1,720,989 research outputs found
Performance of a full-scale anaerobic UASB digester treating blackwater from an urban city district in Helsingborg, Sweden
No full textThe growing global population has increased the demand for circular sanitation solutions that enhance energy and nutrient recovery. Anaerobic digestion (AD) of blackwater (BW) offers a promising solution, but its application in full-scale UASB reactors remains unexplored. This study evaluated the performance of a full-scale UASB (50 m3) treating BW collected from a new city district (Oceanhamnen) located in Helsingborg, Sweden, over 130 weeks, applying two different organic loading rates (OLRs), focusing on COD removal, biogas production, and mass balances for COD, nitrogen, and phosphorus, and compared its performance with previous lab-scale studies. The full-scale UASB achieved its highest COD removal efficiency (88 %) and degree of methanisation (0.77 kgCOD-CH4 kg⁻¹ CODin) during the low organic loading rate (OLR) phase. In the higher OLR phase, COD removal dropped to 72 % due to sludge washout, although the degree of methanisation remained high (0.71 kg COD-CH4 kg⁻¹ CODin). Mass balance results showed 69 % of influent COD was converted into methane, while 28 % remained in the effluent, likely due to sludge washout. The decanted effluent contained 92 % of N and 82 % of P reflecting the low sludge production. Compared with lab-scale studies, the full-scale UASB achieved comparable COD removal and biogas yields despite challenges like sludge washout during the higher OLR. The results confirm that the full-scale application of blackwater treatment is suitable for circular sanitation solutions. Further research is needed to optimize solids retention and reduce effluent COD for sustainable full-scale operations, as well as optimizing the energy balance calculations
Startup and stabilization of anaerobic membrane bioreactors at ambient temperature
No full textThere has been an increasing interest in wastewater treatment in last decades to reduce human footprint. Primarily, anaerobic technology focused on treatment and stabilization of sludge, but now the tendency is to give it a major role in low cost treatment of high/low strength wastewaters, since anaerobic digestion offers energy generation through gas production. Anaerobic membrane bioreactors (AnMBR) combine anaerobic digestion with membrane
filtration. They are becoming a feasible option for treating previous unsuitable low-strength wastewaters, decoupling hydraulic and solid retention times, and providing successful treatment with the benefits of biogas production.
However, the digestion process is optimal at mesophilic or termophilic (35-37 ºC), requiring heating of reactors. The more inexpensive option to treat the wastewater at its ambient temperature is feasible using AnMBR since this type of reactor can offer long sludge retention times.
On the other hand, the digestion equilibrium turns out more sensible and delicate, and performing a proper and robust start-up of AnMBR in ambient temperatures is still challenging.
The aim of the thesis was the successful startup and stabilization of AnMBR systems at ambient temperature (25 ºC) and low organic loading rate (OLR). Reactor operation was monitored, and the most relevant process parameters were considered for the aim.
Two pilot-scale AnMBR’s (120L) were used with an external membrane configuration. The experiment was carried out in 100 days. Substrate feeding consisted of synthetic dairy wastewater with added nutrients solution. The inoculum was provided from a full-scale anaerobic plant at a digester of BV dairy (UK) treating dairy wastewater at 30ºC.
Main operation parameters were monitored every day, along with gas production and methane yield. Laboratory tests were performed twice a week with samples of the reactors and effluent.
A number of parameters were analyzed, the most important of which were total solids content (TSS), alkalinity, fatty acids, biogas content and chemical oxygen demand (COD).
The startup of the two AnMBR’s differed greatly. In System 1, stable conditions were acquired in one month of operation. System 2 failed after 20 days of function, and did not achieve successful startup. It was not possible to fully recover it during the days of study due to dramatically slow growth of microorganisms and low stability of the process.
Thus, satisfactory system performance could be achieved but the ambient anaerobic process was vulnerable to inhibitory conditions. Both systems showed that the delicate process operation required fast corrective measures to prevent digestion failure. Causes of instability and failure were: washout of biomass, high content of VFA, low buffering capacity and poor performance of technical equipment and low pH. However, the digestion could stand a lower pH range than found in literature.
In conclusion, the best parameters to control the startup were pH, alkalinity, methane content, biomass content and organic removal. In this sense, low buffering capacity of a reactor makes it vulnerable to inhibition by sudden pH changes, easily solved by systematic addition of a buffering compound. Finally, the use of simple and fast alkalimetric methodologies can give satisfactory process overview compared to complex and more precise techniques for alkalinity measurement.Outgoin
Startup and stabilization of anaerobic membrane bioreactors at ambient temperature
Get PDFThere has been an increasing interest in wastewater treatment in last decades to reduce human footprint. Primarily, anaerobic technology focused on treatment and stabilization of sludge, but now the tendency is to give it a major role in low cost treatment of high/low strength wastewaters, since anaerobic digestion offers energy generation through gas production. Anaerobic membrane bioreactors (AnMBR) combine anaerobic digestion with membrane
filtration. They are becoming a feasible option for treating previous unsuitable low-strength wastewaters, decoupling hydraulic and solid retention times, and providing successful treatment with the benefits of biogas production.
