Development and economic assessment of different WWTP control strategies for optimal simultaneous removal of carbon, nitrogen and phosphorus

This paper presents the comparison of four control strategies for the A²/O WWTP configuration for simultaneous C, N and P removal. The control strategies: (i) external COD-P control; (ii) external recycle flow-P control; (iii) nitrate control in the last anoxic reactor; (iv) ammonia control in the last aerobic reactor, were combined with other common control loops to build different control structures and were simulated in Matlab/Simulink under different influent conditions. A systematic approach was conducted with all the strategies to assess their potential effectiveness, according to the following steps: theoretical design, setpoint optimization and, finally, a detailed comparison of the control results against a reference operation and an optimized reference scenario. The optimization of the reference operation presented a 7% reduction of the total operational cost. The simulation results showed that some control strategies further reduced 3-7.5% the WWTP operational costs while the effluent quality is greatly improved

Nutrient recovery from waste water treatment plant by sorption processes : technical and economic analysis

In the last years has been performed a huge number of research related to nutrients (mainly N and P) recovery from waste water in order to promote their reuse and also to avoid eutrophication. Recovering nutrient from waste water can promote the circular economy, minimize the environmental footprint of waste water treatment and reduce anthropogenic alteration of nitrogen and phosphorus natural cycle. Among the different techniques studied, sorption is nowadays one of the most interesting alternatives as requires less energy than electrochemical or membrane technologies and sorbents can be regenerated for being reused. Thus, the overall sorption performance of different ion exchangers was characterized for nutrient recovery from waste water treatment plant effluents. Two commercial polymeric resins doped with Hydrated Ferrous Oxide (HFO) (Lewatit FO36 and Fiban-As) were assessed for ammonium and phosphate uptake from waste water streams. Equilibrium and kinetics studies have been performed through batch experiments and the dynamic studies were carried out by fixed-bed column. The experimental study covered from the simplest monocomponent synthetic water (ammonium, phosphate solutions) to the most complex real water from waste water treatment plant (WWTP) which contains ions, TSS and organic matter. Sorption experiments reported for both sorbents high selectivity towards phosphate ions as sorption capacity did not significantly decrease in presence of competing ions. Loaded sorbents were regenerated through alkaline and acid desorption in order to reuse resin and obtain a high concentrated phosphate solution, which could be used for high quality fertilizer production. Results in dynamic flow experiments reported up to 80% of loaded phosphate extraction, although during desorption process was observed sorption capacity decrease up to 30% after three sorption-desorption working cycles. Besides, salt modified synthetic zeolites were assessed for being used both as one charge (di-valent forms) and reusable (mono-valent forms) sorbent. Raw zeolites provided in sodium form as well as it modification in potassium form showed high sorption capacity for ammonium uptake but poor performance for phosphate recovery from waste water streams as the sorption mechanism is mainly ion exchange. Regeneration experiments showed that both Ze-Na and Ze-K can be reused several sorption-desorption working cycles without significant sorption capacity decrease (< 5%). Nevertheless, after salt modification to calcium and magnesium forms, the precipitation of phosphate salts was favoured obtaining hydroxyapatite and struvite in loaded Ze-Ca and Ze-Mg, respectively. As hydroxyapatite’s solubility and phosphorus availability is similar to commercial fertilizers, loaded Ze-Ca could be potentially recycled for agricultural uses. Finally, an economic assessment simulation was performed