Water Quality Parameters related to the presence of organic matter and microorganisms

Autor/es: Navalón Oltra, Sergio

Año de lectura: 2010

Universidad: Politécnica de Valencia

Departamento: Chemistry

Lugar de archivo: Biblioteca Central Universidad Politécnica de Valencia


Plumed of the greatest achievements in public health in the early twentieth century was the introduction of chlorine as a disinfectant in water treatment systems. But today it is known that the chlorine is not effective for the inactivation of some spores, cysts, oocysts or virus. In addition, since 1974 it is known that the chlorine reacts with natural organic matter (MON) of water to yield chlorinated compounds among which are the trihalomethanes (THMs), which are considered potentially carcinogenic compounds, genotoxic and mutagenic. Furthermore, the concentration of THMs is regulated in Spain through the RD 140/2003 to a peak of 100 mg L-1. For these reasons currently some treatment plants work with drinking water disinfectant alternative to chlorine (mainly ClO2 or O3) that have an increased disinfection power and reduce the formation of THMs.
Due to the interaction of chlorine as a disinfectant added to water MON and the formation of disinfection byproducts (SPDs), there have been numerous studies aimed at the characterization of these organic precursors. Generally one can say that the water MON is formed by a hydrophobic fraction (humic acids, fulvic acids and / or lignin derivatives) and a hydrophilic fraction (saccharides, proteins, compounds of polarity medium / high ketone carbonyl groups and / or carboxyl). Of all these compounds, phenol derivatives and beta-dicarbonyl compounds are considered as the main precursors of the SPDs.
In addition to MON water are being detected in the drinking water supplies or many compounds derived from human activity. Some of these compounds have been regulated (eg the presence of pesticides) but currently there is a group of emerging contaminants such as pharmaceuticals.
Given these precedents we undertook a study of the quality parameters related to water and organic matter with microorganisms resistant to chlorination.
Initially we proceeded to characterize the dissolved organic matter of the River Turia (Chapter 3). Among the various conclusions drawn from the study include the abundance of structures derived from polysaccharides and fatty acids. In addition, unexpectedly not observed the presence of humic and fulvic acids. In contrast, acetaminophen has been detected, a compound considered emerging contaminants in water supplies. Given the high content of polysaccharides in the water of the River Turia was to evaluate the behavior of carbohydrates as precursors of THMs in chlorination (Chapter 4). The results indicate that high concentrations of carbohydrates in water can contribute significantly to the formation of THMs.
Previous studies have shown that the presence of metal cations (eg copper) is a determining factor in the formation of THMs. Based on this background and taking into account the high concentration of other metal cations in natural waters evaluate the influence of the presence of Ca +2 and Mg +2 in the formation of THMs in the chlorination of solutions and a sample model Turia river water (Chapter 5). The results indicate that the presence of these ions favors the formation of THMs in the chlorination.
Considering the presence of emerging contaminants evaluated the reactivity of ß-lactam antibiotics (penicillin, amoxicillin and cefadroxil, Chapter 6) and amino acids (tryptophan, tyrosine and histidine, Chapter 7) compared with ClO2. Study concludes that the ClO2 is effective for the elimination of amoxicillin and cefadroxil and inefficient to penicillin. It has also proposed a reaction mechanism of ClO2 for all these compounds is in agreement with data and reactivity of ClO2. Finally, it has been found that when applied as a pretreatment ClO2 to chlorination is a reduction of THMs formed compared to assays in which the solutions have not been pretreated model.
Finally, we have evaluated the efficacy of disinfection of a fiber based photocatalytic TiO2 for the decontamination of water containing microorganisms resistant to chlorination (Cryptosporidium parvum and Giardia lamblia, Chapter 8). The results show that the system is effective in achieving UV/TiO2 full decontamination of these protozoa in lower residence times. Chlorine plays a synergistic role in the system considerably reduces the exposure times required to carry out an effective disinfection.

Ver documento