Managing Wastewater in Coastal Urban Areas (1993) / Chapter Skim
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4 THE PROCESS
4 THE PROCESS
Pages 88-154
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From page 88... ...
With a focus on wastewater considerations, this chapter describes the application of the various steps in the process and the tools and methods needed to implement the process for managing coastal environments. While the Committee on Wastewater Management for Coastal Urban Areas is not aware of any particular situation in which integrated coastal management is being implemented at the fullest possible extent, it has identified several examples where elements of ICM are being developed and used.
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From page 89... ...
The ICM process should be used to determine if reasonable management decisions can be made, based on existing knowledge. Assess Human Expectations A key to the success of dynamic planning is the development of an adequate understanding of human expectations for coastal resources.
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From page 90... ...
Public expectations also will change over time. Identification of new health hazards, results from risk assessments, data from monitoring programs, and results of research into ecosystem impacts lead to changes in how issues are defined over time and the identification of new problems.
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From page 91... ...
The objectives of political decisionmakers often will be unstated because the political environment is one in which the process of decision making tends to dominate the need to articulate the goals of the outcome of the process. Political leaders are often freed from the need to articulate their ultimate objectives for wastewater management.
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From page 92... ...
At this stage, if a large number of issues has been identified, it may be necessary to do a risk screening in order to reduce the universe of concerns to the most major ones. For example, for a Pacific coastal area such as Santa Monica Bay, there has been no concern about dissolved oxygen in the water column, but there are significant public concerns about maintaining safety of bathing beaches, particularly near storm drain outlets.
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From page 93... ...
No problem can be addressed adequately and effectively if it is not tackled on the scale at which it occurs. Wastewater and stormwater associated effects occur across the spectrum of scales from very localized changes in benthic populations around the end of an outfall to large-scale nutrient enrichment due to point and nonpoint source inputs occurring over hundreds of square kilometers.
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From page 94... ...
It is an analytic tool that can be used to estimate potential adverse impacts of urban wastewater and stormwater on the various organisms, populations, communities, and ecosystems inhabiting coastal waters, as well as on the various uses we make of the coastal environment. Risk assessments have been used extensively to determine human cancer risk (NRC 1983~.
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From page 95... ...
Also, ecological risk assessments involve various levels of biological organization and there is great regional variability among populations, communities, and ecosystems. For these and other reasons, a universally accepted methodology for ecological risk assessments has not been constructed yet.
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From page 96... ...
As discussed further in the Assessing Risks section of this chapter and in Appendix A, nutrient enrichment can cause anoxia and hypoxia, dieback of seagrasses, and nuisance algal blooms. While the bay program was not following a formalized framework for integrated coastal management, the approach taken in regard to nutrients clearly illustrates the application of the ICM concepts presented in this report.
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From page 97... ...
Based on the information gained through research and monitoring and risk assessment and modeling, specific goals for nutrient reduction were set in the 1987 Chesapeake Bay Agreement: By July 1988, to develop, adopt, and begin implementation of a basinwide strategy to equitably achieve by the year 2000 at least a 40 percent reduction of nitrogen and phosphorus entering the mainstem of the Chesapeake Bay. The strategy should be based on agreed upon 1985 point source loads and on nonpoint loads in an average rainfall year.
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From page 98... ...
As an example of the latter type of effect, algal blooms or fish kills that diminish the recreational opportunities in the coastal area would create stress as well as economic consequences for those whose livelihood depends on recreation. While recognizing the full breadth of human health affected by damage to the coastal environment, the approach used here will focus on assessing risks for acute and chronic illnesses caused by exposure to hazardous chemicals and microbiological stressors.
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From page 99... ...
1989; IRIS 1993~. Hazardous organic chemicals have entered coastal waters from a number of sources, most of which are due to industrial and agricultural activities.
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From page 100... ...
. These factors should be considered in the construction of exposure scenarios for human health risk assessments.
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From page 101... ...
For problems related to wastewater inputs to the coastal environment, ecological risk assessment can best be broken into two parts: effects due to excessive nutrient inputs and effects from toxic substances. The effects of nutrient inputs to coastal ecosystems have received a tremendous amount of scientific study over the past two decades.
