What’s Trending: Biological Filtration
Biological filtration (biofiltration) for municipal drinking water continues to gain popularity in the marketplace, as it has become an economical and innovative option for treating ammonia and other related contaminants. Through the biological filtration process, ammonia is oxidized, first to nitrite, then immediately to nitrate, which prevents undesired reactions during chemical disinfection. Iron and manganese are often present, in conjunction with ammonia, and can be removed coincidentally during the filtration process. Since chemicals are not required for oxidation, as in most water treatment processes, the operational cost of treatment is minimal. While significantly lowering chemical consumption through this method, backwash frequency can also be reduced.
Biofiltration is applied by controlling air or pure oxygen introduced into a raw water stream prior to filtration. The oxygen source feeds aerobic bacteria that, in turn, oxidizes iron and manganese, treating the water through a biological process and creates an ideal environment for biological growth. During the biological treatment process, ammonia is converted to nitrate with any solids limited to Extracellular Polymeric Substances (EPS) associated with biological growth. Most conventional treatment plants use chlorine or permanganate during the pre-treatment process to oxidize iron, manganese, ammonia and other contaminants. The biological filtration process can reduce or eliminate the need for additional chemicals for final treatment.
Many municipalities encounter ammonia in their water, often found in groundwater aquifers. Reacting with chlorine disinfectants and increasing disinfection doses, ammonia can also create objectionable off-taste and odors. The presence of ammonia is often known to accelerate corrosion of residential, commercial and industrial copper plumbing and cooling systems, raising copper concentrations to undesirable levels for both drinking and discharge into the environment.
Biofiltration processes consists of self-contained pressure filters that can treat water from the well all the way to elevated storage without breaking pressure. Dependent on the levels of iron, manganese and ammonia present, one or more steps of biological treatment may be needed. Biological activity differs within the process chain with respect to the contaminants available, specific acclimation times, as well as the availability of oxygen and other nutrients. As such, the biological filtration process can be optimized through multiple stages of filtration in series. In some cases, it may be beneficial to combine biological filtration with conventional processes.