Page 4: Canadian Guidelines for Domestic Reclaimed Water for Use in Toilet and Urinal Flushing
Canadians are some of the highest per capita users of water in the world. According to Environment Canada's "Freshwater Website"
(www.ec.gc.ca/water), simple changes to water use habits and domestic equipment can reduce water consumption in the home by up to 40%. There are many measures and strategies that can make a significant contribution to reducing water use. Some are quite common, simple and inexpensive, whereas others are relatively new or ground-breaking. One that fits into this latter category is using reclaimed water. There is a growing interest in using reclaimed water within the context of sustainable water management. Other factors that contribute to the interest in reclaimed water use include:
- the opportunity to provide reliable water services in remote or environmentally sensitive locations;
- overburdened traditional water sources;
- the rising costs of meeting drinking water treatment and wastewater discharge standards;
- the potential to reduce domestic wastewater discharges to water bodies;
- seasonal water shortages and droughts (potentially exacerbated by climate change); and
- population movement to large centres, resulting in changes to the spatial patterns of water demand (Anderson et al., 2001).
Despite the advantages of using reclaimed water, pathogens or chemicals in reclaimed water may pose a risk to human health or the environment. Owing to these risks and the low cost of water in Canada, pursuit of water reclamation has been slow. At present, British Columbia is the only Canadian province to have enacted a reclaimed water standard (Municipal Sewage Regulation) for a variety of applications, including for toilet flushing and irrigation (Government of British Columbia, 1999). Alberta legislation (Government of Alberta, 1993) allows the use of treated municipal wastewater for irrigation; in support of the legislation, Alberta Environment (2000) has produced guidelines to aid in evaluating projects. The Atlantic Canada Wastewater Guidelines Manual for Collection, Treatment, and Disposal includes a chapter on reclaimed water use, with a focus on irrigation (Environment Canada, 2006). Other provinces use a caseby- case approach to proposed water reclamation projects. In the absence of guidelines, some jurisdictions are using demonstration or test sites to explore water reclamation (CMHC, 1997; Ho et al., 2001).
Several reports have concluded that guidance and leadership from senior government on reclaimed water are needed to ensure that it is incorporated into future water management strategies (Marsalek et al., 2002; Brandes and Ferguson, 2004). It has been noted that two major barriers to the adoption of water reclamation as a strategy are 1) the lack of standards for plumbing requirements for non-potable water systems and 2) the lack of national guidelines for reclaimed water quality (CMHC, 1997). CSA (2006) has developed CSA Standard B128.01-06/B128.2-06, Design and installation of non-potable water systems/Maintenance and field testing of nonpotable water systems, which addresses plumbing requirements. This current document addresses the second barrier and will contribute to the development of a consistent, national approach for the safe and sustainable use of domestic reclaimed water.
This document provides guidelines for domestic reclaimed water quality as well as guidance on potential elements of a management framework. Part I of the document provides guidance on management frameworks and models, and Part II outlines the scientific basis of the water quality guidelines. The guidelines and management guidance presented in this document are applicable only to water reclamation where the water source is domestic wastewater or greywater and the end use is toilet or urinal flushing, either on site or at a nearby residential or commercial location. Commercial applications are intended to be light commercial uses, such as retail. This document does not cover rainwater harvesting, nor does it cover recycling of stormwater and wastewater that includes industrial sources of contamination.
The limited scope of these guidelines is considered a first step towards broader uses of reclaimed water. The long-term objective is to provide the tools and guidance needed to allow the safe use of reclaimed water for many beneficial purposes, while minimizing the associated human health and environmental risks. The design, installation and maintenance requirements for the plumbing components of non-potable water systems are addressed in CSA Standard B128.1-06/B128.2-06 (CSA, 2006).
These guidelines are intended for use by regulatory authorities, public health professionals, engineering consultants and others with a level of technical understanding of the subject area. The guidelines take a conservative approach to establishing water quality parameters for domestic reclaimed water. Even though exposure to reclaimed water used for toilet or urinal flushing is expected to be low, the potential health effects associated with coming into contact with microbiologically contaminated water are serious enough to warrant a precautionary approach.
This document adopts a risk-based approach in order to ensure that the quality and management of domestic reclaimed water are protective of public health over the long term. The aim of a risk-based approach is to identify all of the potential hazards in a reclaimed water treatment system, assess their potential impact on water quality and on public health, and find ways to mitigate those risks, rather than to simply react when problems occur. Risk management considerations, including elements of a management framework and potential management models, are outlined in Part I. The guidelines are based on risk assessment, including the identification of hazards, assessment of exposure and characterization of risks, as outlined in Part II.
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