Bethany Campbell
Academic and research departments
Faculty of Engineering and Physical Sciences, Department of Chemical and Process Engineering.My research project
Characterisation, removal and recovery of organic contaminants in hydrothermal carbonization process water
Hydrothermal carbonisation (HTC) is a thermochemical conversion process that upgrades wet biomass into a solid, carbonaceous product, with a higher carbon content and hence higher calorific value. This can be used as a fuel, soil amender, or further upgraded into useful products. An obstacle in the industrialisation of hydrothermal carbonisation is the production of large volumes of highly polluted wastewater - water with high COD, BOD and inorganic content. This must be dealt with efficiently to allow the economic and environmental feasibility of the hydrothermal carbonisation process.
My project focuses on the removal and recovery of the organic contaminants in the process water from hydrothermal carbonisation of spent coffee grounds. The aim is to produce dischargeable wastewater, having recovered as much of the organic material as possible, as useful products such as high-quality biogas, which increases the overall energy recovery in the HTC and subsequent process water treatment regime.
My PhD project is in conjunction with and sponsored by Antaco UK Ltd, as well as the University of Surrey.
Supervisors
Research
Research interests
Wastewater Treatment
Green Energy
Biomass Processing
My publications
Publications
This study investigates the long-term performance of the mesophilic (35 °C) anaerobic mono-digestion of process waters (PW) from the hydrothermal carbonisation (HTC) of spent coffee grounds. At an organic loading rate (OLR) of 0.4 gCOD L−1 d−1, initial instability was seen, but after 40 days and supplementary alkalinity, the digestion stabilised with the chemical oxygen demand (COD) in the untreated PW degraded with 37.8–64.6% efficiency and the yield of methane at 0.16 L gCOD−1. An increase in OLR to 0.8 gCOD L−1 d−1 caused a collapse in biogas production, and resulted in severe instability in the reactor, characterised by falling pH and an increasing volatile fatty acid concentration. Comparatively, the digestion of a treated PW (concentrated in nanofiltration and reverse osmosis after removal of the fouling fraction), at OLR between 0.4 and 0.8 gCOD L−1 d−1, was stable over the entire 117 days of treated PW addition, yielded methane at 0.21 L gCOD−1 and the COD was degraded with an average efficiency of 93.5% - the highest efficiency the authors have seen for HTC PW. Further anaerobic digestion of untreated PW at an average OLR of 0.95 gCOD L−1 d−1 was stable for 38 days, with an average COD degradation of 69.6%, and methane production between 0.15 and 0.19 L gCOD−1. The digestion of treated PW produced significantly higher COD degradation and methane yield than untreated PW, which is likely to be related to the removal of refractory and inhibitory organic material in the post-HTC treatment by adsorption of hydrophobic material.