by Hans Peterson, Senior Research Scientist, Saskatchewan Research Council, Saskatoon, Saskatchewan
WHAT ARE THE OPTIONS?
When a small community is faced with poor quality water, water that does not meet acceptable water quality criteria, a search for alternatives is usually started. With more stringent water quality guidelines, an increasing number of water supplies will be listed as unsuitable for a variety of reasons. Regulating agencies target communities to comply with these guidelines. Individuals face the same water quality problems, but are not forced to comply with any guidelines. What is good, bad and ugly with various water sources is discussed below.
Water sources
Two very different raw water sources that can be used to produce drinking water are surface water and groundwater. Surface water is found in dugouts and lakes, and groundwater is found in underground lakes called aquifers. The characteristics of water that has come strictly from runoff to form surface water is quite different from water that has been stored in aquifers. Mixtures of surface and groundwater can be found in both dugouts and shallow aquifers. What is good, what is bad and what is ugly when surface and groundwaters are used?
Dugouts - the good, the bad and the ugly
Surface water that is not influenced by groundwater has some very good features. The quantity of inorganic ions (salts) in the water is small and these waters rarely have problems with specific ions, such as sulphates and iron. Softening is generally unnecessary. Prairie dugout water is quite comparable to drinking water supplied to major cities in North America as far as inorganic compounds are concerned.
The bad about dugout water are the organic substances entering the dugouts through runoff as well as being produced in the dugout by blue-green algae (cyanobacteria), algae, and higher plants. These organics can impart taste and odour to the water.
The ugly part of dugout water is that these organic substances make it more difficult to disinfect the water. In addition, during disinfection, problem compounds are formed. These problem compounds will often be in higher concentrations than what is recommended in the Guidelines for Canadian Drinking Water Quality. Surface waters are also more likely to be contaminated by disease causing organisms (bacteria, viruses, and parasites).
Groundwater - the good, the bad and the ugly
The good in groundwater are the generally low level of disease causing organisms and low levels of dissolved organic substances.
The bad in groundwater are the high content of inorganic ions. The quantity of these ions often makes the water salty. The Guidelines for Canadian Drinking Water Quality for dissolved solids (500 milligrams per litre) and for specific ions (sulphate and iron) are often exceeded. Sulphates can cause stomach upsets and iron stains fixtures etc.; both impart taste to the water.
The ugly compounds in groundwater, for example, arsenic and bromine, are either directly toxic (arsenic), or indirectly toxic (bromine). Bromine reacts with chlorine and ozone during disinfection to form compounds that are quite toxic. Some of these compounds can only be formed in the presence of dissolved organics and, unfortunately, these are likely present in levels that are higher than was previously thought.
Treatment of the bad and the ugly
Prairie Water News is dedicated to improve in-house treatment of the bad and the ugly in dugouts, in groundwater, and in mixtures of these water sources. We invite you to write to Prairie Water News with your experience, both bad and good, as those experiences relate to commercial and homemade systems. To evaluate various treatment options, we will seek the advice from industry, provincial and federal government departments.