The rapid development of the oil and gas industry in the last decades has helped energy security but also led to the production of large amounts of contaminated water. Some of the waste waters from the oil and gas industry contain toxic chemicals, therefore; discharging them into the environment or injecting them into disposal wells may contaminate surface waters and freshwater reservoirs. Accordingly, it is important to treat such contaminated water or at least separate toxic chemicals from the waste waters before discharging them into the environment.
One suitable method to treat oil and gas wastewater is a thermal separation process that can be integrated with low-grade energy and waste heat. Humidification-dehumidification is one of the proven techniques that has been used for water desalination and producing freshwater from seawater. In the current study, we use a novel humidification-dehumidification in a water purification process to separate toxic chemicals such as benzene and toluene from contaminated water. In the humidification section of the process, contaminated water is vaporized in an evaporator and then it mixes with hot air in a mixing chamber. Then the gaseous mixture is sent to a direct contact dehumidifier, which consists of a vertical column filled with packing materials. Cooling water sprays from the top of the dehumidifier column and the gaseous mixture enters from the bottom. As the gaseous mixture travels upwardly through the dehumidifier, water condenses, and contaminants exit with the air in the top stream. The process is carefully controlled so only water condenses while the contaminants and carrier air exit from the top. Treated water is collected from the bottom. The process can operate at low pressure and temperatures with low-grade heat and can be integrated with solar thermal energy.
A laboratory apparatus has been constructed to separate volatile contaminants from contaminated water. This apparatus allows controlling the operating conditions of experiments including temperature, air flow rate, feed water, and cooling water flow rates. This enables evaluations of how parameters like velocity and air-to-water mass ratio affect condensation and separation. The purpose of this work is to do a parametric study and investigate the effects of the above-mentioned parameters on the separation of contaminants and the quality of treated water.