Figure 1: Schematic of the ACTIFLO® CARB Process
What was astounding to me was that the engineer and District accepted the manufacturer’s recommendation after such a short trial of a process that has no operating installations in the US, where the pilot plant did not even simulate how the full scale system would operate and where more proven treatment alternatives, such as ion exchange, tested over longer periods reliably demonstrated equivalent levels of TOC removal…. Such is the influencing power of a large established technology provider!
Finally a Fair Evaluation
In the past few months, more than two years after the PWSD trial, I finally had the opportunity to see the performance of ACTIFLO® CARB in a trial in Georgia operated for at least several weeks on a pilot plant representative of the full-scale process. The objective of the project was to improve TOC removal of the existing water treatment plant to meet tightening EPA standards for disinfection byproducts. As with the PWSD trial, ion exchange pre-treatment was evaluated in parallel but this time it was a fair side-by-side comparison over similar operating periods.
Lo and behold….under steady-state operating conditions the ACTIFLO® CARB process only achieved 52% TOC removal at very high PAC make-up doses and about 40% removal at economically realistic make-up doses. This compared to 66% TOC removal for the ion exchange pretreatment process. As the trial has only recently been completed, specific results will likely be publicly available in early 2011.
In this Georgia project the power and influence of the manufacturer could not overshadow the results of a well thought out and executed trial. While ACTIFLO® CARB has been shown to remove more TOC than coagulation alone, I can't see how the marginal improvement in removal justifies the considerable extra expense.