Should we choose a coconut shell or coal-based filter? Should it be pre-wetted and acid washed?
In the most recent study at the University of Florida, Clean WateR3 researcher and MS student George Grant found there was no significant difference in in paclobutrazol removal between 8x30 mesh coconut or 8x30 mesh coal-based granular activated carbons. This study occurred over a short period of time with a slower flow rate than in a commercial-scale system. It is possible that activated carbon types vary in their shelf-life, but we do not know at this point.
The acid and pre-wetted treatments both reduce the percent ash content and make for a 'cleaner' carbon. The ash content on activated carbon is basically fine dust that will wash away when you first start running the system. The ash will turn water black, and an initial back flow is recommended when new carbon has been installed until this ash is washed out. It’s unknown if there are additional costs associated with these treatments, but in theory, they produce a high quality activated carbon that is easier to handle or install.
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