45 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
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
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
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 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
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)
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
Potential for nutrient recovery and biogas production from blackwater, food waste and greywater in urban source control systems.
No full textIn the last decades, the focus in waste and wastewater treatment systems has shifted towards increased recovery of energy and nutrients. Separation of urban food waste and domestic wastewaters using source control systems could aid this increase; however their effect on overall sustainability is unknown. To obtain indicators for sustainability assessments, five urban systems for collection, transport, treatment and nutrient recovery from blackwater, greywater and food waste were investigated using data from implementations in Sweden or northern Europe. The systems were evaluated against their potential for biogas production and nutrient recovery by the use of mass balances for organic material, nutrients and metals over the system components. The resulting indicators are presented in units suitable for use in future sustainability studies or life cycle assessment of urban waste and wastewater systems. The indicators show that source control systems have the potential to increase biogas production with more than 70% compared to a conventional system and give a high recovery of phosphorus and nitrogen as biofertilizer. The total potential increase in gross energy equivalence for source control systems was 20-100%; the greatest increase shown for vacuum-based systems
Be circular – Från rötrester av svartvatten och köksavfall till flytande gödselmedel
No full textEffektiv användning av ändliga resurser är ett av de främsta målen för en hållbar utveckling. I ett kretsloppsperspektiv skulle näringsrikt avloppsvatten och näring fastlagd i köksavfall kunna bli till flytande gödselmedel till hobbyodlare. Vår utgångspunkt var sidoströmmar från biogasproduktion, både svartvatten (d.v.s. toalettvatten) och den flytande fraktionen av köksavfall. I ett Partnerskap Alnarp projekt mellan SLU, AlnarpFoodTech Ek. för. och RecoLab vid NSVA i Helsingborg undersökte vi bland annat förbättringsområden för att ta fram en tillförlitlig och säker växtnäringsprodukt
Treatment of greywater with nanofiltration for nutrient removal – 2-year experience from Helsingborg
No full textSource-separated sanitation and greywater treatment have become an increasingly attractive alternative to traditional waste-water management systems in recent years due to their potential to combat water scarcity, ease resource recovery, and meet tightening effluent demands. In Helsingborg, Sweden, source-separated wastewater from the new city district of Oceanhamnen is being collected and treated in a new treatment plant (RecoLab) to test, among other issues, how efficient greywater treatment can be in achieving low discharge limits for pollutants. The greywater treatment consists of activated sludge treatment, drum filter micro-sieving, and nanofiltration. In the first two years of operation, the robustness of the treatment system during periods with extreme conditions, e.g., very low and very high organic matter concentrations, was tested. The combination of biological treatment and nanofiltration has achieved stable effluent concentrations below 10 mg/L chemical oxygen demand, 2 mg/L total nitrogen, and 0.2 mg/L total phosphorus as average values for 22 months of operation with an average flow of 43 m3/day. The treatment system for greywater treatment thus shows the possibility to achieve low discharge limits and meet the new proposed effluent demands of the EU Urban Wastewater Treatment Directive
