scholarly journals On the potential of on-line free-surface constructed wetlands for attenuating pesticide losses from agricultural land to surface waters

2019 ◽  
Vol 16 (8) ◽  
pp. 563 ◽  
Author(s):  
Andre Ramos ◽  
Michael J. Whelan ◽  
Ian Guymer ◽  
Raffaella Villa ◽  
Bruce Jefferson
Keyword(s):  
Drinking Water ◽  
Free Surface ◽  
Constructed Wetlands ◽  
Surface Waters ◽  
Constructed Wetland ◽  
Agricultural Land ◽  
Residence Times ◽  
Storm Events ◽  
Solute Exclusion ◽  
On Line

Environmental contextPesticide losses from land to surface waters have the potential to cause ecological damage. Furthermore, pesticides in surface waters present a major challenge for water companies accessing these waters for the domestic supply, in terms of complying with water quality regulations. Here, we evaluate the potential of field- and ditch-scale free-surface constructed wetland systems for reducing pesticide transfers from land to surface waters. AbstractPesticides make important contributions to agriculture but losses from land to water can present problems for environmental management, particularly in catchments where surface waters are abstracted for drinking water. ‘On-line’ constructed wetlands have been proposed as a potential means of reducing pesticide fluxes in drainage ditches and headwater streams. Here, we evaluate the potential of two free-surface constructed wetland systems to reduce pesticide concentrations in surface waters using a combination of field monitoring and dynamic fugacity modelling. We specifically focus on metaldehyde, a commonly used molluscicide that is moderately mobile and has been regularly detected at high concentrations in drinking water supply catchments in the UK over the past few years. We also present data for the herbicide metazachlor. Metaldehyde losses from the upstream catchment were significant, with peak concentrations occurring in the first storm events in early autumn, soon after application. Concentrations and loads appeared to be minimally affected by transit through the monitored wetlands over a range of flow conditions. This was probably due to short solute residence times (quantified via several tracing experiments employing rhodamine WT – a fluorescent dye) exacerbated by solute exclusion phenomena resulting from patchy vegetation. Model analyses of different scenarios suggested that, even for pesticides with short aquatic half-lives, wetland systems would need to exhibit much longer residence times (RTs) than those studied here in order to deliver any appreciable attenuation. If the ratio of wetland surface area to the area of the contributing catchment is assumed to be a surrogate for RT (i.e. not accounting for solute exclusion), then model predictions suggest that this needs to be greater than 1% to yield load reductions of 3 and 7% for metaldehyde and metazachlor respectively.

scholarly journals VERTICAL SUBSURFACE FLOW AND FREE SURFACE FLOW CONSTRUCTED WETLANDS FOR SUSTAINABLE POWER GENERATION AND REAL WASTEWATER SELECTIVE POLLUTANTS REMOVAL

2020 ◽  
Vol 24 (06) ◽  
pp. 91-102
Author(s):  
Zahraa S. Aswad ◽  
◽  
Ahmed H. Ali ◽  
Nadia M. Al-Mhana ◽  
◽  
...  
Keyword(s):  
Power Generation ◽  
Free Surface ◽  
Constructed Wetlands ◽  
Constructed Wetland ◽  
Suspended Solids ◽  
Subsurface Flow ◽  
Free Surface Flow ◽  
Surface Flow ◽  
Removal Efficiencies ◽  
Better Than

A vertical subsurface flow constructed wetland (VSSFCW) and a free surface flow constructed wetland (FSFCW) were set for the objective of comparison the performance of two systems in order to make a decision of the better one for future installation of wastewater treatment system and power generation. Both of the constructed wetlands were planted with Cyperus Alternifolius. During the observation period (19 days or 456 hours), environmental conditions such as pH, temperature, total chemical oxygen demand (COD), phosphate (PO4), nitrate (NO3) ,total suspended solids (TSS), total dissolved solids (TDS), Pb, Cu, and Cd removal efficiencies of the systems were determined. According to the results, final removal efficiencies for the VSSF and FWSF, respectively, were: COD (94.3% and 94.3%),PO4 (84.3% and 75.3%), NO3 (100% and 100%), TSS (96.8% and 85.6%), Pb (65.8% and 81.4%), Cu (more than 94.7% and 89.4%), Cd (85.7% and 88%). The treatment performances of the VSSF were better than that of the FWSF with regard to the removal of suspended solids and nutrients. In FWSF systems, electricity generation performed better than VSSF of 31.4 mV especially with batch system during one wastewater feed is loaded among all of the nineteen days with maximum voltage of 33.7 mV and decreased gradually as oxygen depletion in cathode chamber and less metabolism processes has occurred.

