Findlay G. Edwards

Historical perspectives of urban drainage

Historically, urban drainage systems have been viewed with various perspectives. During different time periods and in different locations, urban drainage has been considered a vital natural resource, a convenient cleansing mechanism, an efficient waste transport medium, a flooding concern, a nuisance wastewater, and a transmitter of disease. In general, climate, topography, geology, scientific knowledge, engineering and construction capabilities, societal values, religious beliefs, and other factors have influenced the local perspective of urban drainage. For as long as humans have been constructing cities these factors have guided and constrained the development of urban drainage solutions. Historical accounts provide glimpses of many interesting and unique urban drainage techniques. This paper will highlight several of these techniques dating from as early as 3000 BC to as recently as the twentieth century. For each example discussed, the overriding perspective of urban drainage for that particular time and place is identified. The presentation will follow a chronological path with the examples categorized into the following four time periods: (1) ancient civilizations, (2) Roman Empire, (3) Post-Roman era to the nineteenth century, and (4) modern day. The paper culminates with a brief summary of the present day perspective of urban drainage.

An evaluation of the urban stormwater pollutant removal efficiency of catch basin inserts.

In a storm sewer system, the catch basin is the interface between surface runoff and the sewer. Responding to the need to improve the quality of stormwater from urban areas and transportation facilities, and spurred by Phase I and II Stormwater Rules from the U.S. Environmental Protection Agency, several companies market catch basin inserts as best management practices for urban water quality management. However, little data have been collected under controlled tests that indicate the pollutant removal efficiency of these inserts when the inflow is near what can be expected to occur in the field. A stormwater simulator was constructed to test inserts under controlled and replicable conditions. The inserts were tested for removal efficiency of total suspended solids (TSS) and total petroleum hydrocarbons (TPH) at an inflow rate of 757 to 814 L/min, with influent pollutant concentrations of 225 mg/L TSS and 30 mg/L TPH. These conditions are similar to stormwater runoff from small commercial sites in the southeastern United States. Results from the tests indicate that at the test flowrate and pollutant concentration, average TSS removal efficiencies ranged from 11 to 42% and, for TPH, the removal efficiency ranged from 10 to 19%.

Ozonation in sequencing batch reactors for reduction of waste solids.

The objective of this research was to study a process modification for reducing the mass of waste sludge from sequencing batch reactors (SBRs) by promoting the use of intracellular products released by ozonation of the biomass. For this purpose, biomass generated in laboratory-scale SBRs was exposed to ozone (O3) as a cell-lysing agent to partially solubilize intracellular material. The results indicated that the application of low doses of ozone reduced the mass of waste sludge production by an average of 29%. This positive aspect of the process was achieved using an average daily ozonation rate of 0.0106 mg O3/mg TSS x h, with slightly less than 2 hours of ozonation per cycle with 3 cycles per day. In addition, the short-term settling characteristics of the ozonated biomass were observed to have improved. A negative aspect of the ozonation process resulted in decreased effluent quality, as determined by measured increases in the soluble chemical oxygen demand, total Kjeldahl nitrogen, and total phosphorus concentrations of reactor effluent.

Pollutant Removal Capacity of Stormwater Catchbasin Inserts

Transportation facilities such as parking lots or maintenance yards often do not have provisions to treat stormwater prior to discharge. Catchbasin inserts can provide a retrofit alternative as a method to meet the new National Pollution Discharge Elimination System Phase II stormwater pollution prevention regulations. Six inserts manufactured by five manufacturers were evaluated for removal of suspended solids, petroleum hydrocarbons, and zinc using a pilot scale catchbasin and a simulated stormwater. At a flowrate of 0.011 to 0.013 m 3 /s (180 to 200 gpm) and pollutant concentrations of 225 to 260 mg/L suspended solids and 30 to 42 mg/L total petroleum hydrocarbon, the inserts were capable of removing 11 to 42 percent of suspended solids and 0 to 40 percent of total petroleum hydrocarbons.

Evaluation of Storm Water Catch Basin Inserts for Transportation Facilities

Transportation facilities such as parking lots and maintenance yards often do not have provisions to treat storm water before discharge. Catch basin inserts can provide a retrofit alternative as a method to meet the new National Pollution Discharge Elimination System Phase II storm water pollution prevention regulations. Inserts produced by four manufacturers were evaluated for removal of suspended solids and petroleum hydrocarbons by using a pilot scale catch basin and synthetic storm water. In addition, the inserts were placed at operating transportation facilities and monitored for operational problems. At a flow rate of approximately 0.013 m3/s (200 gal/min) and pollutant concentrations for total suspended solids (TSS) and total petroleum hydrocarbons (TPH) of 225 mg/L and 31 mg/L, respectively, the inserts were capable of removing 11% to 42% of TSS and 10% to 19% of TPH.

Development of a GIS-Based Stormwater Quality Management Planning Tool

Increased federal regulation of stormwater runoff in recent years has concomitantly increased the interest of engineers, planners, and municipal officials towards the effective planning and design of stormwater management programs. Given the increased attention to stormwater management, the demand for technical tools to solve problems efficiently has arisen. To meet the demand for planning tools that can take advantage of spatial data, a Visual Basic for Applications tool for u se within the ArcGIS 8.x geographic information system (GIS) software package has been created. The GIS tool offers a construction site erosion and sediment control module and a post-construction stormwater management module to aid the development of best management practice (BMP) plans. Within the GIS environment, BMPs can be placed on a site map and the automatic processing can be activated to determine the cost and pollutant removal performance of the BMP plan given spatial data describing site topography, land use/cover, and soil type. Site specific BMP performance and cost information can be input or a database of national cost and performance data can be used by default. BMP plans can be revised and the relative cost and performance of alternative plans determined and compared. The construction site erosion and sediment control module implements an erosion prediction algorithm based on the Revised Universal Soil Loss Equation (RUSLE). The post-construction stormwater management module implements Curve Number hydrology for long-term runoff volume prediction, as well as Event Mean Concentration associated with land use for pollutant load prediction. Monte Carlo water quality simulation and a BMP optimization routine are also being developed for later implementation.