Changes in physical, chemical and microbial parameters were investigated during the composting of municipal sewage sludge. Raw sewage sludge (30% dry matter) was mixed with compost from sewage sludge (85% dry matter) in 3:1 ratio (v/v). The mixture was divided into 4 windrows which were composted under the same conditions except the turning factor. The turning was every 7, 10, 15 days and according to the temperature which must be (55-65°C) for windrow 1 (W1), windrow 2 (W2), windrow 3 (W3) and windrow 4 (W4), respectively. Water was added to adjust the moisture content (40-60%). The composting process consisted of 2 periods; fermentation (12 weeks) and maturation (4 weeks). The results showed that the temperature reached the maximum after 12 weeks for W1 and 11 weeks for W2, W3 and W4 and then decreased. The final compost was nearly odourless and black, especially in case of W4. The general trend indicates a decrease in organic matter, organic carbon and nitrogen (N), whereas ash, potassium (K) and phosphorus (P) increased and consequently C/K and C/P ratios decreased. There was a slight increase in C/N ratio. The pH increased and then decreased to near neutrality at the end. The mesophilic bacteria increased during the fermentation period and decreased after that, whereas the thermophilic ones increased with increasing of temperature, decreased after 2 weeks and increased again during the fermentation period and then decreased. The mesophilic and thermophilic fungi were present during the first week and disappeared after that. The final compost was pathogens-free as indicated by the counts of coliforms and Salmonella.
Numerous studies have been performed on the conversion of individual types of waste into activated carbon (AC). However, this study focused on the evaluation of the simultaneous conversion of different types of wastes (palm, paper, and plastic wastes) into AC via copyrolysis. The tartrazine adsorption capacity onto the produced AC was optimized. The results showed that the carbon content of the AC improved as the calcium hydroxide concentration varied from 0.0 to 2.0 mol L À1 . In addition, the volatile matter and ash content were reduced as the concentration of calcium hydroxide was increased from 0.0 to 2.0 mol L À1 . The tartrazine adsorption capacity of the prepared AC samples increased as the calcium hydroxide concentration increased from 0.5 to 2 mol L À1 at a carbonization temperature of 400°C for 2 h and a final activation temperature of 500°C for 1 h. Effective adsorption occurred at pH 2. The maximum adsorption capacity (74.9 mg g À1 ) was obtained with a contact time of 300 min and an initial tartrazine concentration of 150 ppm. The adsorption kinetics of tartrazine were modeled with pseudo-first order, pseudo-second order, and intraparticle diffusion models, which revealed that the tartrazine adsorption onto the AC showed a best fit with the pseudo-second order kinetic model. The thermodynamic parameters DG 0 , DH 0 , and DS 0 indicated that the adsorption of tartrazine onto the AC was spontaneous and endothermic. The values of DG 0 were between À1.3 and À2.3 kJ mol À1 , and the DH 0 and DS 0 values, in the temperature range of 25-50°C, were 9.12 kJ mol À1 and 35.5 J mol À1 K À1 , respectively. In general, the thermodynamic parameters indicate that the adsorption is spontaneous and endothermic.
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