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Start-up and operational strategies for deammonification plants: - a study with one-stage moving bed biofilm reactors treating reject water
Mälardalen University, School of Business, Society and Engineering, Future Energy Center. Purac AB.ORCID iD: 0000-0001-8869-6513
2019 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

To limit eutrophication, wastewater treatment plants use biological methods to convert degraded nitrogen to nitrogen gas. Deammonification, or partial nitritation in combination with anammox, has been shown to be an energy efficient process. This process is currently implemented in approximately 150 full-scale plants, and mainly on reject waters, the liquid fraction after dewatering of anaerobic digestion at municipal wastewater treatment plants. Implementation has been impeded by the slow growth of anammox bacteria, and 99% of the full-scale plants using the process have been using different methods to inoculate the process with anammox bacteria from elsewhere. Separate reject water installations, however, have shown high nitrous oxide emissions, which could increase the total carbon footprint.

The objective of this thesis was to develop and validate a start-up concept using the moving bed biofilm reactor (MBBR) technique applied to reject water, and to investigate how the operational strategies could be optimized to limit potential nitrous oxide emissions. The results show that a one-stage deammonification process based on the MBBR technology with indigenous anammox bacteria originating from the reject water can be set up within a applicable time frame (<100 days). This was validated in two laboratory reactors and in two full-scale studies. Reject water originating from both mesophilic and thermophilic digested sludge was used. Anammox growth and nitrogen reduction were detected with fluorescence in situ hybridization (FISH) and chemical analysis, respectively. The start-up time was 72 days in the laboratory and 120 days in full-scale. In laboratory scale, there was no improvement in start-up time when adding external anammox inoculum. Results from a screening study of seven reject waters and their content of anammox bacteria using qPCR indicated the presence of 104–105 genome units anammox per mL in reject water, which could be sufficient for starting up deammonification plants within an applicable time frame.

A final case study shows the potential of decreasing nitrous oxide emissions when a full-scale plant treating reject water was modified from nitrification/denitrification using a Sequencing Batch Reactor (SBR) to a deammonification process using the MBBR technique. The nitrous oxide emissions decreased from 10% to 0.1–0.7% of total nitrogen load with the change of operation mode. Further optimization by pH set point led to lower emission values. This effect is thought to be linked to the lower aeration ratio and increase in complete denitrification of dissolved nitrous oxide at higher pH.

Place, publisher, year, edition, pages
Västerås: Mälardalen University , 2019.
Series
Mälardalen University Press Dissertations, ISSN 1651-4238 ; 290
National Category
Water Treatment
Research subject
Energy- and Environmental Engineering
Identifiers
URN: urn:nbn:se:mdh:diva-43258ISBN: 978-91-7485-427-5 (print)OAI: oai:DiVA.org:mdh-43258DiVA, id: diva2:1307246
Public defence
2019-06-10, Delta, Mälardalens högskola, Västerås, 13:15 (English)
Opponent
Supervisors
Funder
Vinnova, 2015-02422Available from: 2019-04-26 Created: 2019-04-26 Last updated: 2019-05-06Bibliographically approved
List of papers
1. Swedish Experience of the Deammonification Process in a Biofilm System
Open this publication in new window or tab >>Swedish Experience of the Deammonification Process in a Biofilm System
2011 (English)In: Swedish experience with deammonification process in biofilm system, 2011, p. 1333-1345Conference paper, Published paper (Refereed)
Abstract [en]

Based on results from many years of pilot plant experiments a one-stage deammonification

process for treatment of supernatant from dewatering of digested sludge has been applied in a

full scale at the Himmerfjärden wastewater treatment plant in the Stockholm region. The plant

was designed for nitrogen load of 480 kg d-1 and is based on the Moving Bed Biofilm Reactor

(MBBR), with about 32% of its volume filled with suspended carriers (K1H, Kaldnes®). An

outer biofilm layer performs nitritation while an inner layer the anammox reaction.

Experience gained from more than 2 years of operation of the plant is presented in the paper. After an

effective start–up period of about 6-7 months (totally 10 months) over 80% nitrogen removal

efficiency was obtained and nitrogen removal rates reached almost 2g m-2 d at a temperature of

28 oC. The nitrite production was the limiting step for the anammox reaction. Intermittent

aeration was used to secure a suitable ratio of aerobic and anaerobic conditions in the biofilm.

Inhibition of the ammonia oxidizers was observed at concentrations over 15 mg l-1 of free

ammonia as NH3. The free ammonia was controlled by a combination of different strategies

including aeration time, influent load and effluent recirculation. Conductivity proved to be a

suitable tool for the process monitoring.

