Density Currents are a Fact of Life

Studies by EPA and others show that density currents form in all activated sludge secondary clarifiers, regardless of size and shape, and have a significant, adverse effect on clarifier performance. These currents form when the denser influent cascades to the bottom of the tank, creating relatively high velocity, jet-like disturbances. These disturbances, or density currents, move in a horizontal plane just above the blanket, picking up the lighter solids and short-circuiting the main clarification volume of the tank. They then travel up the tank walls, transporting these lighter solids to the effluent. The net effect is a significant increase in TSS and a dramatic reduction in retention time.

The NEFCO Stamford Density Current Baffle System is specifically designed to intercept and dissipate these currents and redirect their flow back into the main clarification volume of the tank, increasing hydraulic capacity and producing as much as a fifty percent reduction in total suspended solids. The NEFCO Baffle has been called "...the most cost-effective improvement in clarifier performance available today."

The NEFCO® Density Current Baffle System

NEFCO's patented* Density Current Baffle System is designed for optimum performance, ease of installation and years of trouble free operation. Each baffle is specifically sized and configured to the requirements of the target clarifier. The baffle is curved to match the curvature of the tank, and its specific dimensions, deflection angle and location within the tank are engineered to eliminate short-circuiting and reduce effluent solids.

The Density Current Baffle is comprised of individual baffle sections or "modules." Each module combines the baffle panel, the baffle bracket, the vents and the mounting and stiffening flanges in a one-piece molded fiberglass unit eight feet long that offers a number of advantages:

1. The one-piece, modular design minimizes the number of brackets required. Most other baffles require two brackets per panel.
2. The integrally molded bracket and other reinforcements are designed to ensure that the baffle can withstand the full buoyancy force in the tank. Some other baffles are designed to cantilever from the tank wall without benefit of support brackets.
3. The vents are molded into the baffle's horizontal mounting flange. In other baffles, the vents are holes cut in the laminate and sealed - a secondary operation that creates the possibility of water intrusion and de-lamination.

The baffle modules are attached to the tank wall or the corner of the inboard launder with stainless steel anchors. Mounting holes are factory drilled and sealed. Adjacent modules fasten together at a molded recess that forms a ship-lapped joint. Sections of the baffle may be cut as required to fit around piping and other obstructions. The baffle's laminate features a tough, corrosion-resistant and uv-suppressed fiberglass resin specifically formulated for use in industrial and municipal waste treatment applications.

The NEFCO Density Current Baffle System is used in both new and retrofit applications. The baffle eliminates the problems caused by density currents and short-circuiting, and aids in bringing plants into compliance with permit requirements. At the same time, the baffle can improve the cost-effectiveness of a compliant facility by increasing its hydraulic capacity while maintaining the quality of its effluent.

*NEFCO's modular design is covered by US Patents 5,252,205 and 5,597,483 and Canadian Patent 2100380. This design is also patented in Japan and throughout the EU.