The primary purpose of this chapter is to examine whether there was a significant reduction in effluent BOD loading to the nation's waterways after the technology-based and water quality-based treatment provisions of the CWA were implemented. To fully address this subject, however, it is important to recognize the following:
• Effluent BOD loading comes from several point and nonpoint sources in addition to POTWs.
• BOD is only one of several contaminants that have the potential to affect aquatic resources and the lives and livelihoods of water resource users. Table 2-13 presents some of the concerns and conditions associated with several types of water pollutants.
This section is divided into two subsections. The first subsection briefly describes non-POTW sources of BOD loading, including industrial wastewater treatment facilities, combined sewer overflows (CSOs), urban stormwater runoff, and rural nonpoint sources of pollution. For the purposes of this comparison, urban stormwater runoff includes areas both outside (termed "nonpoint source") and within [meeting the legal definition of a point source in section 502(14) of the CWA] the NPDES stormwater permit program.
The second subsection introduces the National Water Pollution Control Assess-
TABLE 2-13 Pollutant Groups and Related Water Resource Issues
Water Quality Conditions and Concerns
Metals and Toxics
Fish body burden
Shellfish body burden
Mammals body burden
Adsorption/desorption of toxic chemicals Shellfish bed closure Recreational beach closure Anoxic sediments Damage to benthic biota Oil spills Chemical spills
Nuisance algal blooms Toxic algal blooms Fish kills
Shellfish bed closure/loss Loss of seagrass beds/habitat Birds body burden Sediment contamination Drinking water supply Fish kills
Drinking water supply
Habitat destruction/fish spawning Water clarity/transparency Fish kills
Drinking water supply ment Model (NWPCAM)(Bondelid et al., 2000), a modeling tool that can be used to simulate the water quality impact of current (ca. 1995) BOD5 effluent loadings from point and nonpoint sources nationwide. The primary purpose of this exercise is to compare BOD5 effluent loadings from POTWs with BOD5 effluent loadings from other point and nonpoint sources.
Industrial Wastewater Treatment Facilities Many industrial facilities discharge treated wastewater directly to surface waters. Similar to municipal wastewater treatment, industrial wastewater treatment consists of a sequence of physical, biological, and chemical processes designed to remove pollutants that are specific to an industrial facility's manufacturing operations. USEPA's effluent guidelines, prepared for specific categories of industrial groups, define effluent limits in terms of the industry's output production rate (e.g., n kilograms of pollutant discharged per 1,000 kilograms of factory production). Table 2-14 presents median effluent concentrations for conventional and nonconventional pollutants for the industrial categories that account for the largest contributions to effluent loading rates for BOD5.
In contrast to direct industrial dischargers, industrial facilities can also discharge wastewater to sanitary sewer systems, where it mixes with domestic sources of waste-water (indirect industrial dischargers). This wastewater often contains a variety of metals, organic chemicals, and oily wastes that are not common to domestic sources
TABLE 2-14 Effluent Characteristics for Select Major Industry Groups
Inorganic Chemical Products
Organic Chemical Products
Food & Beverages
Iron & Steel
Total P 0.4
Number of facilities 273 Average median design flow (mgd)
Major facilities 2.9
Minor facilities 0.2
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