• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 54
  • 19
  • 4
  • 2
  • 2
  • 2
  • 2
  • 1
  • 1
  • Tagged with
  • 108
  • 108
  • 43
  • 37
  • 33
  • 26
  • 21
  • 20
  • 19
  • 15
  • 15
  • 14
  • 14
  • 13
  • 13
  • 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.

Evaluation of the nutrient removal efficiency of a constructed wetland system

Hart, Kimberly Ann 30 October 2006 (has links)
In north central Texas, USA, free-water surface wetlands have been constructed to treat pre-treated wastewater effluent from the Trinity River. Water quality and vegetation data from the first two years of operation (June 2003 to May 2005) were used to determine cell-to-cell and system-wide removal efficiency of total suspended solids (TSS), total phosphorus (TP) and total nitrogen (TN). The wetland system consisted of one non-vegetated sedimentation basin and a series of four connected, vegetated wetland cells. Temporal analyses displayed varying monthly, seasonal and yearly trends of the wetlands’ concentration of the three parameters. Spatial analysis results confirmed that TSS, TP and TN concentrations were greater at the beginning of the system as compared to the end of the wetland system. Percent reduction analyses showed that the second wetland cell (WC2) was the most efficient in TSS, TP and TN removal, while the last wetland cell (WC4) had the lowest reduction of the three parameters. TSS removal was significant (α = 0.05) moving consecutively among the sites in the wetland system, with exception to the last wetland cell. TP removal was only significant (α = 0.05) moving from the third wetland cell (WC3) to WC4, while TN removal was significant (α = 0.05) moving from the sedimentation basin to the first wetland cell (WC1) and then again moving from WC3 to WC4. Overall removal efficiency of the wetland system (from the Trinity River to WC4) was quite high, with reductions over 97% for TSS, 47% for TP and 67% for TN. N:P ratios decreased moving consecutively throughout the field-scale wetlands. Vegetation analyses found WCs 1 and 3 to contain the greatest vegetation species richness, while WC2 had the lowest richness. The vegetative composition of the four cells was mostly the same. A comparison was conducted between the nutrient reduction efficiency and vegetation data of this wetland system with data from a pilotscale wetland system that was operated from 1992 to 2000. The findings of this study suggest that during the first two years of operation, the wetland system’s performance is comparable to the pilot-scale wetlands which were operated for eight years.

Removal of nutrients from lake water by intergral vertical flow and subsurface flow constructed wetlands

Wu, Pei-shuan 29 July 2008 (has links)
Constructed wetlands (CWs) utilize the natural mechanisms in wetlands to remove pollutants by physical, chemical and biological processes. CWs are one of the ecological engineering methods to purity water quality and has been experimented to assess their capabilities to remove nutrients from eutrophic water bodies of lakes and reserviors. This study was carried out to compare the removal of nutrients between vegetated and unvegetated CWs. The vertical flow bed was placed in the upstream, while the horizontal subsurface flow bed was set in the downstream. Cannaceae was selected to plant in the vegetated CWs. Two kinds of hydraulic retention time (HRT), 3 days and 7 days, were applied and compared with each other in this study. The experimental results show that no significantly difference between vegetated and unvegetated systems. The removal efficiencies of SS, BOD, NH3-N, TP are measure equal to about 80%, 75%, 80% and 65%, respectively, while the removal efficiencies of TN, OP, and COD were reached about 50% and larger. Both of the two systems show high efficiencies for nutrient removal. In the comparison between the two kinds of HRT¡¦s, the HRT controlled at 3 days presented higher removal efficiencies than that controlled at 7 days.

The role of intracellular storage products in biological nutrient removal /

Zeng, Raymond Jianxiong. January 2002 (has links) (PDF)
Thesis (Ph. D.)--University of Queensland, 2002. / Includes bibliographical references.

