New Clarifiers to Increase Capacity at Quebec Water Treatment Plant

An expansion at the Charny Water Treatment Plant in the city of Lévis, Quebec will increase capacity from 26,000 m3/d to a design flow 45,000 m3/d (6.9 mgd to 7.9 mgd) upon commissioning in May 2003.

USFilter's John Meunier Products supplied two Actiflo® ballasted clarification units and plant automation under a US$1.07 million contract with Lévis, a suburb of Quebec City. The Actiflo® units will comprise the first step in treating raw water from the Chaudière River. Actiflo® unit effluent will be further treated by three gravity-flow media filters. The mechanical contractor for the project is Wilfrid Allen of Saint Henri, Quebec.

The Actiflo units' high capacity and small footprint enabled the city to increase total plant treatment capacity within the same space previously occupied by two sludge blanket clarifiers, and without construction of costly new basins.

"The Chaudière River flows through agricultural areas and is among the most polluted rivers in Quebec," said Christian Scott, senior project engineer with USFilter‚s John Meunier Products. "That and highly variable quality caused by rainfalls and spring snow melts make the river water extremely difficult to treat. Pilot testing in winter and summer conditions has documented that the Actiflo® process was the best available to treat the variable flows from the river."

The process is also highly stable in the face of rapid swings in raw water temperature caused by melt water. "Changes in temperature can easily upset the delicate equilibrium required in sludge blanket clarifiers," Christian Scott said. "High process stability is a key reason why Actiflo® is replacing sludge blanket technology as the preferred clarification process in Québec."

The new plant treatment process must meet a provincial turbidity standard of 2.3 NTU, but city officials expect the process to deliver water consistently below 1 NTU. The project includes a process guarantee.

Water utilities worldwide have used the Actiflo® process for more than a decade for treating surface water to produce drinking water. The process has proven stable and efficient, meeting water-quality standards even with the significant seasonal and weather-related variations in turbidity.

The process works on the same principles as conventional water treatment. Both use coagulant for destabilization and flocculant-aid polymer to aggregate suspended materials, which are then removed by settling.

The primary difference in the Actiflo® process is the addition of microsand to speed up floc formation and settling. The microsand aids development of chemical floc far denser and more durable than floc in a conventional clarifier. It also acts as ballast to enhance settling and thus allow shorter detention times and higher clarifier overflow rates. That translates to a smaller system footprint and lower capital costs.

Besides all mechanical and chemical and sand feed components of the Actiflo® system, John Meunier Products provided control and instrumentation and updates SCADA software for the entire plant. Upon completion, all plant processes will be fully automated.

United States Filter Corporation, a Vivendi Environnement company, is North America‚s leading water company providing comprehensive water and wastewater systems and services to commercial, industrial, municipal and residential customers.


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