Managing Wastewater in Coastal Urban Areas (1993) / Chapter Skim
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2 KEY ISSUES RELATING TO WASTEWATER AND STORMWATER MANAGEMENT
2 KEY ISSUES RELATING TO WASTEWATER AND STORMWATER MANAGEMENT
Pages 53-73
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From page 53... ...
Even along a particular coastline, one can find dramatically different environments and ecosystems. Estuaries, where fresh water rivers meet marine waters, have unique circulation patterns depending on tides, runoff, and the physical geometry of the system.
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From page 54... ...
Any such approach would necessarily fail to protect some 1 1 ~ , ~ ~ _ ~ ~ _ ~ ~ ~ A ~ ~ coastal regions and place excessive or ln~II~LlV~ [~Ull~lil~llLb All QL11~1 NUTRIENTS IN COASTAL WATERS Perhaps the most pressing problem in many estuarine and marine systems today is that of nutrient enrichment. While not known to be a problem along most of the open Pacific coast, excess nutrient enrichment, or eutrophication, is a persistent problem in many estuaries, bays, and semi-enclosed water bodies and may be of concern over a large scale in some more open areas alone the Atlantic and Gulf coasts.
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From page 55... ...
Nutrients enter coastal waters from every potential point and nonpoint source including: wastewater treatment plants, agricultural runoff, urban runoff, groundwater discharge, and atmospheric deposition. The relative contribution of nutrients from each of these sources varies from area to area depending on local and regional hydrology, land-use patterns, levels of wastewater treatment, and other management practices.
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From page 56... ...
More s~gn~canny, However, water conservation reduces the need for development of new water supplies. Such development can seriously affect the areas where it occurs as well as divert ecologically important freshwater flows from estuaries and other coastal waters.
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From page 58... ...
The solid material produced from both the secondary and primary processes is referred to as sludge or biosolids. Conventional biological secondary treatment is designed specifically to remove BOD and total suspended solids (TSS)
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From page 59... ...
Thus, while biological secondary treatment serves to remove BOD from the discharge to improve local water quality, it also, in effect, mobilizes nitrogen into regional circulation patterns, which may lead to regional scale eutrophication. In the case of primary effluent, the organic nitrogen in the sediments near the outfall also may solubilize over time, but more slowly.
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From page 60... ...
sources of nitrogen entering the same receiving waters. Another technical tradeoff associated with nitrogen removal is that while better primary treatment enhances biological secondary treatment and Vitrification, it can hinder biological phosphorus removal and denitrification.
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From page 61... ...
STORMWATER AND COMBINED SEWER OVERFLOWS Urban runoff and combined sewer overflows (CSOs) are major contributors to water quality problems in coastal urban areas.
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From page 62... ...
In addition, precipitation in many areas is seasonal so that urban runoff and CSOs may affect coastal waters more during some seasons than others. In central and southern California coastal areas, for example, almost all of the annual rainfall occurs between the first of October and the end of May.
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From page 63... ...
Currently, pollutant removal efficiencies of treatment facilities for CSOs and urban runoff cannot be stated with sufficient confidence to design a facility plan that will limit pollutant loads to a prescribed level. The difficulty in making such predictions stems from the high variability in hydraulic and pollutant loadings that a facility will experience from storm to storm and within a particular storm.
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From page 64... ...
50 t" ~ ~\\~ ~ 5~ ~ Butte, Mr ° Chaffs TN - ~ Cinannab, OH ~ Deco t, Ml U San hanasco, CA Tucson, AZ ~ -- , -it= ~ ~ o 0.02 0.1 0 ~ 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 Basin Storage Volume, inches FIGURE 2.2b Basin overflow frequency versus unit storage volume. (Source: Roesner et al.
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From page 65... ...
from communities having separated stormwater and sanitary sewers (CH2M Hill 1992~. Milwaukee, on the other hand, having jurisdiction over both the combined sewer area and the separate sewered areas, was able to use a single, integrated facility plan to solve both CSO problems and sanitary sewer overflow problems at considerable savings in comparison to possible independent solutions (MMSD 1980~.
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From page 66... ...
In the United States, bacteriological standards for shellfish harvesting waters and recreational waters are set by each state. Standards for shellfish growing waters are generally more consistent nationally and reflect the Food and Drug Administration requirement for interstate transport of harvested shellfish with less than 14 fecal coliforms per 100 milliliters and with no more than 10 percent greater than 43 per 100 milliliters.
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From page 67... ...
For this reason, the absence of coliforms does not guarantee the absence of pathogenic microorganisms in marine waters, sediments, shellfish, or fish. Studies have found limited correlation between indicator bacteria and the presence (or absence)
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From page 68... ...
1991~. These methods will be useful in the performance of sanitary surveys and the development of a risk based approach for determining acceptable levels of specific pathogens in shellfish, recreational waters, and effluents from wastewater treatment plants.
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From page 69... ...
In some cases, the cooperative efforts of stormwater agencies, wastewater agencies, water supply agencies, and other agencies concerned with the region's resources can result in the development of efficient and mutually beneficial solutions. In order to assure continued public support for environmental protection and coastal resource management programs, it is important to develop strategies that make effective use of public funds.
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From page 70... ...
Predictive models used for developing source control programs need to be linked to environmental monitoring data so that the loads and indicators can be correlated and success or failure measured quantitatively. SUMMARY The eight issues identified above form a snapshot of current needs in wastewater and stormwater management in coastal urban areas.
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From page 71... ...
1990. Detection of coliform bacteria in water by polymerase chain reaction and gene probe.
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From page 72... ...
1986. Ambient Water Quality Criteria Document for Bacteria.
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From page 73... ...
from coastal waters.
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