by applying Ze-Ca in the Baix Llobregat Waste Water Treatment Plant, located in the Metropolitan Area of Barcelona. The study reported that the implantation Ze-Ca filtration for nutrient recovery would be economically feasible, despite that more research is required in order to fit technical issues as the loaded sorbent disposal or the capability of loaded zeolites to be used as fertilizer.En los últimos años se han llevado a cabo un gran número de estudios relacionados con la recuperación de nutrientes (sobre todo N y P) de aguas residuales con el fin de promover su reutilización y evitar la eutroficación . Recuperar nutrientes de aguas residuales puede promover la economía sircular , minimizar la huella de los tratamientos de aguas residuales, así como reducir la alteración antropogénica del ciclo natural del nitrógeno y el fósforo. Entre las diferentes técnicas estudiadas, la sorción es actualmente uno de las alternat ivas más Interesantes ya que requiere menos energía que técnicas electróquímicas o las tecnologías de membrana. Además , los sorbentes se pueden regenerar y reutilizar. Así , se ha caracterizado el comportamiento integral de diferentes sorbentes para la recuperación de nutrientes de efluentes de aguas residuales. Se evaluaron dos lntercambiadores iónicos poliméricos comerciales dopados con Óxido de Hierro Hidratado (Lewatit F036 y Fiban-As) para la eliminación de fosfato de corrientes de aguas residuales. Se llevaron a cabo estudios en equilibrio y se caracterizó la cinética mediante experimentos en discontinuo y los experimentos dinámicos se llevaron a cabo mediante columnas de lecho fijo . El estudio experimental cubrió desde soluciones monocomponentes de fosfato hasta corrientes reales de plantas de tratamiento de aguas residuales que contenían iones competidores, sólidos suspendidos y materia orgánica . Los experimentos reportaron para los dos sorbentes una alta selectividad hacia los iones fosfato, ya que no se observó una reducción significativa de la capacidad de sorción en presencia de iones competidores . Los sorbentes cargados se regeneraron mediante desorción alcalina y ácida para reutilizar el sorbents y obtener corrientes con alta concentración de fosfato, que se pueden emplear para la producción de fertilizante de alta calidad. Los resultados en columnas de lecho fijo mostraron una extracción de más del 80% del fosfato sorbido, aunque durante el proceso de desorción se vio una reducción de la capacidad de más del 30% tras tres ciclos de sorción - desorción. Además, se evaluaron zeolitas modificadas mediante tratamiento salino para ser usados tanto como sorbentes de una sola carga (en la forma divalente) como reusables (en la forma monovalente). La zeolita bruta facilitada en la forma sódica, así como la forma potásica mostraron alta capacidad para la eliminación de amonio, pero prácticamente nula capacidad de retención para los iones fosfato, ya que el mecansmo de sorción es principalmente intercambio iónico. Los experimentos de regeneración mostraron que ambas zeolitas se pueden emplear para un gran número de ciclos de sorción-desorción sin perder capacidad (<5%). Tras la modificación salida a las formas cálcica y magnésica, se favorece la precipitación de sales fosfóricas obteniendo hidroxiapatita y estruvita en la Ze-Ca y Ze-Mg cargada, espectivamente. Dada que la solubilidad de la hidroxiapatita, así como la disponibilidad del fósforo de la hidroxiapatita es similar a la de los fertilizantes comerciales, la Ze-Ca cargada puede potencialmente ser reciclado para usar en agricultura. Finalmente, se llevó a cabo una simulación económica empleando Ze-Ca en la Planta de Tratamiento de Aguas Residuales de El Baix Llobregat, situada en la Area metropolitana de Barcelona. El estudio reveló que la implantación de un filtro de Ze-Ca para la recuperación de nutrientes puuede ser económicamente viable , aunque se requieren más estudios para dar solución a aspectos técnicos como la gestión del sorbente cargado o la capacidad real de las zeolitas cargas de ser utilizadas como fertilizante

Nutrient recovery from waste water treatment plant by sorption processes : technical and economic analysis

