25.9 to 106.4 m along the bed length were similar. In conclusion, the C/N ratio and LCI of the four-year-old woodchips showed effects of decomposition and increased woodchip carbon recalcitrance over time, respectively. Keywords: Denitrifying bioreactor, Tile drainage, Water quality, Woodchip bioreactor.

Investigation of different nitrogen reduction routes and their key microbial players in wood chip-driven denitrification beds

Field denitrification beds containing polymeric plant material are increasingly used to eliminate nitrate from agricultural drainage water. They mirror a number of anoxic ecosystems. However, knowledge of the microbial composition, the interaction of microbial species, and the carbon degradation processes within these denitrification systems is sparse. This study revealed several new aspects of the carbon and nitrogen cycle, and these findings can be correlated with the dynamics of the microbial community composition and the activity of key species. Members of the order Pseudomonadales seem to be important players in denitrification at low nitrate concentrations, while a switch to higher nitrate concentrations seems to select for members of the orders Rhodocyclales and Rhizobiales. We observed that high nitrate loading rates lead to an unpredictable transition of the community’s activity from denitrification to dissimilatory reduction of nitrate to ammonium (DNRA). This transition is mirrored by an increase in transcripts of the nitrite reductase gene nrfAH and the increase correlates with the activity of members of the order Ignavibacteriales. Denitrification reactors sustained the development of an archaeal community consisting of members of the Bathyarchaeota and methanogens belonging to the Euryarchaeota. Unexpectedly, the activity of the methanogens positively correlated with the nitrate loading rates.

Batch Test Screening of Industrial Product/Byproduct Filter Materials for Agricultural Drainage Water Treatment

Filter treatment may be a viable means for removing the nitrate (NO3−), phosphate (PO43−), and pesticides discharged with agricultural drainage waters that cause adverse environmental impacts within the U.S. on local, regional, and national scales. Laboratory batch test screening for agricultural drainage water treatment potential was conducted on 58 industrial product/byproduct filter materials grouped into six categories: (1) high carbon content media; (2) high iron content media; (3) high aluminum content media; (4) surfactant modified clay/zeolite; (5) coal combustion residuals; and (6) spent foundry sands. Based on a percent contaminant removal criteria of 75% or greater, seven industrial products/byproducts were found to meet this standard for NO3− alone, 44 met this standard for PO43−, and 25 met this standard for the chlorinated triazine herbicide, atrazine. Using a 50% or greater contaminant removal criteria, five of the industrial product/byproduct filter materials exhibited potential for removing NO3−, PO43−, and atrazine together; eight showed capability for combined NO3− and PO43− removal; 21 showed capability for combined PO43− and atrazine removal; and nine showed capability for combined NO3− and atrazine removal. The results of this study delineated some potential industrial product/byproduct filter materials for drainage water treatment; however, a complete feasibility evaluation for drainage water treatment of any of these filter materials will require much more extensive testing.

ALGAL GROWTH AND NUTRIENTS REMOVAL AS AFFECTED BY NITROGEN SOURCE

The current work was performed aiming at the determine growth line of two different algae species under two different nitrogen sources which in turn affect some nutrients removing from growth medium as an earliest experiment for future use of algae in agricultural drainage water treatment. Two different algae species were tested in the current study to determine their growth potential as they grown with their original growth media and under replacement of original nitrogen source. The first alga was Chlorella vulgaris belonging to Chlorophyta, while the second is Spirulina platensis belonging to Cyanophyta. BG-II growth medium was used for the first one and Zarrouk growth medium was implemented to the second. The original nitrogen source of both media was substituted by low price form as urea by the same equivalent. Daily determination of biomass was performed beside nutrients removal. The results showed that nitrate stimulated growth of both Chlorella and Spirulina algae and urea seems to be the proper in Chlorella growth rather than Spirulina. Maximum nutrient removal or absorption was observed during the early growth period (48 hours). Chlorella vulgaris was found to be more bio-removal agent rather than Spirulina platensis.

