Doctor of Philosophy
Chemical and Biochemical Engineering
Ray, Ajay K.
The remediation of metal-contaminated natural water bodies is prioritized due to metals toxicity, non-biodegradable properties, and accumulative behaviours leading to the increased incidence of adverse health effects. Current investigation is driven by the existing problem of elevated aluminum concentrations in the groundwater of Khibiny alkaline massif (Kola Peninsula). The prohibitive aluminum level exceeding the accepted standard of 0.20 mg L−1 is described as a serious health concern when the groundwater used for the local water supply. The results of comprehensive field data analysis based on chemometric methods applied to the available monitoring data including 12 groundwater quality parameters are reported as well as the outcomes of laboratory study on aluminum adsorption from aqueous solutions. Computed correlation coefficients matrix revealed a statistically significant level of associations between aluminum concentrations and pH values, concentrations of SO42−, NO3−, Cl−. Mathematical models developed by using univariate and multivariate regression methods explained up to 54% of aluminum concentration temporal variability linked to pH, Cl−, NO3− and up to 67.5% of the original dataset total variance. The outcomes of hierarchical cluster analysis suggested data subdivision into three clusters where Al and pH formed a separate cluster. The frequency bands describing dominant variability features of groundwater quality parameters were identified by spectral analysis based on fast Fourier transform algorithm and corresponded approximately to 5–7, 13–17, and 20–34 month periods. Calculated CCME water quality index scores identified a groundwater quality gradual deterioration from fair to marginal category during the monitoring period 1999–2012. Laboratory study of aluminum removal on adsorbents from aqueous solutions considering water-specific natural conditions showed the maximum aluminum uptake of 1.69 mg g−1 by montmorillonite K10 within 120 min at pH 4.0 while TiO2 and vermiculite concrete-supported ferric oxyhydroxide adsorbent were most effective at pH 9.0 obtaining maximum adsorption capacities of 6.85 mg g−1 and 6.75 mg g−1 in 30 min and 240 min, respectively. It was shown that when these two adsorbents worked jointly the capacity reached 8.28 mg g−1 within 60 min at pH 9.0. The changes of each component mass allow controlling contact time to provide required aluminum removal efficiency. No apparent significant effect on aluminum removal by adsorbents tested in the presence of SO42−, NO3−, Cl− was observed at pH 9.0. The current study identifies a possible approach and the reliable foundation of water treatment technology solving the problem of elevated aluminum concentrations in the household water of Khibiny alkaline massif area as well as other locations where the solution of this problem can improve living conditions or industrial technologies.
Popugaeva, Daria, "Analysis and Control of Aluminum Concentration in Groundwater: Mathematical Modelling and Laboratory Study" (2019). Electronic Thesis and Dissertation Repository. 6036.