Effectiveness of Design and Implementation Alternatives for Stormwater Control Measures Modeled at the Watershed Scale.

To evaluate the effectiveness of dispersed stormwater control measures (SCMs), it is important to consider groundwater-surface water interactions and their consequences for stream hydrologic responses relevant to channel geomorphic stability and ecology. This study aimed to evaluate the effectiveness of different SCM design scenarios and implementation alternatives on exceedance levels and volumes of streamflow at the watershed scale. For this purpose, a process-based block-connector model of Sligo Creek, an urban watershed (29 km) in the suburbs of Washington, DC, was used to study the effects of SCM system design on the stream hydrograph.

Introducing bioflocculation boundaries in process control to enhance effluent quality of high-rate contact-stabilization systems.

High-rate activated sludge (HRAS) systems suffer from high variability of effluent quality, clarifier performance, and carbon capture. This study proposed a novel control approach using bioflocculation boundaries for wasting control strategy to enhance effluent quality and stability while still meeting carbon capture goals. The bioflocculation boundaries were developed based on the oxygen uptake rate (OUR) ratio between contactor and stabilizer (feast/famine) in a high-rate contact stabilization (CS) system and this OUR ratio was used to manipulate the wasting setpoint.

Towards more predictive clarification models via experimental determination of flocculent settling coefficient value.

Improved settleability has become an essential feature of new wastewater treatment innovations. To accelerate adoption of such new technologies, improved clarifier models are needed to help with designing and predicting improvement in settleability. In general, the level of mathematics of settling clarifier models has gone far beyond the level of existing experimental methods available to support these models.

Complexity of groundwater age mixing near a seawater intrusion zone based on multiple tracers and Bayesian inference.

Aquifer flow systems near seawater interfaces can be complicated by density-driven flows and the formation of stagnation zones, which inevitably introduces uncertainty into groundwater age-dating. While age-dating has proved effective to understand the seawater intrusion and aquifer salinization process in coastal aquifers, further efforts are needed to propagate model and data uncertainty to the uncertainty associated with the inferred age distributions. This study was performed in a coastal aquifer located close to the Yellow Sea, South Korea, where there is a decreasing trend of groundwater levels due to recent heavy exploitation, raising a warning of induced seawater intrusion.

Nitrate residual as a key parameter to efficiently control partial denitrification coupling with anammox.

Despite the increased research efforts, full-scale implementation of shortcut nitrogen removal strategies has been challenged by the lack of consistent nitrite-oxidizing bacteria out-selection. This paper proposes an alternative path using partial denitrification (PdN) selection coupled with anaerobic ammonium-oxidizing bacteria (AnAOB). A nitrate residual concentration (>2 mg N/L) was identified as the crucial factor for metabolic PdN selection using acetate as a carbon source, unlike the COD/N ratio which was often suggested.

Impact of carbon source and COD/N on the concurrent operation of partial denitrification and anammox.

In this study, concurrent operation of anammox and partial denitrification within a nonacclimated mixed culture system was proposed. The impact of carbon sources (acetate, glycerol, methanol, and ethanol) and COD/NO3 -N ratio on partial denitrification selection under both short- and long-term operations was investigated. Results from short-term testing showed that all carbon sources supported partial denitrification.

Stable Isotopes and Bayesian Modeling Methods of Tracking Sources and Differentiating Bioavailable and Recalcitrant Phosphorus Pools in Suspended Particulate Matter.

Understanding the sources of different phosphorus (P) pools and their bioavailability under imposed biogeochemical environments in a watershed is limited largely due to the lack of appropriate methods. In this research, phosphate oxygen isotope ratios and Bayesian modeling on fingerprinting elements were applied as two novel methods to identify sources and relative recalcitrancy of particulate P pools suspended in water in the continuum of sources from land to the mouth of a coastal estuary to the Chesapeake Bay. Comparative analyses of sizes, relative ratios, and oxygen isotope values of particulate P pools in the creek water suggested that the NaHCO-P pool was bioavailable, whereas NaOH-P and HCl-P pools were recalcitrant during P transport along the creek.

Evaluation of bacterial run and tumble motility parameters through trajectory analysis.

