Just how big of an impact can one or two float switches have? According to reports, a combination of a power outage and failing float switches at Seattle’s West Point Treatment Plant caused millions of gallons of raw sewage and untreated runoff to end up in the United States’ second-largest estuary. The plant, the largest in Washington State, is in the process of cleaning it up and figuring out what went wrong.
On February 9th, the plant experienced electrical failure, which created a large-scale flood. The high levels of water damaged the facility’s network of pumps, motors, and electric panels. Causing dirty, untreated water to end up in Puget Sound were two sets of pipes, which ordinarily discharge wastewater, and float switches, designed to detect high water levels in the tanks. As a result, water flooded nearby areas, and crews had to have the flow bypass the plant and go into the sound.
Since that point, the plant’s been at 50-percent operation, and its process – one in which water is first screened to remove the trash, debris, and some solids and then disinfected and dechlorinated – has been disrupted, removing the second step. This part, in which organisms clean the waste, is essential to meet federal clean-water laws.
The plant, in the meantime, may likely face fines for violating these laws and could have its clean-water permit revoked until it’s fully functional. As well, the sewage, which has amounted to 30 million gallons so far, has had a ripple effect on both marine life and public health, as the sound’s located right next to Seattle’s largest public park.
To recover, the plant has been making repairs, had independent investigators assess the facility, and is putting water-quality monitoring measures in place.
The Importance of Liquid Level Sensors for the Wastewater Industry
While the float switch isn’t solely to blame, these devices play a key role in wastewater treatment, from alarms and leak detection to a sump pump and wet well monitoring to the storage, chemical mixing, and screening control. Avoiding a severe mishap like this can come down to monitoring your switch’s performance and making necessary replacements.
Depending upon what you use the float switch for, your facility could need:
- An Ultrasonic Liquid Level Sensor, a non-contact solution that uses sound pulses and measures the time the pulses take to return.
- Submersible Pressure Level Sensors, which measure hydrostatic pressure and offer continuous measurement from the bottom of a tank or similarly large and deep vessel.
- Optical Liquid Level Sensors, which offer point-level sensing for non-traditional applications and harsh environments. These stainless steel devices have no moving parts and detect fluid via infrared light.