Nitrogen removal from waste treatment pond or activated sludge plant effluents with free-surface wetlands

1995 ◽  
Vol 31 (12) ◽  
pp. 341-351 ◽  
Author(s):  
Alexander J. Horne
Keyword(s):  
Drinking Water ◽  
Free Surface ◽  
Activated Sludge ◽  
Constructed Wetlands ◽  
Nitrogen Removal ◽  
Waste Treatment ◽  
Nitrate Removal ◽  
Dynamic Mode ◽  
Natural Lakes ◽  
The Usa

Due to their dynamic mode of operation, waste treatment pond and activated sludge plant effluents always contain quite large amounts of nitrogen relative to those found in natural lakes, streams, and oceans. Typical activated sludge plant effluents contain 25 mgl-1 N, mostly as ammonia. In most aquatic milieux, concentrations of ammonia > 1 mgl-1 N are potentially toxic to fish and other wildlife. Nitrification and denitrification of activated sludge plant effluent alleviates the ammonia problem at a considerable cost but the discharges still usually contain over 10 mgl-1 NO3-N which exceeds the WHO standard for drinking water. A great advantage of waste treatment pond effluents is that nitrogen is normally already present as nitrate or particulate-N (algae and bacteria), and nitrate concentrations are < 5 mgl-1 NO3-N. However, even 1 mgl-1 of nitrate-N is sufficient to cause eutrophication in unpolluted lakes, streams, and oceans and some of the particulate-N discharged will be recycled to give eutrophication downstream. Where sufficient diluting water is available, these higher effluent concentrations are not a problem. Unfortunately, clean diluting water is becoming a scarce commodity in many areas, particularly the 17 semi-arid states in the USA and in most developing countries where rainfall is needed for drinking water and wildlife support. One solution for nitrogen removal is new design for free surface constructed wetlands which have considerable potential for nitrogen polishing of waste treatment pond effluents. Particulate-N can be removed by using wetlands as large filters but the nitrogen often recycles and is released as ammonia in winter and spring. Denitrification of nitrate to N2 gas removes the problem permanently. In particular, the relatively low BOD, high nitrate and low ammonia effluent from some stabilization ponds is ideal for nitrate removal (denitrification) by free surface wetlands. Rates of nitrate removal of 200 to over 5,000 mg N m-2 d-1 can be achieved with initial nitrate values of 2-14 mgl-1 NO3-N. These rates are 1-2 orders of magnitude greater than occur in most natural lake, estuarine or wetlands sediments and can be mostly attributed to denitrification rather than growth of rooted plants. In two weeks 20 mgl-1 NO3-N can be reduced to less than 1 mgl-1. After wetlands treatment the water is suitable for release into water-depleted live streams or lakes where a low eutrophication potential is vital for native biota. It is recommended that pond effluent be routed thorough constructed wetlands whenever possible since both better water quality and wildlife benefits occur.

scholarly journals Spatial and temporal variation of fecal indicator organisms in two creeks in Beltsville, Maryland

2016 ◽  
Vol 51 (2) ◽  
pp. 167-179 ◽  
Author(s):  
M. D. Stocker ◽  
J. G. Rodriguez-Valentín ◽  
Y. A. Pachepsky ◽  
D. R. Shelton
Keyword(s):  
Cross Sections ◽  
Surface Waters ◽  
Agricultural Land ◽  
Sediment Resuspension ◽  
Spatial And Temporal Variation ◽  
Storm Events ◽  
Indicator Organisms ◽  
Fecal Indicator ◽  
Sampling Locations ◽  
Small Streams

Evaluation of microbial water quality is commonly based on monitoring populations of fecal indicator organisms (FIO) such as Escherichia coli (EC) and enterococci (ENT). The occurrence of elevated FIO concentrations in surface waters after storm events is well documented and has been attributed to runoff and sediment resuspension. The reasons for FIO concentration variation under baseflow conditions are less clear. The objective of this study was to quantify the variability of EC and ENT in two small streams running through agricultural land use areas. FIO concentrations were measured at upstream and downstream locations under baseflow conditions. Concentrations were not significantly different along cross-sections of the streams. Diurnal concentration trends were observed at each of the sampling locations. Significant differences in concentrations between upstream and downstream locations were noted for both creeks during baseflow periods when no runoff or sediment resuspension occurred. A hypothetical explanation is that indicator organisms are released from sediments during baseflow conditions due to the effect of groundwater influx into streams or due to the motility of indicator organisms. If confirmed, this hypothesis may affect our understanding of the role of sediments in the microbial quality of surface waters.

