Novel Constructed Wetland (CWs) Treatment Options for Rural Works

Background: Increasingly stringent discharge consents are being applied for key nutrient parameters including nitrate and ammonia, paired with political and regulatory pressure to also consider emerging pollutants such as pharmaceuticals and personal care products, dictate that identifying appropriate solutions for rural works is critical to future-proofing rural wastewater treatment.
N-removal in CWs is facilitated by the microbial activity, controlled primarily by aerobic/anaerobic conditions. Tidal flow (TF; fill-empty cycles) is a novel configuration of constructed wetland (CW) for wastewater treatment and has shown excellent potential for maximizing N removal by providing both aerobic (NH4-N → NO3-N) and anaerobic (NO3-N → N2O and N2) conditions within a single constructed wetland bed. This has been demonstrated by JHI supervisors in pilot scale (two 3 x 6 m2) TFCWs at a rural works in Aberdeenshire.
The student will utilize the existing pilot scale TFCWs above, mesocosm studies and access to full scale CWs to define optimal operating conditions for novel types of CW. Considered in the context of minimizing pollutant swapping (GHG emissions) and maximizing removal of other key nutrients and emerging contaminants, this will generate a greater understanding of how operating conditions, bed media and macrophytes influence the microbial communities responsible for biological break down of these pollutants. This will enhance our (limited) fundamental knowledge of microbial removal of nitrogen and other key nutrients under novel types of CW where oxygenation is enhanced through design and operating conditions. Understanding how process management selects for complete denitrification and minimizing CO2 and CH4 flux holds the potential for mitigating release of GHGs. Integral to this work will be studies on microbial functional groups involved in N removal (nitrifiers, denitrifiers) and organic matter (OM) turnover (e.g. methanotrophs, methanogens).

Project aim and hypotheses to be tested: The overall aim of this project is to understand how to optimize (in terms of treatment efficiency as well as sustainability criteria) constructed wetlands systems for complete nitrification and denitrification within a single bed. This will be achieved through the following objectives:
• Establish the link between influent operating conditions, rhizosphere oxygen emissions and microbial community structure and function for nitrogen removal.
• Evaluate the pollutant swapping potential of tidal flow CWs for N removal with respect to GHG emissions.
• Evaluate the system performance (water treatment and biomass production) and robustness to changing influent conditions in the context of sustainable treatment systems for rural works

Skills: The project has an interesting degree of interdisciplinarity and there for the student will develop skills in wastewater sampling and physical, chemical and biological characterization of raw and treated wastewaters. These are key skills relevant to the water and wastewater industry, as well as being transferrable more widely. In addition to this, the project direction will encourage the student to develop and utilize molecular microbiology skills to understand the biological mechanisms and organisms involved in nitrification, denitrification and removal of other nutrients and pollutants. They will develop an understanding of current and emerging contaminants of concern (e.g. personal care products, pharmaceuticals, greenhouse gases), relevant to future careers in many spheres of environmental science.
Specific techniques to be applied include: Standard water quality analysis (e.g. pH and conductivity; soluble reactive P, nitrate, ammonium, dissolved organic carbon, total P, total N, major cations, chloride and sulphate biochemical oxygen demand, suspended solids and faecal indicator organisms); Green House Gas emissions from the CW (methane, carbon dioxide and nitrous oxide); Bed DO2, Biomass quality and growth, biodiversity measurement (e.g. invertebrates). Microbiological analyses, such as 16-S Illumina (MiSeq) sequencing for microbial diversity, qPCR quantification of functional genes e.g. Nitrifiers, denitrifiers and methanogens.
Importantly, the student will benefit from being part of active graduate schools at both Cranfield and JHI. Cranfield Water Science Institute and Prof Jefferson have an international reputation for water and wastewater treatment and engineering and work closely with the water industry sector, in particular water companies. This means that the student will gain exposure to (and likely additional sponsorship from) water companies south of the border as well as Scottish Water, providing them with excellent career in-roads within that sector. This perfectly complements the catchment-level understanding they will gain (in addition to the microbiological and biodiversity skills) from the JHI supervisors.