A fluorescence-based assessment of the fate of organic matter in water treated using crude/purified Hibiscus seeds as coagulant in drinking water treatment

Abstract

This study used fluorescence excitation-emission matrices (EEMs) analysis to investigate the characteristics of natural organic matter (NOM) in treated water using okra crude extract (OCE), sabdariffa crude extract (SCE) and kenaf crude extract (KCE) as coagulants. In addition, an assessment of the impact of purified okra protein (POP), purified sabdariffa protein (PSP) and purified kenaf protein (PKP) was undertaken. The performance evaluation of these coagulants in terms of increase or decrease in dissolved organic carbon (DOC) was compared with Peak T fluorescence intensity observed at excitation wavelength 220–230 nm, and emission wavelength 340–360 nm. Fluorescence analysis of water treated with the crude extracts identified the removal of DOC in peaks A and C region whereas the increase in DOC from the protein was predominantly found in peaks T and B region. Furthermore, it was observed that the purified proteins were noted to be capable of reducing the DOC concentration in raw water where all fluorophores were not detected. The application of OCE, SCE and KCE yielded an increase in DOC of 65, 61 and 55% respectively, corresponding to increases of 65, 29 and 54% in peak T fluorescence intensities, at 100 mg/l dose. Furthermore, DOC concentration was reduced by 25, 24 and 18% using POP, PSP and PKP respectively as coagulants with corresponding decreases in fluorescence intensity of 46%, 44 and 36% in POP, PSP and PKP, at a lower dose of 0.1 mg/l. Therefore, it is clear that Peak T fluorescence intensity could be used to characterise organic matter in treated water using natural extracts to assess final water quality.