Leitchfield Wastewater Treatment Plant - Executive Summary
Process Description |
The Leitchfield Wastewater Treatment Plant provides treatment for the wastewater from the City of Leitchfield and surrounding areas. The treatment process generates bio-solids which are removed and disposed of by land application. The treatment effluent is discharged into a nearby creek. Before discharge, the effluent is disinfected using chlorine in its gaseous form. After disinfection, gaseous sulfur dioxide is used to reduce the amount of chlorine to a level that will not harm the receiving creek.
Both chlorine and sulfur dioxide are listed by the Environmental Protection Agency (EPA) as regulated toxic substances. Facilities that handle amounts of chlorine over 2,500 pounds or sulfur dioxide over 5,000 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 chemical release.
The Leitchfield Wastewater Treatment Plant stores a maximum of 4,000 pounds (two-ton contai
ners) of chlorine and 1,200 pounds (eight 150-lb cylinders) of sulfur dioxide. These chemicals are stored in the same building at the wastewater plant. The amount of chlorine stored makes the chlorination process subject to the regulations, however the amount of sulfur dioxide kept on-site is below the regulated quantity. In an effort to minimize the risk of accidental chemical releases, both chlorine and sulfur dioxide have been included in the RMP developed by the Leitchfield Wastewater Treatment Plant.
Accidental Release Prevention and Emergency Response Policies
The policy of the Leitchfield Utilities Commission is that the operation of all chemical facilities will be by trained and knowledgeable personnel only. Therefore, personnel of the wastewater plant are required to attend all training as specified in the RMP. Emergency response procedures are included in the required training. The emergency response plan has been coordinated with the local fire department who is prepared
to respond to an accidental chemical release.
Off-Site Consequence Analyses
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 highly unlikely, but is used as the basis for the analysis of potential risk involved with the use of regulated chemicals and in the development of the risk management program. The alternative release scenario involves a release that is more likely to occur than the worst-case release scenario. These scenarios were analyzed for both chlorine and sulfur dioxide.
A computer model provided by the EPA was used to estimate the distance the regulated chemical could travel and have an impact on the public and the environment. This model utilizes the parameters required by the regul
ations, such as specific atmospheric conditions. In addition, the model was run with scenarios using a "release in enclosed space, in direct contact with outside air" since the chemicals are stored in a vented building. This parameter decreases the rate of release to 55% of the rate of a release happening outdoors.
The worst-case scenario for chlorine analyzed the release of a 1-ton chlorine container over a duration of 10 minutes. The model calculated the distance that the chlorine could travel and have significant impact to be 0.9 mile. This indicates that a worst-case release could potentially affect the public and the environment within a 0.9 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 connecting a full container. Specific operating procedures have been implemented and include opening the chlorine container valve slightly, re-closing it immediately an
d testing for chlorine leaks. Therefore, any leak will be detected and the problem corrected before placing the container in service. Using the model for this scenario, a consequence distance of less than 0.10 mile was determined. This is the minimum distance the model will provide.
The worst-case release scenario for sulfur dioxide involved the release of one 150 lb cylinder over 10 minutes. The model indicated that the population within a 0.20 mile radius of the wastewater treatment plant could potentially be affected by a sulfur dioxide release. Again, this scenario is highly unlikely. A more likely occurrence would be a leak resulting from an improper connection of a new cylinder. As in the chlorine scenario, a sulfur dioxide leak would be detected before placing the cylinder permanently in service. The model indicates a consequence distance of less than 0.10 mile.
Accidental Release Prevention Program
The Leitchfield Wastewater Treatment Plant has developed an accidental releas
e 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 and sulfur dioxide process to prevent or minimize the effects of an accidental chemical release
-Use of written operating procedures to ensure safe operation of the chlorine and sulfur dioxide 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 modifications made to the existing process
-Preventive maintenance program to ensure the continued integrity of process equipment and prevent accidental chemical releases resulting from equipment failure
-Investigation of incidents that resulted in or could have resulted in a chemical release
-Audit of prevent
ion program every three years to verify compliance with the regulations
-Use of control measures such as a dual channel gas detector to minimize the effects of an accidental chemical release
Five-Year Accident History
The Leitchfield Wastewater Treatment Plant has not had any accidental releases of chlorine or sulfur dioxide in the last five years.
Emergency Response Program
The Leitchfield Wastewater Treatment Plant's emergency response plan has been coordinated by the Kentucky Disaster and Emergency Services. This program involves the City of Leitchfield Fire Department which is prepared to respond to chemical releases. The Fire Department and wastewater plant employees receive annual training in emergency response procedures.
Changes to Improve Safety
The Leitchfield Wastewater Treatment Plant is currently in the design phase of a facility expansion. This expansion includes several features to improve safety at the facility. One change includes the removal of the sulfur dioxid
e cylinders from the chlorine building and the use of another safer chemical. Also, the installation of automatic shut-off devices on the chlorine containers is planned. These devices will add a greater degree of safety to the chlorination process.