BNP Engineering News-Record Architectural Record

Packaged Wastewater Treatment through Algae-Based Technology

September 2010
Sponsored by Oldcastle Precast Inc.

By Jackson Bishop; Christopher Limcaco, P.E.

Continuing Education

Use the following learning objectives to focus your study while reading this month’s Continuing Education article.

Learning Objectives - After reading this article, you will be able to:

  1. Define algae-based RAC technology.
  2. Explain algae's role in CO2 levels.
  3. Describe the green virtues, including energy efficiency and reclaimed water reuse, of algae.
  4. Summarize the connection between algae and bacteria.
  5. Discuss algae biomass production, package plant treatment and algae-based biofuels.

Credits: 1.00 HSW

This test is no longer available for credit

This course also qualifies for Professional Development Hours (PDH): Submit certificate of completion for PDH credit to your state licensing board. Check your state licensing board for all laws, rules, regulations and continuing education requirements.


The popularity of algae and its use in everything from food supplements and fuel sources, to filters and fertilizers, seems to be growing like...well, like algae on a sunny day. One algae-based application that is getting a lot of green attention is the packaged treatment of wastewater utilizing RAC's, or Rotating Algal Contactors.

RAC technology employs a series of rotating photosynthetic algal contactor wheels which were designed specifically to grow large amounts of algae. The resulting process is not only a very environmentally friendly method for treating wastewater in packaged systems, it also minimizes the amount of toxic chemicals used in the process, reduces nitrogen and phosphorous, and significantly improves energy efficiency and solids handling.

How it Works

The RAC technology was initially developed for use as an aquatic life support system in mariculture and aquaculture systems. The secret to the success of the algae-based RAC technology is that each wheel provides the proper environment for algal growth. Wave surging and light pulsing are basic environmental conditions required for algae growth and these are provided through the unique system design. The wheels are designed to be significantly buoyant in water, and unlike other rotating wheel systems, require no mechanical drive mechanism as the wheels are rotated using a constant air flow. The wheels are supported in water using a modular plastic grid system. The wheels and all components are made of UV stabilized reprocessed plastics, are lightweight, modular, easily assembled in the field, and corrosion proof.

RAC-Rotating Algal Contactor Wheel Process

Illustration: Jackson Bishop/Elizabeth LaFrance


Originally published in the Sept 27, 2010 issue of Engineering News-Record
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