[ removal of chromium from tannery industries effluent using Aspergillus niger]

Tannery industries effluent contain 100-1000 mg/L Cr[+3] and due to changing to Cr[+6], its direct disposal into environment is potentiqlly hazardous and threaten the health of humans through contaminating to the environment. In the recent years, many studies have been carried out concerning the removal of heavy metals from synthetic effluent using fungi and algae. The aim of this study as a basic and applied, investigation is to assess the possibility of the growth of Aspergillus niger in tannery effluent and its role in removal of Chromium from these industrial wastes. Firstly the chemical quality of tannery effluent was assessed through measuring Cr[3+], total organic Carbon [TOC], total kadjeldal Nitrogen [TKN], Phosphate and pH [based on the latest standard methods for examinations of water and waste water]. The ratio of carbon to nitrogen was adjusted to the optimal rate [C/N=10] prior to inoculation of 0.04-0.24% [dry weight] of A.niger into the effluent samples contained 122.5-1102.5mg/L of initial chromium. The samples were placed in a shaking incubator at 300 degree C, 150 rpm for 24 h. The rate of fungi biomass growth, the ratio of the grown fungi biomass to the chromium concentration and the percentage of chromium removal were then determined. Findings of this experiment showed that the rate of fungi growth was increased in effluent that was initially contained 122.5-1102.5 mg/L of Cr[+3]. However, effluent containing more than 1102.5 mg/L was able to stop the fungi growth. The best values of chromium removal [93.4% was observed at the initial concentration of 245mg/L [dry weight]. Also the rate of biomass growth and the ratio of grown biomass to the chromium concentration were 0.4407% and 18 mg/mg Cr[+3], respectively. A.niger has an optimal growth in the tannery effluent at the chromium concentration of 122.5-245 mg/L. Analysis of variance showed that the initial concentration of chromium in effluent and/or the amount of inocalm have a significant effect on the rate of biomass growth and chromium removal efficiency [p<0.001].The chromium removal efficiency and the ratio of fungi biomass to chromium concentration decreases when the concentration of chromium is higher than 245mg/L

Chromiun bioremoval from tannery industries effluent by Aspergillus oryzae

Recently laboratory studies had recognized the capability of alge, fungi, and bacteria in the removal of heavy metals from industrial effluent. In this research, growth of Aspergillus oryzae in the tanning house effluent, and its capability in chromium bioremoval were assessed. Aspergillus oryzae can grow in different concentration of Cr+, 120-1080 mg/l. Maximum biomass growth and chromium removal rate at pH, 3.3, Cr+3 concentration equal to 240 mg/l and inoculum size equal to 0.12% [dry weight] were 0.25% [dry weight] and 94.2%, respectively. Effects of various factors such as pH, temperature, shaking velocity and nutrients were also investigated. At optimum conditions [ie: pH=5; temperature=30?C, shaking velocity = 150 rpm, and nitrogen source of dihydrogen ammonium phosphate concentration=0.3%], biomass growth and chromium removal rate were found as 0.45% of dry weight and 99.8%, respectively. Effect of detention time showed that after 30h, biomass growth and chromium removal rate were 0.28% and 97.6%, respectively. Statistical studies on factors such as pH, temperature, shaking velocity, type and concentration of nutrients on the "biomass growth" and "residual chromium", showed that all of the factors had significant effects [alpha = 0.05, P < 0.001]. Therefore A.niger capable grow in the tannery industries effluent with 240 mg/l chromium and 97.6% chromium removal rate