The comparison of soy-bean wastes, used tea-leaves and sewage sludge for growing Chlorella pyrenoidosa

Abstract

Aqueous extracts of sewage sludge, used tea-leaves and soy-bean residues have been used as culture media for the cultivation of a unicellular green alga, Chlorella pyrenoidosa. Bristol medium was employed as a control medium for comparison. A preliminary experiment was conducted to search for the most suitable concentration of each culture medium for the growth of C. pyrenoidosa. The following concentrations of the waste materials were chosen for the subsequent cultivation: sludge, 2%; used tea-leaves, 1% and soy-bean residue, 2%. It was discovered that 2% soy-bean residue extract produced the highest growth rate, followed by 2% sludge and Bristol medium, with the used tea-leaves producing the lowest. The cells of C. pyrenoidosa cultivated in sludge extract had a higher uptake of copper, manganese and iron than those cultivated in other media. It was also demonstrated that the acidic condition of the used tea-leaves and the relatively high concentration of copper and lead at the higher concentration of sludge extract (3%) inhibited the growth of C. pyrenoidosa.