Resumen de Evaluating the role of natural organic matter in the operation of a drinking water treatment plant incorporating membrane technologies
This dissertation was entirely conducted and driven to solve the problems caused by natural organic matter (NOM) in a Drinking Water Treatment Plant integrating and Ultrafiltration (UF) and Reverse osmosis (RO) stage. lt relies on the importance of characterizing and monitoring water to improve operation performance by gaining control and taking better decisions; the research conducted aimed at improving the existing methodologies and testing new analytical techniques to characterize NOM, evaluating its impact in the formation of precursors, gaining insight regarding fouling associated to NOM in the UF stage and develop countermeasures to alleviate fouling by esigning more robust systems.
In arder to achieve the goals stated, it was necessary to perform multidisciplinary tasks. On the one hand, sampling events were conducted at different locations within the fuli-s cale water treatment plant; the samples were then analyzed via different analytical devices, some of which are not being commercialized yet. Among the characteritzation techniques, online sensors were installed and tested. ln order to be able to manage and extract the maximum information from the data acquired, different advanced data analysis techniques were employed such as chemometrics.Also, models were implementad to predict water quality outcomes and anticipate events. On the other hand, efforts were driven to evaluate membrane performance by conducting historical data analysis and piloting a bench-scale and semi industrial scale Ultrafiltration plants. Research conducted in bench-scale included programming sequences that mimicked full-scale operation as well as setting data acquisition protocols.
The results obtained provide insights regarding the current NOM characteritzation techniques available up to date.
Fluorescence spectroscopy was found useful to discretize within organic fractions; the technique showed potential to be implementad on line and it provided further information than conventional techniques such as UV absorbance. In spite of that, fluorescence spectroscopy also had some drawbacks and it was concluded that it should be supported with additional techniques such as liquid chromatographyto better characterize NOM. Also, the research conducted was helped understand how the different process stages affect NOM removal, what the influence of NOM in operation is and how NOM affects the water quality outcome. In this line, a study was conducted to determine the influence of operation and water quality in the formation of disinfection by-products with carcinogenic concern (e.g. THMs). The study conducted give an idea ofthe importance that quality has on operation as well as the com plexity to operate efficiently.
Furthermore, a special focus was devoted to the UF stage in which DOM was analyzed by using chromatographic techniques. According to the mass balances conducted at full-scale, surface water feeding the UF stage is composed by approximately 45% of humic substances and 8% of high molecular weight compounds. Under these conditions, approximately 20% of the DOM in the UF was rejected. Regarding the fraction containing high molecular weight compounds, the rejection was almost 60%.
The impact that organic matter exerts in membrane performance was also assessed; the correlation plots obtained during bench-scale experimentation pointed at microbial by-products and humic-like components as the ones showing higher correlations. The mass balances conducted at full-scale showed that humic-like components were more strongly attached to the membranas than the compounds of higher molecular weight. Thus, the first were rather associated to irreversible fouling and the later ones to reversible fouling.
Finally, an effort was driven to evaluate and better manage the cleaning protocols conducted in the UF.The results showed that there was an excess of chemical and hydraulic cleanings in plant. To tackle this problem, an online managing system was proposed .
