Dos Rios Water Recycling Center - Executive Summary

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The Dos Rios Water Recycling Center (WRC) is owned and operated by the San Antonio Water System (SAWS).  The SAWS, a public utility owned by the City of San Antonio, was created in May 1992, and is responsible for treating drinking water and wastewater.  SAWS also owns and operates as a separate utility a chilled water and steam plant, which is a centralized heating and cooling system for the buildings in and around HemisFair Park. 
A seven member Board of Trustees, appointed by the City Council, governs the SAWS. The Mayor appoints the Chair each year and the board elects the vice-chair and secretary.  In 1995, the San Antonio Water System served approximately 1 million people in the urbanized part of Bexar County. This population includes approximately 260,000 separate customers.  By 2050 the population served is expected to increase to 2.2 million. 
SAWS has won awards from the U.S. Environmental Protection Agency for its compliance with strict effluent discharge regulations. Treate 
d wastewater effluent is the principal water supply for Braunig and Calaveras Lakes, the two power plant cooling lakes operated by City Public Service. SAWS is also developing the facilities to distribute treated wastewater as a substitute for aquifer water in park and golf course irrigation and industrial uses.  
SAWS takes pride in observing the most stringent industrial safety precautions in preventing chemical related accidents.  The latest safety technology and monitoring detection systems are used at the Dos Rios facility.  Internal inspections and inspections by staff from the Texas Natural Conservation Commission and EPA are conducted on a routine basis.   
Both active and passive mitigation systems are incorporated into the operation and maintenance of chemical handling systems at Dos Rios.  Our goal is to first prevent accidental releases and second to defuse the impact of an accidental spillage, fire, or explosion if it should occur.  A reportable accidental release has not  
occurred at this site within the last five years.  A search of available records showed that no reportable releases of a regulated material have occurred at this site since it was constructed. 
The SAWS Treatment  Group, which operates the Dos Rios WRC, is also responsible for the operation and maintenance of the System's three other major wastewater treatment plants. These plants treat an average of 130 million gallons of waste water per day and have a total capacity (including an excess margin required by state regulators) of 225 million gallons per day.   Regulated materials used in the treatment process include chlorine and sulfur dioxide. 
Like other water utilities in the state, the Dos Rios WRC is required to disinfect treated effluent prior to discharge to ensure that disease causing bacteria (pathogens) are reduced to a safe level.   Chlorine is a widely used disinfectant in the wastewater industry because, it is effective against a broad spectrum of pathogens.  Chlorine has s 
hown itself to be an effective agent against waterborne bacteria, viruses and most protozoan agents. Sulfur dioxide is used to remove chlorine in waste water prior to stream discharge to reduce aquatic toxicity. 
A Process Hazard Analysis has been performed for both chlorine and sulfur dioxide using estimates and tables from EPA's Guidance for Waste Water Treatment Plants. Assuming a complete rupture of containers, off-site receptors would be impacted.   Because all storage containers used by SAWS must confirm to stringent Department of Transportation (DOT) construction standards the occurrence of a worst case release is not realistic.  Information from the hazard analysis is used to improve emergency planning activities with the San Antonio Fire Department and the Bexar County LEPC.  An analysis of a more likely alternative release (pipe rupture) showed that chlorine or sulfur dioxide would not be expected to extend beyond property lines.  
Chlorine shipping containers are designed fo 
r safety.  U.S. Department of Transportation regulations at 49 CFR 173.304 set the maximum permissible filling density for chlorine containers to 125 percent of the ratio of the weight of chlorine in the container to the weight of water the container will hold at 600F.  Chlorine valves are protected either by protective housing (cylinders) or manhole cover (tank).  In the event of a fire or temperatures exceeding 165 0F, the fusible plugs on chlorine containers melt to relieve pressure. Ton chlorine containers are designed to withstand pressures of at least 330 psig.  Emergency repair kits are available and detectors and alarms are operable. 
A chemical safety management plan for accident prevention, which documents employee training, operation and maintenance procedures and emergency preparedness, is maintained and is on file at the facility's administrative building.  All personnel handling regulated chemicals at Dos Rios are required to be TNRCC certified operators and receive train 
ing in the safe use of chlorine and sulfur dioxide.   Training exercises are routinely held at the facility.  
A procedure is in place to investigate and report any accidental release or "near miss" event.  Lessons learned and findings from these investigations are immediately incorporated into the accident prevention plan.  The regulated chemical safety management plan is reviewed and updated each year during the facility's Tier II submittal process.  A copy of this RMP has been provided to the San Antonio Fire Department and the Bexar County LEPC.
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