Versió amb diverses seccions retallades, per drets de l'editorIn the last years has been performed a huge number of research related to nutrients (mainly N and P) recovery from waste water in order to promote their reuse and also to avoid eutrophication. Recovering nutrient from waste water can promote the circular economy, minimize the environmental footprint of waste water treatment and reduce anthropogenic alteration of nitrogen and phosphorus natural cycle. Among the different techniques studied, sorption is nowadays one of the most interesting alternatives as requires less energy than electrochemical or membrane technologies and sorbents can be regenerated for being reused. Thus, the overall sorption performance of different ion exchangers was characterized for nutrient recovery from waste water treatment plant effluents. Two commercial polymeric resins doped with Hydrated Ferrous Oxide (HFO) (Lewatit FO36 and Fiban-As) were assessed for ammonium and phosphate uptake from waste water streams. Equilibrium and kinetics studies have been performed through batch experiments and the dynamic studies were carried out by fixed-bed column. The experimental study covered from the simplest monocomponent synthetic water (ammonium, phosphate solutions) to the most complex real water from waste water treatment plant (WWTP) which contains ions, TSS and organic matter. Sorption experiments reported for both sorbents high selectivity towards phosphate ions as sorption capacity did not significantly decrease in presence of competing ions. Loaded sorbents were regenerated through alkaline and acid desorption in order to reuse resin and obtain a high concentrated phosphate solution, which could be used for high quality fertilizer production. Results in dynamic flow experiments reported up to 80% of loaded phosphate extraction, although during desorption process was observed sorption capacity decrease up to 30% after three sorption-desorption working cycles. Besides, salt modified synthetic zeolites were assessed for being used both as one charge (di-valent forms) and reusable (mono-valent forms) sorbent. Raw zeolites provided in sodium form as well as it modification in potassium form showed high sorption capacity for ammonium uptake but poor performance for phosphate recovery from waste water streams as the sorption mechanism is mainly ion exchange. Regeneration experiments showed that both Ze-Na and Ze-K can be reused several sorption-desorption working cycles without significant sorption capacity decrease (< 5%). Nevertheless, after salt modification to calcium and magnesium forms, the precipitation of phosphate salts was favoured obtaining hydroxyapatite and struvite in loaded Ze-Ca and Ze-Mg, respectively. As hydroxyapatite’s solubility and phosphorus availability is similar to commercial fertilizers, loaded Ze-Ca could be potentially recycled for agricultural uses. Finally, an economic assessment simulation was performed by applying Ze-Ca in the Baix Llobregat Waste Water Treatment Plant, located in the Metropolitan Area of Barcelona. The study reported that the implantation Ze-Ca filtration for nutrient recovery would be economically feasible, despite that more research is required in order to fit technical issues as the loaded sorbent disposal or the capability of loaded zeolites to be used as fertilizer.En los últimos años se han llevado a cabo un gran número de estudios relacionados con la recuperación de nutrientes (sobre todo N y P) de aguas residuales con el fin de promover su reutilización y evitar la eutroficación . Recuperar nutrientes de aguas residuales puede promover la economía sircular , minimizar la huella de los tratamientos de aguas residuales, así como reducir la alteración antropogénica del ciclo natural del nitrógeno y el fósforo. Entre las diferentes técnicas estudiadas, la sorción es actualmente uno de las alternat ivas más Interesantes ya que requiere menos energía que técnicas electróquímicas o las tecnologías de membrana. Además , los sorbentes se pueden regenerar y reutilizar. Así , se ha caracterizado el comportamiento integral de diferentes sorbentes para la recuperación de nutrientes de efluentes de aguas residuales. Se evaluaron dos lntercambiadores iónicos poliméricos comerciales dopados con Óxido de Hierro Hidratado (Lewatit F036 y Fiban-As) para la eliminación de fosfato de corrientes de aguas residuales. Se llevaron a cabo estudios en equilibrio y se caracterizó la cinética mediante experimentos en discontinuo y los experimentos dinámicos se llevaron a cabo mediante columnas de lecho fijo . El estudio experimental cubrió desde soluciones monocomponentes de fosfato hasta corrientes reales de plantas de tratamiento de aguas residuales que contenían iones competidores, sólidos suspendidos y materia orgánica . Los experimentos reportaron para los dos sorbentes una alta selectividad hacia los iones fosfato, ya que no se observó una reducción significativa de la capacidad de sorción en presencia de iones competidores . Los sorbentes cargados se regeneraron mediante desorción alcalina y ácida para reutilizar el sorbents y obtener corrientes con alta concentración de fosfato, que se pueden emplear para la producción de fertilizante de alta calidad. Los resultados en columnas de lecho fijo mostraron una extracción de más del 80% del fosfato sorbido, aunque durante el proceso de desorción se vio una reducción de la capacidad de más del 30% tras tres ciclos de sorción - desorción. Además, se evaluaron zeolitas modificadas mediante tratamiento salino para ser usados tanto como sorbentes de una sola carga (en la forma divalente) como reusables (en la forma monovalente). La zeolita bruta facilitada en la forma sódica, así como la forma potásica mostraron alta capacidad para la eliminación de amonio, pero prácticamente nula capacidad de retención para los iones fosfato, ya que el mecansmo de sorción es principalmente intercambio iónico. Los experimentos de regeneración mostraron que ambas zeolitas se pueden emplear para un gran número de ciclos de sorción-desorción sin perder capacidad (<5%). Tras la modificación salida a las formas cálcica y magnésica, se favorece la precipitación de sales fosfóricas obteniendo hidroxiapatita y estruvita en la Ze-Ca y Ze-Mg cargada, espectivamente. Dada que la solubilidad de la hidroxiapatita, así como la disponibilidad del fósforo de la hidroxiapatita es similar a la de los fertilizantes comerciales, la Ze-Ca cargada puede potencialmente ser reciclado para usar en agricultura. Finalmente, se llevó a cabo una simulación económica empleando Ze-Ca en la Planta de Tratamiento de Aguas Residuales de El Baix Llobregat, situada en la Area metropolitana de Barcelona. El estudio reveló que la implantación de un filtro de Ze-Ca para la recuperación de nutrientes puuede ser económicamente viable , aunque se requieren más estudios para dar solución a aspectos técnicos como la gestión del sorbente cargado o la capacidad real de las zeolitas cargas de ser utilizadas como fertilizantesPostprint (published version

