Treatment plant upgrade withstands nature's fury

An upgrade by Richmond Valley Council of its Casino sewage treatment plant (STP) has paid immediate dividends by withstanding the fury of June’s storms and flooding without suffering any polluting spills or odours.

The turnkey upgrade — which included retrofitting of fine screening technology by CST Wastewater Solutions — was completed just days before the bad weather along Australia’s east coast dumped more than 160 mm of water on the council region within 48 h.

“The council couldn’t have timed the upgrade any better,” said CST Wastewater Solutions Managing Director Michael Bambridge. “Their foresight and technology upgrade was perfect. The Northern Rivers District of NSW is one of the most flood-prone areas outside of the tropics, where events like this are likely to occur and reoccur, so the investment in new technologies has already paid off.”

The original inlet works at Casino STP were designed with a coarse manual raked bar screen system. The functional components of the treatment process downstream of the bar screen receive a high amount of debris, which formerly impacted the efficiency of the treatment process. The original inlet area also received a high amount of odorous gases, which previously contributed significantly to odours emanating from the treatment plant.

The retrofit project replaced the coarse raked screen design with fine screening technology. This captures more solids to reduce potential blockages in tanks and downstream equipment, while reducing odours by sealing the inlet works and installing new odour control units.

The project’s high-efficiency fine screening SFC technology (screen press for channel installation) is engineered to deliver low-maintenance performance with reduced WHS hazards for municipal and industrial wastewater operators. The SFC allows for a much finer level of screening — 5 mm, compared with typical old systems at 60 mm or more — which has led to a significant reduction in solids in the tanks, while producing more efficient treatment with less maintenance. By cutting the amount of waste that has to be handled by plant operators, it has reduced operational health hazards and improved OHS performance.

The upgrade project also involved fitting new technology into an existing layout, including tailoring the screens to fit into the existing formed channel. The retrofit saw the installation of an SDS 20 compactor with two inlets — one for each screen — to dewater screenings to 25–30% dry solids. Each screen has an enhanced design capacity of 250 L/s flow, providing a total capacity of 500 L/s.

“Not only are the tanks clearer and more efficient now, but the screen extractor also operates on level control and is fully automated, eliminating the previous labour-intensive operator handling of screenings,” Bambridge said.

The technology is widely applicable to other industry and municipal applications, said Bambridge. It is also suitable for applications such as food and beverage, manufacturing and processing, mining, energy and resources camps, where its low-maintenance/high-hygiene qualities are appreciated, as well as agribusiness and remote installations, where low maintenance and high efficiency is a priority for users who don’t need to have specialist staff constantly available.