SCWO is economically attractive for treatment of waste waters that contain organic compounds in concentration of 1-20 wt% in a relatively short time (s to min) and high efficiencies ( 99.99%) at much lower temperatures ( 700?C) and without NOx production. Generic operational conditions for the two processes are as follows: WAO 150-300?C, 10-200 bar and SCWO 374-675?C and 220 bar Considering above mentioned conditions for SCWO, we needed to design a system enables us to produce this nearly high temperature and pressure. This system can provide 700?C temperature and 500 atm pressure, thus we can with system provide supercritical condition for different solvents that set in this range for example acetone, methanol, acetonitrile, and others. Oxidation with supercritical water (SCWO) is hydrothermal waste treatment technologies that use critical medium for oxidizing and destruction of organic wastes. Sodium toluene sulfonate (STS) that is extensively used as a hydrotrope and anticaking agent in detergent industries. The hydrolysis and oxidation of sodium toluene sulfonate (STS) in SCW in the presence of CO 2 in a continuous flow reactor at a constant pressure of 250 bar was studied. Effect of flow rate of water, temperature of the system and the presence of CO 2 in different extent on hydrolysis was investigated. Applied partial factorial design for simultaneous study and optimum condition for interaction between three factors namely flow rate of water ranging from 0.7 to 3.6 mL/min and flow rate of CO 2 ranging from 0.072 to 1.172 mL/min and temperature ranging from 231 ?C to 568 ?C on hydrolysis of STS. Hydrolysis of STS increased approximately by increasing temperature and adding CO 2 in to reaction media. The mechanism and the procedure for hydrolysis of STS by changing of these three factors and introduce the optimum condition (452 ?C , 0.0830 flow rate of CO 2 , 2.3306 flow rate of water) were introduced. Additionally, oxidative decomposition experiments were carried out using hydrogen peroxide as an oxidant for varying oxidation temperature from 200 to 500 ?C in constant pressure of 250 bar. The stoichiometric concentration of H 2 O 2 was investigated and different products were monitored in different concentration of H 2 O 2 .Based on these results, a reaction mechanism was proposed.