More Steps Needed to Protect our Watershed from Salt

The Potomac River and Occoquan Reservoir are becoming saltier and this is a problem for the drinking water supply of Northern Virginia. Analyses from three different studies at multiple locations have found increasing freshwater salinization in Northern Virginia and the Occoquan Reservoir. Regionally, as salt levels have risen, WSSC is seeing discolored water problems related to winter deicing when chloride levels were observed to spike from 40mg/L to 100 mg/L. Increasing chloride levels is from rising sea levels, increased direct and indirect potable reuse of wastewater, the increased amount of pavement and the salting of roads in the winter. Nearly all road salt is eventually washed into adjacent rivers, streams, and groundwater aquifers - road salt is considered the largest contributor to rising salt levels.  

Road salt impacts not only potability of water, but also impact drinking water infrastructure in terms of lifetime and leaks. Water contamination is an emerging and increasing problem for both private well owners and municipal water suppliers. Salt, sodium chloride, spikes have caused changes in water chemistry triggering the lead in solder to be released into the water. Chloride is an aggressive ion that exacerbates corrosion, especially galvanic corrosion in hot water heaters and at soder points where pipes are joined.

Chloride levels are rising nationally in freshwater sources, not just here. We increasingly need to reuse water as we do with the Occoquan Reservoir to meet water demand and with increased population pavement and road building increases and the use of road salt for de-icing also increased especially in the northeast.  Road salt is applied to de-ice roads in the winter for highway safety, with more than 18 million metric tons applied annually and most used in northeastern and midwestern states to ensure public safety. The more paved roads we build, the more salt is used in the winter.

The ICPRB, the Virginia Department of Environmental Quality (VDEQ) and the Northern Virginia Regional Commission have joined together to develop a voluntary Salt Management Strategy published in 2020 to reduce the largest source of salt/ chloride to the Potomac, its tributaries and the Occoquan Watershed, but this alone may not slow the increasing salinization of our source water for drinking as road construction continues at an alarming pace. As we try to encourage the adoption of the voluntary salt management strategy, we keep building roads and paving over the county.

Sodium and chloride the elements that make up salt and break apart in water are washed off road by rain and melting snow and flow into local waterways or seep through soils into groundwater systems with negative impacts on water quality and the environment. Salts pollute drinking water sources and are very costly to remove. The only available technology to remove salt from the source water is reverse osmosis which could cost Fairfax Water alone $1-2 billion to install and requires a significant amount of energy to run.  

We need to do more. There are significant other sources of salt in our watershed. A very obvious one is self-regenerating salt-based water softeners used both in homes and for industries like data centers that use vast amounts of water for cooling. In days past, at the first sign of hard water or often other issues, a salt based conventional water softening system was installed.  Water softening is basically an ion exchange system. The water softening system consists of a mineral tank and a brine (salt) tank. Eventually the surfaces of the beads in the mineral tank become coated with the calcium and magnesium. To clean the beads, a strong salt solution held in the brine tank is flushed through the mineral tank. Sodium chloride is typically used. The excess sodium solution carrying the calcium and magnesium is flushed to the septic system or waste water system and into the environment or Occoquan Reservoir. Some sodium ions remain in the tank attached to the surfaces of the beads and the resin is now regenerated and ready to continue softening the water.

The amount of sodium in water conditioning systems is a real problem for humans and the environment. All of the salt is released into the septic system or wastewater system that does not remove salt. Ultimately, the sodium chloride solution reaches the leach field and groundwater or pass throught the wastewater treatment system and are released to the surface water. Conventional salt-based water softening systems contribute to three problems:
The brine backwash can cause salt buildup in groundwater and other aquatic environments. Water softeners release sodium chloride and other chloride salts into the environment. This can adversely affect groundwater aquifers, streams and rivers. This can add to problems in areas that are already suffering from high concentrations of salts due to road salt application.

Brine backwash in the conventional septic tank had interfered with the digestion of the cellulose fibers and reduced scum layer development, carryover of solids and grease to the distribution system. The brine back wash system uses water to flush itself out regularly. The EPA estimates in that a conventional softener can use up to 10,000 gallons per year for the backwash cycle. 

At this time California, Michigan, Connecticut, Arizona, Massachusetts, and Texas have laws or regulations that limit the use or outright ban traditional salt based water softeners. Personally, I am not a fan of traditional water softeners. I do not care to add all that sodium to my diet. If you are on public water, you should not need to soften your water.