The increased demand for advanced techniques in anaerobic digestion over the last few years has led to the employment of various pre-treatment methods prior to anaerobic digestion to increase gas production. These pre-treatment methods alter the physical and chemical properties of sludge in order to make it more readily degradable by anaerobic digestion. Although the thermal pre-treatment presents high energy consumption, the main part of this energy to heat can be recovered from the biogas produced in the anaerobic process. In this research a mixture of primary and waste activated sludge was thermally pretreated at 100, 125, 150, 175 and 200o C in order to determine the effect of thermal pretreatment on improving the solubilization of sludge by increasing the soluble organic fraction (expressed as soluble COD and VFA). Experimental results proved that the solubilization ratio of sludge is depends on the treatment time and the applied temperature and the optimal temperature ranged between 175 and 200o C. The COD solubilization ratio (at 175o C) increased from 11.2% to 15.1% and 25.1% when the time of treatment increased from 60 min to 120 and 240 min respectively. The experimental data could be fitted to obtain an empirical model (Known as the enzyme-kinetic equation) relating the COD solubilization ratio of sludge and VFA concentration to the applied temperature and the heating time.

Both conventional laparoscopic and LESS extravesical repair of VUF are effective and reproducible and they follow the same principles of open surgical repair. However, LESS repair of VUF seems to be less morbid than conventional laparoscopic repair.

a b s t r a c tSewage sludge conditioning with chemicals has been employed widely to improve thickening and dewatering processes. Although it is a good alternative for process improvement, its cost is high. It is important to find effective and cheap conditioners. Large quantities of cement kiln dust (CKD), which proved to be a good chemical stabilizer of sewage sludge, are emitted from cement factories. In this study, the effect of using CKD on the thickening and dewatering performance of sewage sludge were investigated by zone settling test, free gravity drainage test, specific resistance to filtration (SRF) and natural drying tests. The results indicated that adding CKD to sewage sludge by 60% of total solid could improve the sludge thickening, dewatering as well as stabilization. The settleability of sludge was improved as follows: the zone settling velocity increased from 43. m/kg) and the actual dewatering time required to achieve sludge with solid content more than 20% reduced from 5 to 2 d, while the pH value remained in the required range for stabilization.

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In this study, the effect of thermal pre-treatment (TP) on the physical characteristics and co-digestion of a mixture of food waste and sludge was investigated. The food waste (FW) to sewage sludge (SS) ratio used in this research is 1:2 (VS-based) to form a final concentration of 11.20%. The inoculum to substrate ratio was set at 1:1 (volumebased). Undoubtedly, the results show that TP has changed the physical characteristics of the food waste to sewage sludge mixture. The results show that the pretreatment increased the biogas production from 4385 ml for the untreated reactor to 5685 for the reactor R2(140) at 140 °C and the improvement in biogas production reaches 29.65% in the reactor R2( 140) and the removal of volatile solids was 58.90%. Therefore, after the biomethane potential test, the temperature of 140 °C was found to be optimal in the production of biogas. The optimal condition is to use a mixture of pre-treated SS at the temperature of 140 °C and untreated FW, so TP is recommended to be used in anaerobic digestion of the mixture of food waste and sewage sludge.