Biofiltration technique for removal of waterborne pathogens

Pathogenic agents such as protozoa, bacteria, virus, and helminths disseminate among human community via ingestion of contaminated water and pose a serious concern to public health. Biological filtration method of disinfection is the key step in centralized multistep and decentralized point-of-use water treatment system. A biofilm of indigenous microorganisms fixed on solid surface, called biofilter, is an eco-friendly and economic technique for removal of pollutants and pathogens. Stone, gravel, sand, soil, compost, mesoporous mineral stone, wood chips, etc., exemplify solid bed medium which provide enhanced surface area for microbial adherence and water retention. Slow sand filter (SSF) characterized by slow flow rate (0.1–0.2 m(3)/h) and a biological layer over filter bed called schmutzdecke is fairly efficient in removal of coliform microorganisms such as Giardia, Cryptosporidium, Salmonella, Escherichia coli, total coliform and fecal coliform, fecal streptococci, bacteriophage, and MS2 virus from wastewater. Rapid sand filter characterized by coarser sand and higher flow rate than SSF removes indicator microorganisms efficiently. Stormwater biofilter is popular and effective method for removal of pathogen and involves biological activity and physical retention of pathogen on filter media. Microbial diversity, inoculum size, pH and moisture of medium, temperature, and nutrient content are key parameters governing optimum performance of biofilter system. Therefore, biofiltration can be an efficient bioremediation technology for pathogen removal.