Seasonal performance of denitrifying bioreactors in the Northeastern United States: Field trials

Denitrifying bioreactors are increasingly being used for nitrate removal from agricultural drainage water. Filled with carbon substrates, often woodchips, denitrifying bioreactors provide a favorable anaerobic environment for denitrification. Despite performing well in loess soils in the Midwestern United States, field bioreactors have not yet been evaluated in shallow soils over glacial till that are characteristic for the Northeastern United States. This study, therefore, investigates the performance of bioreactors and provides design criteria for shallow soil with flashy discharges.Paired bioreactors, one filled with woodchips and one with a mixture of woodchip and biochar, were installed in tile drained fields in three landscapes in New York State. The bioreactors were monitored for a three-year period during which, the flow rate, temperature, nitrate (NO3−−N), sulfate (SO42−−S) and dissolved organic carbon (DOC) were measured. Results showed that the average NO3−−N removal efficiency during the three years of observations was about 50%. The NO3−−N removal rate ranged from 0 in winter to 72 g d−1 m−3 in summer. We found that biochar was only effective during the first year in enhancing denitrification, due to the ageing. An index for carbon availability related to NO3−−N removal was developed. During winter, availability of the DOC was a limiting factor in bioreactor performance. Finally, to aid in the design of bioreactors, we developed generalizable relationships between the removal efficiency and hydraulic retention time and temperature.

Comparison of Four Nitrate Removal Kinetic Models in Two Distinct Wetland Restoration Mesocosm Systems

The objective of the study was to determine the kinetic model that best fit observed nitrate removal rates at the mesocosm scale in order to determine ideal loading rates for two future wetland restorations slated to receive pulse flow agricultural drainage water. Four nitrate removal models were investigated: zero order, first order decay, efficiency loss, and Monod. Wetland mesocosms were constructed using the primary soil type (in triplicate) at each of the future wetland restoration sites. Eighteen mesocosm experiments were conducted over two years across seasons. Simulated drainage water was loaded into wetlands as batches, with target nitrate-N levels typically observed in agricultural drainage water (between 2.5 and 10 mg L−1). Nitrate-N removal observed during the experiments provided the basis for calibration and validation of the models. When the predictive strength of each of the four models was assessed, results indicated that the efficiency loss and first order decay models provided the strongest agreement between predicted and measured NO3-N removal rates, and the fit between the two models were comparable. Since the predictive power of these two models were similar, the less complicated first order decay model appeared to be the best choice in predicting appropriate loading rates for the future full-scale wetland restorations.

THE ECONOMIC DIMENSION TO THE PRODUCTION OF FISH LAKE QARUN IN FAYOUM GOVERNORATE

lake Qarun is considered as the third largest lake in the Arab Republic of Egypt, and it is the main reservoir of agriculture drainage water in the province of Fayoum. The salinity increased in the lake Qarun from 32.45% in 2015 to about 34.3% in 2016, which caused declining production of fish, and the disappearance of some fish species with deterioration of the productivity of other species. The fish production by the lake decreased from 41.0% in 1995 to about 20.2% in 2014 of the total production of fish in Fayoum governorate. The study aims to identify the fish production at the lake applying the standard functions of production and costs, estimate the maximum sustainable yield (MSY), maximum rate of fishing efforts, and identify the most important marketing problems facing fishermen. Also, the study searching the marketing problems of fish at Qarun lake.The study results showed that white shrimp represents about 86.7% of total production at the lake, and its relative importance decreased compared with other fish species such as tilapia, mullet and Sole by about 9.54%, 1.91%, 1.82%, respectively .The average total costs were 243.98 Egyptian Pounds / Effort, and the average total revenue was586.36 Egyptian Pounds / Effort. The average net return was 342.37 Egyptian Pounds / Effort, which means that every Egyptian Pound invested in fishing at Lake Qarun had 0.403 Egyptian Pounds.The value of production elasticity, showed that increasing total input used at the Lake Qarun by 1% will increase production by 1.403%. To get the maximum sustainable yield at Lake Qarun, each effort need to produce 331.5 kg / Effort, and the average production of 262.8 kg / Effort.Compare actual and optimal production per effort, last result required to increase production by 68.7 kg / Effort. The production level which maximize profits was 508.0 kg / Effort. The maximum sustainable production (MSY) at the lake was 4303.4 tons per year, an increase of 39.6% from the average study of about 3082.3 tons, period, and that the actual fishing effort and estimated at 542 compound has exceeded the maximum fishing effort to the production estimated at 356 compound, an increase of approximately 52.3%.The most important marketing problem was the lack of market equipment’s by 85.2%, and the most important fishing problem was the disappearance of many species of fish species by 100%, and the most important sources of Lake Qarun water pollution were agricultural, industrial and sewage pollution by 98.4.%, 93.4 %, and 91.8%. respectively