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From page 102... ...
19891. Coastal waters receive large inputs of nutrients from both point and nonpoint sources.
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From page 103... ...
The effects of toxic substances on ecological systems have proven more difficult to study than the effects of nutrients or than human health effects. In general, the science of ecological risk assessment for toxic substances is not as well developed as that for human health risk assessment.
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From page 104... ...
Level Types of Responses Effects at Next Level B iochemical-Cellular Organismal Toxication Metabolic impairment Cellular damage Detoxication Physiological changes Behavior changes Susceptibility to disease Reproductive effort Larval viability Adjustment in rate functions Immune responses Toxic metabolites Disruption in energetics and cellular processes Adaptation Reduction in population performance Regulation and adaptation of populations Population Age/Size structure Effects on species productivity Recruitment and coexisting species Mortality and community Biomass Adjustment of Adaptation of population reproductive output and other demographic characteristics Community Species abundance Replacement by more and Species distribution adaptive competitors Ecosystem Biomass Reduction of secondary Trophic interactions production Ecosystem adaptation No change in structure and function Ecosystems vary in their sensitivity to stress by type and region, and therefore ecological health risk assessments should be specific to the setting of concern. Sensitivity is determined by both physical and ecological parameters.
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From page 105... ...
The basic elements for consideration in ecological health risk assessment are shown in Table 4.2. The fact that ecological risk characterizations are difficult and the results relatively uncertain at higher levels of biological organization does not imply that they cannot be conducted.
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From page 106... ...
at which the ecological risk assessment is conducted. In theory, the scale of ecological organization chosen for the ecological risk assessment is dependent upon both the spatial and temporal scales of the stress and the co-occurring ecosystem component affected by the stress.
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From page 107... ...
have led to the development of methods to establish acceptable chemical levels in bottom materials. These methods, sometimes called Sediment Quality Criteria or Sediment Quality Values, can use models to predict whether a given mass loading of chemicals from an effluent will likely result in toxic sediments.
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From page 108... ...
Multiple sources of materials, including combined sewer overflows (CSOs) and urban runoff, as well as commercial ships, recreational boaters, and beachgoers can cause aesthetic offense.
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From page 109... ...
Sediment Quality Triad Sediment chemical contamination, sediment toxicity, and benthic infauna community structure are measured on the same sediment. Correspondence between sediment chemistry, toxicity, and biological effects is used to determine sediment concentrations that discriminate conditions of minimal, uncertain, and major biological effects.
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From page 110... ...
Risk comparisons could be applied to answer questions such as, does biochemical oxygen demand (BOD) from urban stormwater pose as much risk to a receiving water body as nutrients from publicly owned treatment works (POTWs)
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From page 111... ...
As an example of how these criteria could be used for human health risks, data from Santa Monica Bay were used to compare the risk to humans from swimming with the risk from eating contaminated fish. Using the data, Table 4.5 was constructed.
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From page 112... ...
An ideal comparative risk assessment would include health, ecologic, and aesthetic impacts. Table 4.7 shows an array that was developed as part of the Santa Monica Bay Restoration Project.
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From page 113... ...
THE PROCESS TABLE 4.7 Comparison of the Relative Importance and Understanding of Stressors to Critical Components of Santa Monica Bay \ VALU ED .
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From page 114... ...
Santa Monic Bay: A Case Example Santa Monica Bay in Southern California is currently being evaluated for management options under authority of the Santa Monica Bay Restoration Project, an activity supported by EPA under the National Estuary Program. Santa Monica Bay is a 690 square kilometer indentation along the Southern California Bight.
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From page 115... ...
The Santa Monica Bay Restoration Project defines "the Bay" to include part of the San Pedro Bay shelf, namely the western end along the Palos Verdes Peninsula. Unlike the bay itself, the shelf along the Palos Verdes Peninsula is steep and narrow, within 5 kilometers of shore it plunges into the 850-meter-deep San Pedro Basin.
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From page 116... ...
During 1990 and 1991, the Santa Monica Bay Restoration Project con
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From page 117... ...
were along the Santa Monica coast between these two points. During wet weather, risk increased sharply at the southern sites but only slightly at the Santa Monica area sites.
