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Sutton P.M.,P.M. Sutton and Associates Inc. | Melcer H.,Brown and Caldwell | Schraa O.J.,Hydromantis Inc. | Togna A.P.,Envirogen Technologies Inc.
Water Science and Technology | Year: 2011

A new municipal wastewater treatment flowsheet was developed with the objectives of energy sustainability, and water and nutrient recovery. Energy is derived by shunting a large fraction of the organic carbon in the wastewater to an anaerobic digestion system. Aerobic and anaerobic membrane bioreactors play a key role in energy recovery. Phosphorus and nitrogen are removed from the wastewater and recovered through physical-chemical processes. Computer modeling and simulation results together with energy balance calculations, imply the new flowsheet will result in a dramatic reduction in energy usage at lower treatment plant capital costs in comparison to conventional methods. © IWA Publishing 2010.

Sutton P.M.,P. M. Sutton and Associates Inc. | Rittmann B.E.,Arizona State University | Schraa O.J.,Hydromantis Inc. | Banaszak J.E.,OpenCEL | Togna A.P.,Envirogen Technologies Inc.
Water Science and Technology | Year: 2011

A wastewater-treatment flowsheet was developed to integrate uniquely designed biological processes with physical-chemical unit processes, allowing conversion of the organic carbon in the wastewater to methane, the removal and recovery of phosphorus and nitrogen from the wastewater, and the production of water suitable for reuse. In the flowsheet, energy is derived from the wastewater by first shunting a large fraction of the organic carbon in the wastewater to a solids slurry which is treated via anaerobic digestion. The anaerobic digestion system consists of focused pulsed (FP) pretreatment coupled to anaerobic membrane bioreactors (MBRs). Computer modelling and simulation results are used to optimize design of the system. Energy generation from the system is maximized and costs are reduced by using modest levels of recycle flow from the anaerobic MBRs to the FP pretreatment step. © IWA Publishing 2011.

Clouzot L.,Laval University | Choubert J.-M.,IRSTEA | Cloutier F.,Laval University | Goel R.,Hydromantis Inc. | And 7 more authors.
Water Science and Technology | Year: 2013

Models for predicting the fate of micropollutants (MPs) in wastewater treatment plants (WWTPs) have been developed to provide engineers and decision-makers with tools that they can use to improve their understanding of, and evaluate how to optimize, the removal of MPs and determine their impact on the receiving waters. This paper provides an overview of such models, and discusses the impact of regulation, engineering practice and research on model development. A review of the current status of MP models reveals that a single model cannot represent the wide range of MPs that are present in wastewaters today, and that it is important to start considering classes of MPs based on their chemical structure or ecotoxicological effect, rather than the individual molecules. This paper identifies potential future research areas that comprise (i) considering transformation products in MP removal analysis, (ii) addressing advancements in WWTP treatment technologies, (iii) making use of common approaches to data acquisition for model calibration and (iv) integrating ecotoxicological effects of MPs in receiving waters.

Plosz B.G.,Technical University of Denmark | Plosz B.G.,Norwegian Institute for Water Research | Benedetti L.,Ghent University | Benedetti L.,WaterWays | And 9 more authors.
Water Science and Technology | Year: 2013

This paper provides a comprehensive summary on modelling of micro-pollutants' (MPs) fate and transport in wastewater. It indicates the motivations of MP modelling and summarises and illustrates the current status. Finally, some recommendations are provided to improve and diffuse the use of such models. In brief, we conclude that, in order to predict the contaminant removal in centralised treatment works, considering the dramatic improvement in monitoring and detecting MPs in wastewater, more mechanistic approaches should be used to complement conventional, heuristic and other fate models. This is crucial, as regional risk assessments and model-based evaluations of pollution discharge from urban areas can potentially be used by decision makers to evaluate effluent quality regulation, and assess upgrading requirements, in the future. © 2013 IWA Publishing.

Komatsu K.,Kurita Water Industries Ltd. | Yasui H.,University of Kitakyushu | Goel R.,Hydromantis Inc. | Li Y.Y.,Tohoku University | Noike T.,Nihon University
Water Science and Technology | Year: 2011

A novel process scheme was developed to achieve economically feasible energy recovery from anaerobic digestion. The new process scheme employs a hybrid configuration of mesophilic and thermophilic anaerobic digestion with sludge ozonation: the ozonated sludge is first degraded in a thermophilic digester and then further degraded in a mesophilic digester. In small-scale pilot experiments of the new process scheme, degradation of VSS improved by 3.5% over the control (mesophilic-only configuration) with 20% less ozone consumption. Moreover, biogas conversion also improved by 7.1% over the control. Selective enrichment of inorganic compounds during centrifugation produced a dewatered sludge cake with very low water content (59.4%). This low water content in the sludge cake improved its auto-thermal combustion potential during incineration and added to the overall energy savings. We conducted a case study to evaluate power generation from biogas for a municipal wastewater treatment plant with an average dry weather flow of 43,000 m3/d. Electricity production cost was 5.2 ¢/kWh for the advanced process with power generation, which is lower than the current market price of 7.2 ¢/kWh. The new anaerobic digestion scheme with power generation may reduce greenhouse gas emissions by about 1,000 t-CO2/year compared with the conventional process without power generation. © IWA Publishing 2011.

