Gas Stripping and Contacting

Play Misty for me: Gas Stripping and Gas Contacting

Muddy River employs water spray systems for two general applications: (1) Gas stripping that removes dissolved constituents as a gas, or (2) Gas contacting that dissolves gas constituents into water.  Here is how to achieve optimal performance of gas stripping and gas contacting:

• Maintain a maximum difference in concentration of the constituent between gas phase and water
• Maximize the surface area of water or wastewater in air or other gas by forming tiny droplets
• Prolong the contact time of droplets in air or other gas via a long hold up time
• Provide ideal chemical and physical conditions such as pH and temperature to promote a shift of the constituent from water to air for stripping or visa versa for gas contact. As the Figures below indicate, strip un-ionized ammonia at pH greater than 9.3, and strip un-ionized hydrogen sulphide at pH less than neutral.  The greater the un-ionized portion, the faster and more complete the performance.

Ammonia Ionization vs. pH	Sulphide Ionization vs. pH

Gas Stripping exploits the gas: liquid equilibrium of dissolved constituents such as ammonia or hydrogen sulphide to remove them from water.  Gas stripping applications include:

• Remove ammonia from manure, landfill leachate, or other municipal and industrial wastewaters
• Remove dissolved sulphide from oil and gas processing wastewater, or anaerobic digester effluent

Gas Contacting exploits the gas: liquid equilibrium of gaseous constituents such as carbon dioxide, oxygen, ozone, or hydrogen sulphide for mass transfer from the gas phase to water.  Applications include:

• Neutralization of alkaline or acidic water using carbon dioxide gas, including CO₂ in air
• Oxidation of wastewater constituents using oxygen or ozone
• Scrubbing of air borne constituents such as hydrogen sulphide or odours