Limit Water Age and Improve Water Quality through Modeling, Monitoring and Optimization
- Jeremy Hise, Meric Selbes - Hazen and Sawyer
- Darrin Geldert - Loudoun Water
Water quality concerns, specifically nitrification, have been an increasing issue for water systems across the country and in our own backyard. It is very difficult to predict or model exactly when or where water quality will be degraded to the degree that remedial action is required. Water quality models in a large water system require intensive efforts to accurately model complex reaction schemes between multiple chemical and biological species in both the bulk flow and at the pipe wall. These water quality models must characterize the chemical process across the different areas of the system, accounting for temperature, pipe age and materials, possible sediment and initial water quality. This is all in addition to needing a highly accurate hydraulic model, and beyond the budget of most utilities including ours.
Using water age as a surrogate for water quality provides an expedient method for reviewing areas of water quality concerns and can identify hydraulic surprises. The primary hydraulic modeling software platforms all include water age calculations and can be visualized through “heat” maps or data tables. In addition, source tracing can be used to visualize the hydraulics as water ages in the system.
Storage tanks are often the primary focus of a water age analysis and in particular un-mixed tanks can truly be water quality nightmares, but most systems have far more storage underground in their piping network. This underground volume can mask efforts to create turnover in tanks creating a sloshing of water that is never consumed and transfers back and forth in the water system from storage tank to “storage” pipe. Additionally, boundary areas between pressure zones can alter water movement in unexpected ways. The addition of low age, “fresh” water to one portion of the pressure zone may improve water locally but actually be detrimental to the overall system. Optimization of water age in our system will be presented with model results and real world confirmation of predicted outcomes.
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