Physical and geochemical controls on Manganese cycling in drinking water reservoirs

Abstract

This doctoral research explores how engineered destratification aeration of drinking-water supply reservoirs influences the transport and removal of manganese (Mn), one of the primary problems for UK water utilities. Mn-related issues are common throughout the UK and globally, with utilities spending £ millions annually to address these problems.

The primary research questions are: 1) how do aeration systems influence the distribution of Mn, dissolved oxygen (DO) and mixing, the primary geochemical and physical controls on Mn cycling, within UK reservoirs, and 2) can aeration be optimised to reduce problematic levels of Mn in the water entering the treatment plants?

These questions will be answered based on comprehensive physical and geochemical in situ measurements in three UK aerated drinking-water-supply reservoirs. Given that the need for research focusing on providing clean drinking water for all has been designated as a key global societal challenge by UK government funding bodies EPSRC (Engineering and Physical Sciences Research Council; https://www.ukri.org/councils/epsrc/), NERC (Natural Environment Research Council; https://www.ukri.org/councils/nerc/) and the UN SDG (United Nations Sustainable Development Goals; https://sdgs.un.org/goals), this project is transformative to both practice based water engineering and scientific communities within the UK and beyond.

This research investigates the following hypotheses: 1) Destratification aeration systems and water quality: Destratification aeration systems are a valuable tool for enhancing source-water quality, but effectiveness is likely a function of a series of site-specific, complex factors (e.g., bathymetry, wind conditions, sediment composition) that must be considered for optimal management. Based on the prevalent use of these aeration systems, investigation, and increased understanding of how they influence biogeochemical cycling within reservoirs is needed.

2) Aeration-induced mixing and Mn issues: In contrast to the prevailing management approaches in the UK, which focus on maintaining destratification (i.e., fully mixed reservoirs), aeration induced increases in mixing may contribute to Mn problems via increased sediment resuspension and DO consumption within the water column and sediment, resulting in enhanced release of Mn from the sediment into the source water and worsening overall water quality.

3) Site-specific aeration operation and management: Ultimately, comprehension of how aeration influences the physical and geochemical processes controlling Mn distributions within specific reservoirs will directly lead to improved aeration operations and the more sustainable management of water supplies. More broadly, both in-reservoir and external (e.g., catchment) driven influences may dictate the overall success of reservoir aeration.

Date of Award	24 Jul 2024
Original language	English
Awarding Institution	University of Bath
Supervisor	Lee Bryant (Supervisor) & Thomas Kjeldsen (Supervisor)