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South Bay Water Recycling Project

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Friday, June 29th, 2001 @ 12:25 PM
Subj: waste water
From: (Angelia Neal)

Waste water does not refer to water from your toilet. I am an Environmental Engineer - I should know. There are two main reasons why we treat water. First, we treat water that is gathered from lakes, rivers, streams, and reservoirs to be distributed as potable water for your homes and businesses. Second, we treat water that leaves your homes and businesses to remove any organic or sometimes man-made contamination. This includes all biological, chemical, diseases, toxic - whatever you want to call it - these all have to be removed before releasing the water back into the environment. This released water is called WASTE WATER, because is the leftover after the treatment process, not because it contains waste. This water is most often released into a stream to re-enter the hydrologic cycle. Which eventually downstream becomes someone's river, lake, or reservoir to be treated for use as potable water again. The other type of waste water, which is not what is being used by Calpine, is industrial waste water. Industrial waste water is the water that leaves a processing plant or factory and can be discharged into a nearby stream if they meet EPA standard levels. A majority of industries have begun recycling the waste water. This is a better engineering design, because it is not only avoids the issue of discharging, but it also saves money in the process.

There will be no waste evaporating or floating around in the air...that is just silly. Besides one of the best disinfectants we use is a system called aeration. Most organic material and organism decay and are destroyed when exposed to the atmosphere. This is a common technique used at most sewage treatment plants. Those things that are remaining in the water are destroyed by chlorine or several other methods.

Water Supply The Metcalf Energy Center's cooling water will be recycled water supplied by the South Bay Water Recycling Program. This will minimize the plant's impact on water supplies in the North Coyote Valley area. Currently, the treated and disinfected water from the San Jose/Santa Clara Water Pollution Control Plant is discharged to the Bay. This fresh water is impacting saltwater plants and fish species by diluting the brackish water that supports the fragile ecosystem at the southern end of the Bay. The South Bay Water Recycling Program will supply water to the Metcalf Energy Center from the San Jose/Santa Clara Water Pollution Control Plant. By recycling this fresh water through Metcalf Energy Center's cooling tower, approximately 80% of it will evaporate into the atmosphere. The remaining industrial wastewater will then be discharged to the San Jose sewer system. This approach significantly reduces the current impacts of fresh water discharges to the Bay while minimizing the plant's demands on other fresh water sources.

The remaining 5% of the water required by Metcalf Energy Center will be obtained from the San Jose Municipal Water District. San Jose Municipal Water District provides groundwater to its customers from its groundwater wells in the northern Coyote Valley. Metcalf Energy Center's non-cooling tower needs are comparable to the water demands of a medium-size restaurant. Preliminary studies indicate that the groundwater basin has sufficient capacity to supply the non-cooling water demands. In addition, withdrawing some groundwater from northern portion of the Coyote Valley may reduce flooding that can occur during wet winters because of high groundwater levels. Therefore, the fresh water demands of the Metcalf Energy Center will not have a significant adverse impact on the area's water supply.

Wastewater Quality

The industrial wastewater produced by the Metcalf Energy Center will be returned via the San Jose sewer system to the Water Pollution Control Plant for treatment. The Metcalf Energy Center's industrial wastewater will consist of the discharge from the cooling tower, effluent from the non-cooling water uses and very small amounts of non-toxic chemicals added to control corrosion and fouling of piping and heat exchangers. City staff has evaluated the quantity and composition of Metcalf Energy Center's industrial wastewater and have determined that it will be acceptable for blending with other wastewater received by the Water Pollution Control Plant. Once treated, it will either be discharged to the Bay or return it to SBWR's recycled water distribution system for reuse. Metcalf Energy Center's industrial wastewater will therefore not produce an adverse impact on water quality in the area.

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