Optimisation-based methodology for the design and operation of sustainable wastewater treatment facilities

The treatment of municipal and industrial wastewaters in conventional wastewater treatment plants (WWTPs) requires a significant amount of energy in order to meet ever more stringent discharge regulations. However, the wastewater treatment industry is undergoing a paradigm shift from a focus on waste-stream treatment and contaminant removal to a proactive interest in energy and resource recovery facilities, driven by both economic and environmental incentives. The main objective of this thesis is the development of a decision-making tool in order to identify improvement opportunities in existing WWTPs and to develop new concepts of sustainable wastewater treatment/recovery facilities. The first part of the thesis presents the application of a model-based methodology based on systematic optimisation for improved understanding of the tight interplay between effluent quality, energy use, and fugitive emissions in existing WWTPs. Plant-wide models are developed and calibrated in an objective to predict the performance of two conventional activated sludge plants owned and operated by Sydney Water, Australia. In the first plant, a simulation-based approach is applied to quantify the effect of key operating variables on the effluent quality, energy use, and fugitive emissions. The results show potential for reduced consumption of energy (up to 10-20%) through operational changes only, without compromising effluent quality. It is also found that nitrate (and hence total nitrogen) discharge could be signficantly reduced from its current level with a small increase in energy consumption. These results are also compared to an upgraded plant with reverse osmosis in terms of energy consumption and greenhouse gas emissions. In the second plant, a systematic model-based optimisation approach is applied to investigate the effect of key discharge constraints on the net power consumption. The results show a potential for reduction of energy (20-25%), without compromising the current effluent quality. The nitrate discharge could be reduced from its current level to less than 15 mg/L with no increase in net power consumption and could be further reduced to <5 mg/L subject to a 18% increase in net power consumption upon the addition of an external carbon source. This improved understanding of the relationship between nutrient removal and energy use for these two plants will feed into discussions with environmental regulators regarding nutrient discharge licensing.The second part of the thesis deals with the application of a systematic, model-based methodology for the development of wastewater treatment/resource recovery systems that are both economically and environmentally sustainable. With the array of available treatment and recovery options growing steadily, a superstructure modeling approach based on rigorous mathematical optimisation provides a natural approach for tackling these problems. The development of reliable, yet simple, performance and cost models is a key issue with this approach in order to allow for a reliable solution based on global optimisation. it is argued that commercial wastewater simulators can be used to derive such models. The superstructure modeling framework is also able to account for wastewater and sludge treatment in an integrated system and to incorporate LCA with multi-objective optimisation to identify the inherent trade-off between multiple economic and environmental objectives. This approach is illustrated with two case studies of resource recovery from industrial and municipal wastewaters. The results establish that the proposed methodology is computationally tractable, thereby supporting its application as a decision support system for selection of promising wastewater treatment/resource recovery systems whose development is worth pursuing. Our analysis also suggests that accounting for LCA considerations early on in the design process may lead to dramatic changes in the configuration of future wastewater treatment/recovery facilities.Open Acces

