biofilter

A biofilter is a treatment system that uses a biologically active medium to remove pollutants from air or water through microbial degradation. The core concept relies on a porous substrate that supports a biofilm of bacteria, fungi, and other microorganisms. As contaminants diffuse into the biofilm, they are metabolized, often producing carbon dioxide, water, and inorganic salts as end products.

There are several configurations oriented to different applications. Air biofilters treat odorous compounds and volatile organic compounds emerging from industrial processes, waste facilities, or agricultural operations. Air passes through a packed or loose media bed where microorganisms break down contaminants. Water or wastewater biofilters include packed-bed reactors, trickling filters, rotating biological contactors, and constructed wetlands; these systems provide surfaces for microbial growth and aeration, promoting the oxidation of organic matter and nutrients.

Applications span environmental engineering and ecological management. In industrial and municipal settings, biofilters improve indoor air quality and treat emissions. In wastewater treatment, biofilters reduce biochemical oxygen demand, ammonia, and nutrients. In aquaculture and horticulture, biofilters manage nitrogenous wastes by converting ammonia to nitrite and nitrate, often in conjunction with plants or other filtration stages.

Design considerations include media type and surface area, moisture content, nutrient availability, temperature, pH, and residence time. Performance is influenced by loading rate, odor and contaminant composition, and the stability of the microbial community. Maintenance involves monitoring removal efficiency, preventing clogging, replenishing or replacing media, and ensuring appropriate moisture and aeration. Biofilters offer relatively low energy use and chemical requirements, but require careful management to avoid collapse of the microbial film or odor breakthroughs.