as now used in St. Petersburg in Florida and Rancho Viejo in California, is expected to increase in the future. In both loca of th an important electriologies being te reclamation. Ir lessen health ri 1-7 Biosolids an continues to be one Wastewater sol metals and pa biosolids. Fur home use is p customarily ir the incre concentrat ance and economic palities continues to1-9 as now used in St. Petersburg in Florida and Rancho Viejo in California, is expected to increase in the future. In both locations, treated effluent is used for landscape watering and other nonpotable uses. Most of the reuse of wastewater occurs in the arid and semiarid western and southwestern states of the United States; however, the number of reuse projects is increasing in the south especially in Florida and South Carolina. Because of health and safety concerns, water reuse applications are mostly restricted to nonpotable uses such as landscape and agricultural irrigation. In a report by the National Research Council (1998), it was concluded that indirect potable reuse of reclaimed water (introducing reclaimed water to augment a potable water source before treatment) is viable. The report also stated that direct potable reuse (introducing reclaimed water directly into a water distribution system) was not practicable. Because of the concerns about potential health effects associated with the reclaimed water reuse, plans are proceeding slowly about expanding reuse beyond agricultural and landscape irrigation, groundwater recharge for repelling saltwater intrusion, and nonpotable industrial uses (e.g., boiler water and cooling water). Many of the concerns mentioned in the National Research Council (NRC, 1998) report regarding potential microbial and chemical contamination of water supplies also apply to water sources that receive incidental or unplanned wastewater discharges. A number of communities use water sources that contain a significant wastewater component. Even though these sources, after treatment, meet current drinking water standards, the growing knowledge of the potential impacts of new trace contaminants raises concern. Conventional technologies for both water and wastewater treatment may be incapable of reducing the levels of trace contaminants below where they are not considered as a potential threat to public health. Therefore. new technologies that offer significantly improved levels of treatment or constituent reduction need to be tested and evaluated. Where indirect potable reuse is considered, risk assessment also becomes an important component of a water reuse investigation. Technologies that are suitable for water reuse applications include membranes (pressure driven, electrically driven, and membrane bioreactors), carbon adsorption, advanced oxidation, ion exchange, and air stripping. Membranes are most significant developments as new products are now available for a number of treatment applications. Membranes had been limited previously to desalination, but they are being tested increasingly for wastewater applications to produce high-quality treated effluent suitable for reclamation. Increased levels of contaminant removal not only enhance the product for reuse but also lessen health risks. As indirect potable reuse intensifies to augment existing water supplies, membranes are expected to be one of the predominant treatment technologies. 1-7 Biosolids and Residuals Management The management of the solids and concentrated contaminants removed by treatment has been and continues to be one of the most difficult and expensive problems in the field of wastewater engineering. Wastewater solids are organic products that can be used beneficially after stabilization by processes such as anaerobic digestion and composting. With the advent of regulations that encourage biosolids use, significant efforts have been directed to producing a "clean sludge" (Class A biosolids) that meets heavy metals and pathogen requirements and is suitable for land application. Regulations for Class B biosolids call for reduced density in pathogenic bacteria and enteric viruses, but not to the levels of Class A biosolids. Further, the application of Class B biosolids to land is strictly regulated, and distribution for home use is prohibited. Other treatment plant residuals such as grit and screenings have to be rendered suitable for disposal, customarily in landfills. Landfills usually require some form of dewatering to limit moisture content. With the increased use of membranes, especially in wastewater reuse applications, a new type of residual, brine concentrate, requires further processing and disposal. Solar evaporation ponds and discharge to a saltwater environment are only viable in communities where suitable and environmental geography conditions prevail; brine concentration and residuals solidification are generally to complex and costly to implement. Treatment technologies for solids processing have focused on traditional methods such as thickening, stabilization, dewatering, and drying. Evolution in the technologies has not occurred as rapidly as in liquid treatment processes, but some significant improvements have occurred. Centrifuges that produce a sludge cake with higher solids content, egg-shaped digesters that improve operation, and dryers that minimize water content are just a few examples of products that have come into use in recent years. The developments are largely driven by the need to produce biosolids that are clean, have less volume, and can be used beneficially. Landfills still continue to be used extensively for the disposal of treatment plant solids, either in sludge-only monofills or with municipal solid waste. The number and capacity of landfills, however, have been reduced, and new landfill locations that meet public and regulatory acceptance and economic requirements are increasingly difficult to find. Incineration of solids by large municipalities continues to