The Challenge: Fluctuating Influent & Strict Compliance
Groundwater at the decommissioned Allen Fossil power plant exhibited varying arsenic levels across the site, with some "hot spots" reaching concentrations as high as 5 mg/L. Over decades of operation, coal storage piles leached trace amounts of arsenic into the soil.
The objective was to prevent the expansion of this arsenic plume by creating a centralized treatment hub capable of handling a consistent 300 GPM flow, ensuring the arsenic was removed to levels well below the 1 mg/L discharge mandate.
The Engineering Solution: Precision Phys/Chem
Ecologix Environmental Systems engineered a robust, multi-stage treatment train designed for a 30-year service life.
1. Chemical Co-Precipitation & Oxidation
To transition dissolved arsenic into a filterable solid, the system utilizes an iron-based coagulant. By maintaining a precise pH setpoint (typically between 6.0 and 7.5) within the reaction tanks, the system ensures that arsenic effectively adsorbs onto ferric hydroxide flocs.
- Corrosion Resistance: The chemical reaction tanks were constructed of high-grade fiberglass (FRP). Other steel components feature specialized chemical-resistant epoxy coatings to withstand pH swings and aggressive chemistry.
2. High-Rate Clarification & Polishing (AGFM)
Following the reaction stage, an Ecologix LC-300 lamella clarifier provides rapid settling of the arsenic-laden solids.
- AGFM Technology: The system utilizes Activated Glass Filtration Media (AGFM). Unlike traditional sand filters, AGFM provides superior filtration down to 1 micron, resists fouling, and allows for more effective backwashing, significantly extending the media's operational lifespan.
3. Sludge Management & Dewatering
The iron-arsenic solids captured during clarification are managed through a dedicated solids-handling loop designed for maximum volume reduction:
- Sludge Concentration: Settled solids are moved to sludge holding tanks via dedicated sludge transfer pump skids located beneath the equipment platform.
- Filter Press System: The heart of the dewatering process is a 30 ft3 filter press equipped with a semi-auto plate shifter.
- Integrated Infrastructure: The press is mounted on a galvanized steel platform featuring custom mezzanine and stairway access, allowing operators to safely manage the dewatering process from an elevated vantage point.
- Disposal Logistics: The dried sludge cake drops directly from the press into a 20 yd3 roll-away container. This container is removed via flatbed truck for disposal on a bi-weekly basis, ensuring a clean and continuous operation.
4. Advanced Automation & Integration
The entire plant is controlled by an Allen-Bradley CompactLogix PLC.
- Connectivity: Fully integrated into the plant’s broader SCADA system for site-wide data logging.
- Operator Interface: A local HMI touchscreen provides real-time diagnostics, while remote monitoring allows for off-site oversight and rapid troubleshooting.
Resilience & Performance
Despite global disruptions caused by the COVID-19 pandemic, the project resumed in 2022 and was fully operational by early 2023. The system currently delivers an average effluent quality of less than 0.25 mg/L, consistently outperforming the project's design criteria.
Custom Turn-Key Solutions from Ecologix
The TVA Allen Fossil Groundwater Remediation project highlights our ability to manage complex environmental remediation from "cradle to grave." Whether you are dealing with heavy metal contamination or high-strength industrial wastewater, Ecologix Environmental Systems provides the engineering, fabrication, and programming expertise to solve your toughest challenges.
"The TVA Allen Fossil project highlights our ability to manage complex environmental remediation from cradle to grave."
Request a QuoteRelated Products
Activated Glass Filtration Media
Activated Glass Filtration Media replaces traditional sand media in all filtration applications.
Clarifiers (Incline Plate and Tube)
Ecologix clarifiers are designed for minimal footprint and rapid particle settling.