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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
31

Hydrologic and hydraulic processes in northern treatment peatlands and the significance for phosphorus and nitrogen removal

Ronkanen, A.-K. (Anna-Kaisa) 18 August 2009 (has links)
Abstract The understanding of flow processes is a key to evaluating treatment efficiency in constructed wetlands. This work focuses on the effects of flow paths on phosphorus (P) and nitrogen (N)retention in four treatment wetlands constructed on pristine peatlands in Finland. Particular attention was paid to water residence time, effective flow area and effective flow depth. Both an artificial tracer test and a new method based on the analysis of stable oxygen and hydrogen isotope distributions were employed. Tracer tests were used to calibrate steady-state flow models created using a groundwater modelling MODFLOW code. Furthermore, concentrations of P, Al and Fe in the peat and concentration of N in the surface water were measured. Surface water tracer distributions showed overland flow to be the dominant flow process and it was divided into a preferential flow area and dead zones. Also, active channel formation was observed during the years of the study (2002–2005). The results indicate that the hydraulic performance might deteriorate drastically within a short period of time. The active flow areas in the peatlands comprised only about 40–48% in summer, meaning that large areas with potential for nutrient removal were left unused. Flow simulations showed that a more optimal length of the distribution ditch will create a larger effective flow area and possibly could prevent channel formation. The peat P concentration was 1.8±3.9 mg g-1, and P was accumulated in the preferential flow area. The peat P concentration correlated positively with Al in the Ruka peatland treating wastewater. The results indicate that precipitation chemicals increase the P retention capacity of peatland substantially and maintain P retention at a stable level despite variable P loads. Furthermore, the results indicate that the accumulation of P to peat via adsorption and chemical precipitation is the major P removal process even after 10 years of loading. In Ruka, calculated N concentrations in surface water obtained with a first-order area model, together with regression analysis of the rate constant, were in good agreement with observed N concentrations. If a removal of 70% is to be achieved, the NH4-N loading to the peatland should be below 0.10 mg m2 d-1.
32

Comparison of Nitrogen Retention in Wetlands With Different Depths

Thomas, Jes January 2017 (has links)
The depth of constructed wetlands (CWs) significantly affects the construction investment that influences the efficiency of the CW and is an important design consideration for optimal performance. The aim of the study was to examine the influence of depth on nitrogen retention in 12 pilot scale free surface water CWs in Plönninge (56◦43 45 N, 12◦43 33 E): 6 shallow wetlands with a maximum depth of 0.5 m and 6 deeper wetlands with a maximum depth of 0.8 m. The outlet N concentration in shallow and deep wetlands were found to be significantly different (p<0.05, p= 0.017). Outlet N concentration over the months June to December in deep and shallow wetlands, was found to be significantly different (F (6,60 = 20.594, p< 0.05). and the N concentration in deep and shallow wetlands was significantly different (F (1,10) = 8.087, p<0.05). The N concentration in September was found to be significantly different from those in all other months. The first order rate constant k was calculated for shallow and deep wetlands; higher k value indicates higher nitrogen retention. The deeper wetlands had higher k values than shallow wetlands and was statistically different (p<0.05, p= 0.002) from the k values for shallow wetlands. This implies that the N retention was higher in deeper wetlands than in shallow and was the highest in September. This was most likely due to the effect of temperature and vegetation in the wetlands.
33

