Ocean Reef resident raises concerns of treated waste water at Ocean Reef Marina risking safety for swimmers

A northern suburbs resident wants pipes from a treatment plant upgraded before the Ocean Reef Marina project is complete over fears about water quality. Kim Allen’s concerns come as Mullaloo Beach was closed for two days last Wednesday due to the presence of trichodesmium, a type of blue-green algae often referred to as sea sawdust. Mr Allen, who lives in Ocean Reef overlooking the marina and swims at Mullaloo Beach every day, has long been assessing outfall pipes into the ocean from Beenyup Wastewater Treatment Plant. “The outfall pipe is actually two pipes that are both about 1.2m in diameter and they have diffusers, or sub-pipes, placed every five metres to help to dissipate the treated outfall,” he said. “They’re only in water about seven to eight metres deep; normally those types of diffusers for large plants are in deep water 30 to 40 metres deep a long way off shore. “In 1988, a civil engineering report was conducted because of population growth and indicated the best solution was to extend the initial pipe, which was built in 1977, to extend it to 5.8km off shore into deeper water. “It meant it would have to be pumped. At the moment it is fed by gravity, which is a lot cheaper, so they chose the cheaper option of duplicating the pipe.” Mr Allen said water issues usually arose following north-westerly winds, which sometimes brought an oily film and odour. He said he used drones to track and document plumes in the water, which appeared to come from the outfall pipes to the surface. Mr Allen said he was concerned of the age, shallow depth and short length of the pipes which may not be diluting the waste water far enough from Mullaloo Beach, which was less than 2km south-east. Mr Allen said Hillarys MLA Caitlin Collins organised a meeting last Tuesday — the day before Mullaloo Beach was closed — with the Water Corporation, Department of Water and Environmental Regulation, a representative from Environment Minister Reece Whitby’s office and a representative from Water Minister Simone McGurk’s office. “I presented some of the concerns and observations and then some ideas from the community, predominantly around saying we’d like to see more improved water quality,” he said. “We discussed protocols for beach closure in the event of contamination and pollution. The next day, unbelievably this happened.” He said it was a race against time to upgrade the pipes before the significant Ocean Reef Marina project was complete, which would make upgrades even more difficult and expensive. University of WA environmental engineering professor Anas Ghadouani said the trichodesmium which forced the closure of Mullaloo Beach was most likely brought by ocean circulation but the possibility of it being caused by the nearby outfall was a “valid concern.” “We’re really agnostic about when you do an investigation; you have to list all of the possibilities. The most likely possibility is ocean circulation linked to some sort of heatwave, because you don’t need nutrient-rich water for this particular species to grow,” he said. “If this was another species that was a non-nitrogen fixer, I would lean towards the theory that there would need to be a source of nitrogen.” Professor Ghadouani said testing for other human-linked ingredients such as caffeine, E.coli, steroids or even the contraceptive pill could be a strong indication for outfall pollution. He said the closure of a beach due to algae in Perth should not be downplayed considering how rare the event was. It was more commonly seen in the Swan River. A Water Corporation spokesperson said “recent investigations show no evidence of a link between outfall at the Beenyup Water Resource Recovery Facility and an algal bloom near Mullaloo Beach”. “The outfall, which is 1.6km offshore, is operating as normal and in line with all regulatory conditions,” they said. “We undertake daily monitoring at the facility, as well as monitoring at the outfall and on the shoreline.” A 2022-2023 Water Corporation annual report of the Beenyup facility said an approved management plan was not yet in place for the Ocean Reef outlets.