R.F. MacDonald Co. provides turnkey solution and permanent pump system for moving slurry pond water in green waste decomposition process
In Northern CA, a solid waste site creates an organic compost product by using green waste collected from curbside bins that have been ground to ≤1.5-inch pieces using the Covered Aerated Static Pile (CASP) process for decomposition and pathogen reduction. Liquid management is critical to the process and involves water in contact with green waste in a closed-loop system.
The CASP process encourages organic decomposition and requires an initial addition of water containing common bacteria and fungi. First, contact water is sprayed to inoculate the freshly ground material, which kick-starts the decomposition process.
Excess contact water, not absorbed by the material, is then captured, and allowed to flow back to the contact water pond where it is stored. Finally, the contact water is pumped back to the CASP located at an elevation of 80-feet above the pond to repeat the process.
The R.F. MacDonald Co. Analysis & Solution
The solid waste site had been using rental diesel pumps, which utilized prime assist with foot valves, but large amounts of fine organic solids caused the foot valves to clog and fail. The foot valves were necessary to keep the suction lines flooded during shutdown.
Additionally, the lack of circulation allowed the pond water to become stagnant, producing unwanted odors for the surrounding community.
After excessive pump maintenance and downtime, the pumps were deemed too expensive and unreliable. An economic and permanent solution was required with the desire to use the site’s self-generated electrical power.
Based on a history of success with the customer, R.F. MacDonald Co. was asked to develop a permanent, turnkey pumping solution with full system reliability.
• Piping: Experienced technicians installed 280 feet of 4-inch high-density polyethylene pipe (HDPE).
• Electrical: Controls experts replaced the existing VFD with new control panel on a newly poured concrete pad.
• Fabrication: Skilled pump experts designed and built custom pump stands to easily move the pumps and withstand a corrosive environment.
R.F. MacDonald Co. provided three heavy duty pumps sourced from Toyo-Hevvy. The transfer process uses two pumps as part of a multi-stage design to move the pond water, a light-slurry, uphill to the CASP. The third pump provides circulation within the contact water pond.
One Toyo-Hevvy HNS submersible pump generates 600 GPM at 127 feet of TDH to boost the light-slurry pond water 22 feet uphill to the booster pump. Submersible lift pumps eliminate the challenge of keeping the suction lines flooded and generate ample suction.
The Toyo-Hevvy HNH booster pump generates an additional 127 feet of TDH, pumping over another hill to the CASP green waste pile.
The third pump is a circulation pump, which discharges through 280 feet of HDPE in the shape of a giant T with nozzles located at the ends. This helps evenly circulate the product throughout the pond, which has greatly reduced the amount of odor.
Both booster and circulation applications have worked reliably since startup in December 2020.
R.F. MacDonald Co. is proud to offer reliable pumping solutions for the recycling and green waste decomposition process. Contact us for your liquid handling needs.