Effective depth controls the nitrate removal rates in a water supply reservoir with a high nitrate load.

The Occoquan Reservoir is part of an indirect potable reuse system where a water reclamation plant (WRP) discharges a nitrified product water to prevent the onset of anaerobic conditions in the bottom sediments during the summer months. The elongated narrow shape of the reservoir combined with water temperature gradients in the inlet results in density currents that enhance the transport of nitrate from the surface to the bottom waters. The morphology of the reservoir also causes a longitudinal change in the ratio of water volume to sediment area, herein defined as the effective depth (Z).

Evaluating the performance of a retrofitted stormwater wet pond for treatment of urban runoff.

This paper describes the performance of a retrofitted stormwater retention pond (Ashby Pond) in Northern Virginia, USA. Retrofitting is a common practice which involves modifying existing structures and/or urban landscapes to improve water quality treatment, often compromising standards to meet budgetary and site constraints. Ashby Pond is located in a highly developed headwater watershed of the Potomac River and the Chesapeake Bay.

Effects of nitrate addition on water column methylmercury in Occoquan Reservoir, Virginia, USA.

Mercury bioaccumulation in aquatic biota poses a widespread threat to human and environmental health. Methylmercury (MeHg), the toxic form of mercury, tends to build up under anaerobic conditions in the profundal zones of lakes. In this study we performed a two-year assessment of spatial and temporal patterns of dissolved oxygen, nitrate, MeHg, manganese (Mn) and iron (Fe) in Occoquan Reservoir, a large run-of-the-river drinking water reservoir in Virginia, USA.

Effects of nitrate input from a water reclamation facility on the Occoquan Reservoir water quality.

To manage water quality in the Occoquan Reservoir, Virginia, a water reclamation facility discharges nitrified product water that reduces the release of undesirable substances (e.g., phosphorus, iron, and ammonia) from sediments during periods of hypolimnetic anoxia.

Assessing performance of manufactured treatment devices for the removal of phosphorus from urban stormwater.

Nutrients such as nitrogen and phosphorus in urban runoff can be controlled through a variety of nonstructural and structural controls commonly known as best management practices (BMPs). Manufactured treatment devices (MTDs) are structural BMPs that may be used in portions of a site, often when space is limited. MTDs use a variety of technologies to achieve potentially greater treatment efficiency while reducing spatial requirements.

Characterizing natural organic material from the Occoquan Watershed (Northern Virginia, US) using fluorescence spectroscopy and PARAFAC.

Surface water samples from the Occoquan Watershed (Virginia, US) were collected during summer baseflow conditions and characterized by excitation-emission matrix (EEM) fluorescence spectroscopy and parallel factor analysis (PARAFAC). Based on 55 samples, PARAFAC identified three individual fluorophore moieties, which were attributed to humic-like, fulvic-like, and protein-like materials. The categorization of these seemingly universal fluorophore moieties in aqueous systems was consistent with expected analyte concentrations that were independently measured by traditional wet chemistry techniques.

Effect of alum addition on the performance of submerged membranes for wastewater treatment.

The effect of aluminum sulfate (alum) addition on membrane performance was investigated, with a particular focus on membrane fouling. During initial operation, alum was added and the performance monitored. After terminating alum addition, the transmembrane pressure (TMP), which is indicative of membrane resistance to flow or fouling, increased.

Estrogen receptor agonist fate during wastewater and biosolids treatment processes: a mass balance analysis.

The estrogen receptor agonist fate of hexane extracts from various locations and phases (liquid and solid) within one pilot-scale and two full-scale wastewater treatment facilities were examined by use of the receptor-binding yeast estrogen screen (YES assay). Estrogenic activity was found in samples that contained a high concentration of biological solids and was particularly high in the suspended solid fraction from biosolids treatment facilities. Mass balances revealed that the estrogenic activity associated with the processed biosolids constituted between 5 and 10% of the influent estrogenic activity, while the treated liquid effluent prior to disinfection contained between 26 and 43%.