No abstract

Micropollutants in wastewater present environmental and human health challenges. Powdered activated carbon (PAC) can effectively remove organic micropollutants, but PAC production is energy intensive and expensive. Biochar adsorbents can cost less and sequester carbon; however, net benefits depend on biochar production conditions and treatment capabilities. Here, life cycle assessment was used to compare 10 environmental impacts from the production and use of wood biochar, biosolids biochar, and coal-derived PAC to remove sulfamethoxazole from wastewater. Moderate capacity wood biochar had environmental benefits in four categories (smog, global warming, respiratory effects, noncarcinogenics) linked to energy recovery and carbon sequestration, and environmental impacts worse than PAC in two categories (eutrophication, carcinogenics). Low capacity wood biochar had even larger benefits for global warming, respiratory effects, and noncarcinogenics, but exhibited worse impacts than PAC in five categories due to larger biochar dose requirements to reach the treatment objective. Biosolids biochar had the worst relative environmental performance due to energy use for biosolids drying and the need for supplemental adsorbent. Overall, moderate capacity wood biochar is an environmentally superior alternative to coal-based PAC for micropollutant removal from wastewater, and its use can offset a wastewater facility's carbon footprint.

No abstract

This study examined sorption of the human and veterinary antibiotic sulfamethoxazole (SMX) at environmentally relevant concentrations from laboratory clean water, surface water, stormwater, and wastewater effluent to wood and wastewater-sludge derived biochars produced under a wide range of conditions. SMX sorption by commercial powdered activated carbon (PAC) was also quantified as a benchmark. Wood-based biochar produced around 850 °C performed similarly to PAC. Biochar sorption capacity increased with surface area up to ∼400 m(2)/g. However, a further increase in surface area did not correspond to an increase in sorption capacity. Sorbent H:C ratios correlated with SMX uptake by PAC and wood-based biochars, but not for the sludge-based biochars. This is possibly due to an indirect influence of the high ash content in sludge-based biochars, as the isolated ash fraction exhibited negligible SMX sorption capacity. The presence of dissolved organic matter (DOM) in the natural and anthropogenic waters fouled most of the sorbents (i.e., decreased SMX uptake). The sludge-based biochars experienced less DOM fouling relative to wood-based biochar, particularly in the wastewater effluent. Biochar and PAC sorption kinetics were similar when examined over a contact time of four-hours, suggesting their performance ranking would be consistent at contact times typically utilized in water treatment systems. In the presence of DOM, SMX relative removal (C/C0) was independent of SMX initial concentration when the initial concentration was below 10 μg/L, thus permitting the relative removal results to be applied for different SMX initial concentrations typical of environmental and anthropogenically impacted waters.