Removal of heavy metals, turbidity and coliform from contaminated raw drinking water using Saccharomyces cerevisiae, the Baker's yeast

The efficiency of Saccharomyces cerevisiae (baker's yeast) was investigated for biosorption of Ni, Cu and Al, turbidity and total coliform reduction from raw drinking water and as coagulant aid with alum (aluminum sulphate). Optimization of metal biosorption (at 50 mg/L initial metal ion concentration) using dried baker's yeast was performed using different pH (1–7), bio-sorbent (yeast) dosage (0.02 –2.0 g/L) and contact time (5.0–90 min). S. cerevisiae exhibited high selectivity towards Cu removal compared to Al and Ni at pH 7, 0.5 g yeast dosage and 30 min contact time, which considered the optimum conditions. Concurrently with metal removal bioassay, baker's yeast was tested as a coagulant aid in a parallel assay. Addition of 1.5 mg/L baker's yeast to the optimum dose of alum (24 mg/L) enhanced turbidity removal reaching 95.43% compared to 90% achieved when alum was used alone. Also, total coliform (TC) was reduced by 92.86% from initial density of 280 CFU/100 mL in the raw water when 1.0 mg/L baker's yeast was added to the optimum alum compared to 67.86% with alum alone. Therefore, it is recommended to use baker's yeast as coagulant aid with alum as primary coagulant. Results of the present study confirmed the important role of the baker's yeast for the removal of heavy metals, turbidity and coliform bacteria associated with the raw drinking water at the tested area. Moreover, results exhibited high efficiency of baker's yeast as a coagulant aid in the improvement of the drinking water treatment process performance.