Page 6: Canadian Guidelines for Domestic Reclaimed Water for Use in Toilet and Urinal Flushing
Management of on-site domestic reclaimed water systems is of particular importance. Local and provincial governments will need a comprehensive strategy, such as a multi-barrier approach, to effectively manage domestic reclaimed water systems. The ultimate goal of a multibarrier approach should be to protect public health. The risk management principles outlined in From Source to Tap: The Multi-Barrier Approach to Safe Drinking Water (FPTCDW/CCME, 2004) can be applied to reclaimed water. Reclaimed water systems include the source water to be reclaimed, the treatment system and the distribution/plumbing system. All aspects of the reclaimed water system should be managed in an integrated manner using the principles outlined in Box 2. These have been adapted from the From Source to Tap document (FPTCDW/CCME, 2004) to address the safe management of reclaimed water systems. Management strategies for reclaimed water have also been developed and published by other nations (U.S. EPA, 2005; NRMMC-EPHC, 2006).
Successful implementation of a reclaimed water system includes numerous additional considerations, including plumbing and system management, economics, management models, technology validation and certification, installation and commissioning of new systems, and operational oversight, inspections and monitoring. Plumbing and system management aspects are published as part of CSA Standard B128.01-06/B128.2-06 (CSA, 2006). This standard includes information on minimum plumbing requirements for non-potable water systems, including marking of pipes, backflow prevention, pressure testing, cross-connection testing and proposed maintenance schedules. As such, these details will not be included as part of this document.
It is important to consider the costs and benefits of any water reclamation project. However, it is often difficult to get a true accounting of these costs (Law, 1996; Ni et al., 2003; Radcliffe, 2004). It is recommended that any domestic water reclamation project be evaluated on a case-by-case basis to determine if it is economically feasible. The first step in this process should be to establish a water budget for all of the water uses in the building in question. Water efficiency measures, such as low-flow fixtures, should be adopted as a first step. If reclaiming water is still an attractive or necessary option after this analysis, proponents should consider the following costs: 1) capital costs of treatment system, storage and plumbing; 2) operation and maintenance costs, including electrical, repair, consumables and monitoring; and 3) fees that may be applied for permits and inspections. Other costs may also come to bear, whereas benefits will accrue from reduced water use and reduced need for wastewater treatment capacity. The Canada Mortgage and Housing Corporation website (www.cmhc-schl.gc.ca) includes several case studies of successful and economically feasible reclaimed water projects.
Legislative and policy frameworks
To ensure that human health is adequately protected, legislative and/or policy frameworks should support a clear commitment to the responsible use of reclaimed water (including responsible by-product disposal) and to the application of a preventive risk management approach. Policy frameworks should include the responsibilities for the various aspects of domestic reclaimed water systems, including the responsibilities of authorities, owners and operators. These responsibilities will vary between jurisdictions.
Public involvement and awareness
It is essential to establish and maintain partnerships and communication among the various stakeholders and with members of the public interested in domestic reclaimed water use. Strategies to accomplish this goal may include:
- informing the public about health risks and providing educational materials on issues such as water disinfection, guidelines, conservation issues and costs of providing service;
- providing information on programs or services in place for managing domestic reclaimed water systems; and
- for cluster systems, making monitoring results or summaries available and issuing regular reports about the system, its operation and planned improvements or changes.
Guidelines, standards and objectives
Guidelines, standards and objectives provide responsible authorities, owners and operators with water quality targets that can be used, in conjunction with monitoring, to maintain an acceptable quality of reclaimed water for the intended end use. This may include water quality targets for protecting human health or the environment.
Treatment and distribution
Treatment of reclaimed water is an important part of the multi-barrier approach for protecting public health. Therefore, treatment systems need to be appropriately designed and constructed. There is also a need for a high level of treatment reliability and oversight. Owners and operators should know what to do and whom to contact in case of treatment failure in their reclaimed systems, as well as how to maintain and operate systems effectively. Design and construction of distribution/plumbing systems for reclaimed water systems need to follow guidelines and standards and need to include cross-connection control programs.
