Wattle Park Pumping Station (PS) is located adjacent to an 84 Megalitre reservoir and supplies drinking water to Eastern Adelaide. It is owned by South Australian Water (SAW) and operated by Allwater. Wattle Park is embedded within a leafy section of Adelaide, adjacent and extremely close to residential properties. Customer perception is important to SA Water and the mandatory signage and high fences associated with gas chlorine installations were not consistent with the aesthetic outcome SA Water were looking for. Part of the overall upgrade to the Wattle Park PS involved providing rechlorination systems at the facility. After listening to the concerns of local residents, SAW decided to install Chlorination facilities that did not utilise chlorine gas. SAW considered both bulk sodium hypochlorite and OSEC® and eventually gave the go ahead for duty / standby electrolysers to be installed inside the Wattle Park facility.
Even though the considerations above provided a strong argument for electro-chlorination, there was debate by operations who did express preference for gas chlorine. After several electro-chlorination systems were considered during the design phase, OSEC technology from Wallace & Tiernan® was selected as the preferred system technology. OSEC systems generate a 0.8% solution of sodium hypochlorite by electrolysing a low strength brine solution. The OSEC system requires storage of salt in a salt saturator, which provides a brine solution. Water softeners ensure that the feed water to the OSEC system is free from any hardness. Both the brine and the softened water are fed to the OSEC at 3% brine solution and electrolysed in the generator. Inside the generator, chlorine and hydrogen are liberated at the anodes and at the same time sodium hydroxide is produced at the cathodes. The chlorine and sodium hydroxide then mix to form sodium hypochlorite.
The OSEC® system has been in operation since 2012, without any significant issues raised by operators. There is a strong sense of acceptance for this technology, more so than liquid sodium hypochlorite (12.5%) which loses concentration during storage and needs to be transported to site. An emergency liquid sodium hypochlorite system, that was included as back-up, has never been used. SAW would select electro-chlorination for other sites especially at sites where the installation of gas chlorine would be problematic. The technology has proven itself to be very reliable, has a lesser risk to environmental safety concerns and is easy for site personnel to operate and maintain. For operators the main involvement is to transfer bags of salt, utilising an electric hoist, into the salt saturator. Operators also monitor the process by checking hardness of softened water, water temperature, brine strength, chlorine solution strength and rectifier values.
OSEC technology from Wallace & Tiernan® was selected as the preferred system technology. OSEC systems generate a 0.8% solution of sodium hypochlorite by electrolysing a low strength brine solution.