Journal article
Treatment Intensification of Digester Dewatering Sidestreams via Pilot- and Demonstration-Scale Revolving Algal Biofilms at Municipal Water Resource Recovery Facilities
ACS ES&T engineering, Vol.5(11), pp.3073-3084
11/14/2025
DOI: 10.1021/acsestengg.5c00458
Appears in UI Libraries Support Open Access
Abstract
As water resource recovery facilities (WRRFs) pursue decarbonization, the treatment of concentrated sidestreams from anaerobic digestion offers a critical opportunity to reduce energy use and greenhouse gas emissions. This study evaluated the intensification potential of revolving algal biofilms (RAB) for sidestream nutrient removal via partial nitrification at pilot- and demonstration-scales. RAB systems were deployed at municipal WRRFs in Boulder and Iowa City, treating real dewatering sidestreams across a range of ammonium (NH4+–N) surface area loading rates (SALR) reaching up to 196 g N m–2 d–2. The results demonstrated that RAB systems can achieve partial nitrification while treating such sidestreams. However, sustaining high nitrite accumulation ratios became challenging at NH4+–N SALRs exceeding 30 g m–2 d–1, a threshold well above typical sector norms. In Boulder, increased loading promoted nitrite accumulation, whereas in Iowa City, extreme SALRs inhibited both ammonia- and nitrite-oxidizing bacteria (AOB and NOB), limiting overall nitrification. Nonetheless, limited complete nitrification was observed in Iowa City, likely driven by Candidatus Nitrotoga, an NOB genus tolerant of free ammonia (FA) and free nitrous acid. Although influent NH4+–N concentrations were similar at both sites, Iowa City’s higher pH and loading intensified FA toxicity. Nitrification, rather than biomass uptake, was the dominant NH4+–N removal pathway under high loading. These findings demonstrate that RAB systems can support partial nitrification under elevated loading conditions, highlighting their potential for oxygen-efficient NH4+–N treatment in phototrophic biofilm-based sidestream treatment.
Details
- Title: Subtitle
- Treatment Intensification of Digester Dewatering Sidestreams via Pilot- and Demonstration-Scale Revolving Algal Biofilms at Municipal Water Resource Recovery Facilities
- Creators
- Audrey E. Kocher - University of IowaHunter W. Schroer - University of IowaChristopher A. MarksCraig L. Just - University of Iowa
- Resource Type
- Journal article
- Publication Details
- ACS ES&T engineering, Vol.5(11), pp.3073-3084
- DOI
- 10.1021/acsestengg.5c00458
- ISSN
- 2690-0645
- eISSN
- 2690-0645
- Publisher
- American Chemical Society
- Copyright
- © 2025 The Authors
- Grant note
- Graduate College, University of IowaUniversity of Iowa Holden Comprehensive CenterBioenergy Innovation Fund at the University of Iowa Center for AdvancementDonald E. Bently Professorship: 21-SI-001, 20-SEPF-007 Iowa Economic Development AuthorityIowa Recruitment Fellowship from the University of Iowa Graduate College
We gratefully acknowledge the University of Iowa Holden Comprehensive Center's Microbiome Core for providing microbiome sequencing services and the University of Iowa State Hygienic Laboratory, as well as Boulder's Water Quality and Environmental Services, for conducting water quality analyses. We thank the Iowa City Water Resource Recovery Facility and the Boulder Water Resource Recovery Facility for housing the RAB systems, and we are grateful to Gross-Wen Technologies for developing the RAB system and for their valuable collaboration and technical support. We also thank Maclaine Putney for his technical assistance and expertise in operating the Iowa City RAB and Abigail Toretsky for her time spent operating the Boulder RAB, collecting data, and analyzing samples. Additional thanks to undergraduate researchers Halle Eisfelder, Erin Elshoff, and Cullen McDermott for their assistance with sample collection and lab work. This work was supported financially by the Bioenergy Innovation Fund at the University of Iowa Center for Advancement, the Donald E. Bently Professorship, the Iowa Economic Development Authority (contracts 21-SI-001 and 20-SEPF-007), and the Iowa Recruitment Fellowship from the University of Iowa Graduate College. ChatGPT was used to suggest improvements to writing clarity.
- Language
- English
- Electronic publication date
- 09/10/2025
- Date published
- 11/14/2025
- Academic Unit
- Civil and Environmental Engineering; IIHR--Hydroscience and Engineering
- Record Identifier
- 9984963647702771
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