However, the digestion process is optimal at mesophilic or termophilic (35-37 ºC), requiring heating of reactors. The more inexpensive option to treat the wastewater at its ambient temperature is feasible using AnMBR since this type of reactor can offer long sludge retention times.
On the other hand, the digestion equilibrium turns out more sensible and delicate, and performing a proper and robust start-up of AnMBR in ambient temperatures is still challenging.
The aim of the thesis was the successful startup and stabilization of AnMBR systems at ambient temperature (25 ºC) and low organic loading rate (OLR). Reactor operation was monitored, and the most relevant process parameters were considered for the aim.
Two pilot-scale AnMBR’s (120L) were used with an external membrane configuration. The experiment was carried out in 100 days. Substrate feeding consisted of synthetic dairy wastewater with added nutrients solution. The inoculum was provided from a full-scale anaerobic plant at a digester of BV dairy (UK) treating dairy wastewater at 30ºC.
Main operation parameters were monitored every day, along with gas production and methane yield. Laboratory tests were performed twice a week with samples of the reactors and effluent.
A number of parameters were analyzed, the most important of which were total solids content (TSS), alkalinity, fatty acids, biogas content and chemical oxygen demand (COD).
The startup of the two AnMBR’s differed greatly. In System 1, stable conditions were acquired in one month of operation. System 2 failed after 20 days of function, and did not achieve successful startup. It was not possible to fully recover it during the days of study due to dramatically slow growth of microorganisms and low stability of the process.
Thus, satisfactory system performance could be achieved but the ambient anaerobic process was vulnerable to inhibitory conditions. Both systems showed that the delicate process operation required fast corrective measures to prevent digestion failure. Causes of instability and failure were: washout of biomass, high content of VFA, low buffering capacity and poor performance of technical equipment and low pH. However, the digestion could stand a lower pH range than found in literature.
In conclusion, the best parameters to control the startup were pH, alkalinity, methane content, biomass content and organic removal. In this sense, low buffering capacity of a reactor makes it vulnerable to inhibition by sudden pH changes, easily solved by systematic addition of a buffering compound. Finally, the use of simple and fast alkalimetric methodologies can give satisfactory process overview compared to complex and more precise techniques for alkalinity measurement.Outgoin
Startup and stabilization of anaerobic membrane bioreactors at ambient temperature
No full textThere has been an increasing interest in wastewater treatment in last decades to reduce human footprint. Primarily, anaerobic technology focused on treatment and stabilization of sludge, but now the tendency is to give it a major role in low cost treatment of high/low strength wastewaters, since anaerobic digestion offers energy generation through gas production. Anaerobic membrane bioreactors (AnMBR) combine anaerobic digestion with membrane
filtration. They are becoming a feasible option for treating previous unsuitable low-strength wastewaters, decoupling hydraulic and solid retention times, and providing successful treatment with the benefits of biogas production.
However, the digestion process is optimal at mesophilic or termophilic (35-37 ºC), requiring heating of reactors. The more inexpensive option to treat the wastewater at its ambient temperature is feasible using AnMBR since this type of reactor can offer long sludge retention times.
On the other hand, the digestion equilibrium turns out more sensible and delicate, and performing a proper and robust start-up of AnMBR in ambient temperatures is still challenging.
The aim of the thesis was the successful startup and stabilization of AnMBR systems at ambient temperature (25 ºC) and low organic loading rate (OLR). Reactor operation was monitored, and the most relevant process parameters were considered for the aim.
Two pilot-scale AnMBR’s (120L) were used with an external membrane configuration. The experiment was carried out in 100 days. Substrate feeding consisted of synthetic dairy wastewater with added nutrients solution. The inoculum was provided from a full-scale anaerobic plant at a digester of BV dairy (UK) treating dairy wastewater at 30ºC.
Main operation parameters were monitored every day, along with gas production and methane yield. Laboratory tests were performed twice a week with samples of the reactors and effluent.
A number of parameters were analyzed, the most important of which were total solids content (TSS), alkalinity, fatty acids, biogas content and chemical oxygen demand (COD).
The startup of the two AnMBR’s differed greatly. In System 1, stable conditions were acquired in one month of operation. System 2 failed after 20 days of function, and did not achieve successful startup. It was not possible to fully recover it during the days of study due to dramatically slow growth of microorganisms and low stability of the process.
