WELL-WATER (TANK) AERATION
By Patrick Udeh, Phd

1. Definition of Aeration: Aeration may be defined as the process by which a gaseous phase, such as air and water are brought in contact with each other for the purpose of transferring volatile substances to or from the water. These volatile substances may include, but not limited to ammonia, carbon dioxide, hydrogen sulfide, nitrogen, methane, Trihalomethane compounds such as chloroform, dibromochloromethane, bromodichloromethane, bromoform and other VOCs, as well as various unidentified organic compounds responsible for taste and odor.
   
   
2. Uses of Aeration: Aeration may be used in water treatment for the following reasons:
• Removal of odor causing compounds (taste and odor) such as H²S, NH³ , and CO²
• Removal of volatile organic compounds (VOCs) such as Trihalomethanes (THMs) from water
• Precipitation of inorganic contaminants such as iron and manganese (oxidation of Fe and Mn to form insoluble oxidize that precipitates)
• Removal of radon and silver.
• Water stabilization and disinfection
  
  
3. Types of Aerator: There are several types of aerator, namely:
• Waterfall aerators, which use spray nozzles, cascades, or multiple trays
• Diffusion or bubble aerators, which bubble compressed air through the water
• Mechanical aerators, which employ motor driven impellers or combination air-injection devices.
  
  
4. Limitations of Aeration: The greatest application of aeration is absorption and release of gas such as O², CO², and H²S. Which can cause water to become corrosive.
   
   
5. Recommended Aerator for well water: Diffused or bubble aeration is recommended for well (tank) water. The process consists of contacting gas bubbles with water for the purpose transferring gas to the water or removing VOCs from the water by stripping. The process can be carried out in a tank or clear-well. In bubble aeration, it is assumed that:
• The liquid phase is completely mixed
• The gas phase is plug flow
• The process is at stead state, and
• The inlet VOC gas concentration is zero. The existing air is in equilibrium with the bulk liquid, which is for the minimum air-to-water ratio for bubble aeration. The minimum air-to-water ratio represents the smallest air-to-water ratio that can be applied to a bubble aeration tank to meet the treatment objective.
  
  
6. Do we need aeration in our systems? And if so, why is it required? Yes , aeration is recommended in our systems for the following reasons:
• We have high THM levels in some of our systems
• By 2006, each monitoring system will have to meet the prescribed 80 ppm MCL, rather than averaging all systems in order to meet the required 80 ppm MCL and
• We have taste and odor problem in some of our systems, evidence from water quality customer complaints.
  
  
7. Are we certain, that the problem with the THMs and taste and odor could be resolved by the use of aeration? Yes, based on previous works, past and present literatures, aeration can be used to remove THM compounds such as chloroform, dibromochloromethane, bromodichloromethane, bromoform, and other VOCs. Nevertheless, the distributor, Malibu Water Resource, has volunteered to provide us with their "Koender Electric Aerator System" for trial, which means we could use this system for pilot scale studies.
   
   
8. What is the Koender Electric Aerator System? This is a bubble aerator, specifically made for well water, which is stored in tanks or clear-wells or reservoirs. The system consists of inlet and outlet zones, and air compressor, which are used to bubble compressed air into water. This aerator is powered by a ¼ horse power (110 AC) energy efficient electric motor. The system is designed to produce 1.5ft 3 of air per minute at 5 psi pressure with a maximum 35 psi.
   

For more information on wellwater aeration please see: