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The present review deals with water applications in sub and supercritical conditions with a focus on supercritical water oxidation process (SCWO) as an example of high temperature and pressure technologies. It starts by presenting the advantages of water properties near and beyond the critical point and the major applications exploiting them. Then, it presents a review on SCWO from the description of the process, the reaction mechanism and kinetics to reactor design and modeling. It also presents the main problems and difficulties that delay the SCWO industrial application, and summarizes the main efforts and research to overcome them for a safe, efficient and economic process.

The hydrothermal oxidation is an efficient and clean way for wastewater treatment; it is also an energy self sufficient process under certain conditions, by the mean of the highly exothermic reaction of oxidation.In this present work, we studied the modeling of hydrothermal oxidation of phenol polluted water in supercritical conditions. First we apply a simple mathematical model for tubular reactor, resulting from mass, momentum and energy balances, which is often difficult to solve in its general form. According to adequate simplifications, the profiles of temperature and concentration of chemical species are computed along the reactor; using finite differences with a developed Mathcad program which returns results close to those from experimental works from literature.A design of experiment method was also applied to quantify the influence of operation conditions on the treatment efficiency and on the recovery of the heat generated by the exothermic reaction.

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A drinking water treatment plant, intended for consumption, must produce, under all circumstances, water that meets the standards. While the raw water may have variable characteristics before treatment, to cope with these variations, the design of the installation can use several treatment processes such as coagulation flocculation, decantation, filtration,…..etc.. The experimental study of this research was carried out on the drinking water treatment plant of Oued El Athmania, Mila (36° 27' 1.01" N; 6° 15' 51.98" E) and these physicochemical and bacteriological analyses were carried out on samples taken has 4 levels of the treatment station: (1) raw water , (2) decanted water, (3) filtered water and (4) treated water. The results obtained clearly show that the different processes applied on the treatment chain have a remarkable and variable effect on the quality of the water, as an example the water turbidity were 15.7, 1.8, 1 and 0.61 NTU for the raw water, decanted, filtered and treated water, respectively. The characterization of the treated water (pH, temperature, conductivity, salinity, partial and total alkalinity, organic matter, turbidity, total hardness, color, chemical oxygen demand, nitrite, nitrate, aluminum,  total and fecal coliform, ....) confirms that this water is potable.