By Bunny Mah, Prairie Farm Rehabilitation Administration, Calgary
Many groundwater users in rural areas can relate to the iron removal problems the Hoffs have experienced.
The Hoffs live on a farm near Standard, Alberta, about 80 kilometers east of Calgary. They obtain their water supply from a well. The iron and iron bacteria in their well water causes reddish-brown discolouration and staining on laundry, appliances and fixtures. They have tried as many as three different water treatment systems, but were unable to find a satisfactory solution to their water quality problem.
The Hoffs wanted a reliable, low maintenance and cost-effective system. This quest has led them to co-operate in a demonstration project using the Canadian Water Filter for iron removal.
The Canadian Water Filter is the patent name for a slow sand filtration system developed by Dr. David Manz, in association with the University of Calgary. Its design is based on conventional continuous flow slow sand filter technology with modification to allow for an intermittent mode of operation. In 1994, Dr. Manz was in Chile in support of an International Development Research Centre program for installation of a water filter project to remove pathogens in the water supply of developing countries. It was there that Manz accidentally discovered the capacity of the filter to remove iron. Later, the filtration system was tested in the university laboratory and the iron removal level of 40 mg/L was documented.
In November 1995, with Rural Water Development Program funding from PFRA, a demonstration project using the Canadian Water Filter filtration system was installed on the Hoff farm. One of the objectives of the project is to assess the transferability of the technology to a rural application.
The system is designed for a 5-person household. It consists of a head tank, a twin-filter providing a flow rate of about 1 gallon per minute and a 100 gallon storage tank. Filter materials include pure silicon sand on top of a layer of gravel; all held in a 22-gallon plastic container.
The system is operated by gravity with flow control regulated by float switches in connection with solenoid controlled valves. Water pumped from the well is sprayed into the head tank to allow air contact for oxidation reaction before passing through the filters into the storage tank. When the flow is stopped, there is always a shallow depth of water covering the top of the filter. The only maintenance required is replacement of the top 5 cm of sand, in the Hoff's case, every 6 to 8 months. No backwashing of the filter is required.
Since its installation, monitoring results have shown an iron removal level from groundwater containing 1 to 2 mg/L of iron down to about 0.03 mg/L. Mrs. Hoff is very satisfied with the quality of water for domestic utility uses. For cooking and drinking purposes, post filtration disinfection is necessary. Depending on the flow rate and storage requirements, a typical system costs about $2000.
(Note: The Manz Filtration Process has been selected by the APEGGA Council as the recipient of the APEGGA Project Achievement Award for 1996.)
To contact the author, write to Box 2906, Rm 832, 220-4th Ave. S.E., Calgary, AB T2G 4X3
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