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  • 1.
    Garcia, Indiana
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Engineering.
    Removal of Natural Organic Matter to reduce the presence of Trihalomethanes in drinking water2011Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    In countries located in tropical zones, a critical task in drinking water plants is the removal of the natural organic matter (NOM), particularly during the rainy season when a lot of organic matter is transported by run-off into the water bodies. It provokes overloaded in the plants and they have often needed to be shut down. In the dry season, the NOM removal is also difficult due to its low concentration, and greater coagulant dosages are needed to destabilize the negative charge of the NOM.

    In order to increase the NOM removal, synthetic polymers based on acrylamide are sometimes used as coagulant aids. However, they have been associated with Alzheimerand are carcinogenic. Therefore, the present requirement is to find new treatments affordable for the conditions existing in tropical countries. The application of green compounds has become a responsibility to guarantee the health of the population.

    The situation in Nicaragua is similar to that in many tropical countries. At present, there are ten drinking water plants which use conventional treatment. Nine of them use surface water supplied by rivers, and one uses water from a lake. Many of these plants have problems of continuity, quantity, water quality, and coverage, although the water cost is low.

    The removal of natural organic matter by conventional or enhanced coagulation using aluminium sulphate or chitosan as coagulant while reducing the formation of trihalomethanes (THM) was the aim of this work. Chitosan is an environment-friendly compound that can act as coagulant, flocculant and adsorbent. Adsorption with activated carbon and chitosan has also been studied. The natural organic matter in the source waters was fractionated in order to determine which fractions are removed more easily by coagulation and which are recalcitrant.

    The experimental works was carried out with a period of sampling between 2003 and 2010, taking into consideration the dry and rainy seasons. The results show that conventional coagulation with aluminium sulphate is not sufficient to reduce the presenceof NOM sufficiently to avoid a high level of THM in the disinfection step. The NOM removal is greatly improved by treatment with enhanced coagulation, but a significant amount of NOM is not removed, with a high THM concentration as a consequence. High NOM removal can however be achieved by enhanced coagulation and subsequent adsorption with granular activated carbon.

    Chitosan has good properties as a coagulant in water with a high NOM content and performs well as flocculant. It also has a high adsorption capacity for NOM. Therefore, chitosan could be a good option as a substitute for aluminium sulphate compounds. However, since chitosan does not work properly in the dry season, when the NOM content is low, the use of aluminium sulphate in combination with chitosan should bestudied in more detail. A field with a large potential is the modification of the chitosan structure to increase its capacity for NOM removal and decrease the need for aluminium sulphate. Another advantage of using chitosan is the reduction of the negative impact of shrimp and squat lobster shells on the environment.

  • 2.
    Garcia, Indiana
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Engineering.
    Benavente, Martha
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Engineering.
    Moreno, Luis
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Engineering.
    Sorption kinetics of fulvic and humic acid onto chitosan of different molecular weightsArticle in journal (Other academic)
  • 3.
    Garcia, Indiana
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Engineering.
    Benavente, Martha
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Engineering.
    Moreno, Luis
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Engineering.
    Use of chitosan as coagulant in the removal of natural organic matter from four different raw waters2011In: Proceedings of the 10th International Conference of the European Chitin Society (EUCHIS 2011), 2011, p. 106-110Conference paper (Other academic)
  • 4.
    Garcia, Indiana
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Engineering.
    Moreno, Luis
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Engineering.
    Removal of humic acid by coagulation and flocculation with chitosan2010Article in journal (Other academic)
  • 5.
    Garcia, Indiana
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Engineering.
    Moreno, Luis
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Engineering.
    Removal of natural organic matter from water in Nicaragua to reduce the total exposure cancer riskArticle in journal (Other academic)
  • 6.
    Garcia, Indiana
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Engineering.
    Moreno, Luis
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Engineering.
    Removal of nitrogen and carbon organic matter by chitosan and aluminium sulphate2012In: Water Science and Technology: Water Supply, ISSN 1606-9749, E-ISSN 1607-0798, Vol. 12, no 1, p. 1-10Article in journal (Refereed)
    Abstract [en]

