Roseville operates two large regional wastewater treatment facilities. Every day these plants process up to 30 million gallons of water daily to remove the waste from the water before putting it back into the environment.
We conduct routine rehabilitation and maintenance projects all of the time—anything from changing out switches, sensors, repairing pipes, rebuilding valves and rebuilding power transmission equipment. It is all in a day’s work for the many maintenance workers at our plants.
There are times, however, where we need to conduct larger scope projects that require sharp tack planning and execution, especially for a plant where you cannot simply just shut down.
30-year-old flow meter installed
This summer our Environmental Utilities (EU) maintenance staff replaced a 48” effluent flow meter because of its age at our Dry Creek Wastewater Treatment Plant.
For 30 years, the old flow meter ensured that the amount of water coming from the plant complied with state and federal environmental policies. We needed to replace it for better reliability and accuracy.
What is a flow meter? The flow meter (dark blue in the photo) gives us data to ensure we are within treatment plant compliance and reads the amount of water leaving our plant once treated.
Treatment plants must have access to reliable measurement technology so that they can accurately measure the flow of wastewater through their pipes.
To give some perspective, during the summer months, our Dry Creek plant discharges approximately 11.4 million gallons per day.
As part of the replacement, staff temporarily diverted partially treated wastewater into a storage basin. The flow meter installation took seven hours to complete. To minimize plant disruption, staff performed during low flows, from 3 to 10 a.m. Preparation included detailed job planning, materials procurement, spacer fabrication and collaboration with operations group to ensure all was set to complete the replacement in a safe and efficient manner.
Rehabbing an important treatment process
The process of treating wastewater occurs in several stages. One of the treatment processes uses clarifiers – large diameter, one million gallon tanks (like the picture below), and one of the most vital stages for treatment. While performing summer maintenance activities, EU’s maintenance crew determined that one of the clarifiers was exhibiting signs of excessive corrosion.
What do clarifiers do? When water reaches clarifiers, the speed of partially treated wastewater is reduced to allow settling. Microorganism colonies, stuffed from feasting on the organic material in prior treatment processes, settle to the bottom and are collected with rakes.
While lighter materials, including grease, oils, plastics and soap, float to the top and are skimmed off the surface. Following the clarifiers, the water is filtered and disinfected before it gets discharged to the environment or used for irrigation.
The work involved developing a plan, designing and fabricating new rake arms by internal staff, and making improvements to increase the structural rigidity and safety of personnel while entering the permit required confined space. Additionally, maintenance staff cleaned, white blasted, and epoxy coated all new material to increase its life expectancy.
Project maintains treatment reliability
Material cost for both projects in total was $46,500. All work was performed by internal resources so there was no additional labor cost.
Both projects are needed to ensure our wastewater treatment process remains reliable.