Metro Wastewater Reclamation District - Executive Summary |
|
The Metro Wastewater Reclamation District (Metro Wastewater) operates a wastewater treatment plant located on a 170-acre property in the Denver metropolitan area. Metro Wastewater treats about 150 million gallons per day (MGD) of wastewater from 55 sanitation districts and municipalities. For effective wastewater disinfection, Metro Wastewater uses 90-ton railcars of chlorine (Cl2) and sulfur dioxide (SO2). One-ton cylinders of SO2 and Cl2 are used as backup. The chlorine is used to disinfect the wastewater and the sulfur dioxide is used to dechlorinate the disinfected water before it is discharged to the South Platte River. Metro Wastewater has an effective accident prevention program associated with the disinfection system. The maintenance schedules and activities are computerized and designed to have all maintenance be preventative. Metro Wastewater trains all employees who work on covered processes to ensure the safe operation and maintenance of the disinfection system. Met ro Wastewater's worst-case scenario is the release of 90 tons of SO2 over a 10-minute period. The alternative-case assumes a break in a one-inch pipe from the Cl2 tank car. An assumption of no controls or mitigation is necessary for the leak to reach an off-site endpoint. Ninety percent of Metro Wastewater's maintenance budget is spent on planned or predictive maintenance. The maintenance program is documented on computer. The computer prints daily maintenance tasks that are scheduled to maintain systems in good working order. Paper files back up the computer system. The leak detection system consists of process area detectors that have audible, visible and remote alarms. The remote alarm appears at the Control Systems Operator computer. Additionally, operators inspect the disinfection system every two hours. Process controls include vents, relief valves, check valves, manual shutoffs, automatic shutoffs, alarms, emergency air supply, emergency power, and rupture disks. Th e mitigation system for Cl2 consists of blowers that force air into the Cl2 disinfection system contact chamber. The hazard analysis identified the need for greater traffic control in the ton-cylinder area. Signs and chains have been installed. The operating procedures are not as easy to use as desired. Operating procedures are scheduled for updating in the summer of 1999. Metro Wastewater has no accidents to report for covered processes in the past 5 years. Metro Wastewater is a non-responding facility. The South Adams County Fire District (SACFD) is Metro Wastewater's emergency response organization. There are several remotely activated or automatic shut-off valves to stop pipe leaks. The SACFD has trained with Metro Wastewater's personnel to stop a leak of the chlorine or sulfur dioxide tank cars. Evacuation procedures for plant personnel are well documented. Metro Wastewater has worked closely with the Adams County LEPC, South Adams County Fire District, and other local industries to communicate with the local public. |