Nutrient (nitrogen and phosphorus) pollution is one of America’s most widespread, costly and challenging environmental problems, stated by The United States Environmental Protection Agency (EPA). Consequently, wastewater containing high amounts of nutrients cannot be disposed without first being treated. Current means to remove nutrients involve the use of chemicals and additional energy.

It turns out that algae is able to convert nitrogen and phosphorus from wastewater into biomass and bio-products, thus improving the sustainability of wastewater treatment. One of the new technologies used to harvest algae is revolving algal biofilm (RAB). Most of the algae biomass grows on the revolving belts and is harvested effectively. However, some algae stays in suspension in the water tank. Current technologies to separate algae from water have a large footprint and are not cost-effective due to high energy consumption and capital investment.

i2M has been asked by two water reclamation plants to conduct pilot studies with our ceramic hollow fiber filtration membranes, CERA~DUR. The objectives of these pilot studies are to capture all suspended algal cells left in the water tank, concentrate the algal biomass and deliver high quality permeate water that meet disposal requirements.

Pilot System

Our pilot system was following a Revolving Algal Biofilm system (RAB). Our pilot skid was equipped with one CERA~DUR, having a pore size of 80 nm.

The operating conditions were as follow:

  • Average flux: 150 LMH at 0.5 bar

  • Backwash frequency and duration: 20 seconds every 30 minutes


We successfully dewatered the stream to 5% concentration of algae. We delivered high quality permeate (TSS <1 ppm) water to be disposed. We improved biomass harvesting through a process that reduces energy consumption.