Sono-thermal pre-treatment of waste activated sludge before anaerobic digestion.

Sonication and thermalization can be applied successfully to disrupt the complex waste activated sludge (WAS) floc structure and to release extra and intra cellular polymeric substances into soluble phase along with solubilization of particulate organic matters, before sludge digestion. In this study, sonication has been combined with thermalization to improve its disintegration efficiency. It was aimed that rise in temperature occurring during the sonication of sludge was used to be as an advantage for the following thermalization in the combined pre-treatment. Thus, the effects of sonication, thermalization and sono-thermalization on physical and chemical properties of sludge were investigated separately under different pre-treatment conditions. The disintegration efficiencies of these methods were in the following descending order: sono-thermalization > sonication > thermalization. The optimum operating conditions for sono-thermalization were determined as the combination of 1-min sonication at 1.0 W/mL and thermalization at 80 °C for 1h. The influences of sludge pre-treatment on biodegradability of WAS were experienced with biochemical methane potential assay in batch anaerobic reactors. Relative to the control reactor, total methane production in the sono-thermalized reactor increased by 13.6% and it was more than the sum of relative increases achieved in the sonicated and thermalized reactors. Besides, the volatile solids and total chemical oxygen demand reductions in the sono-thermalized reactor were enhanced as well. However, it was determined that sludge pre-treatment techniques applied in this study was not feasible due to their high energy requirements.

Treatment of combined acid mine drainage (AMD)--flotation circuit effluents from copper mine via Fenton's process.

The treatability of a copper mine wastewater, including heavy metals, AMD, as well as flotation chemicals, with Fenton process was investigated. Fenton process seems advantageous for this treatment, because of Fe(2+) content and low pH of AMD. First, optimum Fe(2+) condition under constant H(2)O(2) was determined, and initial Fe(2+) content of AMD was found sufficient (120 mg/L for removal of chemical oxygen demand (COD) of 6125 mg/L). In the second step, without any additional Fe(2+), optimum H(2)O(2) dosage was determined as 40 mg/L. Fe(2+)/H(2)O(2) molar ratio of 1.8 was enough to achieve the best treatment performance. In all trials, initial pH of AMD was 4.8 and pH adjustment was not performed. Utilization of existing pH and Fe(2+), low H(2)O(2) requirements, and up to 98% treatment performances in COD, turbidity, color, Cu(2+), Zn(2+) made the proposed treatment system promising. Since the reaction occurs stepwise, a two-step kinetic model was applied and calculated theoretical maximum removal rate was consistent to experimental one, which validates the applied model. For the optimum molar ratio (1.8), 140 mL/L sludge of high density (1.094 g/mL), high settling velocity (0.16 cm/s) with low specific resistance (3.15 x 10(8)m/kg) was obtained. High reaction rates and easily dewaterable sludge characteristics also made the proposed method advantageous.

Advanced oxidation of biologically pretreated Baker's Yeast Industry effluents for high recalcitrant COD and color removal.

The aim of this study was to investigate the effectiveness of chemical oxidation by applying ozonation, ozonation with hydrogen peroxide and Fenton's processes for decolorization and residual COD removal of biologically pretreated baker's yeast industry (BYI) effluents. Baker's yeast industry effluents characterizing with high COD, TKN, dark color, and non-biodegradable organic pollutants. The batch tests were performed to determine the optimum operating conditions including pH, O3, H2O2, and FeSO4 dosages, molar ratio of Fe2+/H2O2 and reaction time. It was noticed that H2O2 significantly reduced the reaction times for the same ozone dosages: however, COD and color removals were not remarkable. In the Fenton's oxidation studies, the removal efficiencies of COD and color for 30 min reaction time for three different types of BYI effluents were found about 86 and 92%, respectively. Experimental results of the presented study have clearly indicated that the Fenton's oxidation technology is capable to fate almost all parts of the organics which consist of both soluble initial and microbial inert fractions of COD for baker's yeast effluents. Effluents from the Fenton's oxidation process can satisfy effluent standards for COD and color in general.