simple screening and settling operations to sophisticated biological, chemical, and mechanical operations that can produce water clean enough to reuse. As a general rule, the quality of treated water increases with more sophisticated technologies, as do costs, land-area requirements, energy requirements, and the amount of sludge produced.
While treatment systems and levels of treatment have dominated the debate over wastewater management in coastal urban areas, a number of other factors in managing wastewater are also of considerable importance. As with any program for managing wastes, the most desirable tactic is to eliminate the production of the waste in the first place. While the complete elimination of waste is obviously not possible in the case of sewage, there are several approaches that can reduce the discharge of some constituents and decrease the volume of water discharged. Phosphate detergent bans in several inland regions of the United States have resulted in significant reductions in phosphorus levels entering treatment plants. Water conservation saves on a scarce natural resource in arid regions and can, in some cases, reduce the volume of water, although not the mass of pollutants, requiring treatment. Major reductions in contaminants from industrial dischargers have been achieved in areas where wastewater treatment agencies have instituted pretreatment requirements.
An array of best management practices is available to reduce the volume and improve the quality of urban and agricultural runoff. Improved management practices (e.g., optimization of pesticide application rates and timing) prevent pollutants from getting into runoff. Public education can play a pivotal role in changing behaviors that can lead to local water-quality improvement, such as appropriate methods for disposal of used automobile oil. Other techniques, such as structural controls, are available to slow runoff, allow more water to percolate into the ground, and filter out contaminants. In addition, weirs, moveable dams, and detention areas can provide storage capacity in storm and combined sewer systems which can reduce the frequency and volume of CSOs.
The location and mechanism of a wastewater discharge plays an important role in determining the extent of impact on marine resources. Contaminant concentrations build up in shallow and/or enclosed systems, whereas deep currents in open systems tend to disperse and flush away discharged material more rapidly. Open-ocean discharges through multiport diffusers are diluted rapidly.
Finally, an important feature of any wastewater and stormwater management system is a monitoring and research program. Monitoring provides information on how well the system is working and where problems may arise; and research can lead to improved methods. It is through monitoring and research efforts that new and improved approaches for managing wastewater and stormwater are developed.