Replacing sludge lagoons with decanter centrifuges to reduce disposal costs and restore operational control at a dual-facility water system in North Carolina.
Industry: Municipal Wastewater & Water Treatment
Location: Harnett County, NC
Application: Sludge Dewatering — Lagoon & Alum Sludge
Equipment: (2) CS26-4 Decenter Centrifuge Systems
Scope: New Installation Replacing Sludge Lagoons
Installed: April 2020
- $80,000/MG sludge disposal cost
- 2–3% TS incoming sludge — both facilities
- No operational flexibility with lagoon-only approach
- Dependent on hauler availability for sludge removal Limited control over a critical plant process
THE CHALLENGE
Harnett County operates two facilities: a 42 MGD Water Treatment Plant (WTP) producing alum sludge and a 16 MGD Wastewater Treatment Plant (WWTP) handling lagoon sludge. For years, both facilities relied on sludge lagoons as their primary management method — but the operational and financial consequences were mounting.
Disposal costs had reached $80,000 per million gallons of sludge, with no relief in sight. More pressing was the lack of operational flexibility: the county depended entirely on the availability and willingness of hauling contractors to remove sludge. When haulers were unavailable or capacity was tight, the facility had no alternative — leaving operators with little control over a critical process.
THE SOLUTION
Rather than defaulting to the nearest equipment supplier, Harnett County’s operations team took a deliberate approach. They traveled to Centrisys/CNP headquarters in Kenosha, WI to evaluate the manufacturer directly — touring the facility, reviewing centrifuge systems in operation, and assessing the company’s ability to provide service and support across the full lifecycle of the equipment.
What they found was a manufacturer that understood their specific application: processing both lagoon sludge from a WWTP and alum sludge from a WTP, each with its own feed characteristics, required a centrifuge system with proven versatility and a service team capable of supporting both. Two Centrisys decanter centrifuges were installed in April 2020 — one at each facility — each sized for approximately 225 gpm feed capacity. The facilities typically run 8–9 hours per day, five days a week, processing sludge on a predictable, operator-controlled schedule.
THE RESULTS
- WWTP: Processed 73+ MG of lagoon sludge
- Feed: 2–3% TS in g 25–26% cake out
- Feed: 1–2% TS in g 24–25% cake out
- Schedule: 8–9 hrs/day, 5 days/week — fully operator controlled
- Service: Annual Centrisys inspection under service contract
- ROI: The facility paid for itself within 2.5 to 3 years due to the savings in disposal costs and the savings continue into the future.