The 'behaviour' of five metal biosorbing and biopecipitating bacterial strains, inoculated in a moving-bed sand filter

摘要

For the waste water treatment (chemical nickel line) of a plating company in Vienna, a moving-bed filter (AstraSand filter) has been inoculated using five bacterial strains with a known biosorption and bioprecipitation capacity. By the use of selective media, which were collated to re4solate bacteria out of a mixture, it was shown that the biofilm of the filter system contained approximately 10~6 of autochthonous colony forming units before the inoculation. Above all Pseudomonas spp. and Ni-resistant bacteria were found to be present in the system (autochthonous organisms). After the inoculation additionally Cd-resistant (Alcaligenes eutrophus CH 34) and As-resistant (Pseudomonas mendocina AS 302) bacteria could assert. In comparision to the 'non inoculated' filter operation (2 mg Ni 1~(-1) removed) the removal of nickel could be increased up to 4.9 mg 1~(-1) waste water after the inoculation with selected bacterial strains. By comparing biofilm samples and wash water samples (filtrate and abrased biofilm) it was possible to determine which groups of bacteria took preferably part in the formation of biofilm, or else, which species were discharged with the wash water. By applying this simple methodology the proportions of 'artificial' groups of bacteria could be monitored regarding different modi of filtration and efficiency. Eight month after the inoculation of the moving-bed filter, the 'Biolog' system for taxonomic identification of bacteria was used to identify some re-isolates from the biofilm with better reliability. It could be shown that Alcaligenes eutrophus CH 34 (CDC group JVC-2) could assert against the autochthonous flora, and built the bulk of the biofilm. None of the other inoculated strains could be found with certainty, but some of the re-isolates were related to the genus of Pseudomonas (like AS 302 and K 1/8a) and to the family of Nocardiaceae (like Arthrobacter p. B 7/26). One of the most frequently found autochthonous re4solates, was related to Acinetobacter calcoaceticus BV.