Biological nutrient removal in sequencing batch reactors using fibrouspacking medium

凌偉忠, Ling, Wai-chung, Jackson. January 1996 (has links)
published_or_final_version / Civil and Structural Engineering / Master / Master of Philosophy

Sequencing Batch Moving Bed Biofilm Reactors for Treatment of Cheese Production Wastewater

Tsitouras, Alexandra 14 May 2021 (has links)
Discharging cheese production wastewater with high concentrations of organics and nutrients is detrimental to receiving aquatic systems, as the release of these deleterious substances cause oxygen depletion, and eutrophication respectively. On-site treatment of cheese production wastewater requires the removal of high concentrations of organics and nutrients with a small land footprint to meet regulations. There is therefore a critical need for compact, high-rate, cost-effective wastewater technologies such a as the moving bed biofilm reactor (MBBR). Although MBBR systems have been well established for carbon and nitrogen removal, to date only a limited number of studies have achieved enhanced biological phosphorous removal in sequencing batch moving bed biofilm reactor (SB-MBBR) systems, and only for municipal-strength wastewater. Operating SB-MBBR systems under sequencing batch mode enables the reactor operation to be well synced to the fluctuating influent concentrations and flow characteristics of cheese production wastewaters. Furthermore, cycling between anaerobic and aerobic conditions can be achieved in a single sequencing batch reactor, which can promote the proliferation of poly-phosphate accumulating organisms. The SB-MBBR is studied in this research for the removal of carbon, nitrogen, and phosphorous from cheese production wastewaters. Specifically, the effects of anaerobic staging time, aeration rate, enhanced aerobic operation, and adding a second reactor in series was studied by analyzing the kinetics, biofilm characteristics, and microbiome. Extending the anaerobic staging time was shown to achieve aerobic soluble chemical oxygen demand removal rates of 92.5±2.8 g·m⁻²d⁻¹, by selecting for a thinner biofilm with, with a lower biofilm dry-density and a more rough biofilm surface, and therefore likely a biofilm with an enhanced mass transport. A significant shift in the microbiome was observed with longer anaerobic staging times and lower aeration, whereby possible putative poly-phosphate accumulating organisms including Brachymonas, and Dechloromonas were selected for in greater relative abundances compared to anaerobic bacteria. The total phosphorous removal in the possibly resulted from enhanced biological phosphorous removal, supported by the high abundance of putative poly-phosphate accumulating organisms (43.1±8.4%), which dominated the biofilms in the SB-MBBRs with 120 and 168 minute anaerobic staging times. Finally, total ammonia nitrogen oxidation was achieved through partial nitritation with a two reactor in series configuration with a removal rate of 1.07±0.05 g-N·m⁻²d⁻¹. Two SB-MBBRs operated in series was shown to be the superior strategy for achieving TAN compared to a single SB-MBBR with extended aerobic operation. By operating two SB-MBBRs in series, competition between autotrophic nitrifiers and heterotrophs is averted, and AOB proliferate in the biofilm, achieving TAN oxidation. Since TAN oxidation is likely achieved through partial nitrification, the SB-MBBR technology may be incorporated in a deammonification treatment train. The overall study presents novel information for the SB-MBBR design and operation, along with biofilm and microbiome fundamental findings that will guide future pilot- and full-scale applications of the SB-MBBR to treat cheese production wastewater.

Evaluating Opportunities to Improve Resource Efficiency of Conventional Wastewater Treatment Using the Alga Cladophora glomerata

Szabo, Adam R. 27 September 2012 (has links)
No description available.