Nitrate removal potential of restored wetlands loaded with agricultural drainage water: A mesocosm scale experimental approach

Wetland restoration is often conducted in Eastern U.S. coastal plain watersheds alongside agricultural lands that frequently export significant amounts of nitrogen in drainage water. Restoration plans that incorporate the addition of agricultural drainage water can simultaneously increase the success of achieving a target hydroperiod and reduce discharge of nitrogen to nearby surface water. The potential nitrogen removal effectiveness of two wetland restoration sites with such a restoration plan was evaluated in a two-year mesocosm study. Six large wetland mesocosms (3.5m long×0.9m wide×0.75m deep) along with unplanted controls were used in this experiment. Three replicates of two soils that differed in organic matter and pH were planted with soft-stem bulrush (Schoenoplectus tabernaemontani) and allowed to develop in the two growing seasons prior to the study. Simulated drainage water was loaded into the mesocosms over eighteen batch studies across seasons with target nitrate-N levels between 2.5 to 10mgL−1. Grab samples were collected from the water column and analyzed for nitrate-N, dissolved organic carbon, and chloride, along with other environmental parameters such as pH, water temperature, and soil redox. Seasonally, nitrogen and carbon within the wetland plants and soil were also measured. Multivariate statistical analyses were utilized to determine differences in nitrate-N reductions between treatments. Variables included carbon availability, temperature, antecedent moisture condition, nitrogen loading, and water pH. Contrary to the hypothesis that higher nitrate-N removal rates would be observed in the wetlands with higher organic matter, overall removal rates were higher in the wetland mesocosms containing Deloss soils (WET-Min) (maximum of 726mgm−2d−1) than those containing Scuppernong soil (WET-Org) (maximum of 496mgm−2d−1) and were dependent on daily NO3-N concentrations and season. Significant differences in NO3-N removal were found between seasons and soil types (α=0.05), which helped to provide insight to the expected magnitude of nitrogen removal within these systems throughout the year, and potential mechanisms (i.e. denitrification vs. plant uptake) that will govern these removals.

Performance of an Agricultural Wetland-Reservoir-Irrigation Management System

Constructed wetlands (CW) have gained recognition as a management option for the treatment of various agricultural wastewaters. This study involved the design, construction, and initial evaluation of a wetland-reservoir-irrigation (WRI) system. The system was established in Truro, Nova Scotia, Canada, with the goal to capture, treat, and re-use agricultural sub-surface drainage water. It consisted of a 1.8-ha area of a cropped field that was systematically tile drained. Drainage water was directed through a 2-cell CW and then into a reservoir-irrigation pond. Flow rate hydraulics, residence time distributions, and treatment efficiencies for nitrate-nitrogen (NO3−-N) and Escherichia coli (E. coli) were monitored for 14 months. Mass reductions of NO3−-N and E. coli from the CW were 67.6% and 63.3%, respectively. However, average E. coli concentrations increased to 178 CFU 100 mL−1 in the reservoir during the warm season. It may therefore be best to use reservoir water for irrigation of crops that are not consumed raw. To aid in the future design of similar systems, mean first-order rate constants (ks) for NO3−-N and E. coli were calculated to be 8.0 and 6.4 m y−1, respectively. The volume of water collected in the reservoir exceeded typical irrigation requirements of the drained land and could therefore provide irrigation to additional land beyond the drainage area.