Keywords
Anammox, biofilm, deammonification, nitrogen removal, supernatant, suspended carriers, DeAmmon®
National Category
Water Treatment
Identifiers
urn:nbn:se:mdh:diva-43255 (URN)
Conference
Proceedings of the IWA/Water Environment Federation, Nutrient and Recovery Conference 2011(1), 1067–1079
Available from: 2019-04-26 Created: 2019-04-26 Last updated: 2019-06-25Bibliographically approved
2. Impact of seeding on the start-up of one-stage deammonification MBBRs
Open this publication in new window or tab >>Impact of seeding on the start-up of one-stage deammonification MBBRs
Show others...
2014 (English)In: Environmental technology, ISSN 0959-3330, E-ISSN 1479-487X, Vol. 35, no 22, p. 2767-2773Article in journal (Refereed) Published
Abstract [en]

Treating nitrogen-rich reject water from anaerobically digested sludge with deammonification has become a very beneficial side stream process. One common technique is the one-stage moving bed bioreactors (MBBRs), which in comparison with the other deammonification techniques can be started up without seeding anammox bacteria. This study investigated the impact of biofilm seeding on the start-up of one-stage deammonification MBBRs. Two lab-scale reactors were run in parallel with partial nitritation for 56 days until 11% of the carrier area in one reactor was replaced with fully developed deammonification biofilm to work as the seeding material. The seeded reactor started nitrogen reduction immediately up to a plateau of 1.3gNm−2 d−1; after another 54 days on day 110, the reduction significantly increased. At the same time, the non-seeded reactor also started to reduce nitrogen due to deammonification. The development was followed with both nitrogen analyses and fluorescence in situ hybridization analyses. On day 134, the biofilm in both reactors contained >90% anammox bacteria and reached maximum nitrogen removal rates of 7.5 and 5.6gNm−2 d−1 in the seeded and non-seeded reactor, respectively. Over 80% of the inorganic nitrogen was reduced. In conclusion, the seeding did not contribute to a shorter start-up time or the achieved anammox enrichment, although it did contribute to a partial, immediate nitrogen reduction. The boundary conditions are the most important factors for a successful start-up in a deammonification MBBR system.

Place, publisher, year, edition, pages
Taylor & Francis, 2014
Keywords
deammonification, anammox, MBBR, reject water, seeding, start-up
National Category
Water Treatment
Research subject
Energy- and Environmental Engineering
Identifiers
urn:nbn:se:mdh:diva-43254 (URN)10.1080/09593330.2014.920421 (DOI)
Available from: 2019-04-26 Created: 2019-04-26 Last updated: 2019-06-25Bibliographically approved
3. Sinks and sources of anammox bacteria in a wastewater treatment plant - screening with qPCR
Open this publication in new window or tab >>Sinks and sources of anammox bacteria in a wastewater treatment plant - screening with qPCR
2018 (English)In: Water Science and Technology, ISSN 0273-1223, E-ISSN 1996-9732, Vol. 78, no 2, p. 441-451Article in journal (Refereed) Published
Abstract [en]

The deammonification process, which includes nitritation and anammox bacteria, is an energyefficient nitrogen removal process. Starting up an anammox process in a wastewater treatment plant (WWTP) is still widely believed to require external seeding of anammox bacteria. To demonstrate the principle of a non-seeded anammox start-up, anammox bacteria in potential sources must be quantified. In this study, seven digesters, their substrates and reject water were sampled and quantitative polymerase chain reaction (qPCR) was used to quantify both total and viable anammox bacteria. The results show that mesophilic digesters fed with nitrifying sludge (with high sludge ages) can be classified as a reliable source of anammox bacteria. Sludge hygienization and dewatering of digestate reduce the amount of anammox bacteria by one to two orders of magnitude and can be considered as a sink. The sampled reject waters contained on average &gt;4.0 × 104 copies mL1 and the majority of these cells (&gt;87%) were viable cells. Furthermore, plants with side-stream anammox treatment appear to have higher overall quantities of anammox bacteria than those without such treatment. The present study contributes to the development of sustainable strategies for both startup of anammox reactors and the possibility of improving microbial management in WWTPs.

