Increased standards for risk management and a desire to improve health and safety provisions for its workers and community has resulted in the implementation of an Emergency Gas Scrubber (EGS) to manage the risks posed through the accidental release of chlorine gas at the Hamilton water treatment plant.
Although such an event is highly unlikely, this outcome is similar to work recently undertaken in Australia by major city water agencies there. Currently, there are no other known installations that utilise this specific type of EGS equipment anywhere else in New Zealand municipal water or wastewaster treatment facilities.
A key driver for this project is not only the size of the treatment facility at Hamilton (it is Hamilton’s sole source of water supply), but the plant’s location adjacent to an urban community .
The paper provides an overview of the process that were undertaken from start to finish which commenced with a risk mitigation options assessment that considered not only the “do nothing”, but also options involving an improved public awareness campaign, application of both dry and wet scrubber technology and also conversion of the disinfection system from a gas to a hypochlorite-based solution.
Of particular interest is the formal Quantitative Risk Analysis (QRA) that was carried out to quantify the risk posed by a myriad of failure modes of the existing chlorine system that could lead to an accidental chlorine gas discharge. A formal risk assessment criteria used for this application is in common use in New Zealand and this was supplemented with a set of risk framework criteria used for similar projects in Australia . The outcome of the QRA was a series of risk profiles for various failure scenarios. This analysis was able to inform HCC’s decision making about type of risk mitigation and the extent of the system that was appropriate to implement.
Various steps in the implementation of the system through design and construction to testing/commissioning are discussed, including an overview of the actual EGS technology.
Given this project involves application of anew and rigorous approach to risk management and the implementation of associated technology, this paper should be of interest to a wide range of conference delegates involved in risk assessments and also the operation, maintenance and management of hazardous environments and facilities at municipal treatment plants.