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January 2008 - January 2020
Publications
Publications (186)
A water resource recovery facility sited in a region at a high elevation has experienced the effects of over‐designing its blowers. In this case study, we used off‐gas analysis and site‐specific power tariffs to quantify actual process loading and air requirements, and we quantitatively evaluated various options for blower replacement or upgrade. O...
The imperative to make energy and resource consumption more sustainable is prompting a critical reconsideration of all human endeavors. Within urban water management, the drive to enhance sustainability is grounded in the recognition that water services consume a substantial amount of energy and that wastewater contains valuable resources, includin...
SARS-CoV-2 wastewater surveillance (WWS) at wastewater treatment plants (WWTPs) can reveal sewered community COVID-19 prevalence. For unsewered areas using septic tank systems (STSs) or holding tanks, how to conduct WWS remains unexplored. Here, two large STSs serving Zuma Beach (Malibu, CA) were studied. Supernatant and sludge SARS-CoV-2 concentra...
The 1st edition of the textbook Biological Wastewater Treatment: Principles, Modelling and Design was published in 2008 and it went on to become IWA Publishing's bestseller to date. In 2020, the 2nd updated and extended edition of the textbook was published because, since 2008, the knowledge and understanding of wastewater treatment had advanced ex...
The South Truckee Meadows Water Reclamation Facility (STMWRF) in Washoe County, Nevada, commissioned a biosolids facility with jet aerated aerobic digestion. The jet aerators were not performing as designed, so they were tested on‐site in the new tanks in both clean and process water according to ASCE standards. The aerators failed by substantial m...
Nano‐sized particles in wastewater are generally considered colloids, but their production and size distribution are not well understood. Organic nano‐sized particles are more abundant than engineered nanomaterials in wastewater, where they may cause membrane fouling, harbor pathogens, and transport contaminants to the environment. To our knowledge...
This research evaluated the oxygen transfer efficiency in beds to be used as aerated con- structed wetlands. The research methods included oxygen transfer efficiency evaluations in several bed configurations using diffused aeration systems. Experiments were conducted at two locations with different environmental conditions: a) Talca (Chile), 120 m...
Microplastics have been widely detected in natural and engineered water systems and removing microplastics from various water matrices has become a major challenge. Mini-hydrocyclones (MHCs) have been previously applied to separate mediums of different phases. Given MHCs' capability of separating fine particles from liquid phase, three MHCs were de...
Wastewater reclamation and reuse have the potential to supplement water supplies, offering resiliency in times of drought and helping to meet increased water demands associated with population growth. Non-potable water reuse represents the largest potential reuse market. Yet, economic constraints for new water reuse infrastructure and safety concer...
Most wastewater treatment facilities are built using procedures from previous designs which are predominantly from sites and regions not located at high elevation. Recognizing this limitation, we assessed the effects of elevation above sea level on the suitability of process configurations and technologies as well as their associated energy costs....
Water systems need to become more locally robust and sustainable in view of increased population demands and supply uncertainties. Decentralized treatment is often assumed to have the potential to improve the technical, environmental, and economic performance of current technologies. The techno-economic feasibility of implementing independent build...
The performance of aeration – one of the most costly processes at water resource recovery facilities – is heavily impacted by actual wastewater characteristics which are commonly taken into account using the alpha factor (α). This factor varies depending on hydraulic and organic loading; such variance includes both time and spatial fluctuations. In...
This study demonstrates the potential of an innovative anaerobic treatment technology for municipal biosolids (IntensiCarb), which relies on vacuum evaporation to decouple solids and hydraulic retention times (SRT and HRT). We present proof‐of‐concept experiments using primary sludge and thickened waste activated sludge (50–50 v/v mixture) as feed...
Water resource recovery facilities are major points of electricity demand and exhibit dynamic electricity demand due to their influent load as well as their diurnal and seasonal cycles. This dynamic demand along with the diurnal and seasonal nature of grid electricity cost as well as greenhouse gas emission intensity (i.e., emission produced to gen...
Aeration systems often lack the efficiency to maintain a desired residual dissolved oxygen (DO) concentration in the tank in part because little consideration is given to the dynamic daily and seasonal loading conditions. Although advanced aeration controllers exist, the majority of plants have DO set points typically based on common practice and l...
