Natural organic matter (NOM) in South African waters: NOM characterisation using combined assessment techniques

In order to remove natural organic matter (NOM) from water in a water treatment train, the composition of the NOM in the source water must be taken into account, especially as it may not necessarily be uniform since the composition is dependent on the local environment. The main thrust of this study was to ascertain whether a cocktail of characterisation protocols could help to determine the nature, composition and character of NOM in South African waters. The characterisation of South African water sources was done by sampling 8 different water treatment plants located within the 5 major source water types in South Africa. The NOM composition of all of the samples was first studied by applying conventional techniques (UV, DOC, SUVA and bulk water parameters). NOM characterisation was then further conducted using advanced techniques (BDOC, PRAM and FEEM), which were aimed at developing rapid assessment protocols. The FEEM and UV results revealed that the samples consisted mainly of humic substances with a high UV-254 absorbance, while some samples had marine humic substances and non-humic substances. The samplefs DOC results were within the range of 3.5 to 22.6 mgE..1 C, which was indicative of the extent of variation of NOM quantities in the regions where samples were obtained. The BDOC fraction of the NOM ranged between 12 and 66%, depending on the geographical location of the sampling site. A modified PRAM was utilised to characterise the changes in NOM polarity in the water treatment process. PRAM results also indicated that the NOM samples were mostly hydrophobic. The composition and character of the NOM was found to vary from one water treatment plant to another. Combining conventional and advanced techniques could be a powerful tool for NOM characterisation and for extracting detailed information on NOM character, which should inform its treatability

Characterisation of natural organic matter (NOM) and its removal using cyclodextrin polyurethanes

Natural organic matter (NOM) occurs in all natural water sources when animal and plant material breaks down. NOM in water may react with chlorine and other disinfectants to produce disinfection by-products (DBPs), many of which are either carcinogenic or mutagenic. In this study the NOM content of the raw water from the Vaalkop Water Treatment Plant (which uses both chlorination and ozonation as treatment protocols) was characterised after fractionation on ion-exchange resins. Fractionation at different pH values resulted in the isolation of a neutral, a basic and an acidic component of either predominantly hydrophobic or hydrophilic NOM. In addition, NOM results from 3 open water bodies in Johannesburg were evaluated in the same manner. As expected, NOM from all water sources was predominantly hydrophobic (~60%). Each of the 6 isolated NOM fractions was percolated through synthetic cyclodextrin (CD) polyurethanes to determine the extent to which the CD polymers can remove NOM from water. The hydrophobic basic fraction and the hydrophilic acid fraction were most efficiently removed (24% and 10%, respectively). The remaining fractions were not much affected by the polymer treatment

Humic acid as a model for natural organic matter (NOM) in the removal of odorants from water by cyclodextrin polyurethanes

Current practices in some water-treatment facilities have reported that natural organic matter (NOM) blocks the adsorption sites of activated carbon resulting in lower geosmin and 2-methylisoborneol (2-MIB) removal. Humic acid has been reported to compete with geosmin and 2-MIB removal in the same way. The removal of odour chemicals such as geosmin and 2-MIB is important for potable-water treatment by water supply companies and municipalities. We have previously demonstrated that cyclodextrin polyurethanes are capable of removing a number of organic pollutants from water, but are not able to reduce the levels of NOM significantly. We wished to determine if the polymers would selectively remove geosmin and 2-MIB, despite the presence of NOM. Humic acid was chosen as a model for NOM since NOM constitutes about 70% of humic acid. Results obtained from this study indicate that the presence of humic acids at different concentrations could not affect the removal of geosmin and 2-MIB when cyclodextrin polymers were used since 90% removal was achieved. However the UV-Vis analysis showed a low removal of humic acids (3 to 20%)

Serotonin-Affecting Antidepressant Use in Relation to Platelet Reactivity

Depression is an independent risk factor of cardiovascular disease morbidity. Serotonin is a key neurotransmitter in depressive pathology, contained within platelets, and is a weak activator of platelets. Our study assessed the link between platelet reactivity traits, depression, and antidepressant (AD) use in a large population sample. Our study was conducted in the Framingham Heart Study (n = 3,140), and AD use (n = 563) and aspirin use (n = 681) were noted. Depression was measured using the Center for Epidemiological Studies‐Depression (CES‐D) survey. Platelet reactivity traits were measured across multiple agonists using five distinct assays. We utilized a linear mixed effects model to test associations between platelet traits and depression, adjusting for age, sex, aspirin use, and AD use. Similarly, we analyzed trait associations with any AD use, serotonin‐affecting ADs, and norepinephrine‐affecting ADs, respectively. There were strong associations with reduced platelet function and AD use, particularly with serotonin‐affecting medications. This included lower Optimul epinephrine maximal aggregation (P = 4.87E‐13), higher U46619 half maximal effective concentration (P = 9.09E‐11), lower light transmission aggregometry (LTA) adenosine diphosphate (ADP) final aggregation (P = 1.03E‐05), and higher LTA ADP disaggregation (P = 2.28E‐05). We found similar associations with serotonin‐affecting ADs in an aspirin‐taking subset of our sample. There were no significant associations between platelet traits and depression. In the largest study yet of AD use and platelet function we show that antidepressants, particularly serotonin‐affecting ADs, inhibit platelets. We did not find evidence that depressive symptomatology in the absence of medication is associated with altered platelet function. Our results are consistent with AD use leading to platelet serotonin depletions, decreased stability of platelet aggregates, and overall decreased aggregation to multiple agonists, which may be a mechanism by which ADs increase risk of bleeding and decrease risk of thrombosis