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Suo Xiao--PhD Dissertation-final.pdf (4.22 MB)

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Phagotrophic Algae Based Approaches for Advanced Wastewater Treatment

Xiao, Suo
http://rave.ohiolink.edu/etdc/view?acc_num=akron1542368310384856

Abstract Details

2018, Doctor of Philosophy, University of Akron, Chemical Engineering.
Municipal wastewater treatment plants (WWTPs) generate huge quantities of organic solids such as waste activated sludge (WAS) and waste grease (WG). Large volumes of organics-rich wastewater are also generated by the food industry. The increasing wastewater production and more stringent environmental regulations have created an urgent need in sustainable management of wastewater and organic solids. The microalga Ochromonas danica has unique phagotrophic capability, grows faster than common photosynthetic algae, and produces polyunsaturated fatty acids (PUFA). These properties make O. danica an excellent candidate as the new microbial agent for resource recovery from wastewater by direct ingestion of particulates. In this research, three new phagotrophic algae-based processes were studied for carbon recovery from different wastewater organics including waste activated sludge (WAS), waste grease (WG) and high-strength food wastewaters. WAS contains concentrated bacteria and particulate organics. Currently, its disposal requires costly treatment. Ultrasonication was studied to release WAS particulates and bacteria for direct ingestion by O. danica. Destruction/lysis of strong bacterial cell wall was unnecessary, thus minimizing energy-requirement. Effects of sonication power, duration, and WAS volume were studied with a 3 × 6 × 3 factorial design. Quantitative correlations describing the extent of particulate organics (as Volatile Solids VS) release were established. By proper increase of initial WAS pH, the VS release by sonication could be further improved with lower energy consumption. O. danica growth on the released WAS VS was found to follow the Monod-type kinetics but, unlike the typical Monod dependency for soluble substrates, the specific cell growth rate, ¿, correlated with the prey-to-predator ratio, i.e., the ratio of (fed VS concentration)-to-(initial O. danica concentration), significantly better than with the VS alone. The best-fit kinetics had the following parameters: µmax = 0.198 h-1 and KM = 1.056 (g-VS/g-algae). Batch cultivations in fermentors at pH 5 confirmed algae production under nonsterile conditions using this new technology, giving a high volumetric algae productivity of 2.8 g/L-day with 38% VS reduction and 44.5% O. danica VS yield. Aerobic digestion of the remaining WAS from the sonication step was also compared with digestion of the non-sonicated WAS. The total oxygen uptake required (in mg O2/L) for the remaining WAS to reach the Class B Biosolids requirement in specific oxygen uptake rate was approximately 80% lower, indicating substantially reduced aeration cost. Compared to the conventional aerobic digestion, the new ultrasonication-phagotrophic algae process could offer enhanced overall WAS digestion with lower energy consumption, while producing algae biomass and products. O. danica cultivation was also studied with waste grease (WG, collected from a municipal WWTP) and two types of industrial food wastewaters (from cheese- and apple juice-making plants). The O. danica growing on WG synthesized and up to 67% of intracellular FAs, from the WG with only 15% PUFA. The study showed feasibility of converting WG to PUFA-rich O. danica algae culture, possibly as aquaculture/animal feed. The two industrial food wastewaters were tested for toxicity to O. danica, analyzed for compositions, and identified for major issues to address for the algal production. New process designs were proposed and evaluated. The growth kinetics and yield of O. danica in these food wastewaters were determined. Overall, the research provided fundamental insights of phagotrophic algal growth on different particulate organics including bacteria-sized particles from WAS, WG, and the bacteria grown from food wastewaters. The processes developed will find applications in bioconversion of organics solids for microalgae production and sustainable wastewater treatment.
Lu-Kwang Ju (Advisor)
Nic Leipzig (Committee Member)
Zhenmeng Peng (Committee Member)
John Senko (Committee Member)
Christopher Miller (Committee Member)
234 p.
Chemical Engineering
phagotrophic algae; microalgae production; waste activated sludge; waste grease; industrial food wastewaters; ultrasonication; polyunsaturated fatty acids; sustainability

Recommended Citations

Citations

  • Xiao, S. (2018). Phagotrophic Algae Based Approaches for Advanced Wastewater Treatment [Doctoral dissertation, University of Akron]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=akron1542368310384856

    APA Style (7th edition)

  • Xiao, Suo. Phagotrophic Algae Based Approaches for Advanced Wastewater Treatment. 2018. University of Akron, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=akron1542368310384856.

    MLA Style (8th edition)

  • Xiao, Suo. "Phagotrophic Algae Based Approaches for Advanced Wastewater Treatment." Doctoral dissertation, University of Akron, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=akron1542368310384856

    Chicago Manual of Style (17th edition)

akron1542368310384856
115
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This open access ETD is published by University of Akron and OhioLINK.