In this paper, a method for extraction of the behavior parameters of bacterial migration based on the run and tumble conceptual model is described. The methodology is applied to the microscopic images representing the motile movement of flagellated Azotobacter vinelandii. The bacterial cells are considered to change direction during both runs and tumbles as is evident from the movement trajectories.

Modeling of biotic and abiotic processes affecting phosphate oxygen isotope ratios in a mineral-water-biota system.

Abiotic and biotic reactions operate side by side in the cycling of phosphorus (P) in the environment, but the relative roles of these two reactions vary both spatially and temporally. In biotic reactions, the uptake and release of P are catalyzed by enzymes and thus change phosphate oxygen isotope ratios, while in abiotic reactions, the absence of hydrolysis-condensation reactions results in no apparent changes in isotope composition, except short-term kinetic isotope effect due solely to preferential ion exchange. Therefore, isotope method could be a promising tool to differentiate relative roles of these two reactions in the environment but the relationship of the dynamic concentration and isotope exchange at the biota-water interface is largely unknown.

A flexible modeling framework for hydraulic and water quality performance assessment of stormwater green infrastructure.

A flexible framework has been created for modeling multi-dimensional hydrological and water quality processes within stormwater green infrastructure (GI) practices. The framework conceptualizes GI practices using blocks (spatial features) and connectors (interfaces) representing functional components of a GI. The blocks represent spatial features with the ability to store water (e.

Evaluation of the information content of long-term wastewater characteristics data in relation to activated sludge model parameters.

A parameter estimation framework was used to evaluate the ability of observed data from a full-scale nitrification-denitrification bioreactor to reduce the uncertainty associated with the bio-kinetic and stoichiometric parameters of an activated sludge model (ASM). Samples collected over a period of 150 days from the effluent as well as from the reactor tanks were used. A hybrid genetic algorithm and Bayesian inference were used to perform deterministic and parameter estimations, respectively.

Dual substrate limitation modeling and implications for mainstream deammonification.

Substrate limitation occurs frequently in wastewater treatment and knowledge about microbial behavior at limiting conditions is essential for the use of biokinetic models in system design and optimization. Monod kinetics are well-accepted for modeling growth rates when a single substrate is limiting, but several models exist for treating two or more limiting substrates simultaneously. In this study three dual limitation models (multiplicative, minimum, and Bertolazzi) were compared based on experiments using nitrite-oxidizing bacteria (limited by dissolved oxygen and nitrite) and ANaerobic AMMonia-OXidizing bacteria or Aanammox (limited by ammonium and nitrite) within mixed liquor from deammonification pilots.

Storm Water Management Model: Performance Review and Gap Analysis.

The storm water management model (SWMM) is a widely used tool for urban drainage design and planning. Hundreds of peer-reviewed articles and conference proceedings have been written describing applications of SWMM. This review focuses on collecting information on model performance with respect to calibration and validation in the peer-reviewed literature.

Assessment of the endogenous respiration rate and the observed biomass yield for methanol-fed denitrifying bacteria under anoxic and aerobic conditions.

In this study, the endogenous respiration rate and the observed biomass yield of denitrifying methylotrophic biomass were estimated through measuring changes in denitrification rates (DNR) as a result of maintaining the biomass under methanol deprived conditions. For this purpose, activated sludge biomass from a full-scale wastewater treatment plant was kept in 10-L batch reactors for 8 days under fully aerobic and anoxic conditions at 20 °C without methanol addition. To investigate temperature effects, another biomass sample was placed under starvation conditions over a period of 10 days under aerobic conditions at 25 °C.

Swimming Motility Reduces Deposition to Silica Surfaces.

The transport and fate of bacteria in porous media is influenced by physicochemical and biological properties. This study investigated the effect of swimming motility on the attachment of cells to silica surfaces through comprehensive analysis of cell deposition in model porous media. Distinct motilities were quantified for different strains using global and cluster-based statistical analyses of microscopic images taken under no-flow condition.

Probabilistic parameter estimation of activated sludge processes using Markov Chain Monte Carlo.

One of the most important challenges in making activated sludge models (ASMs) applicable to design problems is identifying the values of its many stoichiometric and kinetic parameters. When wastewater characteristics data from full-scale biological treatment systems are used for parameter estimation, several sources of uncertainty, including uncertainty in measured data, external forcing (e.g.

