Understanding how microbial community contributes to wastewater treatment performance in constructed wetlands within Scotch whisky distilleries

Constructed wetlands (CWs) play a crucial role in biological water treatment, particularly within the Scotch whisky industry. The first parth of this thesis explores methods to enhance biodiversity information from wetlands. It focuses on optimising DNA yield, comparing substrates, and evaluating taxonomic results using ONT MinION and Illumina MiSeq. The research also examines spent lees treatment in mesocosms with various substrates and biochar, analysing biofilm diversity, microbial dynamics, and biochar's impact. Additionally, it assesses seasonal treatment performance and microbial changes in CWs treating whisky wastewater. The study further evaluates pollutant removal by biochars, tests the toxicity of untreated and treated spent lees, and investigates biochar's effectiveness in reducing toxicity and copper adsorption mechanisms.<br/>One aspect of the research focuses on the optimal isolation and processing of bacterial biofilms from gravel substrates in CWs. Various detachment techniques were evaluated, including the duration of agitation during extraction, extraction temperature, and enzyme usage. The study revealed that enzyme treatment significantly increased DNA concentration without significantly affecting bacterial richness. Comparing 16S taxonomy data from Illumina MiSeq and Oxford Nanopore Technologies (ONT) MinION highlighted differences in taxonomic resolution, particularly at the genus level, with MinION sequencing showing poor correlation with Illumina MiSeq data unless the same database was used. The thesis also assesses the performance of different CW substrates, including pea gravel, LECA, and Alfagrog, both with and without the addition of biochar. Among the substrates tested, LECA+biochar and gravel+biochar demonstrated superior results in reducing dissCu (dissolved copper), chemical oxygen demand (COD), dissolved organic carbon (DOC), and modulating pH. These findings indicate the potential of biochar to enhance treatment efficacy, though it was noted that biochar inclusion generally decreased bacterial diversity initially. Over time, however, biochar's presence was beneficial for long-term treatment efficacy. Among the bacterRal classes present Rn the mesocosms that may play a crucRal role<br/>Rn water treatment performance, GammaproteobacterRa, BacteroRdRa and AlphaproteobacterRa should be further RnvestRgated. In terms of fungal classes, the role of Sordariomycetes should be explored in greater depth. In examining the seasonal performance and microbial dynamics of horizontal subsurface flow CWs across different whisky distilleries in Scotland, the research reveals consistent success in dissCu removal throughout the seasons. However, performance variability was observed across seasons for other water quality parameters such as suspended solids, turbidity, DOC, COD, nutrients, and pH. Significant seasonal variations were noted in microbial communities, particularly between CWs, with Gammaproteobacteria, Alphaproteobacteria, and Bacteroidia being the predominant classes. On the other hand, mRcrobRal dRversRty wRthRn each sRte exhRbRted neglRgRble or low level varRatRon across seasons at the class and order levels.<br/>Further investigation into biochar-based treatments for spent lees compared raw biochar produced from softwood (RB), a metal-modified biochar produced from RB (MMB), and a biochar-mineral composite produced from orchard pruning residues (BMC). Some of these treatments effectively raised pH and removed dissCu, with efficacy correlating with biochar dosage. Ecotoxicological assessments using Lepidium sativum hypocotyl length and Escherichia coli growth inhibition tests demonstrated significant reductions in toxicity for spent lees treated with MMB and BMC, underscoring the promising potential of biochar treatments in pollutant removal and environmental risk mitigation.<br/>Following this trend, the use of modified biochar derived from whisky cask cooperage waste as a pretreatment method for spent lees is also explored. NaOH-modified biochar, through additional heat treatment, significantly improved pH and dissCu removal. Column studies supported the efficacy of these modified biochars, showing substantial pH elevation and efficient dissCu removal, with surface characterisation techniques confirming the microprecipitation of Cu ions on the biochar. This approach highlights the potential of biochar as a sustainable and effective pretreatment solution for distillery effluents. Overall, this thesis provides comprehensive insights into optimising CW systems and biochar treatments for effective wastewater management in the whisky industry. The findings contribute to the development of sustainable and circular waste management practices, enhancing the environmental performance of distillery operations and supporting the broader application of CWs and biochar in industrial wastewater treatment.

Name dc:type.qualificationname

Doctor of Philosophy (awarded by UHI)

Level dc:type.qualificationlevel

Doctoral Thesis

Grantor dc:publisher.institution

University of the Highlands and Islands

Year dc:date.issued

2025

Author dc:creator

• Cakin, Ilgaz

Advisors dc:contributor.advisor

• Taggart, Mark
• Morrissey, Barbara

Language dc:language

eng

Identifier

oai:pure.atira.dk:studenttheses/fb88e42a-904b-4527-a6a2-52b7ace87e10

OAI identifier oai:identifier

oai:pure.atira.dk:studenttheses/fb88e42a-904b-4527-a6a2-52b7ace87e10