Waste water treatment

The application of biofilm technology in wastewater treatment originated from the industrial operation of trickling filters in the early 1880s in Wales, Great Britain.

Modern biofilm processes in wastewater treatment can be divided into two categories:

(1) The fixed-medium systems where the biofilm media are static in the reactors and the biological reactions take place in the biofilm developed on the static media, and

(2) The moving-medium systems where the biofilm media are kept continually moving by means of mechanical, hydraulic, or air forces.

The moving-medium systems include rotating biological contactors, moving-bed biofilm reactors, vertically moving biofilm reactors, and fluidized bed biofilm reactors; while the fixed-medium systems include trickling filters and biological aerated filters. Rotating biological contactors (RBC) have been widely used in biological treatment of wastewater for reducing chemical oxygen demand (COD)/biological oxygen demand (BOD) and nitrification/denitrification purposes. Rotating biological contactors treat wastewater streams using a thin biofilm of aerobic microorganisms on rotating cylinders or biodiscs. The rate of rotation is selected to provide optimum contact of the waste stream with the biofilm for efficient oxygen transfer and bioactivity.

One newer method is to develop a complex biofilm, made of many different groups of bacteria working together symbiotically, using recycled plastic media as a support, as shown in the images on this page. The biofilm feeds off wastewater pollutants, leading to the removal of organic carbon and ammonia.