| #Q001 | treatment | treatment | recommended | Surface Water and GUDI Minimum Treatment | drinking water | Generally, minimum treatment of supplies whose source is either surface water or GUDI should include adequate filtration (or technologies providing an equivalent log reduction credit) and disinfection. | Applies to supplies whose source is either surface water or GUDI | high |
| #Q002 | treatment | treatment | recommended | GUDI Treatment as Surface Water | drinking water | GUDI is a groundwater supply that is vulnerable to surface water contamination or contamination by pathogens and, as such, should be treated as a surface water supply. | Applies to Groundwater Under the Direct Influence of surface water (GUDI) | high |
| #Q003 | treatment | treatment | recommended | Multi-Barrier Pathogen Removal Logging | drinking water | As part of the multi-barrier approach to drinking water treatment, pathogen physical log removal credits should be used in conjunction with disinfection credits to meet or exceed overall treatment goals. | | high |
| #Q004 | design | treatment | recommended | Filtration System Turbidity Reduction Goal | drinking water | Where turbidity reduction is required as part of a strategy to meet pathogen removal goals, filtration systems should be designed and operated to reduce turbidity levels as low as reasonably achievable. | Where turbidity reduction is required to meet pathogen removal goals | high |
| #Q005 | operational | treatment | recommended | Minimum HBTL Compliance | drinking water | At a minimum, these systems should meet the HBTL applicable to their specific treatment technologies. | Applies to filtration systems used to meet pathogen removal goals | high |
| #Q006 | monitoring | operational | recommended | Continuous Monitoring of Filter Effluent Turbidity | drinking water | However, it is recommended that both the individual filter effluent turbidity and the combined filter (or clearwell or tank) effluent turbidity be continuously monitored. | Applies to systems filtering to meet pathogen removal goals | high |
| #Q007 | corrective_action | operational | recommended | HBTL Exceedance Corrective Action | drinking water | Action should be initiated if the applicable HBTL is exceeded. | If the applicable Health-Based Treatment Goal (HBTL) is exceeded | high |
| #Q008 | corrective_action | health | recommended | Immediate Action for Never to Exceed Values | drinking water | Any turbidity reading above the "never to exceed" value should be addressed immediately. | If a turbidity reading is above the never to exceed value | high |
| #Q009 | operational | treatment | recommended | System Optimization Target | drinking water | Systems employing filtration for pathogen removal and meeting the applicable HBTL should strive to meet the treated water turbidity target of less than 0.1 NTU. | Applies to systems employing filtration for pathogen removal | high |
| #Q010 | operational | treatment | recommended | Conventional and Direct Filtration Turbidity Target | drinking water | Conventional and direct filtration systems should strive to achieve a treated water turbidity target of less than 0.1 NTU at all times. | Applies to conventional and direct filtration systems | high |
| #Q011 | design | treatment | recommended | Filter-to-Waste Design | drinking water | In general, all filters should be designed so that the filtered water produced immediately after filter backwashing is directed into a waste stream ("filter-to-waste"). | Applies generally to all filters | high |
| #Q012 | operational | treatment | recommended | Maintain Turbidity Below 0.3 NTU | drinking water | Turbidity levels should be consistently kept below 0.3 NTU (with a target of less than 0.1 NTU) throughout the entire filter cycle, with the exception of the filter-to-waste period. | Applies throughout the entire filter cycle, excepting the filter-to-waste period for conventional or direct filtration | high |
| #Q013 | corrective_action | treatment | recommended | Investigation of Turbidity Above 0.3 NTU | drinking water | Waterwork systems using conventional or direct filtration should investigate and minimize any occurrences of turbidity levels above 0.3 NTU. | If turbidity levels rise above 0.3 NTU in conventional or direct filtration systems | high |
| #Q014 | corrective_action | health | recommended | Immediate Action for Turbidity Above 1.0 NTU (Conventional/Direct) | drinking water | Any turbidity values above 1.0 NTU should be investigated and addressed immediately. | If turbidity values are above 1.0 NTU in conventional or direct filtration systems | high |
| #Q015 | operational | treatment | recommended | Slow Sand and Diatomaceous Earth Turbidity Target | drinking water | Slow sand and diatomaceous earth filtration systems should also strive to achieve a treated water turbidity target of less than 0.1 NTU at all times. | Applies to slow sand and diatomaceous earth filtration systems | high |
| #Q016 | operational | treatment | recommended | Slow Sand Filter-to-Waste Operation | drinking water | Slow sand filters should be operated to waste after starting or scraping until the filter effluent is consistently less than the standard required for the system. | Applies after starting or scraping a slow sand filter | high |
