A. Yousef

Treatment Systems for Urban and Highway Run-off in Denmark

To observe the required quality in Danish receiving water systems, pollution from urban and highway run-off is of importance in many cases. There is therefore a potential demand for treatment of the wet-weather flow. An evaluation of relevant treatment methods was carried out for the National Agency for Environmental Protection. The wet detention pond was considered the most efficient and suitable solution for removal of the most important pollutants, i.e. phosphorus and heavy metals, in the storm-water run-off from urban catchments and highways. Recommended design procedures are described and exemplified in this paper.

Removal of contaminants in highway runoff flowing through swales

Abstract Simulated highway runoff was pumped over a well established grassy swale at Maitland Interchange and a newly constructed swale at EPCOT Interchange, near Orlando, Florida to investigate mass transport and removal efficiencies for nutrients and heavy metal concentrations under controlled environments. Dissolved metal concentrations, particularly those existing in ionic species, were better removed than phosphorus and nitrogen. Nutrient concentrations in highway runoff flowing over roadside swales may increase. However percent mass removal of all pollutants were found to be higher than concentration removal due to infiltration.

Changes in phosphorus concentrations due to mixing by motorboats in shallow lakes

Abstract Recreational motorboats equipped with engines varying from 28 to 165 horsepower were operated at three selected Central Florida lakes. Also, a pair of isolation chambers representing aquatic habitats were placed in each lake for control and mixing studies. Mixing in isolation chambers was performed by small electrical motors connected to two blade propellers. Agitation of the water column in the lake mixing stations and inside the isolation chambers increased water turbidities and phosphorus concentrations. The increase in turbidity and phosphorus content occurred at a much higher rate than the rate of decline after cessation of mixing. The increase in phosphorus content could result in an increase in lake productivity as noticed from the increase of chlorophyll a concentrations in lake mixing stations.

Heavy metal accumulation and transport through detention ponds receiving highway runoff

Sediment accumulations and associated heavy metal concentrations into retention/detention ponds receiving highway runoff from several ponds and metal concentrations in various sediment layers were analyzed to determine the extent of vertical migration. Extraction of heavy metals had been evaluated using various solutions including the United States Environmental Protection Agency Toxicity Characteristics Leaching Procedures (TCLP). Also, sediments were incubated under various conditions of redox potential and pH to investigate the effects of changes in sediment conditions on the stability of metal-sediment associations.

Fate of heavy metals in stormwater runoff from highway bridges

Abstract Pollutants associated with runoff water from highway bridges located in Central Florida, USA, were characterized and quantified. These pollutants are directly discharged through scupper drains to adjacent water bodies and floodplains or detained in ponds before being released to lakes and streams. Runoff water contains heavy metals such as lead, zinc, copper, chromium, iron, nickel and cadmium which concentrate in adjacent soils and biota. It appears that soil systems are efficient in removing heavy metals from highway bridge runoff. It is suggested that bridge drainage be directed towards retention/detention ponds or floodplains and direct drainage of bridges in water bodies beneath them should be avoided as much as possible. This paper summarizes several studies conducted by the University of Central Florida for the Florida Department of Transportation and the Federal Highway Administration, U.S.A.

Sediment accumulation in detention or retention ponds

Accumulation of bottom sediments in nine highway wet detention ponds in central to south Florida were investigated. Sediment core samples were collected at each pond and were later analyzed in the laboratory. In-situ measurements of accumulated loose sediment depths above the parent soil in each pond were recorded. Existing models were used to calculate removal efficiency of suspended solids and to estimate the depth of accumulated sediments in each pond. Attempts were made to correlate measured and calculated sediment accumulation rates and the surrounding drainage area.

ANALYSIS OF RAINFALL SERIES IN THE DESIGN OF URBAN DRAINAGE CONTROL SYSTEMS

Abstract Intensity-duration-frequency curves are traditionally used in the design of urban runoff treatment and management systems. The uniform intensity for a specified duration and return period is selected for a design storm without consideration of the inter-event dry periods between two successive rainfall events. For many purposes, especially those related to urban storm pollution control and receiving water impacts, the cumulative effects of successive storm events must be taken into account. This fact requires the selection of design storms where the minimum inter-event dry periods are adjusted to the effect in question. This paper will discuss the concept of inter-event dry periods for evaluation of design storms derived from a rainfall record. As an example the rainfall record for the city of Odense, Denmark, has been analyzed. The basic statistics as well as the importance of the concept will be illustrated.

Transport of heavy metals through accumulated sediments in wet ponds

Abstract Nine detention ponds in Florida were selected to investigate heavy-metal accumulation in their bottom sediments. Core sediments samples were collected from each pond, frozen and divided into six layers. The total metal content and extractable metal by toxicity characteristic leaching procedure (TCLP) were determined for each sediment layer in each pond. The fractions of extractable metals using TCLP exhibited an exponential decline with increasing fine particles (less than 0.062 mm diameter) and organic content. Most of these metals are tightly bound to the bottom sediments, and their transport is very slow. It is feasible to remove the accumulated sediments saturated with metals from the bottom of the ponds for periodic maintenance at relatively long periods, averaging 15 years, to avoid seepage and potential contamination of groundwater beneath the pond.

Modeling and impact of metal accumulation in bottom sediments of wet ponds

Abstract Data from thirteen sites located in south and central Florida were used to evaluate the heavy metal accumulation in the bottom sediments of wet detention ponds. Accumulation rates were calculated for cadmium, chromium, copper, iron, nickel, lead and zinc. Copper, zinc and lead accumulations account for 75 percent or more of the total heavy metal accumulation, excluding iron. Relative accumulation rates for copper, zinc and lead averaged 1:4:8:11.8, respectively. Linear and non-linear predictive equations based on the ratios of total drainage are to pond surface area were developed for copper, lead and zinc accumulation rates. The impact of sediment heavy metal content on benthic organisms was evaluated for nine of the study ponds. Benthic organisms in the bottom sediments showed less species diversity than typical freshwater lakes and copper appeared to be the most detrimental metal to benthic organisms.

Benthic fauna species diversity in six central Florida lakes in summer

The summer macroinvertebrate fauna was studied in six central Florida monomictic lakes during July, 1973. No direct relationships were found between physiochemical conditions and species diversity. Of the 22 species of benthic organisms recorded, only four species were found in all the lakes. Mean species diversity (d) values for the lakes ranged from 0.735 to 1.731.