An optimised and validated surrogate analyte A-TEEM-PARAFAC-PLS technique for detecting and quantifying the biological oxygen demand in surface water.

A 5-day test duration makes BOD5 measurement unsatisfactory and hinders the development of a quick technique. Protein-like fluorescence peaks show a strong correlation between the BOD characteristics and the fluorescence intensities. For identifying and measuring BOD in surface water, a simultaneous absorbance-transmittance and fluorescence excitation-emission matrices (A-TEEM) method combined with PARAFAC (parallel factor) and PLS (partial least squares) analyses was developed using a tyrosine and tryptophan (tyr-trpt) mix as a surrogate analyte for BOD. The use of a surrogate analyte was decided upon due to lack of fluorescent BOD standards. Tyr-trpt mix standard solutions were added to surface water samples to prepare calibration and validation samples. PARAFAC analysis of excitation-emission matrices detected the tyr-trpt mix in surface water. PLS modelling demonstrated significant linearity (R2 = 0.991) between the predicted and measured tyr-trypt mix concentrations, and accuracy and robustness were all acceptable per the ICH Q2 (R2) and ASTM multivariate calibration/validation procedures guidelines. Based on a suitable and workable surrogate analyte method, these results imply that BOD can be detected and quantified using the A-TEEM-PARAFAC-PLS method. Very positive comparability between tyr-trypt mix concentrations was found, suggesting that tyr-trypt mix might eventually take the place of a BOD-based sampling protocol. Overall, this approach offers a novel tool that can be quickly applied in water treatment plant settings and is a step in supporting the trend toward rapid BOD determination in waters. Further studies should demonstrate the wide application of the method using real wastewater samples from various water treatment facilities.

Detection and Quantification of Bisphenol A in Surface Water Using Absorbance-Transmittance and Fluorescence Excitation-Emission Matrices (A-TEEM) Coupled with Multiway Techniques.

In the present protocol, we determined the presence and concentrations of bisphenol A (BPA) spiked in surface water samples using EEM fluorescence spectroscopy in conjunction with modelling using partial least squares (PLS) and parallel factor (PARAFAC). PARAFAC modelling of the EEM fluorescence data obtained from surface water samples contaminated with BPA unraveled four fluorophores including BPA. The best outcomes were obtained for BPA concentration (R2 = 0.996; standard deviation to prediction error's root mean square ratio (RPD) = 3.41; and a Pearson's r value of 0.998). With these values of R2 and Pearson's r, the PLS model showed a strong correlation between the predicted and measured BPA concentrations. The detection and quantification limits of the method were 3.512 and 11.708 micro molar (µM), respectively. In conclusion, BPA can be precisely detected and its concentration in surface water predicted using the PARAFAC and PLS models developed in this study and fluorescence EEM data collected from BPA-contaminated water. It is necessary to spatially relate surface water contamination data with other datasets in order to connect drinking water quality issues with health, environmental restoration, and environmental justice concerns.

Comparative removal efficiencies of natural organic matter by conventional drinking water treatment plants in Zimbabwe and South Africa.

Natural organic matter (NOM) influences the quality and treatability of drinking water; therefore, its removal is paramount. A few studies exist on NOM removal in developing countries, and comparative studies are even fewer globally. This study compared the removal efficiencies for bulk NOM and biodegradable organic carbon (BDOC) fractions of drinking water treatment plants in Zimbabwe (Z) and South Africa (S). NOM removal efficiency at the coagulation stage of plant Z and plant S was 11% and 13%, respectively. The fluorescence index (FI) for the raw water feeding plant Z (1.66) indicated a mixture of both microbial and terrestrially derived NOM, whereas for plant S the FI (4.08) showed terrestrially derived NOM. Based on the log-transformed absorbance at the disinfection stage, plant S had a 58% greater opportunity to produce disinfection by-products than plant Z. The BDOC results for plant Z showed humic fractions were the major substrates for bacterial assimilation, whereas the heterotrophic bacteria in plant S were not particularly selective toward DOC fractions. Overall, the plants had comparable NOM removal performances. PRACTITIONER POINTS: NOM removal efficiency at the coagulation stage of plant Z and plant S was 11% and 13%, respectively. Plant Z had a mixture of both microbial and terrestrially derived NOM, whereas plant S had terrestrially derived NOM. Plant S had a 58% greater opportunity to produce disinfection by-products than plant Z. Humic fractions were the major substrates for bacterial assimilation for plant Z, whereas the heterotrophic bacteria in plant S were not selective towards DOC fractions.