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Anaerobic co-digestion of fish sludge originating from a recirculating aquaculture system

Thesis (MEng) -- Stellenbosch University, 2022.

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Main Author: Netshivhumbe, Rudzani
Other Authors: Goosen, Neill Jurgens
Format: Thesis
Language:en_ZA
Published: Stellenbosch : Stellenbosch University 2022
Subjects:
Recirculating aquaculture systems
Sewage > Purification > Anaerobic treatment
Biomethane production
UCTD
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access_status_str Open Access
author Netshivhumbe, Rudzani
author2 Goosen, Neill Jurgens
author_browse Goosen, Neill Jurgens
Netshivhumbe, Rudzani
author_facet Goosen, Neill Jurgens
Netshivhumbe, Rudzani
author_sort Netshivhumbe, Rudzani
collection Thesis
dc_rights_str_mv Stellenbosch University
description Thesis (MEng) -- Stellenbosch University, 2022.
format Thesis
id oai:scholar.sun.ac.za:10019.1/126168
institution Stellenbosch University (South Africa)
language en_ZA
last_indexed 2026-06-10T12:44:44.746Z
license_str Other β€” see source repository
provenance_str_mv Harvested via OAI-PMH from SUNScholar β€” Stellenbosch University Repository
publishDate 2022
publishDateRange 2022
publishDateSort 2022
publisher Stellenbosch : Stellenbosch University
publisherStr Stellenbosch : Stellenbosch University
record_format dspace
source_str SUNScholar β€” Stellenbosch University Repository
spelling oai:scholar.sun.ac.za:10019.1/126168 Anaerobic co-digestion of fish sludge originating from a recirculating aquaculture system Netshivhumbe, Rudzani Goosen, Neill Jurgens Faloye, F. Gorgens, Johann F. Mamphweli, N.S. Stellenbosch University. Faculty of Engineering. Dept. of Process Engineering. Recirculating aquaculture systems Sewage -- Purification -- Anaerobic treatment Biomethane production UCTD Thesis (MEng) -- Stellenbosch University, 2022. ENGLISH ABSTRACT: Recirculation aquaculture systems (RAS) are considered as sustainable and environmentally friendly aquaculture systems capable of meeting the growing demand of seafood for human consumption. However, RAS produce large quantities of waste sludge from uneaten feed and fish faecal matter, which need to be removed from the recirculating water and treated to prevent adverse environmental impacts. Anaerobic digestion (AD) has been considered as an alternative method to stabilize the amount of organic waste in the environment before its disposal, with the simultaneous production of bio-methane that can serve as a source of energy within RAS. However, there are some drawbacks in the mono-digestion process of fish sludge (FS) such as process inhibition, unbalanced nutrient contents, and low methane yields. The biomethane production from FS, food waste (FW), and fruit & vegetable waste (FVW) was optimized during anaerobic co-digestion using a mixture design. The synergistic and antagonistic interaction effects of the three substrates on specific methane yield, volatile solids reduction, and process stability were evaluated in both batch and semi-continuous mode. A mixture design was used to determine the best mixture compositions of FS, FW, and FVW for specific methane yield and volatile solids removal during the anaerobic co-digestion process based on biomethane potential (BMP) measurements. The results showed that the optimum mixture proportions of FS, FW, and FVW were 63 %, 18 %, and 19 %, respectively. The results showed the maximum methane production and VS removal of 401 mL CH4/gVS and 64%, respectively under the optimum mixture. Anaerobic co-digestion of FS with FW and FVW enhanced the methane yields by 8 folds compared with mono-digestion of FS. The optimum mixture proportions obtained from batch BMP tests were further evaluated in 50 L batch and 30 L semi-continuous pilot-scale digesters to evaluate the effect of organic loading rate (OLR) on biogas production and process performance stability. The methane yield obtained from the batch pilot-scale digester was 272 NmLCH4 /gVS. This was 71 % of the methane yield obtained from the BMP test under the same optimum mixture condition. The batch digester showed no substantial inhibition of the system due to its strong buffering capacity. In semi-continuous mode, the digester was conducted under different OLRs of 1, 2, and 3 π‘”π‘‰π‘†πΏβˆ’1π‘‘βˆ’1 to investigate the impacts of OLR on biogas and methane production, and process performance stability of the anaerobic co-digestion of FS, FV, and fruit and FVW. The highest total biogas and methane production of 388 L/gVS and 67 L/gVS, with a methane content of 66.8% obtained at an OLR of 2 π‘”π‘‰π‘†πΏβˆ’1π‘‘βˆ’1 compared to OLRs of 1 and 3 π‘”π‘‰π‘†πΏβˆ’1π‘‘βˆ’1. The digester showed instabilities or failure at an OLR of 3 π‘”π‘‰π‘†πΏβˆ’1π‘‘βˆ’1 due to acid crash and