Effective management of water reclamation systems is essential to ensure the protection of public health; therefore, management programs need to be in place. There may be opportunities to integrate domestic reclaimed water treatment considerations into existing wastewater treatment programs to manage systems more effectively. Management programs should include basic elements of good practice, such as owner and/or operator training, community involvement, research and development, validation of process efficacy and systems for documentation and reporting. In addition, preventive risk management strategies or plans should be developed for all reclaimed water systems. Owners and operators of reclaimed water treatment systems need to understand, at a basic level, the entire reclaimed water system, the hazards and events that can compromise reclaimed water quality and the preventive measures and operational control necessary for ensuring safe and reliable use of reclaimed water. Regulatory authorities should provide information and support to owners and operators in an ongoing manner so that they understand their responsibilities.
Water quality monitoring for reclaimed water systems can aid in the selection of the type of treatment needed, determine if the treatment system is working properly and ensure that the water is of an acceptable quality for its intended end use.
Experience with private wastewater treatment (e.g., conventional septic systems) has shown that most management programs rely on homeowners to assume full responsibility for the operation and maintenance of their individual systems. However, many of these programs experience problems for a variety of reasons, including:
- a lack of trained service providers;
- no legal authority to hold homeowners accountable for properly maintaining their systems;
- little to no training for homeowners; and
- lack of inspections and monitoring once systems are in place.
To overcome some of these issues, there are several management models and approaches that can be adapted for decentralized reclaimed water quality systems. While decentralized systems will affect fewer people than will large systems, small systems, from a process perspective, have a complexity similar to that of larger systems. Therefore, these systems can be considered moderate to high risk and should have the appropriate management approach and program in place to respond to this level of risk. Table 2 provides some management models, adapted from U.S. EPA (2005), that are applicable to decentralized reclaimed water systems and can be used as part of a management program.
|Typical application||Program description||Benefits||Limitations|
Table 2 Footnotes
|1. Maintenance contract model|
|Systems serving a single-family home|
|2. Operating permit model|
|3. Responsible management entity (RME) operation model|
|4. Responsible management entity (RME) ownership model|
|Cluster systems serving multiple properties under different ownership|
Across the country, the different institutions, arrangements and procedures involved in a management program will depend on many factors, including enabling legislation, available resources and the needs or desire of the individual or community to pursue water recycling. Because of this diversity, management programs and outcomes are also likely to be different from jurisdiction to jurisdiction. Management structures can range from an informal network of partners working under a coordinated framework to a highly structured responsible management entity (RME) that owns or maintains a set of treatment systems. Authorities in each jurisdiction will have to determine what type of management program will best suit the needs of their communities. Preventive risk management strategies or plans should be developed for all reclaimed water systems. The aim is to provide a measurable and ongoing assurance that performance requirements are met and that, as far as possible, faults are detected and corrective actions are taken before there is a negative health impact. While all risk management plans should be consistent with the principles described in the multi-barrier approach, the level of detail and demands of an individual plan should reflect the complexity and potential level of risk associated with the reclaimed water system in question, as well as the capabilities of the system owner/operator.
The design requirements for decentralized treatment systems focus on the protection of public health and water resources. Yet systems must also be affordable. Prescriptive codes simplify design reviews, but limit development options and innovation. Experience has shown that equipment failures are at the root of many waterborne disease outbreaks. In the case of reclaimed water treatment systems, the potential health risks and the need for treatment reliability underscore the need to have system performance validated. Ideally, a technology verification program should be available to provide a reliable, third-party assessment and certification of treatment devices (see Appendix C). Protocols for testing processes or technologies should determine their performance under a variety of upset conditions. There is currently no technology verification program in Canada that targets reclaimed water treatment systems. The NSF International/American National Standards Institute (NSF/ANSI) Standard 40 and Bureau de Normalisation du Québec (BNQ) Standards NQ 3680-910/NQ 3680-915 are examples of standard and testing protocols intended for the certification of on-site wastewater treatment systems; these protocols could conceivably be adapted to meet the requirements for reclaimed water systems, particularly with regard to disinfection. They offer good starting points towards an appropriate reclaimed water technology verification protocol. A limited overview of applicable treatment technologies is provided in Appendix D.
