hydrogen sulfide generation is of concern in collection systems and at treatment facilities. The release of hydrogen sulfide to the atmosphere above sewers and at treatment plant headworks has occurred in a concrete sewers. headworks structures and equipment. and to the release of odors. The control of odors is of increasing environmental concern as residential and commercial development continues to existing treatment plant locations. Odor control facilities including covers for process units. special rentilation equipment, and treatment of odorous gases need to be integrated with treatment plant design Control of hydrogen sulfide is also fundamental to maintaining system reliability Fig 1-3 Facilities used for chemical treatment of odors from treatment facilities The presence of VOCs and VTOCs in wastewater has also necessitated the covering of treatment plant headworks and facilities to treat the compounds before they are released. In ome cases, improved industrial pretreatment has been constructed in the United states during the 1970s and 1980s when large sums of federal money were available for plementation of the CWA(Clean Water Act). Much of the quipment, now over 20 vears old. is reaching the end of its useful life and will need to be replaced. Process changes to improve performance, meet stricter permit requirements and increase capacity will also be needed For these reasons, significant future efforts in the planning and design of wastewater treatment plants in the United States will be directed to modifying improving and expanding existing treatment facilities. Fewer completely new treatment plants will be constructed. In developing countries. opportunities for designing and pletely new facilities may be Fig. 1-4 UV lamps used for the disinfection of wastewater In the U.S. EPA Needs Assessment Survey, the total treatment plant design capacity projected to increase by about 15 percent over the next 20 to 30 vears During this period, the U.S. EPA estimates that approximately 2, 300 new plants may have to be built. most of which will be providing a level of treatment greater than secondary. The design capacity of plants providing greater than secondary treatment is expected to increase by 40 percent in the future (U.S. EPA, 1997). Thus, it is clear that the future trends in wastewater treatment plant design will be for facilities providing higher levels of treatment Some of the innovative treatment methods being utilized in new and upgraded treatment facilities include vortex separators. high rate clarification, membrane bio-reactor pressure-driven membrane filtration and In recent years, numerous proprietary wastewater treatment processes have been developed that offer potential savings in construction and operation. This trend will likely continue, particularly where alternative treatment systems are evaluated or facilities are privatized. Privatization is generally defined as a public-private partnership in which the private partner arranges the fin operation of the treatment facilities. in some cases, the private partner may own the facilities. The reasons for privatization, however, go well beyond the possibility of installing proprietary processes. In the United States, the need for private financing appears to be the principal rationale for privatization, the need to preserve local control appears to be the leading pragmatic rationale against privatization 1-6 Wastewater Reclamation and reuse In many locations where the available supply of fresh water has become inadequate to meet water needs. it is clear that the once-used water collected from communities and municipalities must be viewed not as a waste to be disposed of but as a resource that must be reused. The concept of reuse is becoming accepted more widely as other parts of the country experience water shortages. The use of dual water systems. such 1-81-8 hydrogen sulfide generation is of concern in collection systems and at treatment facilities. The release of hydrogen sulfide to the atmosphere above sewers and at treatment plant headworks has occurred in a number of locations. The release of excess hydrogen sulfide has led to the accelerated corrosion of concrete sewers, headworks structures, and equipment, and to the release of odors. The control of odors is of increasing environmental concern as residential and commercial development continues to approach existing treatment plant locations. Odor control facilities including covers for process units, special ventilation equipment, and treatment of odorous gases need to be integrated with treatment plant design. Control of hydrogen sulfide is also fundamental to maintaining system reliability. Fig 1-3 Facilities used for chemical treatment of odors from treatment facilities The presence of VOCs and VTOCs in wastewater has also necessitated the covering of treatment plant headworks and primary treatment facilities and the installation of special facilities to treat the compounds before they are released. In some cases, improved industrial pretreatment has been employed to eliminate these compounds. Large numbers of wastewater treatment plants were constructed in the United States during the 1970s and 1980s when large sums of federal money were available for implementation of the CWA(Clean Water Act). Much of the equipment, now over 20 years old, is reaching the end of its useful life and will need to be replaced. Process changes to improve performance, meet stricter permit requirements, and increase capacity will also be needed. For these reasons, significant future efforts in the planning and design of wastewater treatment plants in the United States will be directed to modifying, improving, and expanding existing treatment facilities. Fewer completely new treatment plants will be constructed. In developing countries, opportunities for designing and building completely new facilities may be somewhat greater. Fig. 1-4 UV lamps used for the disinfection of wastewater In the U.S. EPA Needs Assessment Survey, the total treatment plant design capacity projected to increase by about 15 percent over the next 20 to 30 years. During this period, the U.S. EPA estimates that approximately 2,300 new plants may have to be built, most of which will be providing a level of treatment greater than secondary. The design capacity of plants providing greater than secondary treatment is expected to increase by 40 percent in the future (U.S. EPA, 1997). Thus, it is clear that the future trends in wastewater treatment plant design will be for facilities providing higher levels of treatment. Some of the innovative treatment methods being utilized in new and upgraded treatment facilities include vortex separators, high rate clarification, membrane bio-reactor, pressure-driven membrane filtration and UV lamps. In recent years, numerous proprietary wastewater treatment processes have been developed that offer potential savings in construction and operation. This trend will likely continue, particularly where alternative treatment systems are evaluated or facilities are privatized. Privatization is generally defined as a public-private partnership in which the private partner arranges the financing, design, building, and operation of the treatment facilities, in some cases, the private partner may own the facilities. The reasons for privatization, however, go well beyond the possibility of installing proprietary processes. In the United States, the need for private financing appears to be the principal rationale for privatization; the need to preserve local control appears to be the leading pragmatic rationale against privatization. 1-6 Wastewater Reclamation and Reuse In many locations where the available supply of fresh water has become inadequate to meet water needs, it is clear that the once-used water collected from communities and municipalities must be viewed not as a waste to be disposed of but as a resource that must be reused. The concept of reuse is becoming accepted more widely as other parts of the country experience water shortages. The use of dual water systems, such