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ESTIMATING URBAN WET-WEATHER POLLUTANT LOADING
Citation:
Fan*, C, D Sullivan*, AND R Field*. ESTIMATING URBAN WET-WEATHER POLLUTANT LOADING. Presented at Water Environment Federation TMDL, 2003 Specialty Conference, Chicago, IL, 11/16-18/2003.
Description:
This paper presents procedures for estimating pollutant loads in urban watersheds emanating from wet-weather flow discharge. Equations for pollutant loading estimates will focus on the effects of wastewater characteristics, sewer flow carrying velocity, and sewer-solids deposition. Equations include daily mass sewer-solids deposition, accumulation of dry-weather street dust-and-dirt, and their washoff rates. The US EPA has developed methods for the determination of deposition rates in small sized sewers (< 18 in. or 500 mm). Shear stress criteria were used to categorize what proportion of particles are likely to deposit from a flow. Hydraulic experimental results indicated that at shear stresses of daily flow < 0.19 N/m2 some 40% of the total solids in transport would deposit. In addition, the US EPA developed a series of regression equations to quantify the daily mass of sewer-solids deposition based on sewerline and catchment-land topographic characteristics. Correlation equations of SS and VSS with BOD5, COD, NH3-N, and heavy metals will also be discussed. Methods for estimating the quantity of dust-and-dirt accumulation on street surfaces during dry weather and their washoff rates during a storm event will be assessed. Feasible best management practices for controlling sewer sediments will be discussed, including source control, upstream sediment trapping, and sewer flushing.