Does carbon reduction increase sustainability? A study in wastewater treatment

This is the author accepted manuscript. The final version is available from Elsevier as an open access article via the DOI in this record.This study investigates the relationships between carbon reduction and sustainability in the context of wastewater treatment, focussing on the impacts of control adjustments, and demonstrates that reducing energy use and/or increasing energy recovery to reduce net energy can be detrimental to sustainability. Factorial sampling is used to derive 315 control options, containing two different control strategies and a range of sludge wastage flow rates and dissolved oxygen setpoints, for evaluation. For each, sustainability indicators including operational costs, net energy and multiple environmental performance measures are calculated. This enables identification of trade-offs between different components of sustainability which must be considered before implementing energy reduction measures. In particular, it is found that the impacts of energy reduction measures on sludge production and nitrogen removal must be considered, as these are worsened in the lowest energy solutions. It also demonstrates that a sufficiently large range of indicators need to be assessed to capture trade-offs present within the environmental component of sustainability. This is because no solutions provided a move towards sustainability with respect to every indicator. Lastly, it is highlighted that improving the energy balance (as may be considered an approach to achieving carbon reduction) is not a reliable means of reducing total greenhouse gas emissions.Thanks are given for the Matlab/Simulink implementation of the BSM2G from the Department of Industrial Engineering and Automation, Lund University, Lund, Sweden. This work forms part of a 5-year fellowship for the last author funded by the UK Engineering & Physical Sciences Research Council (EP/K006924/1)

Probabilistic design and upgrade of wastewater treatment plants in the EU Water Framework directive context

The EU Water Framework Directive requires compliance with effluent and receiving water quality standards. This increased complexity implies that the evaluation of the impact of measures should be evaluated with adequate tools, both from the methodological point of view – by applying systems analysis investigations and modelling uncertainty assessment tools – and by making the developed methodology applicable in practice. Urban wastewater systems (UWWSs) are crucial components of river basins, since they usually contribute significantly to the pollution loads. They also have more flexibility in operation and management than other subsystems as agriculture. One part of this dissertation tries to answer the question “where” to improve the UWWS in a basin by means of systems analysis. A case study is tackled with the help of substance flow analysis (SFA) and of performance indicators. SFA allowed to identify the pressures on the receiving water. The indicators highlighted the critical structures in the basin. The spatial scale of the study was found to be of paramount importance. The other part of this dissertation deals with the question “how” to improve the UWWS, by proposing a systematic methodology to design correction measures, illustrated by the example of WWTP design and upgrade. The first step is the generation of influent time series to be fed to the WWTP models by means of a new phenomenological model of the draining catchment and sewer system. Ten different treatment process configurations were selected for the comparison. Further, eleven upgrade options were selected for evaluation, partly requiring real-time control (RTC) and partly the construction of additional treatment volume. For the immission-based evaluation, the integration of the WWTP model with a river model was made by means of the continuity-based interfacing method (CBIM). The propagation of the uncertainty on model parameters was performed with Monte Carlo simulations. Given the assumed boundary conditions, alternating systems show the best treatment cost-efficiency. RTC upgrades showed good potential for low-cost compliance, but with higher risk of limits exceedance. The immission-based evaluation revealed that considering the system from a holistic point of view can lead to substantial savings

A review on the integration of mainstream P-recovery strategies with enhanced biological phosphorus removal

