Automated closed-loop ROV cleaning for dairy digester
Customer
2.1 million gallon anaerobic digester located in western New York, USA
Problem
The customer had newly built and commissioned the digester one year ago. They wanted to develop a tank preventive maintenance program to optimize the digester, ensure a consistent revenue stream, and avoid a lengthy shutdown and cleanout. The amount of solids removed during Submersible Robot Cleaning System operations would allow them to develop a tailored PM program for the digester going forward.
Potential Costs
Traditional cleanout costs were estimated at $200,000. The RNG lost revenue the customer would have incurred during a 30-day traditional cleaning project and an additional 20 days of digester recommissioning was estimated at $550,000. In total, this process would cost the customer around $775,000.
Solution
Bristola proposed using the 24-inch submersible ROV, entry portal box and sediment separation trailer to remove and dewater the accumulated solids, sand and grit. The cleaning timeline was based on expected sediment accumulation and the customer’s budget. The agreed-upon timeline was 10 days.
Execution
The submersible ROV was deployed through a 24-inch knife gate valve attached via the manway on the tank. The digestate was pumped to the sediment separation trailer. The system removed an average of 112 cubic yards per day (eight-hour workday) and processed an average of 213,000 gallons per day.
Project Costs
The project cost was $118,000 for operating the SRCS on-site for 10 days. The costs of mobilizing pumps, the control station, the dewatering trailer, generators, staff and other ancillary equipment totaled $25,000. The total cost of the project was $143,000.
Summation
Bristola’s SRCS was a great solution for the customer, as it removed accumulated solids without incurring downtime costs, sending staff into a confined space or requiring recommissioning of the digester. The customer saved $632,000 by using the SRCS.
