A mathematical approach to depuration

Two equations can be written to describe the change in bacterial concentrations in the shellfish and the water in depuration units. Analytical solutions of these equations for special conditions and numerical solutions for general conditions indicate that there will always be an initial, rapid decrease in bacteria in the oysters during depuration. With suitable flow rates and loading rates, the die off will be exponential and several orders of magnitude reduction can be achieved within 72 hours. Both very low flow rates and very low loading rates increase the residence time of water in the tank, and therefore depuration will occur slowly after about 24 hours. In addition, the bacterial levels at 72 hours may be quite high for the case of very low flow rates. Further improvements and verification of the model are desired, but use of the model can aid in the design and operation of depuration plants now

Water quality trends in the Northwest River : a report to the Hampton Roads Water Quality Agency

During the initial 208 studies of the Hampton Roads area, no mathematical model of receiving water quality was applied to the Northwest River. At the request of the City of Chesapeake, the HRWQA P003085-03 work program included tasks leading to development of a water quality model of the Northwest River. Data from field studies conducted in 1980 and 1981 and the math model applied to the river have been presented in a companion volume report (Kuo et al., 1982). This report summarizes the results of model simulations made to determine future water quality conditions and trends

Summary of the Hampton Roads 208 Water Quality Modelling Studies

The purpose of· the Hampton Roads 208 Study is to assess the present and future water quality conditions in the study area and to develop a wastewater management plan to achieve certain water quality goals. The study included all major estuaries in the area and, among other thing·s, took account of population and industrial growth, effluent quality {as mandated by PL92-500) and nonpoint sources of pollution. Land use maps for 1976, estimates of future land use, population projections and many other elements of the study initiated in 1974 provided the foundation upon which the water quality work was based. Projections of point source discharges, both flows and pollutant loads, were developed by Betz Environmental Engineers {Task Package 4). The studies of nonpoint sources of pollution were conducted primarily by Malcolm Pirnie Engineers, Inc. {Task Package 5). Twenty-five sites in the two planning districts were sampled during each of two rain events by VIMS during the period March through October 1976. Data from these field studies were used by MPEI to calibrate the mathematical model of surface runoff called STORM {Storm, Treatment, Overflow and Runoff Model). This model then was used to project nonpoint loads at the time of water quality surveys and for future times

Development and application of an index to assess nutrient enrichment in estuaries : a report to the Chesapeake Bay Program, U. S. Environmental Protection Agency

An index is 11 something used or serving to point out , a guide , a sign, token or indication (.14) +. Indexes* such as those used in books, magazines and newspapers are not the subject of this study. Rather we are concerned with the use of indexes in technical fields. Even these are encountered often in everyday life. For example, a recent front-page newspaper article noted that the government\u27s index designed to forecast future economic trends dropped .... after rising for six straight months . An editorial column in the same issue addressed the use of the existing Consumer Price Index as a basis for Social Security cost-of-living adjustments . Economists and other social scientists have utilized indices extensively. Environmental indexes have been proposed but only a few, such as the air pollution index, have been used widely. It appears that environmental indices could be extremely valuable and useful for purposes such as showing trends in water quality resulting from development, implementation of good management practices on land, or higher levels of treatment for wastewaters,(13

Water quality in the small coastal basins

The Small Coastal Basins portion of the Hampton Raods 208 study area includes the Back and Poquoson Rivers on the Virginia Peninsula and Little Creek Harbor and the Lynnhaven Bay system on the southern shore of Chesapeake Bay, as shown in Figure 1. The drainage areas are characteristically small, ranging from only 63 square kilometers for Little Creek Harbor to 156 sq. km,for the Lynnhaven Bay system. All four basins lie entirely within the geological Coastal Plain Province, the low lying area between the Fall Line and the Atlantic Ocean. The soft sediments typical of this province erode easily, so that the rivers have branching or dendritic patterns. Because the topographic relief is slight and the drainage areas are small, none of the basins has continuous free flowing tributaries typical of larger estuaries. The u. S. Geological Survey has no stream gaging stations within the Small Coastal Basins area. ...

Exploiting natural oyster populations through waste heat utilization

Oysters are filter-feeding organisms which can accumulate substances to concentrations far above those found in the surrounding water. Large acreages of estuary bottoms have been classified .as restricted for shellfish culture due to the presence of pollutants in the water and therefore, the likelihood of high levels of pollutants in oysters grown in those environments. Depuration is a natural process whereby oysters and other shellfish cleanse themselves of accumulated contaminants when they are placed in a clean environment. Recent studies have shown that bacterial depuration of oysters is feasible for the waters of Chesapeake Bay. Depuration is not possible, though, when water temperatures are below 10 °c. Furthermore, both the rate of depuration and the reliability of the process increase with higher temperatures for the 100 to 20 ° C range. Utilization of waste heat from power generating stations would allow depuration to continue during winter months and could improve the quality of the product during the spring and fall.https://scholarworks.wm.edu/vimsbooks/1134/thumbnail.jp

The consequences of nutrient enrichment in estuaries

A paper study was conducted to determine the consequences of nutrient enrichment in an estuary. First, a classification scheme was developed to assign- a Level of Nutrient Enrichment to a water body based on concentrations of Total Phosphorus and Total Nitrogen. The impacts of nutrient enrichment on the various uses of estuaries there were described and assessed. Finally, safe nutrient levels for Chesapeake Bay and its tributaries were recommended