Largest-ever Membrane Filtration Process
The Conne River Micmac First Nation community in the Canadian province of Newfoundland has an on-reserve population of approximately 700 people. The reserve is located on the southeast shore of Newfoundland on the Conne River. The reserve covers an area of some 14 square miles. It lies 350 miles from the capital city of St. John's and 110 miles from the nearest services center, Grand Falls.
“The Conne River Micmac Band currently gets its drinking water from a surface source located in the Southwest Pond watershed,” explains Eric Humphries of Design Management Group Ltd. (DMG), the band's engineering consultant. “This current supply is treated by chlorination only and there have been serious concerns about this form of treatment.”
When the Conne River Micmac Band decided to ensure the availability of safe drinking water with a new filtration system, studies showed that organic materials from surface water had to be removed prior to chlorination. If not removed, these organic materials could form potentially cancer-causing byproducts, and newer water-quality standards put strict limits on the allowable concentrations of these compounds.
In order to improve the treatment process of a surface water supply to remove certain cancer-causing organic materials, reserve turned to a membrane filtration solution provided by ITT Industries' Sanitaire division.
Brian Kelly is director of capital projects at Conne River, reporting directly to the chief of council for the community, and has overall responsibility for the project. He provides the project background: “We really promote good health practices within our community and a high-quality water supply has to be a priority. We built a new water and sewer system, including a new dam and sewage lagoon, about 10 years ago, but we've started to see problems with chlorination byproducts. Also, for about the last five years, we've been under a boil order. Most of the homeowners have to buy bottled water for almost everything. Washing is about the only thing that domestic water can be used for."
Filtration Process SpecifiedThe DMG design consultant determined that a process plant using using a proprietary membrane filtration technology from ITT Sanitaire's PCI Membrane Systems unit would do the job. Known as the Fyne process, the filtration plant will produce nearly 400,000 gallons per day of clean drinking water. That exceeds current parameters and includes provisions to meet future needs, which might include the construction of a fish processing operation. With this and other possibilities in mind, the Fyne plant was built to allow for easy expansion.
An alternative to chemical-based processes for removing organic materials, the Fyne process offers several features that are highly attractive to the community. No chemicals are added to the water prior to chlorination, and there is no residual chemical sludge. In addition, the process membranes provide a physical barrier that holds back waterborne pathogens, microbes and viruses, as well as reducing undesirable levels of iron and other metals, which may also be found in surface water.
With DMG's help, a multiple-factor-comparison analysis was used to evaluate the suitability and economy of different methods of water treatment and the PCI system was one of two approaches that were piloted. “Right from day one,” recalls Brian Kelly, “the quality of the water was better than we had ever seen before and, in fact, better than we anticipated. The results made it obvious that the PCI system would have the best impact on the community from the standpoint of water quality and bang for the buck. The PCI people were great to work with as well.”
Surface Water ApplicationsThe PCI membrane filtration technology is widely accepted in small- and medium-sized communities in North America and Europe, which rely on surface water that tends to be heavy with dissolved organic materials (mostly humic and fulvic acids). Heavy chlorination is required for this surface water and can lead to high concentrations of total trihalomethanes (TTHMs) and five haloacetic acids (HAA5s) in the treated water. Studies have shown that TTHMs and HAA5s may be carcinogenic and their presence also has been linked to miscarriages. In the United States, the Stage 1 D/DBP Rule imposes strict limits on TTHMs and HAA5s in small surface-water systems. In Canada, new regulations are in place in Ontario, and similar legislation may soon be introduced in other Canadian provinces. It is expected that chemical coagulation treatment will struggle to meet more stringent limitations, which may be enacted before the next decade.
How the Process WorksThe Conne River facility, the largest of its kind, will be the first Fyne process installation to use spiral nanofiltration membranes rather than the tubular membranes used at earlier Canadian projects, which involved smaller water volumes.
The process is based on a particular membrane filtration process known as nanofiltration. Surface water is prefiltered to remove suspended solids down to 10 microns. This pre-filtered raw water, which still contains large quantities of organic compounds, is then passed, under high pressure, through a series of membrane modules. A fraction of the feed water passes through the membrane, which holds back the disinfection byproduct precursors, along with iron and other undesirable metals, and waterborne bacteria and viruses. These undesirable components are automatically flushed from the system with unused feed water (merely raw water in a more concentrated form) and returned to the river with no chemicals added to it whatsoever. The clean water that has passed through the membrane (the filtrate) then can be safely chlorinated and delivered to the potable water distribution system.
The Fyne plant operates automatically, with very little supervision - the system can be monitored continuously and remotely through an outside telephone line. Routine maintenance includes bi-weekly cleaning of the spiral membranes using pre-filtered feed water and detergent (similar to common household laundry soap). No other chemicals are used, so there are no storage or disposal issues. After cleaning, membrane wash water is stored on site and metered back into the river in accordance with environmental standards, which are expected to become much stricter in the next 10 years.