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From page 118... ...
The highest levels of DDT and PCB contamination have been found in white croaker, which is among the most frequently caught and consumed fish. The white croaker effectively defines a boundary of concern that extends out to about 100 meters deep and from San Pedro to the central-northern shore of Santa Monica Bay.
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From page 119... ...
About 11.4 square kilometers of the Santa Monica Bay sea floor are projected to incur changed benthic communities as a result of current inputs of suspended solids from sewage inputs. This area includes about 1.6 square kilometers, 8 kilometers offshore in the center of Santa Monica Bay shelf and 9.8 square kilometers located 3 kilometers offshore of the Whites Point area of the Palos Verdes shelf.
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From page 120... ...
To illustrate the engineering process this section focuses at first on a single major discharger of wastewater effluent from a POTW; then later in the section the discussion extends to other situations involving multiple point sources and diffuse sources. However, the same general concepts apply i.e., working back from water and sediment quality objectives to find the optimum set of control measures needed.
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From page 121... ...
Ambient Water-Quality Objectives The risk to human health and ecosystems and to our aesthetic appreciation of coastal water is linked directly to ambient water quality, which is often defined by measurable parameters such as concentrations of suspended solids, tonics, nutrients, bacteria and viruses, oil and grease, and dissolved oxygen. For instance, the risk management of pathogens has been systematized by setting standards for surrogates such as coliform bacteria or enterococci bacteria which can be monitored easily.
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From page 126... ...
In using the term environmental-quality driven approach, the implication is that other media effects will be included even though water and sediment are central. Sediment quality objectives are recent developments, as it is now well understood that contaminated sediments are significant contributors to exposure to the ecosystem and humans (through shellfish and benthic fish)
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From page 127... ...
The plan was updated in 1978, 1983, 1988, and 1990; and is currently undergoing another review. Use of an Environmental Quality Driven Approach The Ocean Plan establishes water quality objectives for California's ocean waters.
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From page 128... ...
It does not establish a standard for BOD in effluent nor does it establish treatment requirements for BOD. Effluent Limitations The plan establishes some standards without regard to initial dilution or receiving water conditions.
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From page 129... ...
_ Source control 129 Healthy Ecos ystem , , Water and Sediment Quality _ Objectives _ Aesthetic Enjoyment ~ ~Ocean Environmentl 1 FIGURE 4.4 Overview of water- and sediment-quality driven approach for design of municipal wastewater disposal system. The water-quality/sediment-quality driven approach involves working backward (compared to direction of flow)
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From page 130... ...
The conceptual design then proceeds with a trial choice of outfall and related treatment levels and source control programs necessary to meet the ambient water quality standards. The process involves complex modeling of the transport and fates of contaminants in the ocean after initial dilution.
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From page 131... ...
It is interesting to note that 85 percent removal of suspended solids, even though in a primary tank, is equivalent to the federal requirement for suspended solids removal for secondary treatment (for influent suspended solids less than 200 mg/1~. The environmental-quality driven approach will encourage further innovation in wastewater treatment focused on controlling water and sediment quality as needed.
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From page 132... ...
90 _ . Dept h 100 ft 150 -an l 1 ~200 2l,400ft 27,400 It FIGURE 4.5 Schematic plan and profile of the 120-inch outfall, County Sanitation Districts of Orange County, California.
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From page 133... ...
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From page 134... ...
Various submodels may be combined to produce an overall model that relates pollutant inputs to water and sediment quality for single and multiple sources. These models are fundamental to the water-quality driven approach for system design because the limits on emission for any discharge or nonpoint source may be back-calculated using the models.
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From page 135... ...
Or another example, if the range of uncertainty of a biological effect is a factor of 10, the effect may be of no importance if the upper end of the range is fully acceptable. The preceding discussion relates to the wastewater disposal system for a municipality including source control programs, a treatment plant, and outfall.
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From page 136... ...
Predictive models have a number of uncertainties and need improvement, but nonetheless appropriate engineering systems for wastewater disposal and diffuse source control can be designed to meet prescribed waterand sediment-quality objectives. Since modeling for design of a management plan for pollution control always has some uncertainty covered by safety factors, it is cost-effective to implement a system (such as a waste treatment plants and an outfall)
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From page 137... ...