Majewsky M.,CRP Henri Tudor | Galle T.,CRP Henri Tudor | Bayerle M.,CRP Henri Tudor | Goel R.,Hydromantis Inc. | And 2 more authors.
Water Research | Year: 2011

The effect of mixing regimes and residence time distribution (RTD) on solute transport in wastewater treatment plants (WWTPs) is well understood in environmental engineering. Nevertheless, it is frequently neglected in sampling design and data analysis for the investigation of polar xenobiotic removal efficiencies in WWTPs. Most studies on the latter use 24-h composite samples in influent and effluent. The effluent sampling period is often shifted by the mean hydraulic retention time assuming that this allows a total coverage of the influent load. However, this assumption disregards mixing regime characteristics as well as flow and concentration variability in evaluating xenobiotic removal performances and may consequently lead to biased estimates or even negative elimination efficiencies. The present study aims at developing a modeling approach to estimate xenobiotic removal efficiencies from monitoring data taking the hydraulic RTD in WWTPs into consideration. For this purpose, completely mixed tanks-in-series were applied to address hydraulic mixing regimes in a Luxembourg WWTP. Hydraulic calibration for this WWTP was performed using wastewater conductivity as a tracer. The RTD mixing approach was coupled with first-order biodegradation kinetics for xenobiotics covering three classes of biodegradability during aerobic treatment. Model simulations showed that a daily influent load is distributed over more than one day in the effluent. A 24-h sampling period with an optimal time offset between influent and effluent covers less than the half of the influent load in a dry weather scenario. According to RTD calculations, an optimized sampling strategy covering four consecutive measuring days in the influent would be necessary to estimate the full-scale elimination efficiencies with sufficient accuracy. Daily variations of influent flow and concentrations can substantially affect the reliability of these sampling results. Commonly reported negative removal efficiencies for xenobiotics might therefore be a consequence of biased sampling schemes. In this regard, the present study aims at contributing to bridge the gap between environmental chemistry and engineering practices. © 2011 Elsevier Ltd.

Komatsu K.,Kurita Water Industries Ltd | Yasui H.,University of Kitakyushu | Goel R.,Hydromantis Inc. | Li Y.Y.,Tohoku University | Noike T.,Nihon University
Ozone: Science and Engineering | Year: 2011

Anaerobic digestion with ozonation is a promising process to enhance the digestion efficiency and reduce the sludge quantity for disposal. In this study, new process schemes by incorporating thermophilic digestion were studied for further improvements. Pilot tests were performed with three schemes having mesophilic, ther-mophilic or mesophilic-thermophilic hybrid reactors. In the process scheme with thermophilic digestion, the degradation ratio of VSS components was observed to improve by 5.5% over mesophilic digestion. The amount of ozone consumption could also be reduced by 18%. However, biogas conversion ratio was not improved due to considerable non-degradable organic fraction remaining in soluble form. In batch tests, this soluble fraction was found to readily degrade by mesophilic microorganism. Based on this observation, a mesophilic-thermophilic hybrid flow scheme was developed. In this flow scheme, thermophilic microbes rapidly degraded ozonated sludge and remaining soluble organic components were converted to biogas by mesophilic microbes. This flow scheme reduced ozone consumption as well as improved the biogas conversion of municipal sludge to 78.6%. The cost performance analysis of a municipal WWTP (population equivalent 150,000) considering electricity production resulted in electricity production cost of 5.0 JPY/kWh, lower than the current market price of 9.3 JPY/kWh. © 2011 International Ozone Association.

Liu B.,University of Kitakyushu | Jarvis I.,University of Kitakyushu | Naka D.,University of Kitakyushu | Goel R.,Hydromantis Inc. | Yasui H.,University of Kitakyushu
Water Science and Technology | Year: 2013

Activated Sludge Models (ASMs) are widely used for biological wastewater treatment plant design, optimisation and operation. In commonly used ASMs, the nitrification process is modelled as a one-step process. However, in some process configurations, it is desirable to model the concentration of nitrite nitrogen through a two-step nitrification process. In this study, the benchmark datasets published by the Water Environment Research Foundation (WERF) were used to develop a two-step nitrification model considering the kinetics of Ammonium Oxidising Bacteria (AOB) and Nitrite Oxidising Bacteria (NOB). The WERF datasets were collected from a chemostat reactor fed about 1,000 mg-NH3-N/L synthetic influent with at different sludge retention times of 20, 10 and 5-d, whereas the pH in the reactor varied in the range of 5.8 and 8.8. Supplemental laboratory batch experiments were conducted to assess the toxicity of nitrite-N on nitrifying bacteria. These tests suggested that 500 mg-N/L of nitrite at pH 7.3 was toxic to NOB and resulted in continuous decrease in bulk oxygen uptake rate. To model this phenomenon, a poisoning model was used instead of the traditional Haldane-type inhibition model. The poisoning model for NOB and AOB with different threshold poisonings for unionised NO2-N and NH 3-N concentrations could successfully reproduce the three WERF datasets. © IWA Publishing 2013.

