Performance and metagenomic microbial analysis of a novel, pilot-scale reactor with rotating algal contactors used to treat anaerobic digester sludge filtrate containing high total ammonia

Johnson, Daniel Bryan

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Description

Title

Performance and metagenomic microbial analysis of a novel, pilot-scale reactor with rotating algal contactors used to treat anaerobic digester sludge filtrate containing high total ammonia

Author(s)

Johnson, Daniel Bryan

Issue Date

2019-07-12

Director of Research (if dissertation) or Advisor (if thesis)

Hudson, Robert J.M.

Doctoral Committee Chair(s)

Mulvaney, Richard L

Committee Member(s)

• Wander, Michelle M
• Schideman, Lance
• Canam, Thomas

Department of Study

Natural Res & Env Sci

Discipline

Natural Res & Env Sciences

Degree Granting Institution

University of Illinois at Urbana-Champaign

Degree Name

Ph.D.

Degree Level

Dissertation

Keyword(s)

Algae biofilm, Wastewater,Sidestream treatment, Nitritation, Anaerobic digester centrate, Filtrate, High-strength ammonia, DIC limitation

Abstract

This report details our investigation of a novel, fixed-biofilm algal and bacterial system for the treatment of high-strength municipal anaerobic digester filtrate. Each reactor in the pilot-scale system comprises multiple AlgaewheelTM rotating algal contactors (RACs) that help efficiently oxygenate the anaerobic digester filtrate being treated in a shallow tank. Total ammonia nitrogen (TAN) removal by microbial oxidation and anabolic uptake varied between 45-60% at hydraulic retention times (HRTs) of 0.5-2 days. Of the TAN removed during treatment, >95% was oxidized to nitrite with 27-36% subsequently evolved as N2 and only 3-11% oxidized to nitrate. The low extent of nitrate formation makes biological nutrient removal less costly, since nitrite reduction demands less oxygen, by 25%, and organic carbon, by 40%, than nitrate reduction. In addition, due to the efficient aeration by RACs, it should be possible to design systems for sidestream treatment of digester filtrate that require up to 80% less electricity than are typical for aerobic ammonia oxidation. The composition of microbial assemblages in the biofilms growing on rotating algal contactors (RAC) used in treating high-strength anaerobic digester filtrate were characterized during a 4-month pilot study. Typical RAC-based systems supplied with feedstocks containing high total ammonia and low dissolved inorganic carbon are nitrite-accumulating. The RACs have biofilms on the sunlit exterior RAC surfaces (2 m2) colonized by a mixture of phototrophs, chemoautotrophs, and heterotrophs, whilst the dark, internal media (5 m2) is colonized by chemoautotrophic and heterotrophic bacteria. Using high-throughput 16S V4 analysis processed on a MiSeq platform, we assayed the relative abundance of bacterial V4 16S segments in the RAC biofilms over 4 months of operation from November through February. We were able to detect significant differences in composition between biofilms growing on the interior and exterior of the contactors. The assemblages also changed significantly over the study period. Ten OTUs, most of which were identified to the genus level, accounted for over 75% of the total individuals counted. Nitrosomonas, the common ammonia-oxidizing bacterial genus, was the 10th most abundant OTU and although ubiquitous, it was more frequently located on the inside, dark surfaces of the RACs. Two members of the Xanthomonadaceae, one of which identified as Rhodanaobacter, were also correlated to the inner surface. Brevimundus, Arenimonas, and Flavobacterium were more frequently located on the outer surface of the RAC. Comamonas showed no difference between locations but exhibited the highest abundance in January and February. Overall, this study has demonstrated that there is a significant difference is the bacterial assemblage structure based on the surface location (inside or outside of the RAC) and on the month of the sample which has implication for design and seasonal performance.

Graduation Semester

2019-08

Type of Resource

text

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Copyright and License Information

Copyright 2019 Daniel Johnson

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