Data Collection and Management

Master meters should be installed before and after the water treatment facility to measure the amount of raw water coming into treatment from the raw water supply source and the amount of treated water entering the water distribution system.  Master metering can also be performed at the wellhead of all groundwater production wells (which is a requirement of the state of Colorado) and summed, however, the accuracy of this approach may be compromised if the production well meter readings are not collected within a short time of one another (example, within one hour of each other).  Daily master meter readings are suggested to maintain a high degree of system monitoring (which can include identifying leaks and/or unauthorized uses).

For water systems that only have chemical addition for treatment (e.g., chlorination of groundwater), a single master meter should suffice.  For small and large water utilities with water treatment that may include treatment for removal of metals, salts, organic materials, or other physical/chemical processes, master metering on the treatment plant effluent is strongly recommended.  This recommendation stems from the expectation that some amount of water use and/or water loss will occur during the treatment process.  This loss or use must be accounted for and measured before the treated water is placed into distribution.

Master meters are sized for the transmission pipe and volume of water flow fluctuations expected over a specific period (e.g., over a 2-year life cycle).  It is important to test and maintain master meters on a 6-month to one year basis to monitor the accuracy of the meters and the need for meter repair and/or replacement.

There are a number of typical water uses related to water production and treatment facilities that a water utility should attempt to measure as part of the overall system wide monitoring process.  Often, these production and treatment facility uses are unmetered, such that only educated guesses can be made to estimate volumes and flows.  The more accurately these volumes can be measured, the more accurate estimates can be prepared for non-revenue water and real water loss.

Filter backwash – Many local water treatment facilities utilize pressurized filter beds to remove flocculent and sediments prior to distribution.  Backwashing of these filters is a standard practice, which may occur daily during high water use periods.  Many utilities pump the filter backwash to evaporation pits or other locations where the water does not return to the water system.  These flows are often unmetered.

Reverse osmosis reject – Some local water providers utilize reverse osmosis to treat raw water before it is placed in distribution.  Reverse osmosis uses high pressures to pass raw water through permeable membranes that separate the finished water from the waste stream (i.e., reject) that contains high mineral and salt content.  The reject is often piped to the wastewater treatment facility to be treated and discharged.  The reject water should be, but is not always, metered.

Other water treatment plant uses (shop, turf irrigation, etc.) –other water treatment plant uses such as water use in the shop or for outdoor irrigation may not be metered.  This may be occur if the water taps for the treatment facility is placed before the master meter or if there is no master meter in place.  These types of unmetered uses should be tracked and measured to the extent practical.

Water storage overflow – some water utilities maintain water storage tanks in close proximity to their water production and/or treatment facilities, and may therefore place master meters after the storage facility.  This practice may be effective; however it does not allow tracking of storage facility leaks and/or overflows.  Therefore, it is suggested that master metering be conducted prior to and after storage facilities to eliminate unmetered water use or water loss associated with the storage facility.

Alternative Water Supplies – some water utilities leverage alternative water supplies to support utility water demands.  It is imperative that utilities that utilize alternative water supplies meter all of the import water, including those used for both potable and non-potable uses.

The water utility should track costs related to water production and treatment on a monthly and annual basis as well as on a per unit of water delivered.  The types of data that should be tracked are presented in the in the System Management BMP on data collection and management. Costs should include, but not be limited to, personnel (labor and overhead costs), energy, chemicals, equipment upgrades and maintenance, monitoring (sampling and laboratory costs), reporting and debt service (when appropriate).

The water utility should maintain maps and drawings of their water supply system.  the maps should include source water location(s), transmission piping, and treatment facilities, including storage facilities, prior to distribution piping (which should also be maintained as discussed in the Water Distribution System BMP on data collection and management).  Key to these maps and drawings is the location and size of treatment equipment, master meters, sampling points, and pipe (by size, material and age) to the extent practical.

It is desirable to develop and maintain maps in electronic format to the extent practical, such that updates can be readily made, and information regarding the data collection can be maintained along with the maps and database.  Having the infrastructure information maintained electronically also helps facilitate sharing the data for reporting, grant and loan applications, and other purposes.