Terashima M.,University of Kitakyushu | So M.,University of Kitakyushu | Goel R.,Hydromantis Inc. | Yasui H.,University of Kitakyushu
Journal of Water Process Engineering | Year: 2016

The aeration tank is one of the most important processes in the biological wastewater treatment and water reuse system to remove organic pollutants in wastewater. The prediction of oxygen transfer using the computational fluid dynamics (CFD) method is crucial for minimizing the energy consumption of the aeration tank, which is one of the highest energy consuming units in a wastewater treatment system. Bubble size (dB), which is a critical parameter in the CFD simulations, was investigated for different types of diffusers. CFD calculations were conducted to simulate the hydraulics in different aeration tanks and the calculated values of the volumetric oxygen mass transfer coefficient (KLa) were compared with experimentally measured data. A total of 19 tanks containing clean water and 8 tanks containing wastewater with different diffuser types and aeration intensities were simulated. The KLa values determined for these configurations were fitted using a calibrated dB value specified in the CFD simulations. The results of the calculations indicate that the coarse-bubble diffusers, fine-pore diffusers, and slitted membrane diffusers have bubble sizes of 7–8 mm, 5–6 mm, and approximately 3 mm, respectively. Additionally, CFD simulations were conducted to simulate the flow pattern and calculate the corresponding KLa value when the diffuser configuration was changed. © 2016 Elsevier Ltd

Fabiyi M.,Praxair Inc. | Novak R.A.,Praxair Inc. | Goel R.,Hydromantis Inc. | Snowling S.,Hydromantis Inc.
AIChE Annual Meeting, Conference Proceedings | Year: 2012

In the last decade, stringent regulations have been imposed on the permissible level of Volatile Organic Compound (VOC) emissions from industrial facilities. The clean air act amendments of 1990 and related regulatory extensions (e.g., National Emissions Standards for Hazardous Air Pollutants, NESHAPs) have significantly reduced the acceptable level of Volatile Organic Compound (VOC) emissions from industrial facilities (Woodward & Curran, 2006). A total of 188 organic compounds have been designated Hazardous Air Pollutants (HAPs); facilities which generate or handle these compounds are subject to permitting, monitoring and reporting requirements. Although extensive emissions controls have been implemented in the production process of many industrial facilities, significant amounts of VOCs may appear in the wastewater. These VOCs can be stripped into the air during conveyance through collection systems or during biological treatment. Fate and Transport models are used for a variety of tasks including design, emissions analysis and regulatory reporting. The development of fate & transport models in wastewater collection and treatment systems were spurred by regulatory drivers like the Clean Air Act (Melcer, 1994). A variety of computer-based fate & transport models such as BASTE, EPA Water Models (versions 7, 8 and 9), CORAL, PAVE, SIMS, TORONTO, INTERCEPTOR and Toxchem™ have been applied for addressing the fate of volatile contaminants in collection systems, drop structures, weirs, quiescent surfaces, and wastewater treatment processes (Quigley et al, 2006; Melcer, 1994). EPA Water Models (7, 8 & 9) and Toxchem™ are the most commonly utilized fate and emissions transport modeling platforms in the wastewater industry. In both models, the default aeration options exclusively model the mass transfer behavior as diffused air processes or surface aeration style mechanical mixers. Attempts at modeling the performance of High Purity Oxygen (HPO) based devices have typically required finding the most appropriate approximation to the mass transfer and VOC stripping behavior of HPO aeration systems by modifying default parameters in the diffused air or surface aeration modules (NYSERDA, 2000; Levine et al, 2010; Rodieck et al, 2001). In contrast, an improved modeling approach is employed in the recently released Toxchem™ 4.1 (Hydromantis, 2012), which extends the simulation capabilities of the platform to include the modeling HPO and Sequencing Batch Reactor (SBR) process systems. This paper discusses results for VOC emissions modeling obtained by applying Toxchem™ 4.1 to VOC reduction projects that utilize SBR and HPO systems. We provide a methodology for modifying the default parameters in diffuser and mechanical surface aeration modules in fate and transport models in order to enable VOC emissions characteristics associated with HPO systems to be modeled, and provide comparative analyses on the effect of the approach adopted on simulation results.

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