Aerators & VOC Strippers
Water is contacted with air for two general purposes; to strip volatile components out of the water, and to expose contaminants in the water to oxygen, so these contaminants can be oxidized. Where the processing goal is only stripping of volatile components, the equipment is typically referred to as a VOC stripper or gas stripper. Where the purpose is to oxidize objectionable components, the equipment is referred to as an aerator. The typical stripper and aerator are usually similar in configuration, and aerators often also serve a stripping function as well.
WETS has installed or retrofitted hundreds of aeration and stripping systems for our clients in its over-40 year history, and in this time has developed a wide variety of high efficiency aeration and stripping processes and equipment. Our designs are highly efficient for aeration, VOC stripping and gas stripping. Our unique distributor, vessel internal components, and in-house blower design exhibit very low pressure loss for an optimum flow distribution.
WETS aerators are widely used for iron and manganese oxidation and THM removal. The aerator is designed to perform two basic functions, the introduction of oxygen into water for oxidation of undesirable compounds (typically iron and manganese), and the stripping of volatile compounds from the water (typically H2S and methane).
In the typical aerator design, the aerator is elevated on a dedicated structure and treated water gravity drains into the ground storage tank (GST), sometimes through filters. This is often referred to as an Elevated Aerator. There are also designs where the aerator is on the ground and the treated water is pumped to the GST (Ground Aerator). Ground Aerators are often a client preference, where the water treating facility is near a residential community and the visual of the elevated aerator is considered undesirable.
For aerators performing an oxidation service, filters are often provided for solids removal downstream of the aerator, but not necessarily. Depending on the solids content, it may be permissible to forgo filtration, and allow the solids to settle in the GST. In these cases, provision would have to be made to take pump suction on the GST above the maximum anticipated build-up level.
Aerator designs can differ in the means the air is introduced, how the water is introduced, the vessel internals and the use of cylindrical vs rectangular vessels, depending upon the service. WETS’ designs have generally been positive draft, with air introduced by a blower, with either dumped packing or slat trays. The water is introduced by a liquid distributor of a proprietary WETS design. There is typically no sparger for the air, given the relatively low gas rates and low pressure drop in the system. The WETS design will typically use a bed of dumped plastic packing for the contacting of the water and air.
WETS aerators will typically employ its proprietary forced draft design, introducing air at the base of the equipment. WETS has developed induced draft and natural draft designs, but prefers forced draft over induced draft because in an induced draft design, the blower sees not air but the aerator exhaust gas, which is likely to be corrosive. Forced draft aerators are generally used in preference to natural draft aerators because of better performance over all weather conditions, and the absence of appreciable drift.
Over time, the packing/internals of an aerator are likely to foul with bacteria and/or metal precipitates, leading to performance and operational problems. WETS has been called on for dozens of aerator rehabilitation projects. These projects typically include removal of existing packing/internals, cleaning of the interior, addition of new (typically Lanpac XL) packing, and any additional repairs to piping and blower. If you are having issues with an aerator, give a WETS professional engineer a call, and we can arrange a site visit to discuss how to best resolve the issues.
VOC strippers and degassifiers, similar in configuration to our aerators, target the removal of gases and volatile organic compounds (VOC’s). WETS applications for our VOC strippers and degassifiers have included VOC’s, THM’s, methane, hydrogen sulfide, radon, and benzene/BTX. WETS VOC strippers and degassifiers provide guaranteed high percentage reduction of gases and Volatile Organic Compounds from groundwater sources. WETS forced draft and unique internal packing media are specially selected by our application engineers for maximum efficiency. We also have degassifier designs that work with both low and high iron applications.
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