Habitat Association of Klebsiella Species

1985 ◽  
Vol 6 (2) ◽  
pp. 52-58 ◽  
Author(s):  
Susan T. Bagley
Keyword(s):  
Drinking Water ◽  
Gastrointestinal Tract ◽  
Surface Waters ◽  
Industrial Effluents ◽  
Opportunistic Pathogen ◽  
Habitat Associations ◽  
Habitat Association ◽  
Klebsiella Species ◽  
Almost All ◽  
Polluted Waters

AbstractThe genus Klebsiella is seemingly ubiquitous in terms of its habitat associations. Klebsiella is a common opportunistic pathogen for humans and other animals, as well as being resident or transient flora (particularly in the gastrointestinal tract). Other habitats include sewage, drinking water, soils, surface waters, industrial effluents, and vegetation. Until recently, almost all these Klebsiella have been identified as one species, ie, K. pneumoniae. However, phenotypic and genotypic studies have shown that “K. pneumoniae” actually consists of at least four species, all with distinct characteristics and habitats. General habitat associations of Klebsiella species are as follows: K. pneumoniae—humans, animals, sewage, and polluted waters and soils; K. oxytoca—frequent association with most habitats; K. terrigena— unpolluted surface waters and soils, drinking water, and vegetation; K. planticola—sewage, polluted surface waters, soils, and vegetation; and K. ozaenae/K. rhinoscleromatis—infrequently detected (primarily with humans).

Water Treatment Considerations–Aquatic Humus

1983 ◽  
Vol 15 (S2) ◽  
pp. 95-101 ◽  
Author(s):  
E T Gjessing
Keyword(s):  
Drinking Water ◽  
Water Treatment ◽  
Humic Substances ◽  
Health Effects ◽  
Surface Waters ◽  
Cold Climate ◽  
Treatment Processes ◽  
Aquatic Humus ◽  
Treatment Considerations

For several reasons the surface waters in cold climate areas are coloured due to humic substances. There are two major objections against humus in drinking water, the first is concerned with aesthetical and practical problems and the second is due to indirect negative health effects. There are essentially three different methods in use today for the removal or reduction of humus colour in water: (1) Addition of chemicals with the intention of reducing the “solubility”, (2) Addition of chemicals in order to bleach or mineralize the humus, and (3) Filtration with the intention of removal of coloured particles and some of the “soluble” colour. The treatment processes are discussed.

A Nude Mouse Model as an in vivo Infectivity Assay for Cryptospomdiosis

1993 ◽  
Vol 27 (3-4) ◽  
pp. 65-68 ◽  
Author(s):  
B. H. Kwa ◽  
M. Moyad ◽  
M. A. Pentella ◽  
J. B. Rose
Keyword(s):  
Drinking Water ◽  
Mouse Model ◽  
Nude Mouse ◽  
Cryptosporidium Parvum ◽  
Nude Mice ◽  
Surface Waters ◽  
Nude Mouse Model ◽  
Infectivity Assay ◽  
Limiting Dilution

Cryptosporidium parvum is an important patliogen of diarrlieal disease which has been implicated in several outbreaks associated with contamination of surface waters. In monitoring for C. parvum in drinking water sources, it is important to asce tain the viability, and more importantly, the infectivity of low numbers of recovered oocysts. Groups of 10 Balb/C nude (nu/nu) mice, 4-8 weeks old at time of inoculation, were infected with C. parvum oocysts from naturally infected calves and purified using Sheather's sucrose gradients. Oocysts were counted using the Merifluor IFA kit (Meridian). Each group of 10 mice were infected with 1,10,100 and 1000 oocysts respectively. Numbers of oocysts per inoculation were determined by limiting dilution, and parallel inocula were counted microscopically to ascertain the accuracy of the dilutions. Two uninfected nude mice were kept in each cage to serve as controls. Mouse stools were collected every 4 days, concentrated using the Fekal Kontrate Concentration Kit (Meridian) and oocysts were counted with a UV microscope using the Merifluor IFA Kit (Meridian). Oocyst counts were expressed in terms of number of oocyst/g feces. Mice inoculated with 1000 oocysts began to shed oocysts on day 32, mice inoculated with 100 oocysts began to shed on days 44-48, mice inoculated with 10 oocysts began to shed on days 56-60, and mice inoculated with 1 oocyst shed on days 68-88. All infected mice continued to shed oocysts intermittently and with variable oocyst counts until day 180 when the experiment was terminated. This study established that it is possible to infect nude mice with very low numbers, down to a single oocyst. We are currently in the process of correlating the nude mouse assay with other viability assays.