    River and lake waters were separated into four fractions to study the removal of nitrogen and carbon organic matter using chitosan (CH) and aluminium sulphate (AS). The fractions were very hydrophobic acid, slightly hydrophobic acid, charged hydrophilic acid and neutral hydrophilic. The results showed that the whole and fractionated water from both sources have a markedly hydrophobic character. However, lake water had a lower NOM concentration than river water. The ratio of dissolved organic carbon and dissolved organic nitrogen (DOC/DON) and dissolved inorganic nitrogen to total dissolved nitrogen (DIN/TDN) were higher in the hydrophobic fraction from both sources. Similarly DOC, colour and ultraviolet absorbance at 254 nm (UV254) also presented higher values in the same fraction. Chitosan achieved the better results in the removal of NOM from Boaco water, whole and fractionated, whereas aluminium sulphate achieved better removal from Juigalpa water. DON and DIN were removed by aluminium to about 30%. The DOC/DON and DIN/TDN ratios decreased with both coagulants in whole waters from both sources. The hydrophobic fraction contributed most to the formation of trihalomethanes, slightly hydrophobic acid being the biggest contributor. Lake water led to less THM formation than river water.

  • 7.
    García, Indiana
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology.
    Removal of natural organic matter by enhanced coagulation in Nicaragua2005Licentiate thesis, comprehensive summary (Other scientific)
    Abstract [en]

    The existence of trihalomethanes (THMs) in a drinking water plant of Nicaragua has been investigated in order to see whether the concentration exceeded the maximum contaminant level recommended by the environmental protection agency of the United States (USEPA) and the Nicaragua guidelines. The influence of pH, temperature, chlorine dose and contact time on the formation of THMs were studied. The contents of organic matter measured by surrogate parameters such as total organic carbon, dissolved organic carbon, ultraviolet absorbance and specific ultraviolet absorbance were also determined in order to show which type of organic matter is most reactive with chlorine to form THMs. Models developed by other researchers to predict the formation of trihalomethanes were tested to see whether they can be used to estimate the trihalomethane concentration. In addition, empirical models were development to predict the THM concentration of the drinking water plant analysed. The raw water was treated by conventional and enhanced coagulation and these processes were compared with regard to the removal of natural organic matter (NOM). The significance of the results was assessed using statistic procedures.

    The average concentration of THMs found at the facility is below the USEPA and Nicaragua guideline values. Nevertheless the maximum contaminant level set by USEPA is sometimes exceeded in the rainy season when the raw water is rich in humic substances. Comparison between the water treated by conventional and enhanced coagulation shows that enhanced coagulation considerably diminished the trihalomethane formation and the value after enhanced coagulation never exceeded the guidelines. This is because enhanced coagulation considerably decreases the organic matter due to the high coagulant dose applied. The study of the trihalomethane formation when varying pH, time, temperature and chlorine dose using water treated by conventional and enhanced coagulation showed that higher doses of chlorine, higher pH, higher temperature and a longer time increases the formation of THMs. However, combinations of two and three factors are the opposite. The predicted THM formation equations cannot be used for the water at this facility, since the results shown that the measured THM differs significantly from the THM concentration predicted. Two empirical models were developed from the data for enhanced coagulation, using linear and non-linear regression. These models were tested using the database obtained with conventional coagulation. The non-linear model was shown to be able to predict the formation of THMs in the Boaco drinking water plant.