Acord transformatiu CRUE-CSICPhosphorus (P), an essential nutrient for all organisms, urgently needs to be recovered due to the increasing demand and scarcity of this natural resource. Recovering P from wastewater is a feasible and promising way widely studied nowadays due to the need to remove P in wastewater treatment plants (WWTPs). When enhanced biological P removal (EBPR) is implemented, an innovative option is to recover P from the supernatant streams obtained in the mainstream water line, and then combine it with liquor-crystallisation recovery processes, being the final recovered product struvite, vivianite or hydroxyapatite. The basic idea of these mainstream P-recovery strategies is to take advantage of the ability of polyphosphate accumulating organisms (PAO) to increase P concentration under anaerobic conditions when some carbon source is available. This work shows the mainstream P-recovery technologies reported so far, both in continuous and sequenced batch reactors (SBR) based configurations. The amount of extraction, as a key parameter to balance the recovery efficiency and the maintenance of the EBPR of the system, should be the first design criterion. The maximum value of P-recovery efficiency for long-term operation with an adequate extraction ratio would be around 60%. Other relevant factors (e.g. COD/P ratio of the influent, need for an additional carbon source) and operational parameters (e.g. aeration, SRT, HRT) are also reported and discussed

Literature review on the potential of urban waste for the fertilization of urban agriculture : A closer look at the metropolitan area of Barcelona

Unidad de excelencia María de Maeztu CEX2019-000940-MUrban agriculture (UA) activities are increasing in popularity and importance due to greater food demands and reductions in agricultural land, also advocating for greater local food supply and security as well as the social and community cohesion perspective. This activity also has the potential to enhance the circularity of urban flows, repurposing nutrients from waste sources, increasing their self-sufficiency, reducing nutrient loss into the environment, and avoiding environmental cost of nutrient extraction and synthetization. The present work is aimed at defining recovery technologies outlined in the literature to obtain relevant nutrients such as N and P from waste sources in urban areas. Through literature research tools, the waste sources were defined, differentiating two main groups: (1) food, organic, biowaste and (2) wastewater. Up to 7 recovery strategies were identified for food, organic, and biowaste sources, while 11 strategies were defined for wastewater, mainly focusing on the recovery of N and P, which are applicable in UA in different forms. The potential of the recovered nutrients to cover existing and prospective UA sites was further assessed for the metropolitan area of Barcelona. Nutrient recovery from current composting and anaerobic digestion of urban sourced organic matter obtained each year in the area as well as the composting of wastewater sludge, struvite precipitation and ion exchange in wastewater effluent generated yearly in existing WWTPs were assessed. The results show that the requirements for the current and prospective UA in the area can be met 2.7 to 380.2 times for P and 1.7 to 117.5 times for N depending on the recovery strategy. While the present results are promising, current perceptions, legislation and the implementation and production costs compared to existing markets do not facilitate the application of nutrient recovery strategies, although a change is expected in the near future

Literature review on the potential of urban waste for the fertilization of urban agriculture: A closer look at the metropolitan area of Barcelona

Urban agriculture (UA) activities are increasing in popularity and importance due to greater food demands and reductions in agricultural land, also advocating for greater local food supply and security as well as the social and community cohesion perspective. This activity also has the potential to enhance the circularity of urban flows, repurposing nutrients from waste sources, increasing their self-sufficiency, reducing nutrient loss into the environment, and avoiding environmental cost of nutrient extraction and synthetization.The present work is aimed at defining recovery technologies outlined in the literature to obtain relevant nutrients such as N and P from waste sources in urban areas. Through literature research tools, the waste sources were defined, differentiating two main groups: (1) food, organic, biowaste and (2) wastewater. Up to 7 recovery strategies were identified for food, organic, and biowaste sources, while 11 strategies were defined for wastewater, mainly focusing on the recovery of N and P, which are applicable in UA in different forms.The potential of the recovered nutrients to cover existing and prospective UA sites was further assessed for the metropolitan area of Barcelona. Nutrient recovery from current composting and anaerobic digestion of urban sourced organic matter obtained each year in the area as well as the composting of wastewater sludge, struvite precipitation and ion exchange in wastewater effluent generated yearly in existing WWTPs were assessed. The results show that the requirements for the current and prospective UA in the area can be met 2.7 to 380.2 times for P and 1.7 to 117.5 times for N depending on the recovery strategy. While the present results are promising, current perceptions, legislation and the implementation and production costs compared to existing markets do not facilitate the application of nutrient recovery strategies, although a change is expected in the near future