Island Water Assoc., Inc. Reverse Osmosis Plant - Executive Summary |
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ISLAND WATER ASSOCIATION REVERSE OSMOSIS TREATMENT FACILITY EXECUTIVE SUMMARY The Island Water Association Reverse Osmosis Plant (Facility) provides potable water to the residents of Sanibel and Captiva Islands for drinking and fire fighting. The Facility also removes Hydrogen Sulfide (H2S), salt and other substances from the brackish water prior to distribution. The Facility uses one regulated substance, chlorine (CAS 7782-50-5) as a disinfectant to treat potable water during the chlorination processes. To accomplish this goal, raw water is pumped from deep brackish wells to the facility. Upon entering the Facility, the raw water is chemically treated, filtered and passed into the Reverse Osmosis (RO) treatment system where the salt is removed and the water is divided into two components. The first component is composed of concentrated salt water (brine) and H2S, which must undergo further treatment prior to being discharged into the Gulf of Mexico. The second component is ref erred to as "permeate" or "product water" which will be treated further (post-treated permeate) before being distributed to Facility customers. The Facility also uses chlorine in the sulfide conversion system to eliminate H2S from the permeate. Once sulfide conversion has been accomplished, additional chlorine is added to the treated permeate to allow for adequate disinfection. The brine effluent from the RO process is also chlorinated in order to remove hydrogen sulfide. It is then aerated to add oxygen and remove any trace H2S before being discharged into the Gulf of Mexico. While the chlorination systems at the Facility used for removing H2S, disinfecting the permeate and treating brine are comprised of separate systems, the technology and equipment utilized are the same. The chlorination processes at the facility are operated under a vacuum which is created by the ejectors. In the chlorination processes, chlorine gas is pulled from the supply cylinders into chlorinators. From the chlorinators, the chlorine gas flows to the ejectors that mix the chlorine gas with a side stream of pre-treated permeate to form a high concentration (approximately 500 parts per million (ppm)) chlorine solution. The chlorine solution then flows into each stream to be treated. The Facility performed a Process Hazard Analysis (PHA) to address the hazards in the chlorination processes and to evaluate and control where the potential for a chlorine release exists. Employees were involved in determining hazards of the process and subsequent consequences. The chlorination processes were found to be operating safely and no changes were implemented. The hazard assessment was performed on the chlorination processes using the United States Environmental Protection Agency RMP*CompTM. Model. The worst-case release scenario was assumed to be the release of a one ton cylinder for a duration of 10 minutes in an enclosed building. The alternative release scenario selected for the Facility w as a failure scenario developed during the process hazard review and analysis. In this scenario, the PHA team determined that a leak may develop at a fuse plug on a one ton cylinder due to corrosion or a poor bond between the lead alloy and the plug retainer would be the most likely cause of a chlorine gas release. The cylinders are constructed in compliance with applicable codes and standards and are hydrostatically tested as required. Therefore, the likelihood of this scenario occurring is minimal and an accidental release of this type has not occurred at the Facility since it initiated operation. In addition, the Facility has the capability of responding to and stopping the leak. For both scenarios, the off-site consequence analysis indicated that off-site receptors could be potentially impacted by the release of chlorine. Although off-site areas would be impacted, we believe that safety procedures and mitigation measures will reduce the potential for off-site consequences an d subsequent risks to the surrounding community. Our safety devices include chlorine leak detectors, alarms automatically notify the Sanibel Island Police and Fire Departments, and an automatic system shut-off feature triggered by a loss in system vacuum. In addition, the chlorine cylinders are housed in a building with exhaust fans and vents, which would dilute the chlorine gas concentration should a release occur. In order to fulfill the requirements of the Risk Management Program (RMP), we have developed an accidental release prevention program and emergency action plan for our facility. The accidental release prevention program satisfies the requirements for the EPA RMP and the OSHA PSM programs. The prevention program ensures that our facility is operated under safe conditions and that any risk of an accidental release of chlorine is minimized. The program has been written to reduce the potential of an accidental release due to human error, or equipment failure at our facilit y. In order to prevent the release of chlorine due to human error, our prevention program ensures that operating procedures are current and reviewed annually. Training also plays a vital part in our program. Employees and contractors working on the chlorination processes are required to be trained in the chlorination processes and the hazards of chlorine. To prevent equipment failure that could result in an accidental release, our program ensures that equipment inspections, tests, and preventive maintenance are in accordance with accepted engineering practices and includes manufacturer's recommendations. All chlorine cylinders are examined upon delivery and are rejected if there are any signs of damage. In addition, equipment pertaining to the chlorine process is visually inspected daily. The potential for a chlorine release is greatly reduced in the chlorination processes due to the use of a vacuum system from the point of chlorine withdrawal to its point of mixing with a wa ter stream. In the event that there is a failure in chlorination equipment, the system will automatically shutoff (i.e. failsafe). In the event that a chlorine release occurs and evacuation is necessary, all employees except the emergency response team, are required to go to the nearest emergency chlorine shelter identified in the evacuation plan and wait for the "all clear" from the emergency response team. The emergency action plan consists of evacuation procedures, facility emergency numbers, and coordination with Sanibel Island Fire Department. The plan also addresses notification procedures to the public and the local emergency response agency. The prevention program ensures that our facility is operated under safe conditions and that any risk of an accidental release of chlorine is minimized. The program has been written to reduce the potential of an accidental release due to human error, or equipment failure at our facility. In order to prevent the release of chlorine d ue to human error, our prevention program ensures that operating procedures are current and reviewed annually. All existing and proposed future chlorination equipment has been designed according to applicable standards and codes. The Facility maintains records and documentation on equipment inspection and tests. Precautions are taken to ensure that new equipment and processes are inspected and tested, that all changes on the process are authorized, and employees are informed of changes. Active employee participation will ensure the success of the RMP at our facility. Employees have been assigned various tasks to ensure that all elements of the RMP are implemented. We have developed many different forms to assist employees in recording and documenting the various elements of the RMP. The Facility has coordinated the information contained in the RMP with the Local Emergency Planning Committee and is willing to conduct tours of our Facility for members of the public. |