Understanding micro contaminants in recycled water

Throughout history, intentionally or not, people have recycled water. As a result, it is not unusual for rivers to receive discharges of municipal, agricultural, and industrial wastes from upstream communities while water supplies are being drawn downstream. This has occurred to such a degree that, for example, during the dry season, the water in California's Santa Ana River largely consists of wastewater effluent. Despite this situation, effluent-dominated waters provide habitat for aquatic organisms and are often used to supply water. The extent of such unplanned water recycling is likely to increase as restoration and maintenance of aquatic ecosystems, urban expansion, and agricultural production exert growing pressures on limited water supplies. The introduction of wastewater effluent into drinking water aquifers and surface waters as a deliberately planned activity is becoming more common throughout the world. Such undertakings are already an important element of water resource planning in some regions of the United States. There are several schemes for using recycled water. Nonpotable water recycling supports activities such as highway landscaping and irrigation of golf courses and is publicly accepted. Indirect potable reuse involves the introduction of recycled water into a system where it may eventually be used as a potable water source. Although indirect potable water recycling is less common, numerous projects are operating or are being planned in the United States. But while an increased reliance on such water recycling may be necessary to stretch a scarce resource, the potential health and ecological effects of exposure to chemical contaminants in recycled water are not well understood.