Thus, satisfactory system performance could be achieved but the ambient anaerobic process was vulnerable to inhibitory conditions. Both systems showed that the delicate process operation required fast corrective measures to prevent digestion failure. Causes of instability and failure were: washout of biomass, high content of VFA, low buffering capacity and poor performance of technical equipment and low pH. However, the digestion could stand a lower pH range than found in literature.
In conclusion, the best parameters to control the startup were pH, alkalinity, methane content, biomass content and organic removal. In this sense, low buffering capacity of a reactor makes it vulnerable to inhibition by sudden pH changes, easily solved by systematic addition of a buffering compound. Finally, the use of simple and fast alkalimetric methodologies can give satisfactory process overview compared to complex and more precise techniques for alkalinity measurement.Outgoin
Enhancing anaerobic digestion in urban wastewater management
Get PDFThe thesis investigates how anaerobic digestion could be utilized to improve wastewater management,specifically in regards to future expected regulation on sludge management in Sweden.Two possible paths of applying anaerobic digestion are investigated. First, the usage of thermophilic anaerobicdigestion of sludge in order to achieve pathogen hygienization. Second, the usage of anaerobic digestion totreat wastewaters at decreased temperature. The evaluation of each path was made through practical labscale experiments. Additionally, the benefits of each path was compared through desk top environmentalimpact studies and economic analysis.The results for the first path showed that thermophilic anaerobic digestion renders high pathogen hygienizationeven at relative short exposure times. However no additional beneficial impact on biogas production or thereduction of organic micropollutants was found. The results for the second path showed that the difficulty ofoperating the sensitive anaerobic digestion process at low temperatures can be partly overcome by simpleengineering batch tests. Furthermore, the dissolved methane in the effluent wastewaters can be extractedusing membrane contactors. Finally, the environmental impact assessment showed that increased resourcerecovery from wastewater, as well as decreased climate impact, can be achieved by applying anaerobicdigestion on source separated domestic wastewaster.The economic evaluation of the two paths showed that the implementation of source separation systems isexpensive compared to implementing the needed thermophilic hygienization. However, source separationsystems would greatly boost nutrient recovery from cities to agriculture which complies well with the goals ofthe Swedish Environmental Protection Agency
Enhancing anaerobic digestion in urban wastewater management [Elektronisk resurs]
No full textThe thesis investigates how anaerobic digestion could be utilized to improve wastewater management, specifically in regards to future expected regulation on sludge management in Sweden. Two possible paths of applying anaerobic digestion are investigated. First, the usage of thermophilic anaerobic digestion of sludge in order to achieve pathogen hygienization. Second, the usage of anaerobic digestion to treat wastewaters at decreased temperature. The evaluation of each path was made through practical lab scale experiments. Additionally, the benefits of each path was compared through desk top environmental impact studies and economic analysis. The results for the first path showed that thermophilic anaerobic digestion renders high pathogen hygienization even at relative short exposure times. However no additional beneficial impact on biogas production or the reduction of organic micropollutants was found. The results for the second path showed that the difficulty of operating the sensitive anaerobic digestion process at low temperatures can be partly overcome by simple engineering batch tests. Furthermore, the dissolved methane in the effluent wastewaters can be extracted using membrane contactors. Finally, the environmental impact assessment showed that increased resource recovery from wastewater, as well as decreased climate impact, can be achieved by applying anaerobic digestion on source separated domestic wastewaster. The economic evaluation of the two paths showed that the implementation of source separation systems is expensive compared to implementing the needed thermophilic hygienization. However, source separation systems would greatly boost nutrient recovery from cities to agriculture which complies well with the goals of the Swedish Environmental Protection Agency
Recycling – The future urban sink for wastewater and organic waste
No full textThe world’s population is estimated to reach 11 billion in this century, with some 8.5 billion living in urban areas. Cities become unprecedented hot spots of demand for virgin water and food, as well as producers of large volumes of valuable waste. The recycling of urban nutrient-rich liquid and solid waste as fertilizer in agriculture will thus be of benefit to both sectors. The analysis suggests that recycling has the potential to become the ultimate sink for organic waste and wastewater, while simultaneously securing the supply of food and fertilizers, and reducing both local and global environmental impacts. Presently, harmful chemical substances from various consumer products in our chemical society are disposed of in urban waste flows and hamper recovery and reuse. A combination of counter measures such as not mixing nutrient-rich blackwater with grey water polluted with chemical compounds, are crucial. The sludge from the small volume of blackwater can contribute enough fertilizers to secure global food supplies by the year 2100. The voluminous grey water will contain few pathogenic microorganisms and can be treated for non-potable reuse. Three urban arrangements are analysed: Singapore (entire city), Helsingborg in Sweden (city district), and Bangalore in India (eco-house)
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
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