Life Sciences: Continuous Effluent Decontamination
The decontamination of liquid hazardous infectious waste streams in research and production laboratories has taken a leap forward in safety and efficacy with the introduction of new technology. When discussing waste disposal for high-level containment labs—where waste may contain organisms that could pose serious health hazards such as the recent SARS outbreak—operational safety and system efficacy are paramount.
Several issues must be addressed when considering effluent decontamination technology, including the following:
*The need to develop industry validation standards and to standardize components and manufacturing processes
*The quick and safe diagnosis and repair of problems
*Ease of use
*Hidden costs associated with system installation and maintenance
Beyond Kill Tanks
Kill tank technology offers safety checks, but systems may lack advanced controls to ensure that their components are working properly. They may also fail to continually measure the effectiveness of the decontamination process itself. For these reasons, kill tank systems can also be challenging to use correctly. Improper use may result in unwanted discharge of hazardous effluent, thus exposing operators and repair personnel to unsafe conditions.
Because kill tanks are built differently for each facility, the lack of consistency in design can result in slower, less efficient repair and replacement. Service staff can encounter unforeseen obstacles because valves and other critical components – even between two tanks in the same facility – are not in predictable and consistent locations.
Cost is another consideration. Hidden costs are inherent in the kill tank design. The large space demanded by the system and containment basin, the need for generous spare parts inventories, and the requirement for high efficiency filtration for ventilating the area all add significantly to the cost of a kill tank system.
Continuous Effluent Decontamination
A new technology alternative called the Continuous Effluent Decontamination (CEDTM) System from Steris Corporation has been tested in the laboratory and in the field and is validated for use in multiple types of research, production, and bio-containment environments (see Photo 1 and Table 1).
The new CED system is designed to replace the larger multi-step kill tank system and offers a number of critical advantages that result in improvements in efficacy, reliability, safety, and cost effectiveness. The CED system’s footprint is 3 1/2 x 5 sq ft plus a 45” diameter buffer tank. The total system occupies approximately two-thirds to three-fourths of the space required for a kill tank system.
The technology addresses the flaws of the kill tank method with features that include built-in diagnostic controls, redundant processing systems, and independent safety zones. Following is a description of how the system works and a discussion of critical issues that pharmaceutical, research, and biocontainment industries need to know about the new technology.
How It Works
The CED processes effluent through a continuous system consisting of a heating zone and two independent cooling zones. Waste is fed to the system through a buffer tank that buffers the peaks and valleys of flow throughout the day. The three major systems are:
1. Buffer Tank
Incoming biologically contaminated effluent is stored in a tank custom-specified to handle that particular location’s needs at the required levels. Tanks are manufactured of AISI 316L stainless steel and are automatically steam sterilizable in place if required. The buffer tank operates at atmospheric pressure, and is equipped with a filtered vent (for sterilizing air to the room), an inspection port, and openings for CIP (Clean-In-Place) media. Level controls monitor tank contents and automatically begin the CED operation at predetermined levels.
2. Decontamination System
Effluent is pumped into multiple heat exchangers, in series with one another, which are steam-heated to 302°F (150°C). A length of pipe immediately downstream of the first set of heat exchangers is monitored at two check points to assure that the temperature reaches and holds at the prescribed setting. Dual magnetically coupled pumps ensure uninterrupted processing.
3. Cooling System
Decontaminated effluent is cycled through one of two sets of cooling exchangers. If the desired temperature has not yet been reached, the waste is recirculated, cooled and reheated. Once the desired temperature has been reached at the check points, the waste is diverted to the second set of cooling exchangers and cooled to below the required 140°F (60°C) before being safely discharged.
The CED is a closed and sealed system with independent zones for each function – pre-filtering, buffering, venting, and decontaminating – each with controls that provide continuous confirmation that the system is working properly. Separate sensors monitor water temperature at two different locations in the system to ensure that the proper temperature is achieved throughout the system before waste is discharged. And in the unlikely event of a failure, a hard-wired circuit shuts down the system and closes off all outlet valves. The system was lab tested for performance and biologically tested with spore-forming organisms—the same organisms used to test traditional steam sterilizers. To meet specific facility needs the buffer tank can be sized to hold 1000 to 8000 liters and the processing system can be sized from 100 liters/hour to 1000 liters/hour.
Water levels are monitored in the buffer tank and the system shuts down automatically if the level rises above a predetermined point. Automatic self-testing of the entire system occurs each time the system is started after a shutdown or alarm condition. Once activated, the system does a complete check of all valves and scans for leaks. The decontamination cycle will not start if all tests are not completed successfully. To protect against leaking, the dual pumps are magnetically coupled so no penetration is required through the pipes. And in the unlikely event of a system leak, a capture basin safely contains the liquid within the safety cabinet and a level sensor shuts down the system and activates an operator alarm.
A Programmable Logic Controller (PLC) automatically controls the CED to a safe state in the event of any mechanical failure or loop fault. Prior to any maintenance procedure, automatic valves isolate every section of the system for steam sterilization. During routine cleaning, the control system prevents CIP procedures unless the buffer tank and associated piping have first been sterilized. To perform I/O testing and calibration, operators must have a password. Multiple levels of access allow operators, supervisors and service personnel to view, configure, and edit processes and/or calibrate instruments, modify inputs and outputs, and change passwords according to their authorized responsibilities. Multiple alarms (text, visual, audible) notify appropriate personnel of disturbances in any part of the system.
The CED system offers many advantages over kill tanks, and allows research, production, and bio-containment facilities to safely process nearly any biologically contaminated liquid effluent before discharge.