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Congratulations to Dr. Xiaoran Chu and Dr. Siti Suhailah Rosli on completing their PhD’s.

Dr Chu was entitled “Oxidation of algae beyond cyanobacteria: Revealing the oxidation mechanisms and kinetics of resilient green algae and diatoms in water treatment.” Her research addresses the challenges posed by harmful and nuisance algal blooms (HNABs) and associated algal organic matter (AOM) in drinking water sources. She examined the oxidation mechanisms and kinetics of common chemical oxidants (free chlorine, potassium permanganate, and hydrogen peroxide) on green algae (Chlorella vulgaris), comparing them with cyanobacteria (Microcystis aeruginosa) and diatoms (Fragilaria sp.).

The study found that the oxidation pathways of these oxidants on C. vulgaris involved four stages: membrane damage, pigment scavenging, internal cell structure damage, and complete cell rupture. The presence of bacterial populations was shown to significantly affect the oxidation rates.

Dr. Chu's findings suggest future research should focus on the interference of coexisting microorganisms during oxidation and refine traditional empirical models based on varying cell concentrations. If you found the topic fascinating too, find the thesis in the ���������¼� library ()!

Dr Rosli PhD was entitled “Reduction of the water footprint of microalgal photobioreactors via wastewater reuse”. Her study aims to further minimise water consumption in wastewater algal photobioreactors by reusing the secondary treated wastewater. In particular, the impacts of harvesting methods, mode of operation (batch or continuous), and the reuse ratios were examined in relation to algal growth, nutrient availability, biomass composition, and dissolved organic matter (DOC) build up. Initially, the optimal reuse ratio was evaluated under batch conditions using synthetic wastewater, that mimicked secondary treated effluent. To maintain healthy C. vulgaris production, the addition of 50% fresh synthetic wastewater after one cycle was necessary. The use of microfiltration (MF) membrane kept accumulated DOC lower than 15 mg/L at each reuse cycle, enabling C. vulgaris to grow well in the spent synthetic wastewater. However, the reuse of spent real wastewater after centrifugation or flocculation-sedimentation with chitosan could only be used for two growth cycles before the C. vulgaris cell counts started to decrease. In continuous cultivation using a submerged ultrafiltration (UF) membrane photobioreactor (MPBR), the permeate-based spent real wastewater could be reused for up to 33 days. In all experiments, the DOC content shows an increased with each successive reuse cycle, mainly due to the release and accumulation of carbohydrates in the reactor. However, the cultivation of C. vulgaris biomass in spent real wastewater was mainly impacted by the accumulation of humic substances and copper in the spent medium. Overall, the reuse of wastewater in batch and continuous modes for multiple cycles was feasible, leading to a reduction in water and nutrients consumption of up to 50%. Additionally, the use of MF provides a suitable barrier to reuse the spent wastewater without compromising algal cell growth. Her thesis is also available in the library (via this ).