How is Water Filtered with Char?
For water treatment, contaminants diffuse into char pores (absorption) where they bind to char surfaces (adsorption). As noted, the large porosity and high surface area of Biochars provide many reactive sites
for the attachment of dissolved compounds.
These reactive sites can also bind non-problematic dissolved organic matter present in all natural waters as well as the targeted hazardous contaminants. This organic matter can clog the char pores and make it less effective; to mitigate this occurrence, a filtration system uses gravel and sand filters to remove a large portion of the organic matter from the water before it encounters the char. The idea is to achieve a high level of treatment prior to the char filter, to “save the carbon” for removing the SOCs.
Biochar filters do differ from Activated Carbon filters in a couple key ways. Local Biochar is ideally made from agricultural and forestry residues and/or sustainably harvested renewable woody biomass whereas most commercial ACs are made from (nonrenewable) coal. Both local Biochars and ACs undergo a carbonization step where the feedstock is heated to several hundred degrees C under restricted oxygen. Commercial ACs are subsequently “activated” in a \n additional step that requires processing not usually available in rural areas. Compared with AC, locally-produced Biochars may contain substantial proportions of incompletely carbonized tars and oily compounds (especially if the Biochar is produced at a temperature below ~ 600 °C). Local Biochars may also contain a high proportion of ash depending on the feedstock (such as rice hulls).
Since the Local Biochars are not “activated” and may contain higher proportions of ash or residual tars and oils, they may not have the same water filtration capacity as commercial ACs, and so, the water filtration design will use a greater amount of Biochar as compensation.
Instructions for use:
Remove from outside bag, place inner bag in toilet, wait 5-10 seconds before flushing. Safe around children and pets, safe to use in RV and compost toilets.