Abstract
In this work, the effect of the addition of some nutrients on fungal growth and removal of Cr(III) were investigated. The
considered fungi, isolated from real tanning factory environment were Phanerochaete chrysosporium, Aspergillus niger and A.
oryzae. Firstly, the optimal conditions for fungal growth were determined as a function of pH, contact time, temperature and
agitation speed. Secondly, the effect of the addition of some nutrients on fungal growth was examined. Without the addition of
any nutrient, the best growth conditions were found to be pH 5, 30oC temperature, 150 rpm agitation speed and 30 hours contact
time. Except sodium nitrite, all tested nutrients, namely NH4Cl, (NH4)2SO4, NaNO2, NaNO3, NH4H2PO4, and KH2PO4, enhanced
fungal growth, and hence Cr(III) removal which appeared clearly related to growth. NH4H2PO4 (in the range 4-6 g/L) was found
to be the most efficient nitrogen source for fungal growth, resulting in an increase of fungal concentrations from an initial value
of 0.8 g/L to maximum values of 4.8, 4.1 and 4.4 g/L for A. niger, A. oryzae and P. chrysosporium, respectively. Regarding
phosphorus supply, 8 g/L KH2PO4 was found to be the optimum amount, leading to 5.7 g/L of biomass and hence an almost total
chromium removal, showing the positive phosphorus effect on growth. Under the optimum conditions, chromium was almost
totally removed (at least 99.8 %) for Aspergillus species, and especially A. niger, which appeared to be more efficient than P.
chrysosporium. Maximum removal efficiencies on tanning effluent were 63, 52 and 43% for A. niger, A. oryzae and P.
chrysosporium, respectively. These results are promising considering the high chromium content of the real effluent (1000 –
1300 mg/L).