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Rotating Biological Contactors (RBCs) treat wastewater by utilizing bundles of plastic media sheets covered with biological organisms. These bundles rotate continuously while being 40 percent submerged in a wastewater tank. The problem is that RBCs can have the cumulative effect of a very large humidifier, raising building humidity levels to above 80% due to the high moisture and corrosive gases they stir up. RBCs are often installed with little regard to heating, ventilation and air conditioning (HVAC) requirements, which can lead to failure of these systems. Even when properly designed, HVAC systems often fail from the high humidity and corrosive gases. We provide a simple, cost effective approach that can be retrofitted to existing RBCs. It’s a solution designed to address the problem head on.

Uncovered RBC’s in an enclosed environment result in significant heating bills due to building operators keeping interior temperatures above the Dew Point to prevent condensation. They also can generate toxic gases such as hydrogen sulfide and odors resulting in:

  • Significant condensation on walls, and ceilings, often dripping off surfaces depending on time of the year

  • Severe corrosion of equipment such as motors, bearings, and electrical components

  • Mold on walls & ceilings

  • Mold spores within the enclosed environment that workers breath on a daily basis

  • Rot of wooden structures such as roof trusses or walls

  • Paint peeling and deterioration of walls

  • Darkening of pipes such as brass and iron due to hydrogen sulfide

  • Significant corrosion to any ferric items such as steel trusses

  • Odors

If not addressed, these problems lead to costly repairs, unhealthy working environment, and poor aesthetics. Bearings and motors routinely exposed to high humidity and corrosive gases will fail more frequently leading to more costly repairs and poor performance. Wooden structures that are not protected can eventually rot to the point that complete replacement such as roof structures and building walls is required.


A custom designed cover that encloses the RBC to contain moisture, odors and harmful gases before venting them outside of the building. Key components include a frame made entirely of heavy wall 304 stainless steel tubing; a heavy duty clear vinyl cover that allows for continued visibility of the RBC, and can be removed easily for maintenance; and an exhaust system that keeps the cover under constant negative pressure, preventing moisture, gases, and odor’s from ever entering the building atmosphere.

Our RBC covers have the following key features: 

  • Made entirely of 304 stainless steel and covered with removable heavy gauge vinyl material 

  • The cover is custom designed to meet the specific requirements of the RBC installation 

  • Components are made to be assembled in the field. All components fit through a standard 3’ door frame 

  • Designed to keep RBC bearings, gearbox, and motor outside of the RBC environment, decreasing costly maintenance issues 

  • Cover can be removed with little effort to perform maintenance 

  • Custom features can be added, such as access ports for chemical addition, instrumentation, etc. 

  • No heavy equipment such as cranes needed for installation; the heaviest individual component weighs less then 100 lbs. 

  • Stainless steel drip trays included to contain splashing generated by rotating media bundles. 

  • Unlike other cover systems, our system redirects the moisture and water to the interior tank.  Other systems still allow the water on the upper lip of the tank causing significant corrosion

  • The resulting low humidity level within the building reduces winter heating demand and summer ventilation requirements resulting in substantially lower heating costs

Contact us about having custom covers made up for your facility

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