Enteric virus removal/inactivation by coal-based media

Four coal-based media, viz. alum-pretreated or ferric hydroxide-impregnated Giridih bituminous coal and lignite (alum-GBC, Fe---GBC, alum-lignite and Fe---Lignite) were laboratory tested to assess their potential in removing/inactivating enteric viruses in water. Batch-sorption screening tests, employing a poliovirus-spiked (3.10 × 107−1.49 × 108 PFU 1−1) canal water, indicated high poliovirus sorption by Fe---GBC (7.07 × 106 PFU g−1) and alum-GBC (5.70 × 106 PFU g−1) in a short contact time of 5 min. Based on the results of further batch-sorption tests, using silver-incorporated media (alum/Ag---GBC, alum-GBC---Ag and Fe---GBC---Ag), as well as aesthetic water quality consideration and previous findings on removal of coliforms and turbidity, alum/Ag---GBC, alum-GBC and alum-GBC---Ag were included in downflow column studies (bed depth 10 cm; flow rate 99 ml h−1; bed flowthrough time 4.76 min), employing poliovirus-spiked (1.95 × 105−2.68 × 107 PFU 1−1) canal water. All three media showed potential in removing/inactivating enteric viruses. In a separate column study (bed depth 25.4 cm; flow rate 500 ml h−1; flowthrough time 7.7 min), employing a joint challenge of poliovirus and rotavirus (2.47 × 107 PFU 1−1), alum/Ag---GBC removed 59.3–86.5% of the viruses along with more than 99% reduction in indigenous heterotrophic bacteria. Alum/silver-pretreated bituminous coal medium appears promising for use in household water filters in rural areas of the developing world. However, improved medium preparation to further enhance its efficiency is needed; also, its efficacy in removing/inactivating indigenous enteric bacteria, viruses and protozoa has to be ensured and practicalities or economics of application need to be considered.