This work introduces a novel analytical study that considers renewable oxygen generation (or green oxygen) for the aeration of the activated sludge processes. This is achieved by leveraging the operation of large-scale electrolyzer systems used for renewable energy storage. This study discusses the potential synergistic interaction that renewable h...
Naturally occurring nanoparticles (NONPs) in wastewater are generally considered colloids, but their production and size distribution are not well understood. NONPs are more abundant than engineered nanoparticles (ENPs) in wastewater, where they may cause membrane fouling, harbour pathogens, and transport contaminants to the environment. In this st...
Hydrocyclones exploit density gradients for the centrifugal separation of dispersions in continuous liquid. The selection geometrics for optimal separation is case‐specific like media's characteristics. The existing optimization methods based on CFD provides a powerful analytical tool, while requires long computational times. The most common praxis...
The effect of bioreactor configurations on the dynamics of aeration modelling was investigated by incorporating three different correlations from the literature to estimate α-factors into the aeration model. Estimated air flow rates using the three correlations were then validated against experimental data obtained from pilot sequencing batch react...
Computational fluid dynamics (CFD) is used to simulate a bubble column reactor operating in the bubbly (homogenous) regime. The Euler–Euler two-fluid model, integrated with the population balance model (PBM), is adopted to compute the flow and bubble size distribution (BSD). The CFD-PBM model is validated against published experimental data for BSD...
The installation of satellite water resource recovery facilities (WRRFs) has strengthened the ability to provide cheap and reliable recycled water to meet the increasing water demand of expanding cities. As a result, recent studies have attempted to address the problem of how to optimally integrate satellite systems with other sectors of the urban...
The inlet section of hydrocyclone has a significant effect on separation efficiency. However, in most existing studies the inlet of conventional hydrocyclones (CH) only serves as a channel for the mixed liquid to enter the hydrocyclone body. Based on CH's tangential inlet with a rectangular section, a novel hydrocyclone with medium rearrangement in...
Aeration is a major contributor to the high energy demand in municipal wastewater treatment plants. Thus, it is important to understand the dynamic impact of wastewater characteristics on oxygen transfer efficiency to develop suitable control strategies for minimizing energy consumption since aeration efficiency is influenced by the biodegradation...
Nitrous oxide (N2O) gas transfer was studied in a full-scale process to correlate liquid phase N2O concentrations with gas phase N2O emissions and compare methods of determining the volumetric mass transfer coefficient, KLa. Off-gas and liquid phase monitoring were conducted at the Viikinmäki wastewater treatment plant (WWTP) over a two-week period...
California es el estado con mayores ingresos por exportación de productos agrícolas en Estados Unidos. En la definición de agua exportada se contabiliza el agua contenida físicamente en los productos agrícolas cultivados y transportados fuera de una frontera geográfica, adicionalmente se incluye la evapotranspiración inducida por el riego del culti...
The goal of this study is to analyze the impact on operating costs for different combinations of manual valve positions. In this study the set of optimal manual valve configurations are identified through the implementation of a multi-objective optimization algorithm. Data from a full-scale facility was used to develop a dynamic model of the air su...
The goal of this study is to implement a new clarifier process simulator for the analysis of the thickening of oils and solids from produced waters. Flow control of the underflow and clarified effluent streams provides insight on the removal efficiency for both oils and solids. Data from a full-scale facility in China were used to build the model....
The link between aeration efficiency and biosorption capacity in water resource recovery facilities was extensively investigated, with special emphasis on wastewater characteristics and the development of strategies to maximize adsorption. Biosorption of oxygen transfer inhibitors (i.e., surfactants, colloidal, and soluble fractions) was examined b...
The ongoing COVID-19 pandemic is, undeniably, a substantial shock to our civilization which has revealed the value of public services that relate to public health. Ensuring a safe and reliable water supply and maintaining water sanitation has become ever more critical during the pandemic. For this reason, researchers and practitioners have promptly...
Fouling is an issue associated with all sensor instrumentation deployed in wastewater that causes a loss in sensitivity and reproducibility of the sensor elements, thus requiring frequent re-calibration. This paper presents a comprehensive analysis of the fouling development in activated sludge process with a case study on ammonium sensors and Ion-...