Bayesian process-identification in bacteria transport in porous media.

A Bayesian parameter estimation approach is developed for the estimation of joint probability distribution functions for colloid and bacterial fate and transport model parameters describing breakthrough curves (BTCs) obtained through porous media column studies, and is applied to data involving different ionic strength solutions to fit models of differing complexity. Our approach focuses on the simultaneous fitting of a number of BTCs representing different conditions, and it provides a measure of the goodness of model structure, namely Deviance Information Criteria (DIC). Comparison of DIC per model fit enables the evaluation of the significance of various processes through step-wise increases in complexity due to the addition of process model components.

Flagella-mediated differences in deposition dynamics for Azotobacter vinelandii in porous media.

A multiscale approach was designed to study the effects of flagella on deposition dynamics of Azotobacter vinelandii in porous media, independent of motility. In a radial stagnation point flow cell (RSPF), the deposition rate of a flagellated strain with limited motility, DJ77, was higher than that of a nonflagellated (Fla(-)) strain on quartz. In contrast, Fla(-) strain deposition exceeded that of DJ77 in two-dimensional silicon microfluidic models (micromodels) and in columns packed with glass beads.

A stochastic stormwater quality volume-sizing method with first flush emphasis.

A Monte Carlo simulation technique was applied to assess the effect of stormwater quality volume captured by best management practices (BMPs) on the frequency of discharging concentrations of constituents above certain designated threshold limits. The method used an assumption of a power law relationship between the cumulative load and flow to incorporate the first flush effect. The exponent of this relationship was considered a random variable and its frequency distribution was obtained from 78 measured pollutographs from three urban highway sites in West Los Angeles, California.

A biogeochemical model of contaminant fate and transport in river waters and sediments.

A quasi-two-dimensional model is presented for simulating transport and transformation of contaminant species in river waters and sediments, taking into account the effect of both biotic and abiotic geochemical reactions on the contaminant fate and mobility. The model considers the downstream transport of dissolved and sediment-associated species, and the mass transfer with bed sediments due to erosion and resuspension, using linked advection-dispersion-reaction equations. The model also couples both equations to the reactive transport within bed sediment phases.

Mathematical modeling of first flush in highway storm runoff using genetic algorithm.

A mechanistic model was developed to predict the highway runoff pollutographs during precipitation events. Pollutants were assumed to be in two phases, attached to the pavement surface and mobile in the runoff water. Detachment and reattachment of contaminants were considered as rate-limited processes and the detachment rate was assumed to be a function of flow velocity by a power expression.

Approximation of a radial diffusion model with a multiple-rate model for hetero-disperse particle mixtures.

An innovative method is proposed for approximation of the set of radial diffusion equations governing mass exchange between aqueous bulk phase and intra-particle phase for a hetero-disperse mixture of particles such as those occurring in suspension in surface water, in riverine/estuarine sediment beds, in soils and in aquifer materials. For this purpose the temporal variation of concentration at several uniformly distributed points within a normalized representative particle with spherical, cylindrical or planar shape is fitted with a 2-domain linear reversible mass exchange model. The approximation method is then superposed in order to generalize the model to a hetero-disperse mixture of particles.

A stochastic simulation procedure for selecting herbicides with minimum environmental impact.

A mathematical environmental transport model of roadside applied herbicides at the site scale (approximately 100 m) was stochastically applied using a Monte-Carlo technique to simulate the concentrations of 33 herbicides in stormwater runoff. Field surveys, laboratory sorption data, and literature data were used to generate probability distribution functions for model input parameters to allow extrapolation of the model to the regional scale. Predicted concentrations were compared to EPA acute toxicity end points for aquatic organisms to determine the frequency of potentiallytoxic outcomes.

Modeling colloid-facilitated transport of multi-species contaminants in unsaturated porous media.

Colloid-facilitated transport has been recognized as a potentially important and overlooked contaminant transport process. In particular, it has been observed that conventional two phase sorption models are often unable to explain transport of highly sorbing compounds in the subsurface appropriately in the presence of colloids. In this study a one-dimensional model for colloid-facilitated transport of chemicals in unsaturated porous media is developed.