Engineered Wetlands and Reactive Bed Filters for Treatment of Landfill Leachate

Kietliñska, Agnieszka January 2004 (has links)
The main objectives of this study were to investigate (i) anovel wetland treatment technology and (ii) selected bed filtermedia for the removal of contaminants from landfill leachate. Areview of the literature concerning experiences of the use ofconstructed wetlands (CW) for the removal of nitrogen fromlandfill leachate, showed that at least three groups oftreatment systems are in practice: sub-surface flow wetlands,hybrid systems (a combination of vertical and horizontal flowwetlands) and, compact constructed wetland (CCW). Most of thesetypeswere generally effective in reducing nitrogen (N,e.g.NH4-N, dominant N species in leachate) down toeffluent concentrations of about 10 mg L-1. Unfortunately, very little evidence ofresponsible mechanisms for the removal of N was presented,although some data indicated denitrification. The treatmentperformance of a compact constructed wetland (CCW) applied atthe Tveta Landfill, Södertälje, Sweden, wasevaluated. Chemically purified leachate and untreated leachatewere applied in periods of 7 day submergence and 7 day drainageto different sections of the CCW. The removal efficiency variedbetween 40 and 82%, and a mass removal rate of up to 5.1 g m2d-1was achieved. The chemical pre-treatment had adecisive role for the highest removal efficiencies obtained andit was unclear whether that treatment enhanced the efficiencybecause of lower toxicity and/or content of fewer competingcations. The possible combination of bed filter media and CCWas an ecotechnological treatment method for landfill leachatewas investigated by bench-scale laboratory column experiments.Reactive filter media (sorbents) was selected from their knownor suggested capacities for removal of heavy metals, nitrogenand phosphorus. Quartz sand or natural sand from an esker wasused as reference medium. Peat was used as an additionalcomponent in mixtures with the reactive media Polonite®(product from the bedrock opoka) and blastfurnace slag (BFS). A small column study also involved zeolite.Phosphorus was efficiently removed by Polonite®and NH4-N to some extent. Concerning metal removal, thebest performance was found as well for Polonite®, especially for Mn, Fe, Zn and Cu. The BFSshowed good removal efficiency for Cu, Ni and Mo. The removalof different elements was suggested to be a combination ofseveral factors,e.g.precipitation, ion exchange and adsorption. Priorto full-scale application of reactive filters at a landfillsite, matrix selection, filter design and operationalprocedures must be developed. Keywords:Blast furnace slag; Compact constructedwetland; Metals; Nitrogen; Polonite; Sorbents
34

A CRITICAL EXAMINATION OF STORM WATER RUNOFF MANAGEMENT TECHNIQUES: THE MILL CREEK WATERSHED CASE STUDY, OHIO

CAI, PUCHUN 01 July 2003 (has links)
No description available.
35

Phosphorus Retention and Fractionation in Masonry Sand and Light Weight Expanded Shale Used as Substrate in a Subsurface Flow Wetland

Forbes, Margaret G. 08 1900 (has links)
Constructed wetlands are considered an inefficient technology for long-term phosphorus (P) removal. The P retention effectiveness of subsurface wetlands can be improved by using appropriate substrates. The objectives of this study were to: (i) use sorption isotherms to estimate the P sorption capacity of the two materials, masonry sand and light weight expanded shale; (ii) describe dissolved P removal in small (2.7 m3) subsurface flow wetlands; (iii) quantify the forms of P retained by the substrates in the pilot cells; and (iv) use resulting data to assess the technical and economic feasibility of the most promising system to remove P. The P sorption capacity of masonry sand and expanded shale, as determined with Langmuir isotherms, was 60 mg/kg and 971 mg/kg respectively. In the pilot cells receiving secondarily treated wastewater, cells containing expanded shale retained a greater proportion of the incoming P (50.8 percent) than cells containing masonry sand (14.5 percent). After a year of operation, samples were analyzed for total P (TP) and total inorganic P (TIP). Subsamples were fractionated into labile-P, Fe+Al-bound P, humic-P, Ca+Mg-bound P, and residual-P. Means and standard deviations of TP retained by the expanded shale and masonry sand were 349 + 169 and 11.9 + 18.6 mg/kg respectively. The largest forms of P retained by the expanded shale pilot cells were Fe+Al- bound P (108 mg/kg), followed by labile-P (46.7 mg/kg) and humic-P (39.8). Increases in the P forms of masonry sand were greatest in labile-P (7.5 mg/kg). The cost of an expanded shale wetland is within the range of costs conventional technologies for P removal. Accurate cost comparisons are dependent upon expansion capacity of the system under consideration. Materials with a high P sorption capacity also have potential for enhancing P removal in other constructed wetland applications such as stormwater wetlands and wetlands for treating agricultural runoff.
36

Managing Cattail (Typha latifolia) Growth in Wetland Systems

Sharp, Jessica Little 08 1900 (has links)
Nutrient availability, water depth, competition, and soil management effects on cattail (Typha latifolia) growth in wetland systems were examined. Soluble reactive phosphorous (SRP), nitrate-nitrogen (NO3-N), and ammonia-nitrogen (NH3-N) removals were tested at a constructed wetland receiving municipal wastewater effluent. Over all, no significant differences in nutrients occurred between diverse planted and cattail areas. T. latifolia seeds, under the canopy of Eleochoris macrostachya, had low seed germination. Established stands of emergent vegetation can prevent cattail colonization and spread. Germination of T. latifolia at various water depths was tested, and depth impacts on cattail seedling growth and survival were ascertained using various moist soil management techniques in three ponds. Water levels at 0cm and >40cm can adversely impact cattail establishment.
37

