The demand for ‘greener’ wastewater treatment (WWT) is increasing globally. In particular, there is a need for more sustainable ‘passive’ approaches that do not rely so heavily (if at all) on hard engineering and continuous energy and chemical intervention/inputs. Within the Scotch whisky industry, the use of reed beds (or very similar systems, such as floating ecosystem technology) is increasing, and is seen as a potentially sustainable low-cost/low-intervention solution which can provide significant added benefits; enhancing local biodiversity, visual aesthetics and carbon capture (i.e., if ‘harvestable’ biomass plants are used). Many Scottish distilleries now utilize reed beds for their WWT – and underpinning such change is now a sector-wide ‘Environmental Strategy’ for the Scotch whisky industry (https://www.scotch-whisky.org.uk/insights/sustainability/environmental-strategy/
), central to which are targets to reduce energy use, sustainably manage water resources and reduce the sectors carbon footprint (all clearly in alignment with reed bed use). However, at present, reed beds represent a somewhat ‘variable’ solution for WWT (even when consistent reed bed designs are used), which can work well in some situations but relatively poorly in others. The main purpose of such systems is ultimately to remove potential pollutants from distillery effluents (i.e., reduce copper, biological oxygen demand (BOD) or other chemical components of concern), but their efficacy can vary with respect to location and over time. This then poses potential risks to the whisky sector given that discharges are regulated through SEPA discharge consents (for return of treated water to receiving burns/streams). Currently, the underlying causes of variability in performance of reed beds are poorly defined – but based on what little is known, good vs poor performance is likely related to one or more of several factors, e.g., flow rate, climate, input water quality, water (geo)chemistry, temporal factors (age of bed) and organisms present in the reed bed.
What is currently lacking is a cost-effective approach that can provide critical insight into the causes of good vs poor reed bed performance. Available assessments tend to be restricted to some standard/simple measurements of water quality, e.g., of BOD, pH, Cu, temperature – but these alone are often insufficient to identify why the reed bed succeeds/fails. While such measurements provide information on ‘function’ (i.e., how well the system is working) and can be used to consider geochemical processes (i.e., potential for binding of Cu to dissolved organic fractions), they say little about the biotic processes and biological community underpinning that ‘function’. To obtain such insight, a much deeper understanding of the reed bed system is needed (beyond geochemistry alone), given that these are complex ‘natural’ systems wherein bacteria, algae, plants, invertebrates, etc., are all collectively acting together to help attain WWT. A new tool that can now be applied to help us understand differences in the reed bed community is ‘metagenomic barcoding’ - which can now rapidly and comprehensively assess differences in community structure (i.e., of bacterial and algal communities), permitting linkages to be made with water quality observations (alongside other key local environmental factors). By making such critical links between reed bed ‘community’, water (geo)chemistry and reed bed ‘function’, the capacity to then identify underlying causes of underperformance, and thus design appropriate engineering solutions, will be substantially enhanced.
Key PhD Aims/Objectives:
1. Characterize key differences in biological communities present across a spectrum (good vs poor performing) of different reed-bed based WWT systems in Scotch whisky distilleries using metagenomic barcoding methods.
2. Undertake a detailed assessment of both input and output water quality at selected study sites throughout the seasonal cycle – allowing quantification of temporal and spatial variation in efficacy and performance; alongside a clear understanding of the water geochemistry at each site and the likely abiotic processes at play.
3. Establish the nature of associations between differing levels of performance with variations in reed bed characteristics – i.e., water quality/geochemistry, reed bed environment, climate, altitude, exposure, plants used, algal/bacterial communities present, etc.
4. Define a standardized, minimum cost sampling and analysis protocol (a new ‘toolkit’) in respect of reed beds (regarding metagenomic analysis and water quality parameters) that will be diagnostically useful in respect of the extent and cause of reed bed underperformance (for use both within and beyond the Scotch whisky sector).