Algae-based living sensor for water quality monitoring

• Main Author: Tan, Jonathan Teck Hong
• Other Authors: Dalton Tay Chor Yong
• Format: Final Year Project
• Language: English
• Published: Nanyang Technological University 2021
• Subjects: Engineering::Materials
• Online Access: https://hdl.handle.net/10356/148243
• Institution: Nanyang Technological University

The leaching of metallic pollutants into the drinking water supply is a serious environmental issue across the world. Current methods of water testing, including the use of Phaeodactylum tricornutum or P.tricornutum diatoms, have several limitations such as inconsistencies caused by different diatom morphotypes and slow speed that hinder their effectiveness. In a potential improvement of water testing using diatoms, the diatoms can undergo microencapsulation in small, gelatinous beads via electro-encapsulation and a chemical reaction between sodium alginate and calcium chloride. The concentration of the diatoms in the beads were determined to have a directly proportional relationship with the intensity of the chlorophyll a fluorescence emitted by the beads during fluorescence testing with a microplate reader. The diatom beads were then exposed to different concentrations of several metallic toxicants in solution form, with the concentrations of the metal solutions being made around the maximum permitted concentration of the metal in question in drinking water set by regulatory bodies like the Public Utilities Board (PUB). The average fluorescence intensity of the diatoms upon exposure to the metal solution after certain time intervals up to 24 hours was measured. It was determined that the diatom beads were able to differentiate between hazardous and non-hazardous (to people via consumption) concentrations of some metals such as copper and zinc almost immediately after exposure, but not for others (such as barium and nickel). When a comparative study between the beads and non-encapsulated diatoms was conducted, it was observed that the beads do not reduce variability in the data that is likely due to agglomeration of diatoms and inconsistent distribution of diatoms in the beads. Conflicting data from the comparative study prevented a definitive conclusion on whether microencapsulation of the diatoms improves on the ability of P.tricornutum to act as a living sensor for water quality monitoring, but the diatom beads definitely showed potential in detecting potentially harmful concentrations of certain toxicants several hours after exposure. Further tests using different (potentially organic or biological) toxicants and on-site samples instead of laboratory samples, improvements on tests conducted in this study and the development of a water testing device containing diatom beads are definitely recommended to ascertain the capabilities of the microencapsulated diatoms as acting as reliable water testing agents.