Enhancement of nitrogen removal in subsurface flow constructed wetlands employing a 2-stage configuration, an unsaturated zone, and recirculation

1995 ◽  
Vol 32 (3) ◽  
pp. 59-67 ◽  
Author(s):  
Kevin D. White
Keyword(s):  
Constructed Wetlands ◽  
Nitrogen Removal ◽  
Constructed Wetland ◽  
Subsurface Flow ◽  
Great Promise ◽  
Effluent Recirculation ◽  
Wetland Treatment ◽  
Subsurface Flow Constructed Wetlands ◽  
Inlet Zone ◽  
Bod Removal

Constructed wetland technology is currently evolving into an acceptable, economically competitive alternative for many wastewater treatment applications. Although showing great promise for removing carbonaceous materials from wastewater, wetland systems have not been as successful at nitrification. This is primarily due to oxygen limitations. Nitrification does occur in conventional wetland treatment systems, but typically requires long hydraulic retention times. This paper describes a study that first evaluated the capability of subsurface flow constructed wetlands to treat a high strength seafood processor wastewater and then evaluated passive aeration configurations and effluent recirculation with respect to nitrogen treatment efficiency. The first stage of a 2-stage wetland treatment system exhibited a relatively short hydraulic retention time and was designed for BOD removal only. The second stage wetland employed an unsaturated inlet zone and effluent recirculation to enhance nitrification. Results indicate that organic loading, and thus BOD removal, in the first stage wetland is key to optimal nitrification. Passive aeration through an unsaturated inlet zone and recirculation achieved up to 65-70 per cent ammonia nitrogen removal at hydraulic retention times of about 3.5 days. Inlet zone configuration and effluent recirculation is shown to enhance the nitrogen removal capability of constructed wetland treatment systems.

Viruses and Water: Problems, Detection, and Control

1993 ◽  
Vol 27 (7-8) ◽  
pp. 127-133 ◽  
Author(s):  
H. Dizer ◽  
J. Dürkop ◽  
A. Grohmann ◽  
H. Kopecka ◽  
J. M. López-Pila
Keyword(s):  
Drinking Water ◽  
Surface Waters ◽  
Membrane Filtration ◽  
Wastewater Treatment Plants ◽  
Health Hazard ◽  
Primary Source ◽  
Detection Methods ◽  
Secondary Effluent ◽  
Naturally Occurring ◽  
Water Problems

Secondary effluent of wastewater treatment plants contains a high number of viruses and other pathogens, which pose a health risk to the population, (especially when receiv ng waters are used for bathing and swimming, or for growing shellfish. In areas with a high density of population, where drinking water supply is dependent on surface waters and contaminated rivers are the primary source of drinking water, failure of the filtration or of the disinfection step, or of any other “barriers” supposed to warrant safe potable water, will increase the risk of health hazard for the consumer. We have compared the efficiency of viral elimination in secondary effluent by flocculation, uv rradiation and membrane filtration taking naturally occurring, or additionally seeded f2 phages, as indicator for viruses. Flocculation decreased the number of phages present in secondary effluent by more than two logs. If combined with uv irradiation, the elimination reached five additional logs. Membrane filtration eliminated essentially all naturally occurring phages. Improvement of the quality of surface waters calls for a refinement of detection methods for viruses. We have found that the polymerase chain reaction (PCR) might be used for detecting viruses in surface waters.

Phosphorus Leaching Under Cut Grassland

1999 ◽  
Vol 39 (12) ◽  
pp. 63-67 ◽  
Author(s):  
B. L. Turner ◽  
P. M. Haygarth
Keyword(s):  
Surface Waters ◽  
Large Scale ◽  
Agricultural Land ◽  
Algal Growth ◽  
Soil Types ◽  
P Fractions ◽  
Inorganic P ◽  
Potential Source ◽  
Significant Mechanism ◽  
Total P

Phosphorus (P) transfer from agricultural land to surface waters can contribute to eutrophication, excess algal growth and associated water quality problems. Grasslands have a high potential for P transfer, as they receive P inputs as mineral fertiliser and concentrates cycled through livestock manures. The transfer of P can occur through surface and subsurface pathways, although the capacity of most soils to fix inorganic P has meant that subsurface P transfer by leaching mechanisms has often been perceived as negligible. We investigated this using large-scale monolith lysimeters (135 cm deep, 80 cm diameter) to monitor leachate P under four grassland soil types. Leachate was collected during the 1997–98 drainage year and analysed for a range of P fractions. Mean concentrations of total P routinely exceeded 100 μg l−1 from all soil types and, therefore, exceeded P concentrations above which eutrophication and algal growth can occur. The majority of the leachate P was in algal-available Mo-reactive (inorganic) forms, although a large proportion occurred in unreactive (organic) forms. We suggest that subsurface transfer by leaching can represent a significant mechanism for agricultural P transfer from some soils and must be given greater consideration as a potential source of diffuse P pollution to surface waters.

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