Iranian Journal of Chemical Engineering (IJChE)

Abstract The biosorption of Cd(II) ions from aqueous solutions by dried activated sludge was investigated as a function of initial pH, initial cadmium ion concentration, adsorbent mass, adsorbent particle size and temperature. Biosorption experiments were performed using activated sludge of the systems of wastewater refining of milk factory. The results showed that increasing the initial pH from 2 to 5.5 and the adsorbent mass from 0.5g to 2g increased the removal efficiency from 11% to 68% and 68% to 79% respectively. Increasing the adsorbent particle sizes from smaller than 0.063mm to greater than 0.5mm and the initial cadmium ion concentration from 15ppm to 120ppm decreased the removal efficiency from 77% to 67% and 80% to 54% respectively. The equilibrium data fitted both the Langmuir and Freundlich adsorption models, but the Freundlich isotherm was found to fit the experimental data slightly better than the Langmuir isotherm. The characteristic parameters for each isotherm have been determined. Maximum adsorption capacity (q 0) was calculated at different temperatures (303, 318, and 333 K) 1.283, 1.581 and 1.726 mg/g, respectively. The dimensionless separation factor (RL) showed that the activated sludge of milk factory can be used for the removal of cadmium ions from aqueous solutions. The results (n, RL) represented good and favorable adsorption. Therefore, the activated sludge could remove Cd(II) ions effectively from aqueous solution.

Abstract This paper indicates that activated sludge under certain conditions can achieve levels of polyhydroxyalkanoates (PHA) accumulation which would enable the economic recovery of this precursor of biodegradable plastics. The effects of C/N ratio and temperature on polyhydroxyalkanoates production were evaluated. Acetate uptake, ammonium consumption, oxygen uptake and PHA production were studied under aerobic, growth rate limiting conditions. Sludge fed with acetate showed the capability to accumulate PHA to about 6% and 20.5% of cell dry weight at 30 °C and C/N =21.74 after 42 and 72 h, respectively. The accumulation of PHA strongly depends on temperature, with less PHA formation at higher temperature. The average values of maximum growth rate (q„•Cx), affinity constant (K02) and kLa were determined 0.266 mgl-Y , 0.556 mgt' and 0.1422 s-1, respectively.

Abstract  A case study is presented in which two modifications of activated sludge treatment of complex chemical wastewater are experimentally compared: a combination of common activated sludge with powdered activated carbon treatment (PACT), and bioaugmentation of activated sludge treatment (BAST). Industrial wastewater of Pars Oil Refinery that was passed through an oil recovery stage was used to investigate the effect of furfural on two treatment processes in the range between 100-2000 ppm. Furfural was added manually. For comparison, furfural, COD, MLSS (Mixed Liquor Suspended Solids) concentrations and SVI (Sludge Volume Index) were measured daily. The results show a little higher COD removal efficiency in PACT system and the same furfural removal in both methods. But, it should be mentioned that at low HRT (Hydraulic Retention Time), BAST system showed better results in both furfural and COD removal than PACT system. SVI measurement shows that settability of effluent sludge in BAST system was always better than in PACT system. Because of rapid growth of microbial biomass in BAST system, the MLSS concentration in this modification was higher than in PACT system and in this way, BAST system has a lower requirement to return sludge than PACT system. Finally, it could be concluded that BAST system may be an attractive alternative to existing PACT system and if the former is used, it will result in both high performance and optimum conditions with economical operation.