Constructed Floodplain Wetland Effectiveness for Stormwater Management

Ludwig, Andrea L. 04 August 2010 (has links)
A 0.2-hectare wetland was constructed in the floodplain of Opequon Creek in Northern Virginia as a best management practice (BMP) for stormwater management. The research goals were to 1) determine if wetland hydrology existed and quantify the role of groundwater exchange in the constructed wetland (CW) water budget, 2) estimate wetland hydraulic characteristics during overbank flows, and 3) quantify the event-scale nutrient assimilative capacity of the constructed wetland. CW water table elevations and hydraulic gradients were measured through an array of nested piezometers. During controlled flooding events, stream water was pumped from the creek and amended with nutrients and a conservative tracer in two seasons to determine hydraulic characteristics and nutrient reduction. Samples were collected at the inlet, outlet structure, and at three locations along three transects along the wetland flowpath. Water table elevation monitoring demonstrated that wetland hydrology existed on the site. The mean residence time of the wetland was found to be 100 min for flow-rates of 4.25-5.1 m3/min. Residence time distributions of the high and low marsh features identified a considerable degree of flow dispersion. Manning's n varied between macrotopographic features and was significantly higher in the spring event as compared to the fall event, likely due to the presence of rigid-stem vegetation. Average wetland n was 0.62. Total suspended solid concentrations decreased with increasing residence time during both experiments. Mass reduction of pollutants were 73% total suspended solids (TSS), 54% ammonia-nitrogen (NH3-N), 16% nitrate-N (NO3-N), 16% total nitrogen (TN), 23% orthophosphate-phosphorus (PO4-P), and 37% total P (TP) in the fall, and 69% TSS, 58% NH3-N, 7% NO3-N, 22% TN, 8% PO4-P, and 25% TP in the spring. Linear regression of mass flux over the event hydrograph was used to determine pollutant removal rates between the wetland inlet and outlet. Pollutant removal rates were determined through linear regression of mass flux and were higher in the spring event than in the fall. Dissolved nitrogen species were more rapidly removed than dissolved phosphorus. TSS, TP, and TN removal were greater and faster than dissolved nutrient species, suggesting that physical settling was the dominant removal mechanism for stormwater pollutants. / Ph. D.

Photosynthetic Oxygenation and Nutrient Utilization by Chlorella vulgaris in a Hybrid Membrane Bioreactor and Algal Membrane Photobioreactor System

Najm, Yasmeen Hani Kamal 11 1900 (has links)
Aerobic activated sludge membrane bioreactors (AS-MBR) in municipal wastewater treatment are compact systems that can efficiently perform biological organic oxidation. However, aerobic processes require mechanical aeration accounting for over 40% of total expenditure of a wastewater facility. Additionally, a global urgency for nutrient (Nitrogen/Phosphorus) removal strategies due to surges of eutrophication events requires complex MBR configurations. An innovative and cost-effective process was developed with a dual income-stream: high-quality treated effluent and value-added microalgal biomass for several applications. The proposed process involved several integrated components; an ultrafiltration AS-MBR for organic oxidation followed by a microalgal membrane photobioreactor (MPBR) to remove nutrients (N/P) through assimilation while simultaneously photosynthetically generating dissolved oxygen effluent that was recirculated back into the AS-MBR, thereby reducing the need for mechanical aeration for oxidation. A lab-scale system was fed with a synthetic medium-strength municipal wastewater. The microalgal species C. vulgaris was initially tested in batch trials as a proof-of-concept study on its potential as a photosynthetic oxygenator for the AS-MBR and identify its nutrient utilization efficiencies. The MPBR and MBR were later constructed for continuous operation, with the aim to identify an optimal process configuration. The unit processes were subsequently isolated, where the AS-MBR was subjected to a modelled algal effluent to assesses the impact of varying influent characteristics and effluent recycle rates. A microbial community analysis was performed by high-throughput sequencing and a statistical data-driven modeling approach to assess treatment performances. The MPBR stage was then subjected to the effluent achieved by the AS-MBR stage under varying operating conditions to assess its treatment performance and the resulting algal biomass biochemical composition to identify its suitability for bioethanol, biodiesel, or animal feed production. The findings of this study ultimately confirmed the ability of C. vulgaris to support the AS-MBR for organic removal and fractional nutrient removal by supplying the oxygen demand, and further achieve an effluent polish stage for nutrient removal. The process configuration also demonstrated the ability to achieve a high microalgal biomass production with the potential of extracting valuable products as an added benefit of the wastewater treatment.

