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Title:Effects of hydrothermal liquefaction on algal toxins from harmful algae blooms
Author(s):Gunderson, Kathryn Grace
Advisor(s):Nguyen, Thanh H.; Schideman , Lance C.
Department / Program:Civil & Environmental Eng
Discipline:Environ Engr in Civil Engr
Degree Granting Institution:University of Illinois at Urbana-Champaign
Subject(s):hydrothermal liquefaction
algal toxins
harmful algae blooms
Abstract:The formation of harmful algae blooms (HABs) in natural waters is an intensifying issue throughout the world and poses risks to the environment due in part to the toxins they release. A promising mitigation technique is to physically collect the HABs from the environment and convert them into biofuel via hydrothermal liquefaction (HTL). A large coproduct of the HTL process is the aqueous product (HTLaq), which could be discharged back into the environment or recycled for beneficial reuse applications. The purpose of our study was to determine the effects of HTL and some post treatment processes on the fate of the algal toxins in HTLaq. Samples were collected from Chautauqua Lake, NY, and experiments were conducted at the benchtop scale. HTL provided removal to below instrument detection limits for the seven algal toxins tested in HTLaq (microcystins RR, LR, YR, LY, LA, LW, and nodularin) when operated at 300 °C for 30 minutes, which provided an average percent removal of 98% across the seven toxins tested. Additionally, optimization of temperatures was explored to determine how the HTL operating temperature affects the destruction of the seven algal toxins tested. In these temperature optimization experiments, a DI water “blank” matrix spiked to known toxin concentrations was reacted in sealed pipes for 15 min at 175, 200, and 250 °C. In the blank spiked matrix, all seven toxins were removed below instrument detection limit at 250 °C, but the six microcystins and nodularin behaved differently below 250 °C. At 200 °C and below the microcystins were above instrument detection limit, and the percent removal decreased from ≥99% to 90%. Percent removal of nodularin was 41% at 175 °C and 48% at 200 °C. A temperature experiment with the algae feedstock was conducted at the low end of the HTL range at 175 °C for 15 minutes, MC-LR was 74% destroyed and nodularin was 63% destroyed. Therefore, it is recommended that HTL reaction conditions be at least 250 °C for 15 minutes to provide maximum removal of algal toxins. For further treatment of the HTLaq, nanofiltration (NF) was tested for the removal of known MC-LR and nodularin breakdown products. Untargeted LC/MS analysis on the HTLaq, NF retentate, and NF permeate showed that NF had ≥95% removal of nine previously identified MC-LR and nodularin intermediate breakdown products. The destruction of algal toxins adds to the value of HTL conversion as a mitigation strategy for HABs.
Issue Date:2021-07-22
Rights Information:Copyright 2021 Kathryn Gunderson
Date Available in IDEALS:2022-01-12
Date Deposited:2021-08

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