Questioning the ongoing use of chlorine gas – is it the safest method?

When it comes to purifying water for consumption, there have long been questions raised around the safety of current processes involving chlorine gas. So much so, that the necessity of Emergency Shutdown Devices (ESD) have become as close to an industry standard there can be without formal legislation. These devices, however, are looking like an interim solution for an industry that is now innovating beyond the current practice employed all over the world – chlorine gas could be a thing of the past, and take ESD’s into redundancy with them.

“I think the whole industry will eventually move away from chlorine gas as the conversation around safety and environmental impact becomes more prevalent,” says Matt Wagland, Technical Sales of WestWater Enterprises. “While safety is the biggest motivator, cost, transportation, and storage are all playing their part in the search for change too,” he says.

Taking it back to Emergency Shutdown Devices for a moment and in laymen’s terms, ESD’s are installed in chlorine gas plants to reduce the risk of a deadly chlorine gas leak. The automated systems continuously monitor the levels of gas in the air via a leak detector, and should a leak occur, the ESD’s trigger an instant shutdown response and the plant is evacuated of all staff – keeping workers and the surrounding community safe.

While the aim of all ESD’s are the same, they are all not created equal and Wagland describes how the team at WestWater Enterprises are innovating these systems for a sharper and safer response.

“The technique used in a standard shutdown system is a pneumatic, air operated valve but there are some limitations to this technique, basically because it means that you have to store and maintain a whole other energy system in the plant, one that can be faulty,” says Wagland.

“Our team have innovated an electric actuator which works with a specially designed DC motor and gearbox. It mounts on the top of the chlorine gas drum and uses battery power rather than compressed air,” says Wagland. “This device has a lot less chance of fault as it stores its own battery power that holds usage for 24 hours should there be a power outage. The self testing device also checks its own battery everyday, limiting staff hours and the risk of a fault.”

“The industry has been employing leak detectors for approximately 15 years, however it is only the last 5 years or so that we have been using the information from the leak detector to trigger an emergency, automated shutdown with the installation of an ESD.”

“ESD’s were historically only installed when the chlorine gas plant was near a school but the Water Corporation are now moving towards a standard where all of their treatment plants will have an emergency shutdown device as well as a leak detector.”

While the need for ESD’s are now high in an industry that employs chlorine gas as the main method for making water safe, the movement towards a whole new disinfectant methodology is becoming imperative. “Chlorine gas is used in most towns in Australia as it is currently the most reliable way to disinfect water, and the easiest, but the effects of chlorine gas to humans and the environment can be dire,” says Wagland. “Our whole job is centered around safety – safety to operators in the workforce, and for houses and communities around the treatment plant – so using an alternative to chlorine gas is a priority for us.”

The Centre for Disease Control and Prevention describe some of the effects of chlorine gas as it removes oxygen from the air and combines with moisture to create an acid, such as struggling to breathe, chest pain, burning pain, fluid in the lungs, and nausea and vomiting.

“In my opinion, no site in Australia will be using Chlorine Gas in the future … It may not ever happen, especially when you are talking about large scale sites such as the Mundaring Weir, but I believe that the Water Corporation will try to eliminate it [chlorine gas] as best as they can.”

WestWater is the sole user of an electrochlorination process in replacement of chlorine gas in Western Australia and have installed the system in mine sites and three community locations for the Water Corporation. “As far as I know, we are the only ones that have completed the whole process and are successfully running electrochlorination plants in Australia,” says Wagland.

Electrochlorination uses a brine solution to create the chlorine in a concealed environment. A large tank of salted water (brine) is passed through a DC cell, therefore removing hydrogen from the solution and leaving the chlorine solution that is then dosed into the water. Creating this chemical reaction onsite means that staff are only buying, transporting, handling, and storing a salt solution which is a lot safer than the highly toxic chlorine gas.

“Another benefit to the electrochlorination treatment process, beyond the safety aspect which is of course the biggest motivator, is that it is a cheaper process,” says Wagland.  “Because you are making the disinfectant using salt onsite, there is not the high transport cost that comes along with the movement of chlorine gas.”