Evaluation des potentialités de traitement par phytoépuration du lisier de porc en région PACA : paramètres chimiques, microbiologiques et macrophytiques / Evaluation of an integrated constructed wetland to manage pig manure under Mediterranean climate

Nehmtow, Julie 16 December 2015 (has links)
L’objectif de la thèse était de développer un procédé de traitement des lisiers de porc par zone humide artificielle (ZHA) adapté aux contraintes du climat méditerranéen ainsi qu’à celles des éleveurs porcins. Le lisier de porc présentant des teneurs en ammonium (NH4+) toxiques pour les espèces végétales, il a été nécessaire de prétraiter le lisier. Des expérimentations sur le prétraitement du lisier de porc par aération continue (30 jours) à petite (12 litres) et moyenne échelles (300 litres) ont donc été conduites, et ont permis une diminution des concentrations en NH4+ en dessous des seuils de tolérance végétale. Cependant, la volatilisation de l’ammoniac semble avoir été le processus majoritairement à l’origine des abattements observés (phénomène d'ihnibition). Afin d’améliorer la diminution du NH4+, des produits d’ensemencement microbiens commerciaux ont été utilisés sans que leur effet n'ait pu être mis en évidence. Lors des expérimentations à moyenne échelle, le lisier prétraité a été amendé en ZHA (mésocosmes constitués d’un filtre à écoulement vertical suivi d’un filtre à écoulement horizontal). La forte variabilité phénotypique en système expérimental des macrophytes sélectionnés et prélevés dans le milieu naturel environnant (Carex hispida, Typha latifolia, Carex cuprina, Iris pseudacorus, Alisma lanceolatum et Juncus effusus), a été illustrée. Lors des apports en lisier dans la ZHA, les espèces végétales ont répondu différement, soulignant l’intérêt des cortèges multi-spécifiques. Les premiers résultats épuratoires ont été probants. Cependant l’étude des processus épuratoires a mis en lumière la problématique de leur durabilité. / The aim of the thesis was to develop a treatment process of pig manure by constructed wetland (CW) and designed in order to be adapted to the Mediterranean climate constraints and those of pig farmers. However hog manure has concentrations above 2 g.l-1 of ammonium (NH4+), toxic to the plants. It is therefore necessary to establish a slurry pre-treatment step. The thesis has included experiments including pre-treatment of pig slurry by continuous aeration (30 days) to small (12 liters) and medium scale (300 liters). Commercial products for microbial seeding were also used. The results showed that the aeration of pig manure did allow lower concentrations of NH4+ below plant tolerance threshold. However, the ammonia volatilization process appears to be the leading cause behind the observed reductions (inhibition phenomenom). No effect could be demonstrated for microbial treatments. During meso-scale experiments, the CW was amended with the pre-treated slurry (mesocosms made of a vertical flow filter followed by a horizontal flow filter). As a first step, the high phenotypic variability of macrophytes (taken from the natural environment) in experimental system was illustrated and discussed. After manure application, the selected plant species (Carex hispida, Typha latifolia, Carex cuprina Iris pseudacorus, Alisma lanceolatum and Juncus effusus) have presented different responses, emphasizing the importance of multi-species selection for the CW. Finally, the first purifying results were conclusive. However the study of the underlying purifying processes has highlighted the issue of sustainability of these phenomena.
38

Tratamento de ?gua residu?ria de bovinocultura de leite, utilizando leitos cultivados / Wastewater treatment of dairy cattle using constructed wetlands

