Consumption Box 3.10 Conservation and Domestic Water Consumption, Canada

BOX 3.10

Canada: Conservation and Domestic Water Consumption

The average domestic water consumption by households in Canada is approximately 350–400 liters per person per day (300 liters per day for indoor use and 100 liters per day for outdoor use). Canadians use considerably more water than do most other nationalities. Consequently, summer water fl ows from mountain glaciers and annual snowpacks are diminishing. Sustaining access to water is therefore an important conservation goal in Canada.

Domestic water is used in bathrooms (toilets, showers, and faucets), kitchens (dishwashing and food preparation), and laundry facilities. Based on typical values, the charts illustrate the percentages of water used for these activities through conventional and low-fl ow fi xtures.

These values are based on a family of four people, as shown in the table:

Clothes washer, 13.2%

Dishwasher, 2.6% Conventional Fixtures

Cooking & Cleaning, 12.9%

Toilet, 20.6%

Faucets, 14.7%

Showerhead, 37.7% Reduction, 52.0% Low-Flow Fixtures

Toilet, 5.9%

Showerhead, 17.0%

Cooking & Cleaning, 23.0% Faucets, 10.6%

Dishwasher, 0.6% Clothes washer, 2.8%

WATER CONSUMPTION FIXTURE FAMILY USE CONVENTIONAL FIXTURE LOW-FLOW FIXTURE

Showerhead 8 minutes/person/day 15 liters/minute 7 liters/minute Toilets 5 fl ushes/person/day 13 liters per fl ush 6 liters to fl ush solids 3 liters to fl ush liquids Faucets 5 minutes/person/day 10 liters/minute 7 liters/minute Kitchen (cooking and cleaning) 15 minutes/day 10 liters/minute 7 liters/minute Conventional dishwasher 1 use/day 33 liters per use 8 liters per use Clothes washer (top loader) 7 uses/week 170 liters per use 36 liters per use

The toilet is the most important source of water consumption in the home. Over 70 percent of water use occurs in the bathroom. Toilets and showerheads thus represent the best opportunities for water reduction in the home.

Low-fl ow fi xtures include dual-fl ush toilets. These toilets have two fl ush buttons: one provides a 3-liter fl ush for urine; the other provides a 6-liter fl ush for solids. Showerheads and faucets may be designed to reduce fl ows without a noticeable reduction in performance. New appliances such as dishwashers and front-loading clothes washers have signifi cantly lower water needs. Low-fl ow fi xtures may reduce water consumption in the home by over 50 percent, from approximately 1,200 liters per day (interior use) to 600 liters per day. This does not include outdoor use for landscaping.

Source: Adapted from The Living Home (2008).

cultural activities are still common in parks, along streets, and in public and residential gardens. Effi cient irrigation in these areas helps improve water use and sector sustainability. Irrigation should be properly timed to avoid peak daily temperatures and reduce evaporation and evapotranspiration losses. Effi cient irrigation systems, such as drip irrigation, subsurface irrigation, and sprinkler irrigation should be used.

Wastewater treatment and sludge disposal Location of the wastewater treatment plant: Wastewater treatment plants are not popular facilities. While wastewater is generated within

residential centers, residents generally pressure governments to locate wastewater treatment plants far from their neighborhoods. In general, plants need to be located as close as possible to sewage generation sources and downwind of communities; they need to discard wastewater downstream of neighborhoods and water works facilities if there is an intermediary river. The plant also needs to be centrally located to minimize the energy consumption of sewage transfer and effl uent disposal or reuse. There are often trade-off s among these confl icting interests.

Process of wastewater treatment: There is a wide range of sewage treatment processes. As much as possible, priority should be given to biological treatment processes to avoid the use of hazardous chemicals. It is also important to treat domestic and industrial sewage separately. Moreover, legislation is needed to prohibit nonbiodegradable domestic detergents and the disposal of hazardous wastes, such as heavy metals, pesticides, hydrocarbons, and medical wastes, into the city sewerage system. Awareness campaigns and public participation are essential to these eff orts. Activated sludge treatment plants are common around the world and lauded for their effi ciency and relatively compact size. However, the treatment processes are energy intensive. Treatment plants with extended lagoons consume much less energy and are cheaper to construct, though they need more land.

Sludge management: In addition to treated effl uent, wastewater treatment plants produce sludge, which is composed of biomass and settled biological material. If the biological content has been appropriately digested, sludge may be a valuable resource for composting, fertilizing, or generating methane. Generated methane may be captured and used as an energy resource. Commonly, treatment plants are equipped with gas turbines and generators that use methane to produce electricity. The generated electricity may be suffi cient to cover most of the electricity demand for treatment, or it may be sold to the distribution grid. Special legislation may encourage plant operators to sell electricity or subsidize production costs through carbon fi nance funds. These funds promote technologies that reduce greenhouse gas emissions such as carbon dioxide, which is linked to global warming and climate change.

In traditional plants, sludge is often discarded in the sea or dumped into solid waste landfi lls. These practices are falling out of favor because they risk harming the marine environment and polluting groundwater.

Energy effi ciency

Energy is often the dominant factor that determines the cost of water and wastewater services. The energy needs of these services may vary from less than 1 kilowatt-hour to many kilowatthours per cubic meter of treated water. The amount of required energy depends on the following factors:

• Distance and elevation of water sources relative to service areas • Topography of service areas • Depth of groundwater aquifers (if applicable) • Location of wastewater treatment and disposal facilities • Energy consumption in water production and wastewater treatment facilities • Energy recovery ratios at wastewater treatment plants via sludge digestion • Energy recovery ratios at desalination plants • Levels of technical and commercial water losses • Confi guration and design of the water distribution and wastewater collection systems • Modes of operation of the water distribution system

There is a strong and direct relationship between water use and energy savings. This link has led to the expression Watergy. Box 3.11 summarizes the scope of Watergy within the water sector, such as in demand management and supply management and the synergy between the two in terms of system design and operation.