Authorities will need to ensure the proper installation and functioning of a system prior to commissioning and should adhere to the requirements of CSA Standard B128.01-06/B128.2-06, Design and installation of non-potable water systems/Maintenance and field testing of nonpotable water systems, for field-testing of a new system (CSA, 2006). Of particular importance is preventing cross-connections with potable water plumbing lines and the use of air gaps wherever possible (air gaps that are properly designed are preferred over backflow prevention devices) (NOWRA, 2004). In addition to the CSA Standard B128.01-06/B128.2-06 requirements, authorities should verify that sensors and monitoring instrumentation are functioning properly and that the treatment system is meeting the effluent water quality requirements (see Section 2.0). Note that it may take up to three weeks for biological systems to reach equilibrium or steady-state operation following start-up or a significant process change. Additional specific requirements may be imposed to fit local conditions and capabilities.
As part of a management program, authorities should consider certification or licensing of installers, as well as appropriate training. These recommendations are not meant as a substitute for applicable legal requirements. Interested parties should ensure that they are aware of, and adhere to, any applicable legal requirements where a system is under consideration.
As previously noted, any management program should be developed with due consideration given to protection of public health, water quality guidelines, regulatory authority capacity, administrative and operational capacity, and the local political, social and economic climate. Once effluent water quality parameters are verified upon start-up, as described in Section 2.0, frequent sampling of decentralized and small-scale/on-site wastewater treatment systems may be too resource intensive and expensive to be practical. In addition, statistics such as median and average values have very little meaning when assessing small-system water quality, where samples may be collected on only an annual or biannual basis (NOWRA, 2004). For such systems, it is recommended that monitoring be based on robust secondary parameters, such as motor performance, fluid pressure, temperature and flow, in addition to monitoring chlorine residuals or turbidity with simple tests or sensors that do not require frequent calibration. Verification of effluent water quality could be conducted on a periodic basis (e.g., biannually) and whenever the operational parameters show change in the system.
Once a treatment system has been shown to be capable of achieving the required water quality under specific operating conditions, verification of those operating conditions should be sufficient to verify continued performance. For example, once a specific chlorine dosage and residual concentration have been demonstrated to achieve the bacteriological water quality criteria, then verifying dosage and chlorine residual levels should be sufficient for routine monitoring. Periodic water quality sampling/analyses can be used to support this routine monitoring. Dosage can be verified by monitoring chlorine tank liquid levels, and chlorine residuals can be monitored using oxidation-reduction potential or other sensors on a real-time basis (as opposed to daily bacteriological verification sampling and testing). Chlorine residuals can also be monitored using simple chlorine test strips.
Those parameters that can be measured with automated equipment are most reliable when the equipment is used on a continuous basis and is equipped with an alarm. They may represent critical control points. Disinfection and power supply are two such critical control points. A disinfection system should be tested anywhere from daily to weekly, depending on the magnitude of the potential risk. For example, cases of gastrointestinal illness occurring in a household with a reclaimed water system may result in a higher level of pathogens in the wastewater entering the reclaimed system. It may therefore be advisable to monitor the operation of the disinfection system more closely to ensure that it is working properly. Levels of chlorine residual can be used to monitor a chlorine disinfection system. A backup power supply (e.g., battery or small generator) should be considered for short-term power loss. Consideration should be given to the use of telemetry where appropriate to allow better operational oversight.
Management programs should focus on proper operation and preventive maintenance (including by-product disposal) to ensure long-term system performance. All systems should have written operating and maintenance instructions. CSA Standard B128.01-06/B128.2-06 provides a maintenance schedule for various components of non-potable water systems, such as pumps, filter systems, storage and pressure tanks. This is in contrast to the more traditional
"endpoint" evaluation of water quality that focuses on system failure or malfunction. The elements described in this section are intended to provide a starting point for developing and implementing an effective management program.
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