Primary screening is gaining interest as a method to achieve removal performances comparable to primary clarification while reducing the footprint and increasing operational elasticity. Aeration efficiency indicators in a pilot sequential batch reactor (SBR) and a full scale water resource recovery facility (WRRF) were investigated after the implem...
Diffused aeration is the most implemented method for oxygen transfer in municipal activated sludge systems and governs the economics of the entire treatment process. Empirical observations are typically used to regulate airflow distribution through the adjustment of manual valves. However, due to the associated degrees of freedom, the identificatio...
Evaluating the sustainability of wastewater management alternatives is a challenging task. This paper proposes an innovative methodology to assess and compare the sustainability of four wastewater management alternatives: a) centralised water resource recovery facility (WRRF) based on activated sludge (AS); b) centralised WRRF with membrane bioreac...
The so-called fourth revolution in the water sector will encounter the Big data and Artificial Intelligence (AI) revolution. The current data surplus stemming from all types of devices together with the relentless increase in computer capacity is revolutionizing almost all existing sectors, and the water sector will not be an exception. Combining t...
The aerobic granular sludge process is an alternative to the conventional activated sludge process adopted in water resource recovery facilities. This study presents the first independent assessment of aerobic granular sludge technology in terms of oxygen transfer efficiency and nutrient removal performance. Using off-gas testing, a full-depth pilo...
This project examined the impact of wastewater characteristics on the performance and operation of high-rate carbon removal processes. The research focused on evaluating the improvements or deterioration of the capture of the various chemical oxygen demand fractions in the treated waste stream by conducting detailed mass balances on organics. A con...
Gas-liquid mass transfer in wastewater treatment processes has received considerable attention over the last decades both from academia and industry. Indeed, improvements in modelling gas-liquid-mass transfer can bring huge benefits in terms of reaction rates, plant energy expenditure, acid-base equilibria and greenhouse gas emissions. Despite thes...
Cellulose from toilet paper is a significant fraction of particulate organics, which is recoverable. For the first time, comprehensive mapping and tracking the fate of cellulose across various unit processes at full‐scale in two water resource recovery facilities located in North America and Europe was undertaken. The influent cellulose content acc...
Wine production is one of the leading sectors of the food processing industry. The wine industry produces a large amount of wastewater characterized by a high strength in terms of organic pollution and large variability throughout the year. Most of the organic matter is soluble and easily biodegradable. On the other hand, nitrogen and phosphorous a...
In this review, the factors affecting the transfer of oxygen in activated sludge processes using fine‐pore diffusers for water resource recovery are critically discussed. In water resource recovery facilities, the energy required for aeration constitutes 50% to 80% of the total energy consumed by the plant. This critical review highlights the use o...
Real-time quantification of the ammonium content in water resource recovery facilities (WRRFs) has raised attention in recent years for both monitoring and process control. Ion-selective-electrodes are a viable solution for online ammonium measurements with increasing number of installations worldwide. This paper describes a year-long field evaluat...
Biosolids or sludge management has become an environmental and economic challenge for water resource recovery facilities (WRRFs) and municipalities around the world. The electric energy and operational costs linked to the solid processing stage can account for 20% and 53% of the overall treatment respectively, and as such they are primary factors a...
The wastewater industry is currently facing dramatic changes, shifting away from energy-intensive wastewater treatment towards low-energy, sustainable technologies capable of achieving energy positive operation and resource recovery. The latter will shift the focus of the wastewater industry to how one could manage and extract resources from the wa...
The goal of this study was to demonstrate the application of off-gas measurements to quantify the load imbalance amongst nominally-identical and parallel aerated units, using OUR as indicator.
Water resource recovery facilities (WRRFs) contribute to climate change and air pollution, as they are anthropogenic
potential sources of direct and indirect emission of greenhouse gases (GHGs). Studies concerning the monitoring and accounting for GHG emissions fromWRRFs are of increasing interest. In this study, the floating hood technique for gas...
The existing wastewater treatment infrastructure has not adequately established an efficient and sustainable use of energy, water, and nutrients. A proposed scheme based on source separation and water-efficient use is compared to the current wastewater management paradigm (one largely based on activated sludge) using techno-economic terms. This pap...
This study aims at showing the effect of primary filtration with the Salsnes Filter technology on the particulate matter removal and consequently on energy footprints of wastewater treatment processes. We benchmarked a treatment plant in the Netherlands characterized by two parallel treatment trains, with and without primary filtration before biolo...