accumulation of VFA of 11g/L. An OLR of 1- 2 π‘”π‘‰π‘†πΏβˆ’1π‘‘βˆ’1 is recommended for anaerobic co-digestion of FS, FW, and FVW in semi-continuous digesters because of less inhibitor indicators observed. AFRIKAANS OPSOMMING: Hersirkuleringsakwakultuursisteme (RAS) word beskou as volhoubare en omgewingsvriendelike akwakultuursisteme in staat om aan die groeiende aanvraag van seekos vir menslike gebruik te voldoen. RAS produseer egter groot hoeveelhede afvalslyk van ongeΓ«ete voer en visfekalieΓ«, wat verwyder moet word uit die hersirkulerende water en behandel moet word om nadelige omgewingsimpak te verhoed. Anaerobiese vertering (AD) is oorweeg as ’n alternatiewe metode om die hoeveelheid organiese afval in die omgewing te stabiliseer voor dit verwyder word, met die gelyktydige produksie van biometaan wat as ’n bron van energie binne RAS kan dien. Daar is egter sommige nadele in die monoverteringsproses van visslyk (FS) soos prosesinhibisie, ongebalanseerde nutriΓ«ntinhoud, en lae metaanopbrengs. Die biometaanproduksie uit FS, voedselafval (FW), en vrugte-en-groente-afval (FVW) is geoptimaliseer gedurende anaerobiese kovertering deur ’n mengselontwerp te gebruik. Die sinergistiese en antagonistiese interaksie-effek van die drie substrate op spesifieke metaanopbrengs, vlugtige vastestofreduksie, en prosesstabiliteit is geΓ«valueer in beide lot- en semi-aaneenlopende modes. ’n Mengselontwerp is gebruik om die beste mengselkomposisies van FS, FW, en FVW vir spesifieke metaanopbrengs en vlugtige vastestofverwydering gedurende die anaerobiese koverteringproses gebaseer op biometaanpotensiaal (BMP) mates, te bepaal. Die resultate het gewys dat die optimale mengselproporsies van FS, FW, en FVW 63%, 18% en 19% onderskeidelik was. Die resultate het getoon dat maksimum metaanproduksie en VS-verwydering van 401 mL CH4/gVS en 64%, onderskeidelik onder die optimale mengsel was. Anaerobiese kovertering van FS met FW en FVW het die metaanopbrengste 8 keer verhoog in vergelyking met monovertering van FS. Die optimale mengselproporsies verkry van lot BMP-toetse is verder geΓ«valueer in 50 L-lot en 30 L-semi-aaneenlopende loodskaalverteerders om die effek van organiese ladingstempo (OLR) op biogasproduksie en prosesdoeltreffendheidstabiliteit te evalueer. Die metaanopbrengs verkry uit die lotloodskaalverteerder was 272 NmLCH/gVS. Dit was 71% van die metaanopbrengs verkry uit die BMP-toets onder dieselfde optimale mengselkondisies. Die lotverteerder het geen substansiΓ«le inhibisie van die sisteem getoon nie as gevolg van sy sterk bufferkapasiteit. In semi-aaneenlopende mode, is die verteerder onder verskillende OLRe van 1, 2, en 3 π‘”π‘‰π‘†πΏβˆ’1π‘‘βˆ’1 uitgevoer om die impak van OLR op biogas en metaanproduksie, en prosesdoeltreffendheidstabiliteit van die anaerobiese kovertering van FS, FV, en vrugte en FVW, te ondersoek. Die hoogste totaal biogas en metaanproduksie was 388 L/gVS en 67 L/gVS, met ’n metaaninhoud van 66.8% verkry by ’n OLR van 2 π‘”π‘‰π‘†πΏβˆ’1π‘‘βˆ’1 in vergelyking met OLRe van 1 en 3 π‘”π‘‰π‘†πΏβˆ’1π‘‘βˆ’1. Die verteerder het onstabiliteite of mislukking getoon by ’n OLR van 3 π‘”π‘‰π‘†πΏβˆ’1π‘‘βˆ’1 as gevolg van suurineenstorting en akkumulasie van VFA van 11 g/L. ’n OLR van 1-2 π‘”π‘‰π‘†πΏβˆ’1π‘‘βˆ’1 word voorgestel vir anaerobiese kovertering van FS, FW en FVW in semi-aaneenlopende verteerders as gevolg van minder inhiberende indikators waargeneem. Masters 2022-11-23T12:30:30Z 2023-01-16T12:53:34Z 2022-11-23T12:30:30Z 2023-01-16T12:53:34Z 2022-12 Thesis http://hdl.handle.net/10019.1/126168 en_ZA Stellenbosch University 145 pages : illustrations application/pdf Stellenbosch : Stellenbosch University
spellingShingle Recirculating aquaculture systems
Sewage -- Purification -- Anaerobic treatment
Biomethane production
UCTD
Netshivhumbe, Rudzani
Anaerobic co-digestion of fish sludge originating from a recirculating aquaculture system
title Anaerobic co-digestion of fish sludge originating from a recirculating aquaculture system
title_full Anaerobic co-digestion of fish sludge originating from a recirculating aquaculture system
title_fullStr Anaerobic co-digestion of fish sludge originating from a recirculating aquaculture system
title_full_unstemmed Anaerobic co-digestion of fish sludge originating from a recirculating aquaculture system
title_short Anaerobic co-digestion of fish sludge originating from a recirculating aquaculture system
title_sort anaerobic co digestion of fish sludge originating from a recirculating aquaculture system
topic Recirculating aquaculture systems
Sewage -- Purification -- Anaerobic treatment
Biomethane production
UCTD
url http://hdl.handle.net/10019.1/126168
work_keys_str_mv AT netshivhumberudzani anaerobiccodigestionoffishsludgeoriginatingfromarecirculatingaquaculturesystem

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