| #Q017 | corrective_action | treatment | recommended | Investigation of Turbidity Above 1.0 NTU (Slow Sand/Diatomaceous Earth) | drinking water | Waterworks systems using slow sand or diatomaceous earth filtration should investigate and minimize any occurrences of turbidity levels above 1.0 NTU. | If turbidity levels rise above 1.0 NTU in slow sand or diatomaceous earth filtration systems | high |
| #Q018 | reporting | operational | recommended | Flag Exceedances in Slow Sand/Diatomaceous Earth Systems | drinking water | Operators of slow sand and diatomaceous earth filtration systems should compare readings with operational monitoring records and flag any results above 1.0 NTU as exceedances of the HBTL. | If turbidity results are above 1.0 NTU | high |
| #Q019 | corrective_action | health | recommended | Immediate Action for Turbidity Above 3.0 NTU | drinking water | Any turbidity levels above 3.0 NTU should be investigated and addressed immediately. | If turbidity levels are above 3.0 NTU in slow sand or diatomaceous earth systems | high |
| #Q020 | operational | treatment | recommended | Membrane Filtration Turbidity Reduction | drinking water | Membrane filtration systems should reduce turbidity to as low as reasonably achievable. | Applies to membrane filtration systems | high |
| #Q021 | operational | treatment | recommended | Membrane Integrity Breach Interpretation | drinking water | Any increase in turbidity above 0.1 NTU should be considered a potential breach in the integrity of either the membrane filtration unit or an individual filter cartridge. | If turbidity increases above 0.1 NTU in membrane filtration systems | high |
| #Q022 | corrective_action | operational | recommended | Membrane Integrity Investigation Trigger | drinking water | To allow systems some flexibility for addressing any uncertainty in turbidity measurements but also recognizing that any values above 0.1 NTU may represent an integrity breach, measurements greater than 0.1 NTU for a period of greater than 15 minutes should immediately trigger an investigation of the membrane unit integrity. | If measurements are greater than 0.1 NTU for a period of greater than 15 minutes | high |
| #Q023 | administrative | health | recommended | Case-by-Case Assessment of Protection Requirements | drinking water | Assessing whether a water supply and treatment system's performance satisfies requirements sufficient to be protective of public health should be done on a case-by-case basis. | Applies to other systems such as those filtering for non-pathogen reasons or using UV | high |
| #Q024 | design | health | recommended | Groundwater Well Protection Measures | drinking water | ensure that groundwater wells are properly constructed and maintained, are located in areas where there is minimum potential for contamination and have appropriate wellhead protection measures in place | Applies to systems using groundwater sources | high |
| #Q025 | treatment | health | recommended | Groundwater Virus Reduction | drinking water | ensure that treatment is sufficient to achieve a 4-log reduction of viruses by disinfection where required; it is important to confirm that elevated turbidity levels will not compromise any disinfection process in place, including residual disinfection in the distribution system. | Applies to systems using groundwater sources where required | high |
| #Q026 | monitoring | operational | recommended | Distribution System Turbidity Monitoring | drinking water | All drinking water systems should monitor and control turbidity throughout the entire distribution system including areas with long retention times, decreased disinfectant residual, or that have demonstrated deteriorating water quality. | Applies to the entire distribution system | high |
| #Q027 | corrective_action | operational | recommended | Investigation of Rapid Turbidity Increases | drinking water | If an unusual, rapid, or unexpected increase in turbidity levels does occur, the system should be inspected and the cause determined. | If an unusual, rapid, or unexpected increase in turbidity levels occurs in the distribution system | high |
| #Q028 | monitoring | operational | recommended | Source Water Turbidity Measurement Frequency | drinking water | For conventional and direct filtration (i.e., continuous feed of a coagulant with mixing ahead of filtration), source water turbidity levels should be measured at least daily just prior to the point of addition of treatment chemicals. | Applies to conventional and direct filtration | high |
| #Q029 | monitoring | operational | recommended | Conventional and Direct Filter Effluent Measurement | drinking water | Treated water turbidity levels from individual filters should be continuously measured (with an online turbidimeter) at intervals no longer than five minutes apart at a point in each individual filter effluent line. | Applies to conventional and direct filtration | high |
| #Q030 | monitoring | operational | recommended | Combined Filter Effluent Monitoring (Conventional/Direct) | drinking water | The combined filter effluent should also be monitored at some point downstream of the combined filter effluent line or the clearwell or tank. | Applies to conventional and direct filtration | high |