Biofilm formation influences the most energy-demanding process in the waste water treatment cycle. Biofilm growth on the surface of wastewater aeration diffusers in water resource recovery facilities (WRRFs) can increase the energy requirements up to 50% in less than 2 years. The impact of biofilms in aeration diffusers was quantified and assessed...
In this review, the factors affecting the transfer of oxygen in activated sludge processes using fine-pore diffusers for water resource recovery are critically discussed. In water resource recovery facilities, the energy required for aeration constitutes 50% to 80% of the total energy consumed by the plant. This critical review highlights the use o...
A model was developed for a water resources recovery facility (WRRF) activated sludge process (ASP) in Modified Ludzack-Ettinger (MLE) configuration. Amplification of air requirements and its associated energy consumptions were observed as a result of concurrent circadian variations in ASP influent flow and carbonaceous/nitrogenous constituent conc...
An existing bead-beating DNA extraction protocol was employed to compare the DNA extraction recovery and fragment quality of 6 different aeration diffuser biofilms. Escherichia coli, Gordonia amarae, and mixed liquor were used as controls. The fraction of total DNAbiofilm decreased monotonically with increasing number of beat beatings (BB) when the...
Mixing is the driver for the energy footprint of water resource recovery in lagoons. With the availability of solar-powered equipment, one potential measure to decrease the environmental impacts of treatment is to transition to an off-the-grid treatment. We studied the comparative scenarios of an existing grid-powered mixer and a solar-powered mixe...
The fundamental mechanism behind biosorption to recover carbon from wastewater through high-rate activated sludge (HRAS) system is insufficiently studied. The most accepted method of quantifying biosorption capacity of activated sludge depends on higher settling velocity solids. As HRAS had different settling characteristics and in addition, raw wa...
The production of zinc nanomaterial has increased significantly over the past several years and, as a result, nanoparticles have navigated their way into wastewater streams. The transportation and toxicity of zinc nanomaterial within the wastewater treatment processes is not well known. In this study, the zinc nanomaterial and its fate were charact...
This work aims at developing a new software tool for the monitoring, control and mitigation of the carbon footprint of WWTPs, called C-FOOT-CTRL. GHG emissions are emitted from various stages of treatment in a WWTP. Currently, in developed countries the energy required for wastewater treatment accounts for approximately 3% of the total electricity...
Due to the importance of wastewater aeration in meeting treatment requirements and due to its elevated energy intensity, it is important to describe the real nature of an aeration system to improve design and specification, performance prediction, energy consumption, and process sustainability. Because organic loadings drive aeration efficiency to...
The project C-FOOT-CTRL develops a standalone software tool composed by different modules. An on-line data module is in charge of communicating to different on-line data providers and sending these data to the Database module. Model predictions based on on-line input data and mechanistic models including N2O emission calculation will provide on-lin...
The emissions of the major greenhouse gases (GHGs), i.e. carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O) from water resource recovery facilities (WRRFs) are of increasing concern in the water industry. In order to produce useful and comparable information for monitoring, assessing, and reporting GHG emissions from WRRFs, there is a nee...
In this study the carbon footprint and power demand of tannery wastewater treatment processes for the largest bovine leather producing regions were quantified and analysed. Moreover, we present a case in which we benchmarked the carbon footprint and energy demand analysis of tannery wastewater treatment to municipal wastewater treatment. We quantif...
Achieving energy neutrality has shifted focus towards aeration system optimization, due to the high energy consumption of aeration processes in modern advanced wastewater treatment plants. A study on fine bubble diffuser fouling and mitigation, quantified by dynamic wet pressure (DWP), oxygen transfer efficiency and alpha was carried out in Blue Pl...
This research systematically studied the behavior of aeration diffuser efficiency over time, and its relation to the energy usage per diffuser. Twelve diffusers were selected for a one year fouling study. Comprehensive aeration efficiency projections were carried out in two WRRFs with different influent rates, and the influence of operating conditi...
The Intergovernmental Panel on Climate Change (IPCC) reported that all carbon dioxide (CO2) emissions generated by water resource recovery facilities (WRRFs) during treatment are modern, based on available literature. Therefore, such emissions were omitted from IPCC's greenhouse gas (GHG) accounting procedures. However, a fraction of wastewater's c...