OHA Drinking Water Services
Maximum Daily Combined Filter Effluent Turbidity

The information on this page is the maximum measured turbidity from daily sampling at a point after filtration and representative of filtered water from all filters combined, prior to disinfection. This data is referred to as the maximum daily combined filter effluent (CFE) turbidity and is reported each month by public water systems treating surface water or groundwater under the direct influence of surface water sources.

Information about Turbidity
  • Turbidity is a measure of water clarity causing water to appear cloudy or muddy.
  • Particles of soil, silt, organic matter, and microbes can all contribute to turbidity.
  • High turbidity can affect water treatment and interfere with disinfection as particles can shield microbes like viruses and bacteria; therefore, turbidity is monitored as an indicator of filter performance and to help ensure effective disinfection.
  • Turbidity is measured each day of operation directly after filtration using a turbidity meter or sensor (nephelometry) and the results are reported in Nephelometric Turbidity Units (NTU). Not all filter plants need to operate every day, so gaps in daily data may exist.
To learn more about turbidity and how turbidity removal through treatment can be optimized, visit our Surface Water Treatment Resources page.

How to use this dashboard
To view the data for a particular water system, please refer to the steps below.
  • Select Water System – You can select the water system from the Water System ID dropdown menu or type in a water system ID# or name into the search bar.
  • Select Treatment Plant - You can choose to view data from all surface water treatment plants the selected water system operates or choose to view data from just one plant. Please clear this selection before choosing another water system.
  • Filter by Date - You can filter the results by entering or selecting specific dates from a calendar. The slider bar may also be used to adjust the date range. The graphs will automatically update as you change the date range.
  • Click the 'Turbidity Data page' button at the top-right to view the tabular data of the selected water system.
  • Column Graph – The upper bar graph displays the average of the combined filter effluent (CFE) turbidity data reported each month for the selected date range.
  • Line Graph – The lower line graph displays the individual data points for the selected date range with the y-axis on a logarithmic scale, which helps display a wider range of values (e.g., 0.001 – 100+ NTU). The optimized treatment goal is displayed as a thicker horizontal line at either 0.10 NTU for conventional or direct filtration, 0.05 NTU for membrane filtration, or 1 NTU for other filtration types.
  • View Statistics - The table to the right of the graphs displays statistics (e.g., min, max, etc.) related to the data available from the selected date range.
  • Determine if Goal Met - In the last 'Goal Met' box, you can select the option 'no', to see samples that have turbidity higher than the optimized treatment goal established for that type of filtration system or select 'yes' to view only values that have met the goal for the selected date range.
    • Goals are representative of optimized treatment and not regulatory limits.
    • Water systems are encouraged to optimize treatment such that 95% of the values reported in any given 12-month period meet the goal. This is referred to as the 95th Percentile shown in the statistics.
    • As shown in the statistics table, a plant with optimized performance should have a 95th percentile turbidity (NTU) less than or equal to the optimized turbidity goal.
    • Similarly, the percent of samples meeting the goal (%) is shown and an optimized plant should have 95% of results less than or equal to the goal.