Tratamento de efluentes de curtume com consórcio de microalgas

Pena, Aline de Cássia Campos January 2017 (has links)
Os efluentes líquidos de curtumes apresentam altas cargas orgânicas e de poluentes que devem ser tratados corretamente para atingir os padrões legais para seu descarte, evitando a eutrofização de corpos hídricos e poluição das águas. O acabamento do couro é o estágio final da produção, onde o couro recebe as características desejadas de acordo com os produtos e artigos que serão produzidos. Os efluentes das etapas de processamento para acabamento do couro são responsáveis por conterem poluentes químicos devido ao uso de corantes, surfactantes, metais tóxicos, agentes emulsificantes, recurtentes, óleos, pigmentos, resinas, entre outros produtos químicos adicionados. As microalgas têm sido alvo de vários estudos no âmbito de tratamento de efluentes, devido à sua capacidade de remover diversos nutrientes, matéria orgânica do meio e por serem formas mais limpas e econômicas de tratar os poluentes. Diante disto, o objetivo deste trabalho foi avaliar o emprego de um consórcio de microalgas para tratamento de efluentes de um curtume e analisar a capacidade de remoção de poluentes que são nutrientes para estes microrganismos. Os efluentes foram caracterizados ao longo dos ensaios com o consórcio de microalgas por meio de Nitrogênio Total (NT), Amônia (NH3), Fósforo (P-PO4), Carbono total (CT), Carbono Orgânico Total (COT), Carbono inorgânico (CI), DQO e Demanda Biológica de Oxigênio (DBO) e foi acompanhado o crescimento das microalgas. Para os experimentos foram coletados efluentes em três estágios distintos em uma estação de tratamento: efluente bruto (B), efluente após tratamento primário de coagulação/floculação (P) e efluente após ao tratamento biológico secundário (S). Os resultados com concentração de efluente de 50%, diluídos em água destilada (A), após 16 dias de cultivo, mostraram que houve crescimento do consórcio nos três efluentes com um crescimento máximo de 1,77 g L-1 no efluente Bruto (50B50A). Na sequência, foi testado o cultivo em efluente bruto (100B) e em efluentes compostos nas seguintes proporções: 50% efluente bruto + 50% efluente após tratamento biológico (50B50S) e 25% efluente bruto + 75% efluente após tratamento biológico (25B75S). Foi possível cultivar o consórcio no efluente bruto sem diluição, entretanto os resultados foram ruins, pois o mesmo apresentou baixo crescimento e, consequentemente, baixos níveis de remoção de nutrientes. Com o efluente composto 25B75S percebeu-se morte rápida das microalgas, uma vez que o efluente apresentava baixas concentrações de nutrientes. Em contrapartida, no efluente 50B50S foram atingidos valores efetivos de crescimento e remoção de nutrientes. Em cultivos fotoautotrófico, mixotrófico e heterotrófico de efluente composto 50B50S e de 75% efluente bruto + 25% efluente após tratamento biológico (75B25S), os melhores resultados foram atingidos no efluente 75B25S no cultivo fotoautotrófico, crescendo até 1,42 g L-1 e atingindo valores de remoção de NNH3, Nitrogênio Total (NT), DQO, carbono orgânico total (TOC) e demanda biológica de oxigênio (DBO5), de 99,90%, 74,89%, 56,70%, 58,18% e 20,68%, respectivamente. Ao obter a microalga isolada Tetraselmis sp. predominante no consórcio foi analisado os parâmetros anteriores em cultivo fotoautotrófico, além disso foi verificada a quantidade de lipídio presente na biomassa. A microalga Tetraselmis sp. apresentou um crescimento notório no cultivo fotoautotrófico com remoções eficientes dos parâmetros e 5,0% de lipídio no peso seco. / Liquid effluents from tanneries present high organic and pollutant loads and must be treated correctly to meet the legal standards for effluent disposal and to avoid eutrophication of water bodies and water pollution. The leather finish is the final stage of production, where the leather receives the desired characteristics according to leather goods and articles. The effluents from the processing steps for leather finishing are responsible for containing chemical pollutants due to the use of dyes, surfactants, toxic metals, emulsifying agents, retanning agents, oils, pigments, resins, among other chemicals added. Microalgae have been the subject of several studies in the field of effluent treatment due to their ability to remove various nutrients, organic matter from the environment and to be cleaner and more economical ways to treat pollutants. In this work, the growth of a microalgae consortium for the treatment of effluents from a tannery was analyzed and the capacity of removal of Total Nitrogen (NT), Ammonia (NH3), Phosphorus (P-PO4), Total Carbon ), Total Organic Carbon (COD), COD and Biological Oxygen Demand (DBO), as well as the growth of microalgae biomass in these effluents. The effluents were characterized before and after the trials with the microalgae consortium. Effluents were collected in three distinct stages at a treatment plant: crude effluent (B), effluent after primary coagulation / flocculation (P) treatment and effluent after secondary biological treatment (S). The results with 50% effluent concentration, diluted in distilled water (A) after 16 days of cultivation, showed that there was a consortium growth in the three effluents with a maximum growth of 1.77 g L-1 in the crude effluent (50P50A). (50B50S) and 25% crude effluent + 75% effluent after biological treatment (25B75S) were tested in the following proportions: 50% crude effluent + 50% effluent after biological treatment (50B50S). It was not possible to cultivate the consortium in pure crude effluent, since it presented low growth and, consequently, low levels of nutrient removal. With the compound effluent 25B75S it was observed rapid death of the microalgae, since the effluent presented low concentrations of nutrients. On the other hand, in the effluent 50B50S, effective values of growth and nutrient removal were achieved. In photoautotrophic, mixotrophic and heterotrophic cultures of 50B50S effluent and 75% crude effluent + 25% effluent after biological treatment (75B25S), the best results were reached in the effluent 75B25S in photoautotrophic cultivation, growing up to 1.42 g L-1 and reaching values of removal of N-NH3, total nitrogen (NT), (DQO), total organic carbon (COT) and biological oxygen demand (DBO), of 99.90%, 74.89%, 56.70%, 58.18% and 20.68%, respectively. By obtaining the isolated microalgae Tetraselmis sp., predominant in the consortium and analyzed and the previous parameters in photoautotrophic cultivation, in addition to being verified the amount of lipid present in the biomass. The microalgae Tetraselmis sp. showed a notable growth in photoautotrophic cultivation with efficient removal of the parameters and 5.0% of lipid in dry weight.