Place, publisher, year, edition, pages
IWA Publishing, 2018
Keywords
Anaerobic ammonium oxidizing bacteria (anammox), Digestion, Full-scale, QPCR, Reject water treatment, Start-up strategy, Anaerobic digestion, Bacteria, Nitrogen removal, Polymerase chain reaction, Seed, Sewage pumping plants, Sludge digestion, Water treatment, Water treatment plants, ANAMMOX, Reject water treatments, Wastewater treatment
National Category
Environmental Engineering
Identifiers
urn:nbn:se:mdh:diva-40740 (URN)10.2166/wst.2018.318 (DOI)000445517400020 ()30101779 (PubMedID)2-s2.0-85052107611 (Scopus ID)
Available from: 2018-09-07 Created: 2018-09-07 Last updated: 2019-08-15Bibliographically approved
4. Rapid start-up of one-stage deammonification MBBR without addition of external inoculum
Open this publication in new window or tab >>Rapid start-up of one-stage deammonification MBBR without addition of external inoculum
2016 (English)In: WATER SCIENCE AND TECHNOLOGY, ISSN 0273-1223, Vol. 74, no 11, p. 2541-2550Article in journal (Refereed) Published
Abstract [en]

In recent years, the anammox process has emerged as a useful method for robust and efficient nitrogen removal in wastewater treatment plants (WWTPs). This paper evaluates a one-stage deammonification (nitritation and anammox) start-up using carrier material without using anammox inoculum. A continuous laboratory-scale process was followed by full-scale operation with reject water from the digesters at Bekkelaget WWTP in Oslo, Norway. A third laboratory reactor was run in operational mode to verify the suitability of reject water from thermophilic digestion for the deammonification process. The two start-ups presented were run with indigenous bacterial populations, intermittent aeration and dilution, to favour growth of the anammox bacterial branches. Evaluation was done by chemical and fluorescence in situ hybridization analyses. The results demonstrate that anammox culture can be set up in a one-stage process only using indigenous anammox bacteria and that a full-scale start-up process can be completed in less than 120 days.

Keywords
anammox, deammonification, full scale, start-up, thermophilic digestion
National Category
Earth and Related Environmental Sciences
Identifiers
urn:nbn:se:mdh:diva-34762 (URN)10.2166/wst.2016.406 (DOI)000391264900004 ()2-s2.0-85021857681 (Scopus ID)
Available from: 2017-02-16 Created: 2017-02-16 Last updated: 2019-04-26
5. Full-scale comparison of N2O emissions from SBR N/DN operation versus one-stage deammonification MBBR treating reject water: - and optimization with pHset-point
Open this publication in new window or tab >>Full-scale comparison of N2O emissions from SBR N/DN operation versus one-stage deammonification MBBR treating reject water: - and optimization with pHset-point
2019 (English)In: Water Science and Technology, ISSN 0273-1223, E-ISSN 1996-9732, Vol. 79, no 8, p. 1616-1625Article in journal (Refereed) Published
Abstract [en]

To be able to fulfill the Paris agreement regarding anthropogenic greenhouse gases, all potential 12 emissions must be mitigated. Wastewater treatment plants should aim to eliminate emissions of the 13 most potent greenhouse gas, nitrous oxide. In this study, these emissions were measured at a full-scale 14 reject water treatment tank during two different operation modes: nitrification/denitrification (N/DN) 15 operating as a sequencing batch reactor (SBR), and deammonification (nitritation/anammox) as a moving 16 bed biofilm reactor (MBBR). Nitrous oxide was measured both in the water phase and in the off-gas. The 17 treatment process emitted significantly less nitrous oxide in deammonification mode 0.14-0.7 %, 18 compared to 10 % of Total Nitrogen in N/DN mode. The decrease can be linked to the change feeding 19 strategy, concentration in nitrite, load of ammonia oxidized, shorter aeration time, no ethanol dosage 20 and the introduction of biofilm. Further, evaluation was done how the operational pH set point 21 influenced the emissions in deammonification mode. Lower concentrations of nitrous oxide was 22 measured in water phase at higher pH (7.5-7.6) than at lower pH (6.6-7.1). This is believed to be mainly 23 because of the lower aeration ratio and increased complete denitrification at the higher pH set point.

Keywords
biological nitrogen removal, nitrous oxide (N2O) emissions, deammonification, pH
National Category
Water Treatment
Research subject
Energy- and Environmental Engineering
Identifiers
urn:nbn:se:mdh:diva-43256 (URN)10.2166/wst.2019.163 (DOI)000474351200020 ()31169520 (PubMedID)2-s2.0-85067434025 (Scopus ID)
Conference
IWA Nutrient Removal and Recovery Conference18 - 21 November 2018, Brisbane, Australia
Available from: 2019-04-26 Created: 2019-04-26 Last updated: 2019-10-11Bibliographically approved

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Citation style
  • apa
  • ieee
  • modern-language-association-8th-edition
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  • Other locale
More languages
Output format
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