pH adjustment with Soda ash (Sodium carbonate) powder
O.B Curtis plant at Jackson, Mississipi
Two identical silo upgrade completed to raise the pH of a drinking water plant
Context:
The O.B.Curtis WaterTreatment Plant of the City of Jackson,MS called on Cornerstone Engineering LLC and Sodimate Inc. to help retrofit their two (2) old soda ash silo systems used for pH regulation.
This project was a perfect opportunity for Sodimate to showcase it’s unique ability to make drastic changes to an existing installation without overhauling the complete system, something that preserves time and money for the customer.
Goal:
To adjust the pH and ensure a treatment production capacity of 50 MGD, the new process produces a finished water with pH of 9.5 with an alkalinity of about 32 mg/L.
Previous installation
Initially the O.B Curtis team was using lime for pH adjustment: The problem with lime is that it was not mixing well with the water and alkalinity was not high enough. The lime was falling out of suspension too soon in the distribution causing lead to leach into the water.
Then an incomplete retrofit was by done using existing lime slaker tanks and lime transfer pumps with soda ash and reusing the vibratory bin activators in the current identical silos. Additionally, the vibratory bin activator technology was causing overconsolidation of the soda ash powder in the cone sections. The system was also impacted by the lack of dehumidifiers on the silos.
Sodimate equipement included in the Cornerstone Engineering’s design protocol:
After Sodimate Inc. was selected as the equipment vendor in this project, Sodimate worked closely with Hemphill Construction to install two state-of-the-art systems which included the mechanical bin activators, the dehumidiers and replacement of the dust collectors on the two (2) silos. The slaker tanks were replaced with two (2) identical soda ash slurry tank at the ground level.
Instead of having the soda ash slurry pumped directly into the stream, Cornerstone Engineering LLC recommissioned the unsed 8,000 gallon bulk tank to get more soda ash storage capacity.
Sodimate supplied two (2) identical systems for two (2) silos. However, the rotary lobe pumps and controls were provided by others. The soda ash systems supplied by Sodimate are generally described below:
- Two (2) mechanical bin activator ZDM that fit on the existing cone;
- Two (2) chainwheel slide gates;
- Two (2) metering screw;
- Two (2) injectors;
- Two (2) slurry tanks (800 gal made of HDPE with mixers);
- Two (2) water supply lines with regulation valves;
- Two (2) dehumidifiers; and
- Two (2) dust collectors.
The soda ash slurry will be pumped into day tanks where the average injection flow is at 5 GPM.
Performances achieved
Sodimate designed its system for a dry injection of 1,700 lb per hour. After a total of five (5) days on site with Hemphill Construction and Cornerstone Engineering, the City of Jackson officials gave the approval to run the installation full time. Mr. Maruicka McKenzie, Sr., president of Cornerstone Engineering, said, “The system is running pretty good now. We are using an injection of dry soda ash powder at about 900 lbs per hour. The metering pumps are running at about 5 gpm.”
Cornerstone Engineering plans to further refine the system. This will be accomplished by adding a dilution water system to the metering pump feed lines to allow to run the metering pumps faster and to provide for greater pH control.