Effects of Rainfall and Polysilicon Industrial Pretreated Effluent on Biological Nitrogen Removal

Lu, Yi-chieh 04 September 2012 (has links)
The biological treatment is one of the commonly methods of wastewater treatment plant in wastewater treatment processes. The biological treatment can meet water quality standards required by the plant in response to different sewage conditions and qualities. It can purify high pollution loading sewage through the use of microbial metabolic transformation. Through effectively protecting and using water resources, the ecological balance of ocean and river can be maintained and environmental quality can be improved in consequence. This study analyzes the operations of a wastewater treatment plant, which is part of an urban sewage system. The major sources of inflow to the plant are domestic sewage, followed by rainfall runoff and industrial wastewater. The biological treatment system adopted in the plant is "Biological Nutrient Removal (BNR)". The reason for using BNR is to prevent eutrophication of downstream water bodies due to untreated nitrogen, phosphorus and other nutrient substances in discharged sewages. The design of BNR, which is called "A2O activated sludge method", would increase the anaerobic-anaerobic mixing process for simultaneous removal of the sewage of organic carbon, nitrogen, phosphorus and BOD. The study collected the data to analyze the impacts of extreme weather event, i.e. Typhoon Morakot, and the effects of newly developed industrial, i.e. polysilicon industry. Water quality data of inflow and outflow sewages starting from January 2009 to December 2011 were compiled to perform statistical analyses. By plotting various time series figures, the study can effectively explore the variations of pollutant removal under the two designated situations in the biological treatment system. The results show the abnormal increase in conductivity of effluent which has decreased pollutant removal since August 2010. Besides, the confluence of rainwater and sewage has severely affected the efficiency and quality of the biological treatment process during a typhoon or heavy rain event. This study has identified the potential impacts on a BNR plant which can provide the administration to enhance the effectiveness of the biological treatment plant and the function of sewage purification stability control.

Page generated in 0.0615 seconds