Organic micropollutants (OMPs) are ubiquitous in aqueous environments and are a growing public health concern globally, particularly in low- and middle-income countries where pollution is severe. Biochar is a low-cost sorbent alternative to activated carbon (AC) for control of OMPs in water treatment, but biochar improvement techniques are needed that are appropriate for low-cost, decentralized biochar production and application across drinking water (DW), stormwater (SW), and wastewater (WW) treatment. Ash content significantly influences biochar performance, but the impacts of ash on biochar production and OMP sorption are not well understood. In addition, background dissolved organic matter (DOM) can reduce biochar sorption of OMPs through direct competition and pore blockage fouling, yet DOM impacts on biochar performance lack thorough evaluation. The objectives of this dissertation are: (i) improve biochar sorption of aqueous OMPs using low-cost techniques, (ii) determine feedstock inherent ash content impacts on biochar characteristics and performance, (iii) evaluate catalytic ash constituents impacting biochar, and (iv) develop systematic understanding of DOM fouling of biochar adsorbents.
Biochars from three feedstocks were produced using various pre-pyrolysis–ash, acid, base, alkali- and alkali-earth metal (AAEM)–and post-pyrolysis treatments–double heating–and tested in batch and column treatment scenarios for sorption of two OMPs: 2,4-dichlorophenoxyacetic acid and sulfamethoxazole. Batch sorption tests were conducted in deionized water, DW, WW, and SW, and flow-through column tests were conducted in DW and WW. Feedstock ash impacts were dependent on inherent ash content, and an optimal feedstock ash content is proposed. Base pretreatment improved performance by over an order of magnitude. Ash and acid pretreatments enhanced performance by a factor of 3 to 10, and ash pretreatment with double heating produced a biochar that outperformed AC in batch tests and performed within a factor of two in columns. DOM competition and pore blockage fouling were linked to non-micropore and micropore surface areas, respectively. DOM preloading batch experiments were used to accurately predict performance in flow-through columns. Small molecular weight UV254-absorbing DOM increased competitive effects by a factor of 3 relative to larger UV254-absorbing DOM, and UVA254 proved a viable tool for biochar performance prediction and treatment system monitoring.
|Advisor:||Summers, R. Scott|
|Commitee:||Knappe, Detlef, Cook, Sherri, Rosario-Ortiz, Fernando, Linden, Karl|
|School:||University of Colorado at Boulder|
|Department:||Civil, Environmental, and Architectural Engineering|
|School Location:||United States -- Colorado|
|Source:||DAI-B 82/3(E), Dissertation Abstracts International|
|Subjects:||Environmental engineering, Engineering|
|Keywords:||Ash, Biochar, Dissolved organic matter, Organic micropollutant, Sorption, Water treatment|
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