Progression of river BOD/DO modeling for water quality management.

A historical perspective of river BOD/DO modeling using the Streeter-Phelps equation in the past century is presented with cases in the United States, Taiwan, and India. The main emphasis is on the regulatory aspects of modeling during the five decades following the passage of the 1972 Clean Water Act (CWA) in the United States. Success of the CWA in river clean-up is demonstrated via BOD/DO modeling for management use.

Attenuation, transport, and management of estrogens: A review.

Overabundance of endocrine disruptors (EDs), such as steroid estrogens, in the natural environment disrupts hormone synthesis in aquatic organisms. Livestock and wastewater outflows contribute measurable quantities of steroid estrogens into the environment where they are picked up and transported via surface runoff and feedlot effluents into water matrices. E1, E2β, E2α, E3 and EE2 are the most prevalent estrogens in these environmental systems.

Tracking the fate and transport of estrogens following rainfall events.

Surface runoff following rainfall events can transport estrogens from agricultural land to water systems, causing potential risks to aquatic biota. This study adopted two simple models, the wash-off and empirical models, to quantify the pathway of three prevalent manure-borne estrogens, estrone (E1), 17β-estradiol (E2β) and 17α-estradiol (E2α), from agricultural land to the receiving water following rainfall events. The complex interconversion of the three estrogens during attenuation was considered in the models.

Modeling the fate and transport of 17β-estradiol in the South River watershed in Virginia.

Hormones excreted by livestock metabolisms often enter surface water through feces and urine and can potentially cause adverse impacts to aquatic biota. This study involved a modeling analysis of 17β-estradiol (E2), a prevalent estrogen, in the South River watershed located in Augusta County, Virginia from 2013 to 2015. Cattle manure, poultry litter, biosolids, septic systems, and wastewater treatment plants (WWTPs) were considered as sources of E2 in this study.

Spatially variable deoxygenation in the Danshui River: improvement in model calibration.

A modeling study of the Danshui River, Taiwan, reveals that in-stream BOD deoxygenation rates vary significantly along the river as a result of the highly variable strength of wastewater discharges, which directly reflect the effluent characteristics. A comprehensive field data gathering and lab analysis effort for the study site is presented. Results of the data analyses yielded spatially variable CBOD deoxygenation and nitrification rates, which were incorporated in a model of the river.

Effects of sorption kinetics on the fate and transport of pharmaceuticals in estuaries.

Many current fate and transport models based on the assumption of instantaneous sorption equilibrium of contaminants in the water column may not be valid for certain pharmaceuticals with long times to reach sorption equilibrium. In this study, a sorption kinetics model was developed and incorporated into a water quality model for the Patuxent River Estuary to evaluate the effect of sorption kinetics. Model results indicate that the assumption of instantaneous sorption equilibrium results in significant under-prediction of water column concentrations for some pharmaceuticals.

A GIS-based generic real-time risk assessment framework and decision tools for chemical spills in the river basin.

This paper presents a generic framework and decision tools of real-time risk assessment on Emergency Environmental Decision Support System for response to chemical spills in river basin. The generic "4-step-3-model" framework is able to delineate the warning area and the impact on vulnerable receptors considering four types of hazards referring to functional area, societal impact, and human health and ecology system. Decision tools including the stand-alone system and software components were implemented on GIS platform.

Predicting EDC concentrations in a river mixing zone.

The fate and transport of endocrine disrupting chemicals (EDCs) in ambient river waters is a major concern associated with effluents from municipal wastewater treatment plants (WWTPs). This paper presents a methodology for quantifying the spatial distribution of EDCs in a river mixing zone. The core of the technical analysis is based on a two-dimensional steady-state analytical model characterized by ambient turbulence in the receiving water.

Modeling arsenic in the Patuxent Estuary.

A water quality model was developed to track the fate and transport of four arsenic species in the Patuxent Estuary: arsenate (As(V)), arsenite (As(III)), methylarsonate (MMA), and dimethylarsinate (DMA). Processes simulated include mass transport, solid-liquid partitioning with suspended solids, uptake and transformation of As(V) by phytoplankton, oxidation of As(III), demethylation of MMA and DMA, and settling/deposition/ resuspension of particulate arsenic in the water column. A sediment module was also developed and linked with the water column to generate fluxes of inorganic arsenic from the sediment bed.

Three-dimensional modeling of fecal coliform in the Tidal Basin and Washington Channel, Washington, DC.

Fecal coliform are widely used as bacterial indicator in the United States and around the world. Fecal coliform impaired water is highly possible to be polluted by pathogenic bacteria. The Tidal Basin and Washington Channel in Washington, DC are on the Total Maximum Daily Load (TMDL) list due to the high fecal coliform level.

A hybrid neural-genetic algorithm for reservoir water quality management.

A combined neural network and genetic algorithm (GA) was developed for water quality management of Feitsui Reservoir in Taiwan. First, an artificial neural network (ANN) model was employed to simulate the behavior of nutrient loads into the reservoir. The data from watershed loads, precipitation in the watershed, and outflow were used in the ANN model to forecast the total phosphorus concentration in the reservoir.

Modeling sediment impact on the transport of fecal bacteria.

Sediment storage of fecal bacteria has been observed for a long time. However, limited modeling efforts have been conducted to dynamically and explicitly study the impact of sediment on the transport of fecal bacteria. In this paper, a modeling framework based on the Environmental Fluid Dynamics Code (EFDC) model has been proposed.