Lebanon Wastewater Treatment Plant - Executive Summary
Process Description |
The Lebanon Wastewater Treatment Plant provides treatment for the wastewater from the City of Lebanon and surrounding communities. This treatment process involves the use of chlorine for disinfection of the plant effluent before it is discharged into the Cumberland River.
Chlorine is listed by the Environmental Protection Agency (EPA) as a regulated toxic substance. Facilities that handle amounts of chlorine over 2,500 pounds are required by the EPA to develop a Risk Management Program (RMP) to reduce the risk to employees and the public of injury from an accidental release of chlorine. The Lebanon Wastewater Treatment Plant stores a maximum of 8,000 pounds (four 1-ton containers) of chlorine. The chlorine building houses only three containers, therefore at times one container is stored outside.
Accidental Release Prevention and Emergency Response Policies
The operation of all chlorine equipment will be by trained and knowledgeable personnel only. All operators
at the plant that are involved in the chlorine process are trained annually on the potential health hazards of chlorine, the operation of chlorine equipment and emergency response procedures. An important part of the emergency response policy is the cooperation of the facility with local emergency response agencies.
Off-Site Consequence Analysis
RMP regulations require the analysis of a worst-case release scenario and an alternative release scenario to determine the area that could potentially be affected by a chemical release. The EPA defines the worst-case release scenario as "the greatest amount held in a single vessel ... released as a gas over 10 minutes". This scenario is not very likely to occur, but is used as the basis for the analysis of potential risk involved with the use of toxic chemicals. The alternative release scenario involves a more likely chemical release than the worst-case release scenario.
A computer model provided by the EPA was used to estimate the distance
that chlorine could travel during an accidental release while impacting the public and the environment. This model uses the specific atmospheric conditions and other parameters required by the regulations.
The worst-case scenario for chlorine analyzed the release of a 1-ton chlorine container located outside over a 10 minute period. The model calculated the distance that the chlorine could travel in an urban area and have significant impact to be 1.3 miles. This indicates that a worst-case release could potentially affect the residential population and the environment within a 1.3 mile radius of the wastewater treatment plant.
For the alternative release scenario, a review of the chlorination process determined that a leak was most likely to occur when changing to a full container. Specific operating procedures are in place which include testing for chlorine leaks immediately after connecting the new container. Therefore, if an improper connection is made, the resulting leak will b
e detected and corrected before placing the container in service. A consequence distance of 0.10 mile was determined for this situation which is the minimum distance the model will provide.
Accidental Release Prevention Program
The Lebanon Wastewater Treatment Plant has developed an accidental release prevention program which meets the requirements of the EPA Risk Management Program and OSHA Process Safety Management and includes the following elements:
-Analysis of hazards involved with the chlorine process to prevent or minimize the effects of an accidental chemical release
-Use of written operating procedures to ensure safe operation of the chlorine equipment and prevention of accidental chemical releases
-Annual operator training in chemical hazards, operating procedures, emergency response to accidental chemical releases and use of self-contained breathing apparatus (SCBA)
-Prestartup safety review and contractor safety program for any modifications made to the existing process
-Preventive maintenance program to ensure the continued integrity of process equipment and prevent accidental chemical releases resulting from mechanical failure
-Investigation of incidents that resulted in or could have resulted in a chemical release
-Audit of prevention program every three years to verify compliance with the regulations
-Use of control measures such as a leak detector to minimize the effects of an accidental chemical release
Five-Year Accident History
No accidental chlorine releases have occurred at the Lebanon Wastewater Treatment Plant in the past five
Emergency Response Program
The Lebanon Wastewater Treatment Plant is included in the community emergency response plan developed by the Wilson County Emergency Management Agency (WEMA). The plant has appropriate procedures in place to notify WEMA when there is a need to respond.
Changes to Improve Safety
During the evaluation of the existing chlorine process, it was determined that although adequate sa
fety mechanisms are currently in place, further steps could be taken to provide an even safer environment. This includes the installation of automatic shut-off devices on the chlorine containers and the relocation of the regulator valves so that all gas lines will operate under a vacuum rather than under pressure. With the lines under vacuum, if a break occurs, the regulator valves would close and stop the flow of chlorine from the container. It is anticipated that these changes will be made by the end of this year.