Point-of-use treatment of multiple drinking water contaminants by white spruce biochar

Simple sorbent technologies from local biomass may be used to reduce chemical contaminants in residences at the point-of-use scale (POU). Production techniques and sorptive performances of White Spruce biochar against multiple drinking water contaminants (As, F-, TOC, Cl2) using small scale column tests (SSCTs) were studied. SSCTs were conducted to project POU performance envisioning applications would consist of matching sorbent particle sizes and empty beds contact times (EBCTs). Biochars were produced under laboratory conditions in the absence of oxygen at 550oC using auger-based pyrolysis and at 1000oC with low-oxygen, custom gasification. Differences in production technologies and corresponding temperatures impacted each biochar's ability to effectively sorb targeted compounds. Initial percent breakthroughs for low-temperature pyrolyzed biochar (PB) were >50% for each contaminant excluding fluoride while high-temperature gasified biochars (GB1 & GB2) remained <50% for each contaminant excluding arsenic. Results indicate that gasified biochars effectively removed organic compounds due to their increased surface areas and available microporosity while pyrolyzed biochar was more successful in removing inorganic compounds with their large fractions of remaining parent or partially transformed organic functional groups. Both biochar types were able to reduce free chlorine concentration at >10,000 bed volumes, one of the two generated gasified chars (GB2) performed similar to commercial activated carbon with specific regards to dechlorination. Scanning electron microscopy and BET analyses confirmed the role of temperature in surface area production and pore size distribution indicating greater values with increasing temperatures. Biochar BET values in increasing order: 0.62 m2/g (PB), 413 m2/g (GB2) and 414 m2/g (GB1), respectively. This research provides evidence that supports local biomass could be converted into porous sorbent medias capable of reducing a wide range of chemical constituents in fixed-bed filtration applications at the POU scale.