City of Niagara Falls Wastewater Treatment Plant - Executive Summary
Description of Facility and Activities : |
The City of Niagara Falls Wastewater Treatment Plant (WWTP), located at 1200 Buffalo Avenue, is the largest municipal physical-chemical activated carbon treatment facility in the country. The unique process treats a blend of industrial, commercial and residential wastewater, removing a wide variety of pollutants before discharging treated effluent back into the Niagara River. The plant was designed for a daily flow of 48 million gallons per day (mgd), although currently an average of 32 mgd is received. Because of the citys combined sewer collection system, the plant was built for a hydraulic peak flow of 85 mgd, which is still achieved during large magnitude storms.
A variety of chemicals are used in different stages of the treatment process. Chlorine is the only chemical in use at the plant which has been identified by the Environmental Protection Agency as having the potential to cause significant offsite consequences in the event of an acc
idental release; it is for that reason that this document has been prepared. Although natural gas is used for building heating and activated carbon regeneration, there are no flammables subject to regulation in storage at the facility.
Chlorine is received at the plant in liquid form via railroad tank cars with a capacity of 90 tons each. No more than one full railcar is onsite at any one time. Once connected to the feed piping, the liquid chlorine is fed as needed to evaporators, which change the chemical from a liquid to a gas. The gaseous chlorine is then fed to chlorinators, which combine the gas with treated effluent to produce a chlorine solution. The resulting solution is then piped to the treatment process for disinfection and oxidation. The chlorine solution is added to carbon filter effluent, which is wastewater that has undergone carbon treatment but is prior to final discharge. Chemically, the chlorine simultaneously oxidizes reduced chemicals and disinfects the flow by ki
lling the microrganisms normally contained in sewage.
Cost-efficient chemical oxidization of carbon filter effluent is necessary as long as the activated carbon filters are employed as a secondary treatment unit process. Plant final effluent disinfection will also likely remain a requirement. Thus, the need to store and use chlorine as a part of the wastewater treatment process here is not expected to change in the near future.
Safety Practices :
The wastewater treatment plant has a comprehensive safety program designed to properly address safety issues and operate the facility in a manner which is safe to the employees and the public while accomplishing the mission of protecting the environment. Elements of the program mirror the Process Safety Management Program, which include process safety information, process hazard analysis, operating procedures, training, mechanical integrity, management of change, pre-startup reviews, compliance audits, incident investigations, employee part
icipation, hot work permits, a preventative maintenance program and contractor activities.
Standard Operating Procedures and Safety Directives address a wide range of safety related issues, including confined space entries, unsafe condition reports, safety glasses, hard hats and safety shoes, respirator usage, forklift operation, accident reviews, designated smoking and eating areas, hot work permits, lock, tag and try procedure, line or equipment breaking procedure, safety suggestions, accident reporting, tracking health effects, hearing conservation, emergency evacuations, employee medical emergencies, and laboratory exposure to hazardous chemicals.
Material Safety Data Sheets (MSDS) are required for all chemicals bought onto the treatment plant site, including chlorine. They document the properties of the chemicals, and typically contain information about toxicity, permissible exposure limits, physical data, reactivity data, corrosivity data, thermal and chemical stability data,
and hazards of substance mixtures. Copies of all MSDS sheets are kept in the Operations Control Room, available for quick access.
Emergency Response Program :
In the event of a chlorine release, a response plan is followed, allowing plant staff to handle the emergency. Anyone onsite who observes either a gas release or a liquid release is to notify the Shift Operations Supervisor (SOS) immediately. The SOS then determines the magnitude of the problem. If it is of a minor nature, he may direct plant operators to shutdown the affected process or to deploy personal protective equipment and close the chlorine supply valve on the active railcar. If the release is more serious, the SOS may initiate a facility evacuation and/or call for outside assistance to control the release. The Niagara Falls Fire Department remains our primary contact for emergency response and coordination. Chemtrec remains our secondary contact for emergency response. Once outside assistance is contacted, plant staff
then support the emergency responders efforts in isolating and stopping the leakage. Plant evacuation drills are conducted on a periodic basis.
The wastewater treatment facility is also covered by the City's Emergency Response Plan, which was created to deal with industrial incidents involving toxic chemicals, but also other emergencies such as floods, fires, aircraft crashes, earthquakes and severe storms.
Five-year Accident History :
There have been no reportable accidental releases of chlorine, as either gas or liquid, during the past five years. This is despite using an average of 1300 tons per year (over this same period) for the treatment of wastewater. The plant staff continues to strive for the goal of zero accidents & zero release of chlorine, as well as all other treatment chemicals and fuels.
Planned Changes to Improve Safety :
The wastewater treatment plant staff periodically consider changes to the chlorination system equipment and procedures in order to enhance safe
ty, operability and maintainability. Changes are implemented as needed. Currently contemplated improvements include chlorinator updating and ejector relocation.
Worst Case Scenario :
As required by EPA regulation, a worst case scenario for chlorine release from the facility was evaluated. For these purposes, it was assumed that a full railcar would suddenly breach, releasing its entire contents over a 10 minute period. Using a release rate of 18,000 lbs/minute leaving the site in an atmospheric plume, EPA Offsite Consequence Analysis guidance reference tables (dated 5/24/96) estimated a distance of over 25 miles to reach the toxic endpoint. Although the plume would be carried by the prevailing winds in one direction, there are approximately 1,100,000 people residing within a 25 mile radius (all directions) of the chlorine railcar parking area. An occurrance of the worst case scenario is considered highly unlikely.
Alternate Case Scenario :
As required by EPA regulation, an alternat
e case scenario for chlorine release from the facility was evaluated. For these purposes, it was assumed that a significant break in the outside liquid chlorine line would release chlorine at a rate of 133 lbs/min. It was further assumed that plant staff would have difficulty responding, thus requiring 60 minutes to activate outside assistance and stop the leak. EPA Offsite Consequence Analysis guidance reference tables (dated 5/24/96) were again used to estimate a distance to the plume's toxic endpoint, now at a distance of 1.5 miles. Although this plume would also be carried by the prevailing winds in one direction, there are approximately 23,000 people residing within a 1.5 mile radius (all directions) of the chlorine liquid pipline area of the treatment plant.