Riverside Wastewater Treatment Plant - Executive Summary
The City of Andalusia Riverside Wastewater Treatment Plant's (WWTP) accidental release prevention policy involves a unified approach that integrates technologies, procedures, and management practices. At this facility, we handle chlorine which is considered hazardous by EPA. While chlorine can be potentially hazardous, years of development and progressive safety practices make chlorination a safe, reliable, and effective method of disinfection. It is our policy to adhere to all applicable Federal and State rules and regulations. Safety depends upon the manner in which we handle chlorine combined with the safety devices inherent in the design of this facility combined with the safe handling procedures that we use and the training of our personnel. |
Our emergency response policy involves the preparation of an emergency operation plan that includes procedures for notification of the local emergency response agencies and notification of any potentially affected neighbors. The plan is in co
mpliance with the EPA Emergency Response Program requirements.
The Riverside Wastewater Treatment Plant employs the extended aeration process to convert the City of Andalusia's wastewater flow into a properly treated effluent. The city's wastewater flow is collected by a network of gravity sewers and outfalls that flow toward the treatment plant or, where prohibited by terrain, pumped toward the plant. The treated wastewater is discharged into the Conecuh River. The principle components of the plant are an administration building, raw sewage pump station and static screen, oxidation ditches with intra-channel boat clarifiers, sludge drying beds, parshall flume, chemical building that contains a chemical room and a room with chlorine feed equipment, and an oxygen saturator. The amount of chlorine handled is two one-ton containers. Wastewater treatment operators inspect the facility and safety equipment daily.
The offsite consequence analysis includes consideration of two chlorine rel
ease scenarios, identified as "worst-case release" and " alternative release". EPA defines the first scenario as "the maximum quantity in the largest vessel ... is released as a gas over 10 minutes," due to an unspecified failure. The alternative release is defined as "more likely to occur than the worst-case scenario". The assessment includes atmospheric dispersion modeling to determine the distance traveled by the chlorine released before its concentration decreases to the toxic endpoint selected by EPA as 0.0084 mg/l, which is the Emergency Response Planning Guideline Level 2 (ERPG-2). Also, the potentially affected populations and environmental receptors must be estimated.
The worst-case release scenario at the Riverside WWTP involves a failure of a one-ton cylinder (a total of 2,000 lb of chlorine). The offsite consequence analysis for this scenario was performed following conditions pre-defined by EPA, namely the release of the entire amount as a gas in 10 minutes, use of the on
e-hour average ERPG-2 as the toxic endpoint, and consideration of the population residing within a full circle with radius corresponding to the toxic endpoint distance. Also EPA-mandated meteorological conditions, namely Stability F, wind speed of 1.5 m/sec, highest daily maximum temperature of 116 degrees F, and average humidity of 65% were used. The distance to the toxic endpoint is 1 mile and the estimated residential population potentially affected is 448.
The alternative release scenario involves a gasket leak from the valve to the regulator. The amount of chlorine released is 60 lb at an average rate of 2 lb/min. released for 30 minutes. Toxic endpoint distance to the ERPG-2 level was obtained. The meteorological conditions used were Stability D, wind speed 3 m/s, average air temperature 77 degrees F, and average humidity of 65%. The estimated distance traveled to the toxic endpoint is 0.1 mile and the estimated residential population affected is 5. An emergency shutdown system
is an active mitigation considered.
Modeling for the worst-case and alternative release scenarios were performed using EPA RMP*Comp.
The general Riverside WWTP accidental release prevention program is based on the following key elements:
* Training of the operators
* Preventive maintenance program
* State-of-the-art process and safety equipment
* Use of effective operating procedures
* Implementation of an inspection program
Chemical-specific prevention steps include availability of MSD Respirators, awareness of the hazardous and toxic properties of chlorine, and the presence of chlorine detectors.
No accidental releases of chlorine have occurred at this facility in the past five years.
The facility's emergency response program has been coordinated (reviewed) by the Andalusia Fire and Police Departments. The program includes guidelines for personnel in the event of an emergency situation and includes procedures for notification of proper authorities. Analysis was conducted
to determine the vulnerability of the WWTP to various factors that could create emergency situations and to outline the proper procedures for responding to each situation.