by James Laughlin
I recently toured the Lakeview Water Treatment Plant serving the Region of Peel, Ontario. The 96 mgd expansion is being billed as the world’s largest immersed membrane ultrafiltration plant and the first large-scale operation to combine ozone and biologically activated carbon (BAC) pretreatment with immersed ultrafiltration membranes.
I always enjoy touring treatment facilities, whether large or small, new or old. While I write about drinking water and wastewater treatment equipment almost every day, it’s a rare treat to see that equipment in operation.
The Lakeview plant was still undergoing shake-down testing when I joined a tour hosted by GE Water Technologies. The facility uses ZeeWeed UF membranes supplied by Zenon, which was acquired by GE last year.
While the membrane system was certainly a highlight of the tour, our group had the chance to visit every inch of the facility - starting with the pumping room where raw water from Lake Ontario is brought into the facility and following through the treatment process to the point where the water is sent to the distribution system.
Being new, everything about the plant was spotless. And except for the pump rooms, it was an oddly quiet facility. Of course it’s state of the art and the entire plant can be operated by one person from a central control room.
The membrane facility is in addition to the Region of Peel’s 56-year-old 148 mgd conventional treatment plant. The decision to use membranes for the new facility was driven by a variety of factors, including space constraints, future expansion capabilities and the declining cost of membrane systems. The ozone/BAC/membrane treatment train was selected in part because of its ability to meet anticipated future regulations.
Pretreatment with ozone and BAC removes up to 90 percent of the organic foulants prior to membrane filtration, enabling the membranes to operate at higher flux rates with longer run-times between cleanings. The treatment train has consistently produced treated water with at least 4-log removal of Cryptosporidium, turbidity of less than 0.1 NTU and insignificant levels of disinfection byproducts.
The treatment process starts by adding chlorine at the plant intake to control zebra mussels. The water is then be pre-screened and pumped to a feed header that can supply either the conventional treatment plant or the expansion. Water that is directed to the advanced treatment train is treated with caustic to adjust the pH to a level that is acceptable for the BACC. Ozone, generated from liquid oxygen, is added to provide 1-log inactivation of Cryptosporidium and also oxidize organic compounds that cause taste and odor problems. Sodium bisulfite is added to the ozone-contacted water for quenching prior to releasing it to the BACC.
After ozonation, the water travels by gravity to the deep-bed activated carbon filters for removal of organics and taste and odor control. The BACC also acts as a roughing filter for turbidity removal. From the BACC, the water flows by gravity to the membrane filtration tanks.
Lakeview has 12 membrane process trains, each consisting of a 14,500-gallon tank that can hold up to seven ZeeWeed membrane cassettes. Eleven of the trains will operate at all times, with the 12th train operating on demand, whenever one of the others is taken out of service for cleaning, scheduled maintenance or testing.
James Laughlin, Editor
