Liu, X.; (2010) Removal of humic substances from water using solar irradiation and granular activated carbon adsorption. Doctoral thesis , UCL (University College London).

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Abstract

For the existing water treatment processes, difficulties in removing humic substances (HS) to improve drinking water quality, and safety, have created the demand for exploring novel options to enhance HS removal. Here a combination of solar irradiation and granular activated carbon (GAC) adsorption is proposed. It aims to make use of the most freely available and abundant energy source, sunlight, to improve the performance of GAC adsorption process. An investigation into how characteristics of HS vary under natural sunlight and how this influences the subsequent removal of HS by GAC adsorption was carried out. Bulk water parameters, and more specifically, UV absorbance at 254 nm (UV254), as well as dissolved organic carbon (DOC) were used in conjunction with molecular weight (MW) to evaluate the performance of the solar-GAC method. The observation was made that solar irradiation led to a decrease in DOC, UV254 and MW of HS. The high MW components were photodegraded into smaller molecules, even with very low solar intensity in winter. Significant photodegradation of small molecules was also achievable by exposure to natural sunlight alone. Pre-treatment using solar irradiation was shown to successfully improve the GAC adsorption performance on HS removal, increasing the DOC removal from 69 % to 95 %. An up to three-fold increase in the adsorption capacity of GAC for the irradiated HS was observed. Solar collectors were found to effectively enhance the photodegradation of HS, and consequently enhance the removal of HS by GAC adsorption. The application of solar collectors could be a viable option for humic water treatment. The proposed solar irradiation-GAC adsorption method provides a new approach for the treatment of humic rich waters. The utilization of solar irradiation in water treatment processes is considered a sustainable and promising field.

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