Due to the general lack of feasible options to increase the initial dilution significantly at the discharge points, it is necessary to impose corrective measures on land, such as the banning of toxics for dispersed urban use (e.g., the elimination of lead from gasoline) , better street cleaning, detention basins, skimming devices for floatables, and storage and diversions to treatment plants during dry weather.
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From page 138... ...
The initial dilution is thus not relevant, and only the regional circulation and sedimentation processes determine how much becomes trapped in sediments versus the net transport to the deep ocean. If the residence time of a body of coastal water is short (days to months)
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From page 139... ...
In recent years, because of source control, the concentration of contaminants in digested sludge has been steadily decreasing. Reduction in toxicants is required for safe land disposal and incineration as well.
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From page 140... ...
Sometimes, however, the extra costs of energy and facilities and the cross-media impacts of dewatering the sludge and transporting it to places where it can be used beneficially may not outweigh the environmental costs of ocean disposal. Cross-Media Considerations All of the foregoing discussion focused primarily on water and sediment quality and the development of appropriate engineering works and management strategies to produce the desired water and sediment quality while still disposing of wastewater and storm water.
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From page 141... ...
The simplest example of the impact of this consideration is seen in the construction of municipal treatment plants. In these cases, the end of federal grant support means that customers now
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From page 142... ...
One illustration will demonstrate the impact of these factors. In some situations, the engineering and cost analysis may suggest that the most technically practical solution to a wastewater management problem is discharge of advanced primary effluent through a very long outfall.
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From page 143... ...
2. Predictive models have a number of uncertainties and need improvement, but, nonetheless, appropriate engineering systems for wastewater disposal and diffuse source control can be designed to meet prescribed water and sediment quality objectives.
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From page 144... ...
Having a clear picture of this institutional setting is essential to any attempt to improve wastewater management. Institutions are fragmented in at least three different ways: hierarchically, geographically, and functionally.
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From page 145... ...
Just as the process of risk management takes account of a wide range of possible actions and interventions in seeking the most appropriate strategy, it is important to consider all feasible management tools in devising management plans. But coastal wastewater management takes place in a fragmented, multi-institutional setting, where no one entity has the means or the mandate to set overall objectives or compel specific actions by others.
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From page 146... ...
No wastewater management strategy should be considered in isolation. An intricate network of laws, regulations, and policies is already in place and must be recognized in the development of any new policy.
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From page 147... ...
Wastewater management programs can be financed in numerous ways. These ways include the use of general tax revenue, dedicated tax revenue, user charges, intergovernmental transfers, and debt (long term or short term)
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From page 148... ...
For these reasons and more, selection of the appropriate plan is only partly the responsibility of experts. It is the task of planners and analysts to insure that all plans meet the following tests: Adequacy-Each plan must satisfy the primary goals of wastewater management: to protect the fundamental functions and biological richness of the ecosystem and to maintain important human uses.
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From page 149... ...
Research provides knowledge about the significance of various environmental changes, importance of different impacts, and potential for various technologies and management controls to be effective in mitigating impacts and protecting the environment. Research activities can also contribute new insights to the understanding of human expectations for the coastal environment and the economic impacts of alternative management strategies.
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From page 150... ...
. monitoring designed principally to meet regulatory compliance needs generally does not adequately answer questions about the regional and national risks of pollutant inputs to public health, coastal environmental quality, or living resources.
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From page 151... ...
Research aimed at reducing these uncertainties would improve understanding and provide insight on how to manage the risks. The survey of anglers now under way to develop better estimates of fish consumption in Santa Monica Bay is a good example of a research effort aimed at refining information on risks.
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From page 152... ...
Whittier, California: County Sanitation Districts of Los Angeles County. CBP (Chesapeake Bay Program)
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From page 153... ...
1988. The State of Santa Monica Bay: Part One: Assessment of Conditions and Pollution Impacts.
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From page 154... ...
1992. Progress Update: Santa Monica Bay Restoration Project 1991-92.
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