| #Q031 | monitoring | operational | recommended | Slow Sand Filter Effluent Measurement | drinking water | For slow sand or diatomaceous earth filtration, treated water turbidity levels from individual filters should be continuously measured (with an online turbidimeter) at intervals no longer than five minutes apart at a point in each individual filter effluent line. | Applies to slow sand or diatomaceous earth filtration | high |
| #Q032 | monitoring | operational | recommended | Combined Filter Effluent Monitoring (Slow Sand) | drinking water | The combined filter effluent should also be monitored at some point downstream of the combined filter effluent line or the clearwell or tank. | Applies to slow sand or diatomaceous earth filtration | high |
| #Q033 | monitoring | operational | recommended | Membrane Filter Effluent Measurement | drinking water | For membrane filtration, treated water turbidity levels from individual membrane units should be continuously measured (with an online turbidimeter) at intervals no longer than five minutes apart at a point in each individual filter effluent line. | Applies to membrane filtration | high |
| #Q034 | monitoring | operational | recommended | Combined Filter Effluent Monitoring (Membrane) | drinking water | The combined filter effluent should also be monitored at some point downstream of the combined filter effluent line or the clearwell or tank. | Applies to membrane filtration | high |
| #Q035 | design | operational | recommended | Membrane Unit Turbidity Sensitivity Design | drinking water | Consideration should be given in the design of membrane units to ensure that the level of sensitivity is sufficient to detect membrane breaches with turbidity monitoring or other integrity testing. | Applies to the design of membrane filtration units | high |
| #Q036 | corrective_action | health | recommended | Investigation of Distribution Turbidity Increases | drinking water | However, unusual, rapid, or unexpected increases in distribution system turbidity can be indicative of deteriorating water quality and should be investigated. | Upon detection of unusual, rapid, or unexpected increases in distribution system turbidity | high |
| #Q037 | treatment | health | recommended | Pathogen Reduction for Alternative Filtration | drinking water | In cases where pathogen reduction goals need to be met, the treatment technologies selected, including disinfection, should reliably achieve a minimum 3-log reduction for Giardia lamblia cysts and Cryptosporidium oocysts and a minimum 4-log reduction for viruses. | In cases where alternative filtration technologies are used and pathogen reduction goals need to be met | high |
| #Q038 | administrative | treatment | recommended | Establishment of Alternative Filtration Turbidity Levels | drinking water | Turbidity levels of filtered water from alternative technologies should be established by the responsible authority taking into account data from challenge testing or other methods used to demonstrate the effectiveness of the filtration technology. | Applies to filtered water from alternative filtration technologies | high |
| #Q039 | administrative | health | recommended | Vulnerabilities Assessment for Filtration Exemption | drinking water | Vulnerabilities assessment :Ensure a detailed current understanding of hazards inherent to the water source. | When considering exempting drinking water systems from filtration requirements | high |
| #Q040 | administrative | health | recommended | Source Water Protection Documentation | drinking water | Source water protection :A thorough understanding of measures being taken by all stakeholders to protect the source water should be maintained and documented over time. | When considering exempting drinking water systems from filtration requirements | high |
| #Q041 | operational | operational | recommended | Filtration Exemption Inspection Requirement | drinking water | Inspection and verification : Undertake adequate inspection and preventative maintenance from source to tap on a regular basis. | When considering exempting drinking water systems from filtration requirements | high |
| #Q042 | reporting | operational | recommended | Documentation of Maintenance and Upgrades | drinking water | Activities should be well documented such that a history of maintenance, upgrades and optimization approaches can be demonstrated over time. | When considering exempting drinking water systems from filtration requirements | high |
| #Q043 | treatment | health | mandatory | Minimum Pathogen Reduction Without Filtration | drinking water | Treatment : Whether or not filtration technology is in place, the drinking water treatment process must still achieve a minimum 3-log reduction of Giardia lamblia cysts and Cryptosporidium oocysts and a 4-log reduction of viruses. | Applies whether or not filtration technology is in place | high |
| #Q044 | treatment | health | mandatory | Multi-Disinfectant Strategy for Non-Filtration | drinking water | Utilities using surface water or GUDI that are considering not using filtration will need to treat source waters for all three types of organisms (protozoa, viruses and bacteria), using a multi-disinfectant strategy. | When a utility using surface water or GUDI considers not using filtration | high |