  • 8.
    García, Indiana
    et al.
    KTH, Superseded Departments, Chemical Engineering and Technology.
    Moreno, Luis
    KTH, Superseded Departments, Chemical Engineering and Technology.
    Drinking Water Treatment Plants in Nicaragua: a short review2003In: Proceeding of the IWA Asia Pacific Regional Conference, 2003Conference paper (Refereed)
  • 9.
    García, Indiana
    et al.
    KTH, Superseded Departments, Chemical Engineering and Technology.
    Moreno, Luis
    KTH, Superseded Departments, Chemical Engineering and Technology.
    Influence of Enhanced Coagulation in the removal of Natural Organic Matter to avoid formation of Trihalomethane in a drinking water plant in Nicaragua2004Conference paper (Refereed)
  • 10.
    García, Indiana
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology.
    Moreno, Luis
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology.
    Presence of trihalomethanes in drinking water plants in Nicaragua2006In: Journal of Water Supply: Research and Technology - Aqua, ISSN 0003-7214, E-ISSN 1365-2087, Vol. 55, no 3, p. 221-231Article in journal (Refereed)
    Abstract [en]

    The impact of enhanced coagulation on the formation of trihalomethanes (THMS) from drinking water was studied in four treatment plants in Nicaragua. Enhanced and conventional coagulation techniques were compared with regard to the removal of natural organic matter (NOM), which was measured by surrogate paramametres. The enhanced coagulation process showed a better removal of NOM, and as a consequence the THM formation was up to 50% lower than with conventional coagulation. The influences of chlorine dosage, temperature, PH and contact time on the THM formation in water treated by enhanced and conventional coagulation were also studied.

  • 11.
    García, Indiana
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Engineering.
    Moreno, Luis
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Engineering.
    Use of GAC after enhanced coagulation for the removal of natural organic matter from water for purification2009In: Water Science and Technology: Water Supply, ISSN 1606-9749, E-ISSN 1607-0798, Vol. 9, no 2, p. 173-180Article in journal (Refereed)
    Abstract [en]

    Filtration with granular activated carbon (GAC) after an enhanced coagulation (EC) process was evaluated in order to determine the effectiveness of GAC in the reduction of natural organic matter (NOM), which should result in much lower formation of trihalomethane in the disinfection step. The results show that a combination of EC and GAC considerably reduces the organic matter content, which is mainly fulvic acid. This type of organic matter is removed with high coagulant dosages which neutralize their high anionic charge. A further reduction of NOM is achieved due the adsorption of NOM by GAC. As a result, the average trihalomethane (THM) concentration was only 14.5±5 mg L-1. Enhanced coagulation alone decreased the NOM concentration by 50%, but the remaining NOM reacted in the chlorination step and a higher average THM concentration was found (38±23 mg L-1). An average THM concentration of 73.8±41.2 mg L-1 was found at the drinking water plant of Boaco when conventional treatment was used. This THM concentration sometimes exceeds the maximum contaminant level of 80 mg L-1 established by the United States Environmental Protection Agency (USEPA), but not the Nicaraguan threshold of 460 mg L-1.

  • 12.
    García, Indiana
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology.
    Moreno, Luis
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology.
    Use of pH, contact time, chlorine dose, temperature on the formation of trihalomethane and some empirical models for predicting trihalomethane formation2006In: WIT Transactions on Ecology and the Environment, 2006, p. 411-421Conference paper (Refereed)
    Abstract [en]

    An empirical model for predicting trihalomethane (THMs) formation, using linear and nonlinear regression, was carried out using a database built when the influence of enhanced coagulation on the formation of THMs was studied. These experiments were done under different conditions of pH, temperature, chlorine dosages and contact time; and two types of coagulation (enhanced and conventional). This database was first used to compare the formation of trihalomethane obtained in these experiments with some existing predictive models. Because the values measured experimentally did not agree enough with the values from the predictive models for both coagulation types, new ones were developed using the results of enhanced coagulation experiments. In order to test the predictive capacity of the models, both linear and non-linear models, were used to predict the formation of THMs using the database obtained from the conventional coagulation experiments. The nonlinear model gave best results in comparison with the linear model. The results were statistically validated by analysis of variance and other statistics parameters.

  • 13.
    García, Indiana
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology.
    Moreno, Luis
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology.
    Use of two different coagulants for the removal of organic matter from a drinking water.2005Conference paper (Refereed)
1 - 13 of 13
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