MERIDIAN WASTEWATER TREATMENT PLANT - Executive Summary |
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The Accidental Release Prevention and Emergency Response Policies at Our Faciltiy. This faciltiy, as a City of Meridian Division, must operate under the safety guidelines set fourth in the City of Meridian Safety Manual. The manual contains information in general such as the duties and responsibilities of every city employee as regards safety and also specific safety rules conerning the special hazards of each division. Our division has a safety committee member who is able to report and discuss hazards with other ommittee members and the City Risk Manager who oversees all safety concerns. We also have a specific budget set aside for safety purchases including personal protective devices and training videos on hazards and safe handling of chemicals which are shown to all employees. Since our operation requires the use of two toxic chmeicals we are all aware of the dangers of improper use and handling. Only qualified operators operate the systems that use these chemicals. Our Facility and the Regulated Substances Handled This facility is the wastewater treatment plant for the City of Meridian. The treatment processes we employ are settling, heavy solids removal, biological treatment, chlorination and dechlorination. Our treated wastewater is released into Sowashee Creek so it must meet standards set by the Environmental Protection Agency and the Department of Environmental Quality for the State of Mississippi. The chlorination process disinfects the treated wastewater as it leaves the plant. By mixing chlorine with the water, disease causing organisms are destroyed. Since chlorine is also toxic to fish and other stream life it must be removed before the wastewater enters the creek. Sulfur dioxide is mixed with the chlorinated water after disinfection occurs to remove the final traces of chlorine. The maximum amount of chlorine at this plant does not exceed 12,000 pounds and the maximum amount of sulfur dioxide does not exceed 8,000 pounds. The Wors t-Case Release Scenario and the Alternative Release Scenarios. Worst-Case Scenario In our scenario, a one ton cylinder of chlorine is slammed into the building by an inexperienced operator on the delivery truck. The impact causes the protective end cap to fall off and the gas connection valve to snap. The cylinder is completely emptied in ten minutes and the resulting gas cloud could, in theory, cover a circle with a 1.3 mile radius in all directions from the point of release. It is more likely that the cloud would drift dependent on wind direction with upwind locations in the circle showing little or no effect. Some residences and businesses are within the 1.3 mile circle. Alternative Release Scenario, Chlorine A more likely release of chlorine could be caused by a sudden break in the half inch line leading from the chlorine cylinders to the regulator. This is the only place in the system after the tanks that automatic shutoff would not occur. It is likely that someone would cause the break by dropping something on the line or pushing something into it with enough force to snap it. Since the manual shutoff is adjacent to the line, only a small amount of chlorine would be released, probably no more than two minutes release time with 37 pounds per minute releasing. The circle radius this time would be 0.1 mile which, while beyond the facility property in some directions, does not include any residences or businesses. Alternative Release Scenario, Sulfur Dioxide Even though the sulfur dioxide process works the same way as the chlorine process does, the scenario is a little different since it is a newer process and has the vacuum regulators mounted directly on the sulfur dioxide cylinders. In this scenario, we have a supposedly empty cylinder being unhooked without first turning the valve off. There would be enough gas left in the cylinder to release a burst of sulfur dioxide. The operator would be startled and by the time he realized what happened and got the valve turned off a minute would have gone by. this would release 18 pounds of sulfur dioxide which is enough to exit the faciltiy and cover a 0.1 mile radius circle. No residences or businesses are in this area. The data used in determining scenarios was obtained from tables in Risk Management Program Guidance for Publicly Owned Treatment Works. Census block tables and census maps were used along with city and county maps to estimate population and determine public and environmental receptors. The General Accidental Release Prevention Program and Chemical Specific Prevention Steps All wastewaer treatment plant operators in Mississippi must be schooled and tested by the State of Mississippi to obtain a license and must accrue continuing education credits to keep a license. Part of this schooling is in the handling of toxic chemicals but the greatest knowledge and respect of toxics comes from on the job training. The actual operation of our chlorination and dechlorinatio n systems is not likely to cause accidental releases. This facility is manned 24 hours a day. The operators are required to check the systems three times in eight hours but they also walk by numerous times. The most hazardous time we identified at our facility is when the cylinders ae unhooked from the systems and new ones hooked up such as the sulfur dioxide alternative scenario previously described. At this plant, only the two most senior operators perform this operation. They do it together so they can check each other and assure everything is done according to proper procedures. We follow the equipment manufacturers recommendations and have a yearly maintenance check by a trained repair and technical assistance company. All equipment is taken apart, cleaned, repaired or replaced as needed. This ompany is also on call at any time for advice over the phone or a service call if necessary. The Five Year Accident History There have been no toxic chemical accidental releases at this facility in the last five years. The Emergency Response Program Our emergency responders are the Meridian Fire Department. They are fully trained in the use of emergency air equipment and in the use of the emergency repair kits we have available to fix leaking tanks. All shifts of the two closest fire stations have been to our facility to actually see where our chemicals are kept and the locations of the repair kits. The Director of Lauderdale County Emergency Management Association has also been here to discuss with us, the Fire Department and Police Department the possiblity of scheduling mock emergency drills on site. Since our facility complies with the Emergency Planning and Community Right to Know Act (EPCRA), we are already included in emergency planning. Planned Changes to Improve Safety We are planning to submit for budget approval several improvements to our systems. The dechlorination system needs vent hoses on top of the tanks that end near the sensor. The c hlorination system needs tanks mounted regulators to prevent a situtaion as described in the chlorine alternative release scenario. |