Cleaner Irrigation Water ... Naturally

Success Stories

The sun is both friend and foe to farmers. In recent years it's been an enemy to fruit and vegetable producers in several regions across Canada, including Nova Scotia, by causing drought conditions and, therefore, water shortages.

These shortages have forced farmers to look at other water sources for their crops, with water from streams and rivers being the most common approach taken.

Unfortunately, however, recent water quality monitoring reveals surface waters in many farmed regions exceed the Canadian Council of Ministers of the Environment (CCME) guidelines for fecal coliforms.

When that water is applied to crops that are eaten raw without being properly washed, it poses a public health risk to humans, according to Dr. Rob Jamieson of the Department of Process Engineering and Applied Science at Dalhousie University in Halifax.

As a result, Dr. Jamieson explains, some concerned farmers have installed disinfection systems for their operations and have been chlorinating the irrigation water. "That's a little expensive and requires a lot more effort and expertise to do. We thought maybe there's an easier way."

In May 2005, with funding from the Canada-Nova Scotia Water Supply Expansion Program, Jamieson and a team of researchers began studying ways to manage pathogen levels in irrigation water through extended storage.

"One of the most cost-effective solutions is to store the water in a reservoir for a period of time and let the organisms die off naturally," said Jamieson, explaining they are conducting two experiments to study how fast the microorganisms die off using this method.

One experiment involves examining how aeration, commonly used to control algal blooms within reservoirs, affects microbial persistence.

The second experiment looks at the influence of chemical and environmental parameters, such as temperature and solar radiation, on microbial survival.

It turns out that the sun, which caused the drought conditions in the first place, helps clean the water so well that pathogen levels drop to almost zero.

In Regina, Saskatchewan, where the same experiments are being conducted, Larry Braul, a senior water quality engineer with Agriculture and Agri-Food Canada - Prairie Farm Rehabilitation Administration (AAFC-PFRA), said they found quite a reduction.

"Just by ponding the water and allowing it to be exposed to the sun, we get rapid die off," said Braul, explaining they've seen 99 percent of pathogens die off in one day with just direct exposure. It improves to 99.9 percent reduction if aeration is also used.

"This is phenomenal," said Braul, adding both Nova Scotia and Saskatchewan researchers are seeing similar results.

This summer, Jamieson's team will perform more survival studies. They will also develop a computer-modelling tool to predict storage times for natural storage disinfection. That tool will then help them develop resource materials to assist producers in managing the microbial quality of their irrigation water supply through natural inactivation processes.

"This could be a very cost effective way to ensure irrigation water is not posing any public health risks," said Jamieson.

The Canada-Nova Scotia Water Supply Expansion Program is the provincial component of the National Water Supply Expansion Program (NWSEP), a federal-provincial program to help develop, enhance and protect agricultural water supplies across Canada.

For more information on the NWSEP or the Nova Scotia component, please contact 902-896-3652, or visit the program Web site.