| #Q045 | operational | health | mandatory | Disinfection By-Product Minimization | drinking water | The drinking water treatment process will also need to be operated to minimize the formation of disinfection by-products. | When considering exempting drinking water systems from filtration requirements | high |
| #Q046 | design | health | recommended | Distribution System Maintenance and Disinfectant Residual | drinking water | Distribution : The distribution system should be appropriately designed, maintained and monitored in accordance with established best practice, and a disinfectant residual should be maintained throughout the distribution system. | When considering exempting drinking water systems from filtration requirements | high |
| #Q047 | administrative | operational | recommended | Contingency and Emergency Response Planning | drinking water | Contingency or emergency response planning : Also recommended is a well-developed site-specific response plan for episodes of elevated source water turbidity brought about by extreme weather or other unforeseen changes in source water quality that may challenge the drinking water treatment system in place. | When considering exempting drinking water systems from filtration requirements | high |
| #Q048 | administrative | reporting | recommended | Integrated Microbiological Guidance Application | drinking water | Because of the potential relationship between turbidity levels and microorganisms, this document should be read in conjunction with all guideline technical documents on microbiological parameters. | When interpreting turbidity guidelines | high |
| #Q049 | corrective_action | operational | recommended | HBTL Exceedance Action Determination | drinking water | The actions initiated to address exceedances of the HBTL will be dependent on site-specific considerations and should be determined by the responsible authority on a case-by-case basis, taking into account local knowledge of the system's capabilities and performance. | Upon exceedance of the Health-Based Treatment Goal (HBTL) | high |
| #Q050 | operational | treatment | recommended | Groundwater General Turbidity Goal | drinking water | For systems that use groundwater that is not under the direct influence of surface water, which are considered less vulnerable to faecal contamination, turbidity should generally be below 1.0 NTU. | Applies to groundwater systems not under the direct influence of surface water | high |
| #Q051 | monitoring | operational | guideline | Groundwater Best Practice Monitoring | drinking water | Best practice for these systems includes appropriate well siting, construction and maintenance, as well as monitoring source water turbidity and ensuring that turbidity levels do not interfere with the disinfection and distribution of the water supply. | Applies as best practice for groundwater systems | high |
| #Q052 | operational | operational | guideline | Distribution System Entry Turbidity Goal | drinking water | For effective operation of the distribution system, it is good practice to ensure that water entering the distribution system has turbidity levels below 1.0 NTU. | Applies to water entering the distribution system | high |
| #Q053 | operational | treatment | recommended | Non-Pathogen Removal System Turbidity Goal | drinking water | For systems that may be filtering for reasons other than pathogen removal (e.g., removing DBP precursors, improving disinfection, or consumer acceptance) or using UV disinfection, a turbidity level of 1.0 NTU or less is recommended. | Systems filtering for reasons other than pathogen removal or using UV disinfection | high |
| #Q054 | administrative | reporting | recommended | Documentation of Source Characteristics | drinking water | Characteristics of the watershed or wellhead area (such as microbial/chemical hazards and quality fluctuations) should be well documented and maintained to inform ongoing risk management. | Applicable when considering exemptions from filtration requirements | high |
| #Q055 | administrative | reporting | recommended | Filtration Exemption Decision Basis | drinking water | The decision to exempt a waterworks from filtration requirements should be made by the appropriate authority based on site-specific considerations, including historical and ongoing monitoring data. | Applicable to surface water and GUDI systems seeking filtration exemption | high |
| #Q056 | administrative | reporting | recommended | Authority Guidance Acquisition | drinking water | Specific guidance related to the implementation of drinking water guidelines should be obtained from the appropriate drinking water authority in the affected jurisdiction. | Note regarding implementation of drinking water guidelines | high |
| #Q057 | operational | treatment | recommended | System Optimization Plan Implementation | drinking water | Developing and implementing a system optimization plan will improve filter performance and help ensure that systems are achieving the appropriate log removal credits. | As part of system optimization to meet treated water turbidity targets | high |
| #Q058 | operational | treatment | recommended | Application of Validated Improvements | drinking water | waterworks are encouraged to apply validated improvements and optimize existing systems as a matter of best practice. | As part of the multi-barrier approach and system optimization | high |