Water Treatment: Sudbury retrofits water plant using ultrafiltration

Communities across Canada have been taking a hard look at how they treat their drinking water, and in many cases have decided to include membrane technology as part of a multi-barrier approach. Membranes occupy less space than conventional filtration technologies and are used not only for new water plant construction, but for upgrading existing plants as well.

The City of Greater Sudbury operates many communal drinking water treatment systems, treating both groundwater and surface water. One of its facilities, the David Street Drinking Water Treatment Plant, treats water from Ramsey Lake. Ramsey Lake is a high quality surface water adjacent to some of the most developed urban areas of the city. While supporting a variety of recreational uses, the raw lake water has historically been of high bacteriological quality, although aesthetic parameters such as manganese, iron and to a lesser extent turbidity have been a concern in recent years.

The existing treatment facility consists of a micro-strainer building and a pump station, dating to 1895. In order to improve the quality of treated water and bring the plant in compliance with the new Ontario Drinking Water Protection Regulation 459/00, the city will carry out improvements including ZENON ZeeWeed 1000 ultrafiltration for particulate removal. This Canadian-developed and manufactured system places hollow fibres of a proprietary polymeric membrane in process tanks filled with raw water. Unlike most filtration processes, suction is applied to the ZeeWeed membrane, pulling clean water through the microscopic pores and leaving the unwanted particles on the outside of the membrane.

The ability to run by suction allowed the design engineers to design a plant using a siphon, eliminating the need for intermittent pumping, saving both space and energy. Raw water is pumped into the membrane process tanks, and treated water is drawn through the immersed membranes by the siphon that supplies water to the high lift pumps. Reject water created during filter backwash is conveyed to a second stage of membrane filtration, resulting in an overall plant recovery of 99%. This plant will be one of the most efficient plants in North America.

Using Zenon’s membrane technology allowed the existing site to be re-used. Part of the structure built in 1950 was demolished and 40 ML/d of membrane treatment capacity in a new 30 x 16 m structure was installed in its place. Conventional technologies would not fit on the existing Davis Street site, which would have resulted in relocating the entire plant at considerable cost. The $20-million plant upgrade is being funded equally by the city, provincial and federal governments.

Specifications and drawings for the project were prepared by CH2M Hill Canada, working in conjunction with NYB Architects and Northland Engineering.

ZENON’s immersed membrane technology is currently used in many Canadian communities, including: Collingwood, Thunder Bay, Rothesay, Parry Sound, Sioux Lookout, Picture Butte, Loyalist Township, Little Current and Walkerton.

By Scott Lenhardt, P.Eng.

ZENON Environmental, Oakville, Ont.