MICROBIAL UPTAKE OF HEAVY-METALS IN SLOW SAND FILTERS

This paper is concerned with the microbiological uptake of heavy metal s in slow sand filtration (SSF) and the determination of active biomas s by organic nitrogen analysis described herein. The heavy metal accum ulation and the total biomass in the schmutzdecke scrapings were deter mined and compared. The heavy metals were extracted from the sand scra pings by means of HNO3-HCl digestion. The percentage nitrogen content of volatile solids (VS) for the same sand scrapings were determined, a nd this measure was taken as being directly equivalent to the biomass in the schmutzdecke scrapings. The results show that the more the biom ass, the greater the metal accumulation, which indicates microbiologic al accumulation/uptake rather than simple adsorption of heavy metals i n SSF.