Almeida, Gilda Vieira de 29 February 2016 (has links)
Submitted by Celso Magalhaes (celsomagalhaes@ufrrj.br) on 2017-11-07T16:36:09Z No. of bitstreams: 1 2016 - Gilda Vieira de Almeida.pdf: 1316919 bytes, checksum: c03bdccc4b150c7dd6900dacd899cb3d (MD5) / Made available in DSpace on 2017-11-07T16:36:09Z (GMT). No. of bitstreams: 1 2016 - Gilda Vieira de Almeida.pdf: 1316919 bytes, checksum: c03bdccc4b150c7dd6900dacd899cb3d (MD5) Previous issue date: 2016-02-29 / Funda??o Carlos Chagas Filho de Amparo ? Pesquisa do Estado do RJ - FAPERJ / The amount of waste produced daily by dairy cattle is one of the biggest problems in intensive management systems. The disposal of waste from animal facilities has constituted a challenge for breeders and experts as it involves technical, health and economics. In this context, the objective of this study was to evaluate the efficiency of use of a wetlands constructed cultivated with rice in the treatment of wastewater from dairy production. For that it was built a pilot treatment plant consists of: septic tank, anaerobic filter, inert filter and wetlands constructed. Efficiency is evaluated based on the following parameters: chemical oxygen demand (COD), phosphorus, ammonia, nitrate, nitrite, total nitrogen Kjeldahl (NTK), electrical conductivity, turbidity, color and pH. The septic tank had a color and turbidity removal in 45 and 59%, respectively. The anaerobic filter presented chemical demand for oxygen removal, color nitrate and turbidity, of 36%, 41%, 17% and 32%, respectively. In the inert filter material was the reduction of chemical oxygen demand parameters at 5%, 10% nitrate, color 19% Turbidity 9% increase in ammonia and 2%. The SAC recorded removals of 35% of chemical oxygen demand, 43% turbidity, 23% colored, 1.5% phosphorus, 18% of ammonia, nitrate and 7% 17% Total Kjeldahl nitrogen. The treatment plant showed a reduction of chemical oxygen demand by 67%, phosphorus by 27%, ammonia by 25%, nitrate 81% nitrite in 72%, the total Kjeldahl nitrogen by 41%, electrical conductivity by 18%, color 71% and 85% in turbidity. The analyzes conducted over five months of the experiment showed that the removal of organic matter and turbidity in the constructed wetland system planted with rice remained in accordance with the literature, however, the nitrogen removal was lower than that found in the literature. Low nitrogen removal can be attributed to high organic load associated with low hydraulic retention time / A quantidade de dejetos produzidos diariamente pela bovinocultura leiteira ? um dos maiores problemas em sistemas de manejo intensivo. A disposi??o dos res?duos das instala??es animais tem se constitu?do em um desafio para criadores e especialistas, pois envolve aspectos t?cnicos, sanit?rios e econ?micos. Nesse contexto, o objetivo deste trabalho foi avaliar a efici?ncia da utiliza??o de um sistema de alagado constru?do (SAC) cultivado com arroz no tratamento da ?gua residu?ria de bovinocultura de leite. Para isso, foi constru?da uma esta??o piloto de tratamento composta por: tanque s?ptico, filtro anaer?bio, filtro de material inerte e SAC. A efici?ncia foi avaliada a partir dos seguintes par?metros: demanda qu?mica de oxig?nio (DQO), f?sforo, am?nia, nitrato, nitrito, nitrog?nio total Kjeldahl (NTK), condutividade el?trica, turbidez, cor e pH. O tanque s?ptico apresentou uma remo??o de cor e turbidez, em 45 e 59%, respectivamente. O filtro anaer?bio apresentou remo??es de demanda qu?mica de oxig?nio, nitrato cor e turbidez, de 36%, 41%, 17% e 32%, respectivamente. No filtro de material inerte houve a redu??o dos par?metros demanda qu?mica de oxig?nio em 5%, nitrato em 10%, cor em 19%, turbidez em 9% e acr?scimo na am?nia de 2%. O SAC apresentou remo??es de 35% de demanda qu?mica de oxig?nio, 43% de turbidez, 23% de cor, 1,5% de f?sforo, 18% de am?nia, 7% nitrato e 17% nitrog?nio total Kjeldahl. A esta??o de tratamento apresentou uma redu??o de demanda qu?mica de oxig?nio em 67%, f?sforo em 27%, am?nia em 25%, nitrato em 81%, nitrito em 72%, nitrog?nio total Kjeldahl em 41%, condutividade el?trica em 18%, cor em 71% e de turbidez em 85%. As an?lises realizadas ao longo de cinco meses de experimento permitiram concluir que a remo??o de mat?ria org?nica e turbidez no sistema alagado constru?do cultivado com arroz mantiveram-se de acordo com a literatura, no entanto a remo??o de nitrog?nio foi abaixo da encontrada na literatura. A baixa remo??o do nitrog?nio pode ser atribu?da a elevada carga org?nica associada ao baixo tempo de deten??o hidr?ulica
39

