Assessing natural organic matter (NOM) characteristics in South African surface waters using fluorescence-based surrogate tools: biodegradability and treatment optimization perspectives

ABSTRACT The variable biodegradability and compositional complexity of natural organic matter (NOM) in surface waters pose an appreciable challenge for drinking water treatment. The study characterized NOM found in nine South African water sources for predicting treatability under regional conditions by integrating biodegradability dissolved organic carbon (BDOC) analysis, fluorescence excitation-emission matrix (EEM) spectroscopy, optical analysis, and bulk parameters, such as specific UV absorbance (SUVA), UV254 and dissolved organic carbon (DOC). Water sources that exhibited the highest BDOC potential index included Umzinto, Hazelmere, Mona, and Mtwalume (3.55, 2.21, 2.06, and 1.73, respectively). Strong Peak B, T, and M intensities were experienced by these sites, for example, Umzinto peak intensities were 0.32, 0.74, and 2.49 RU, respectively, indicative of the presence of the NOM pool largely influenced by microbial activity, likely derived from diffuse anthropogenic inflow or recent biological production. Water sources exhibiting such fluorescence profiles characteristic of a NOM pool with high biological reactivity are expected to respond well to treatment stages such as slow sand filtration, biologically active carbon (BAC), or biofiltration. The findings demonstrate the need for developing tailored treatment strategies based on site-specific NOM characteristics. Data-driven approaches helping utilities move toward adaptive water quality management have been proven.