Towns and cities in Saskatchewan produce billions of litres of wastewater every year. Cities like Saskatoon or Regina can produce 70 million litres of wastewater in a day. Although it is treated, nutrients and pollutants remain, reducing water quality when the effluent is released to rivers.
Municipal Wastewater Effluent (MWWE) is a complex mixture of human waste, suspended solids, debris, and a variety of chemicals from residential, commercial and industrial sources, as well as runoff. Sewage contains pathogenic microorganisms, nutrients like phosphorus-that contribute to eutrophication or aging of water bodies, and even residues of pharmaceuticals and endocrine disrupting substances.
Occasionally, pathogenic organisms make their way from sewage systems back into the municipal water supply, as was the case in North Battleford in 2001 when hundreds of people were made sick by cryptosporidium contamination.
Most water demand and most effluence occur in the Saskatchewan-Qu'Appelle systems. As the population of the these basins increases, along with the demand for water, and as riverflows decrease due to climate change, water quality will become an increasingly important issue. One of the most effective ways to protect and improve water quality will be to eliminate pollutants at the point of origin, before they enter the river.
Most MWWE treatment systems involve a combination of physical, chemical and biological processes, but a number of alternative systems have been designed to use mainly enhanced biological processes. Today, thousands of engineered wetlands are being used to treat wastewater all over the world.
System Ecotechnologies Inc. is a Saskatoon company that has designed about 90 wetland treatment systems on several continents, including a number in the Prairie region. Their engineered wetlands consist of shallow lagoons or channels stocked with cattail, bulrush and a number of other aquatic plants. These plants absorb nutrients and pollutants, and offer large contact surfaces for microbial attachment and growth. The natural microbial populations in the wetland also assimilate nutrients and degrade pollutants such as heavy metals. Wetlands can offer increased treatment efficiency over conventional systems, often at a lower cost.
In addition to treating wastewater, wetland systems provide harvestable biomass, which can be used to produce animal feed, soil conditioners, energy pellets, biogas and ethanol. Wetlands also provide wildlife habitat.
One system designed by System Ecotechnologies is a 68 acre engineered wetland that treats sewage from the City of Estevan and ultimately provides water to cool SaskPower's Boundary Dam power station.
In warm climates, engineered wetlands can handle waste volumes from major cities. In colder climates like Saskatchewan, the volume of wastes from a city like Saskatoon or Regina may be too high for wetland treatment, since the system is only active about five months a year. However, wetland treatment works well for smaller communities, reservations, parks, trailer parks, and work camps and for treating industrial wastes. Engineered wetlands could also operate effectively on the city subdivision level.
Another approach is to find more effective ways to treat human waste at the household level, before it enters the sewage system.
For example, over the past 20 years, Barry Mitschke's Lumsden home has been an experiment in environmentally friendly living. One feature is a composting toilet that handles human wastes and organic garbage. Chutes run from two toilets and the kitchen area to a tank that can handle wastes from the family and any number of guests. Composted wastes are removed annually and composted outside for an additional year to ensure the finished material is safe for use as a soil amendment.
Human waste is about 90 percent water. A composting toilet is designed to aerate the waste so most of it can be vented as water vapour and gas. A mixture of microorganisms added to the remaining solid waste transform it into compost. Composting toilets are becoming common in cottages and rural properties.
Mitschke's house is also designed to recycle gray water-the wastewater from kitchen sinks, basins, laundry and showers. Instead of running down the drain, this water is stored in a buried, vertical culvert. The water can be safely used to irrigate lawns and trees.
Gray water recycling reduces the nutrients entering water bodies. Rarely practiced in Canada, it is common in many countries, and in the U.S. states of Florida and California, were water shortages are common. Gray water can also be recycled to flush toilets or water lawns.
Composting and enhanced biological treatment mimic natural processes, eliminating waste before it enters the river system, protecting not only human users but also fish and wildlife. Typically, these systems are also more energy efficient and cost effective.