New high-rate process resolves pre-treatment bottleneck at the City of Red Deer WTP

Implementing high-rate, ballasted flocculation at the City of Red Deer’s Water Treatment Plant No. 2 has resolved capacity issues in the plant’s pretreatment process. The largest Actiflo installation in Western Canada, the new pretreatment process has doubled the plant’s pretreatment capacity in half the footprint of the previous facility.

Faced with increasing water demand from a growing population as well as changes to water quality standards, the City of Red Deer retained Associated Engineering to complete a Water Treatment Master Plan in February 2001. The Plan provides the framework for the City’s water treatment needs for the foreseeable future.

Recently, the City entered into agreements to provide drinking water to communities north of Red Deer by 2006. The demands of the regional system required immediate upgrades at the City of Red Deer’s Water Treatment Plant No. 2. The City retained Associated Engineering to design and oversee construction of the recommended works.

The immediate concern was the capacity bottleneck in the plant’s pretreatment stage, particularly during the spring. During spring runoff, the Red Deer River, the plant’s water source, tends to carry extra organic materials as well as mud and silt stirred up by increased water flow. During spring, Water Treatment Plant No. 2’s existing solids contact clarifiers were limited to a capacity of 43 million litres per day, compared to their design capacity of 75 million litres per day.

After successful pilot testing, two “Actiflo‚” high-rate, ballasted flocculation/clarification systems were selected for pretreatment improvements. Actiflo‚ employs “microsand” and polymer to assist fine particles in the raw water to agglomerate, forming larger, denser (“ballasted”) floc. The ballasted floc settles quickly in lamella (inclined plate) clarifiers, resulting in clarified water.

 
The system’s small footprint allowed the two Actiflo systems to fit into one of the plant’s two existing 20 metre by 20 metre solids contact clarifiers. The clarification retrofit doubles the pretreatment capacity.

The new pretreatment system has continued to operate and perform successfully since its commissioning in May 2004. Upgrading the pretreatment process has improved the plant’s performance, reducing the previous strain evident during spring runoff. Each Actiflo train has consistently produced clarified water well below 1.0 NTU, at varying flows from 30 million litres per day to 60 million litres per day.

The Associated Engineering team included Barry Vallance (Project Manager and Process Leader), Scott Witzke, Risco Protic, and Corinne Wotton.