| #Q001 | treatment | treatment | recommended | Minimum Treatment for Surface Water and GUDI | drinking water | Generally, minimum treatment of supplies derived from surface water sources or groundwater under the direct influence of surface water (GUDI) should include adequate filtration (or technologies providing an equivalent log reduction credit) and disinfection. | Applies to supplies derived from surface water sources or groundwater under the direct influence of surface water (GUDI) | high |
| #Q002 | operational | operational | recommended | Filtration System Turbidity Target | drinking water | To maximize protection of public health from microbial contamination, filtration systems should strive to achieve the turbidity target of 0.1 NTU. | Applies to filtration systems | high |
| #Q003 | design | operational | recommended | Filtration System Optimization and Design | drinking water | However, filtration systems should be designed, operated and appropriately optimized to decrease turbidity levels as low as reasonably achievable and strive to achieve a treated water turbidity target from individual filters of less than 0.1 NTU at all times. | Applies to filtration systems and individual filters | high |
| #Q004 | operational | operational | guidance | Turbidity Target Best Practice for Unfiltered Systems | drinking water | Where filtration is not required to meet pathogen removal goals, it is best practice to keep turbidity levels below 1.0 NTU to minimize the potential for interference with disinfection. | Where filtration is not required to meet pathogen removal goals | high |
| #Q005 | operational | operational | guidance | Turbidity Good Practice for Distribution System Entry | drinking water | In addition, to minimize particulate loading and effectively operate the distribution system, it is also good practice to ensure that water entering the distribution system has turbidity levels below 1.0 NTU. | Water entering the distribution system | high |