What is the quality of recycled water?
Recycled water meets strict federal, state and county health and safety requirements. Of the three quality standards for recycled water in California, Sunnyvale’s is of the highest quality. Although it is not approved for drinking, it is second in purity only to potable water.
Is recycled water safe to use on my expensive ornamental landscaping?
Recycled water is safe to use on lawns and most ornamental landscaping. The primary concern with using recycled water on landscaping is its elevated levels of salinity relative to most potable water sources. The higher salinity levels may impact certain salt-sensitive plants or trees, possibly including redwood trees.
For sensitive plants, factors such as irrigation practices, local soil types and drainage play an important role in regulating impacts. The City can provide reference materials on request for customers’ use in evaluating potential impacts.
Does recycled water used for irrigation provide fertilizer value?
Yes, recycled water contains trace amounts of nitrogen and other plant nutrients. The City regularly monitors its recycled water for constituents relevant to irrigation use, and can provide that data upon request.
Can recycled water be used in cooling towers?
Yes, if the towers are equipped with drift eliminators and use a biocide. The higher level of salinity (TDS) in recycled water may result in the need to operate with fewer concentration “cycles.” Corrosion control is always a consideration with cooling towers. Ammonia, which is present at 5-15 mg/L during the winter months, may cause corrosion of copper-based metals (copper, brass, bronze). The City can provide water quality data upon request for the recycled water it produces.
How does recycled water differ from “graywater”?
Recycled water is wastewater treated to a high level for approved non-potable uses. It is used primarily for landscape irrigation, but other approved uses include cooling tower make-up water, use in commercial laundries, car washes, and non-residential toilets.
Graywater is defined in the California Water Code as “…untreated wastewater which has not been contaminated by any toilet discharge, has not been affected by infectious, contaminated, or unhealthy bodily wastes, and which does not present a threat from contamination by unhealthful processing, manufacturing, or operating wastes. Graywater includes wastewater from bathtubs, showers, bathroom washbasins, clothes washing machines, and laundry tubs but does not include wastewater from kitchen sinks or dishwashers.” Graywater may only be used to irrigate landscaping at the site where the graywater is generated. Sunnyvale does not exercise jurisdiction over customer-owned graywater systems.
Are there issues with regrowth of microorganisms in storage tanks, ponds and distribution systems and how do you control it? Is there chlorine residual in the distribution system?
Yes, regrowth of microorganisms can occur in storage tanks, ponds and distribution systems. This occurs in all water systems, but can happen faster with recycled water due to the residual nutrients it contains. To prevent regrowth and development of biofilms in the recycled water distribution system, the water entering Sunnyvale’s system has a chlorine residual of about 3 mg/L. The chlorine residual level declines as it travels through the system and storage tank, so a chlorine residual may or may not be present in water delivered to a site. Water retained in ornamental ponds or fountains may require additional treatment to prevent microorganism (including algae) growth.
Windows Media Player
Word Viewer
Excel Viewer
PowerPoint Viewer
