Horizontal Air Sparging System

The choice of materials for air sparging is quite flexible, but several design factors must be considered. First, there can be a considerable pressure drop along the length of a horizontal air sparge well, so the slot size must be properly designed. By designing the pipe as a pressure vessel, pressure drop along the length of the pipe is accommodated and air dispersion is equalized across the length of the slotted zone. In some cases, the pipe is perforated with a graduated pattern of holes—small in diameter and loosely scattered near the supply end, becoming larger in diameter and more densely congregated at the closed end of the well. DTD engineers have designed many horizontal air sparging systems that have performed in the field with excellent results. For systems requiring an extremely rigorous approach, or for turn key designs that include blower parameters and mechanical and electrical design, we work closely with firms like Star Environmental, who specialize in system design.

A second consideration is whether or not to use a sand pack or other filter around the sparge line. For a horizontal air sparging system under continuous operation it is unlikely that soil fines will find their way into the perforated pipe to cause clogging. However, if the system is pulsed or cycled, depending on the native materials it is possible that plugging of the air line can occur. In most cases a double-ended installation, where the sparge lines are accessible from the surface at both ends, is preferred to permit periodic maintenance of the well. Recent developments in casing design, such as the new EnviroFlex well screens, prevent siltation within the well screen for much lower cost than pre-pack systems, and may be manufactured with any desired perforation or slot pattern to meet design criteria.

Finally, the temperature of the air (or steam) supply must be considered. For normal air temperatures, ordinary high-density polyethylene (HDPE) pipe is sufficient for air supply. Air sparging systems that inject heated air are often specified with stainless steel pipe, which is quite expensive. Some alternatives to stainless steel include carbon steel, high-temperature polyethylene (HTPE) or CPVC—all of these materials can withstand elevated temperatures, are easier to install, cost far less, and are more readily available than stainless.