Wc. Leung et al., Removal and recovery of heavy metals by bacteria isolated from activated sludge treating industrial effluents and municipal wastewater, WATER SCI T, 41(12), 2000, pp. 233-240
A total of nineteen metal-resistant and non-resistant bacteria from activat
ed sludge treating both metal-contaminated industrial effluents and municip
al wastewater were isolated and identified. These included both Gram-positi
ve (e.g. Micrococcus) and Gram-negative (e.g. Pseudomonas) bacteria. The bi
osorption capacity of these strains for five different heavy metals (copper
, nickel, zinc, lead and chromium) was determined at pH 5 and initial metal
concentration 100 mg/L. Pseudomonas pseudoalcaligenes and Micrococcus lute
us were found to be capable of removing significant amounts of copper and l
ead. Hence, they were selected for further investigations. Langmuir adsorpt
ion isotherms adequately represented the distribution of copper and lead fo
r both species. The study of pH effect on metal removal for both species in
dicated that the metal biosorption increased with increasing pH from 2 to 6
. The effect of competing cations on biosorption of P. pseudoalcaligenes wa
s studied. Sulphuric acid (0.05 M) was the most efficient desorption medium
among the eleven reagents tested. Over 90% of copper sorbed on the cells o
f M, luteus could be recovered by washing with 0.05 M sulphuric acid within
five minutes. The biosorbent was used for at least five biosorption and de
sorption cycles without loss of copper removal capacity. Immobilization of
M. luteus in 2% calcium alginate and 10% polyacrylamide gel beads increased
copper uptake by 61%.