STUDY OF BACTERIAL COMMUNITIES : – A WASTEWATER TREATMENT PERSPECTIVE

Rodriguez Caballero, Adrian January 2011 (has links)
In this thesis, the application of molecular microbiology methods to understand wastewater treatment bio-reactions is described. Two different wastewater treatment systems were chosen for the experimental work. Firstly; the activated sludge processes at two different facilities in Sweden (Västerås and Eskilstuna) were investigated and compared in a context where low temperatures can affect the efficiency of the nitrogen removal performance in terms of nitrification. Initially, fluorescence in situ hybridization (FISH) was utilised in order to quantify some of the species involved in ammonia and nitrite oxidation at Västerås, providing information on how the different communities react to decreasing temperatures. Then, the polymerase chain reaction (PCR), cloning-sequencing method was employed in order to study the composition of the ammonia oxidizing bacteria (AOB) community at the same two wastewater treatment plants (WWTPs). Secondly; the potential use of constructed wetlands for the treatment of winery wastewater was studied. High ethanol concentration artificial wastewater with and without inorganic nutrients (nitrates and phosphates) was fed in a set of pilot-scale constructed wetlands. Pollutant removal performance and enzyme activity tests were carried out. Additionally, the bacterial community structure was investigated by means of denaturing gradient gel electrophoresis (DGGE). In the first set of studies it was shown that the AOB population which plays a major role in nitrifying reactors presented a seasonal shift and a higher diversity at Västerås during winter time, while the nitrification performance maintained stable levels and the ammonia removal efficiency increased. Thus, the higher ammonia removal efficiency at Västerås could be related to the diversity of the AOB population composition. Lastly, when constructed wetlands were in focus, the differential effects of ethanol and nutrients over the chemical oxygen demand (COD) removal performance were proven. In fact, the addition of nutrients on one of the experimental wetlands increased the COD (ethanol) removal and supported the maintenance of a bacterial population similar to the control wetland (no ethanol added). In conclusion, both studies proved a strong relationship between process performance (pollution removal) and the dynamics of the bacterial communities involved.
40

Performance of a Surface-Flow Constructed Wetland Treating Landfill Surface-Water Runoff

Hick, Justin 11 June 2013 (has links)
Landfills are a major potential source of groundwater and surface-water contamination. The compounds that can leach from landfilled materials include dissolved organic matter, inorganic macrocomponents, heavy metals, and xebobiotic organic compounds. Landfill surface-water runoff poses a threat to the environment due to high mobility, but has not been rigorously characterized with regards to common pollutants found in landfills. It is well documented that constructed wetlands can serve as an effective treatment option for many pollutants found in landfills. The Napanee Landfill has constructed a wetland in order to treat surface-water runoff coming off the landfill. The objectives of this study were to: 1) characterize the water chemistry of surface-water runoff for an inactive landfill; 2) evaluate the treatment potential for the constructed wetland system at the Napanee Landfill; and, 3) recommend design, maintenance, and operative improvements to enhance effluent water quality. The analysis of the landfill surface-water runoff entering the Napanee Landfill constructed wetland included the pollutants nitrate, ammonia, sulphate, phosphorus, and chloride. The median inflow and outflow concentrations for all of the observed pollutants did not exceed Canadian federal or provincial water quality guidelines. There were sampling days where ammonia, phosphorus, and chloride exceeded guidelines at the inflow and days where ammonia and chloride exceeded guidelines at the outflow. The only pollutant that saw a statistically significant decrease in concentrations was sulphate, with a change of 38% from the inflow to the outflow. Other changes of note were nitrate and phosphorus concentrations increasing by 50% and 23% respectively from the inflow to the outflow. There are a variety of improvements that can be made to the Napanee Landfill constructed wetland that would increase the treatment efficiency of ammonia. Incorporating a vertical-flow wetland would increase available surface area for nitrifying bacteria growth and would provide more oxygen for nitrification processes; both would increase the potential for significant ammonia treatment. Overall, the concentrations of the pollutants found in the surface-water runoff coming off of the Napanee Landfill constructed wetland did not pose a significant threat to the environment at the time of sampling and treatment processes were only successful in reducing sulphate pollutant concentrations.

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