From the Clouds to the Tap: Part 3

Last month we discussed how increasingly strict standards for water quality led to the need to build a water treatment plant.

Because this would be extremely expensive for a very small system (as Draper Irrigation was in the early 60s), the company considered many ways to avoid building a plant. One approach would have been to sue the federal government for the right not to treat the water at all. Some very large water systems – such as the ones serving New York City and parts of California – do not treat their water; they simply make their watersheds off-limits to people, then chlorinate the water. However, the company decided not to pursue this option.

In 1970, the company received a loan for $577,000 from the Farmers’ Home Loan Administration and began construction at our site on Wasatch Boulevard, in what was then an unincorporated area high above Draper (it is now part of Sandy, and is above the Hidden Valley Golf Course).

The plant, completed in July 1971, used a flocculation and sedimentation process, which was state-of-the-art at the time. The plant was designed to treat 3.3 million gallons per day (MGD) using these steps:

  • Flash mix: Add the chemicals that will be used in the process.
  • Flocculation: Chemicals attach to impurities in the water and create flocs, which look somewhat like snowflakes.
  • Sedimentation: Water is put into a basin, where the flocs (which contain the impurities) settle to the bottom.
  • Filtration.
  • Chlorination.

This system was satisfactory for many years, but regulations for water quality continued to become more stringent. By the early 1990s, it became obvious that the existing treatment plant would need updating in order to meet the stricter water quality standards that would go into effect in 2002. In addition, with the ongoing growth in Draper, the company planned to double the capacity of the treatment plant.

The company investigated different membrane technologies for ultrafiltration of the water, and chose the Zeeweed® membranes offered by ZENON Corporation, now a part of GE Water and Process Technologies.

The updated treatment plant, which went into operation in April 2004, has the same footprint as the original 1971 plant, but can now process 6.6 MGD, more than twice the capacity of the old plant. Using the same technology in the same space, it would be possible to increase capacity further to over 9 MGD.

Even more importantly, the water that comes out of the revamped treatment plant is ten times cleaner than the water treated with the old flocculation and sedimentation method.

The new ultrafiltration processing requires much more electricity than the old method of treatment, so the company installed a hydroelectric generator at the same time. This generator provides much of the electricity needed to power the treatment plant.