Q: Can the granular ferric oxide media be optimized for longer life?
A: Media life typically ranges from 6 months to 6 years, depending on water quality levels. Media usage can be optimized in multiple parallel flow adsorber systems via staging. The media life cycle for each adsorber is staggered such that one is operating in the latter stages of its life while others are operating at earlier stages of media life. The adsorber with the oldest media can operate to 12-14 ppb arsenic breakthrough because its water is blended with other adsorbers discharging water with arsenic in the 2-6 ppb range. The treated water from the adsorbers contains an arsenic level of about 8 ppb.
Although systems are usually simple to operate, owners may consider the additional backup of service agreements to support the most effective operation of the system to extend media life and undertake media change-out when required.
Q: What does De Nora’s media replacement service include?
A: When an operation’s arsenic removal media is approaching exhaustion, the operator, with assistance from a De Nora subcontractor, sends a sample of the media to De Nora’s certified laboratory for the EPA’s TCLP metals (or CA’s STLC metals) analysis. Once analyzed, the media can be scheduled for replacement. On the day prior to replacement, the operator drains the adsorber(s) of water prior to initiating the media change out (MCO). The subcontractor transfers the spent media into trucks or sacks for disposal. The site is cleaned and the equipment is ready to be placed back into service, and the contractor hauls the spent media to a disposal site, securing all of the proper paperwork.
Q: Besides media replacement and disposal, what can the client expect from this service?
A: De Nora’s process oversight of the MCO ensures that the operation is conducted properly with close attention to detail. A De Nora process engineer oversees the operation, inspecting the interior of the vessel and monitoring the new media chlorination and backwashing after media installation. The engineer also assesses the past performance of the media based upon the volume treated, then compares that it with original performance expectations. With an updated comprehensive water analysis from the client for the assays listed in De Nora’s site qualification form, the overseeing engineer can determine if any adjustments to the bed volumes (or million gals) should be made. In addition, he or she determines if any internal lining coating repairs need to be made and checks the system’s instruments for operability and reliability. The engineer reviews the current mode of operation with the client, identifies any ongoing problems, and makes recommendations for improvement. A few weeks after completion, an MCO report on the service is issued to the client, which includes the status of the spent media disposal.
* Bayoxide® is the registered trademark of Bayer AG and used by Lanxess Corporation under license from Bayer AG