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Removal of nitrogen and carbon organic matter by chitosan and aluminium sulphate
KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Engineering.
KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Engineering.ORCID iD: 0000-0001-8241-2225
2012 (English)In: Water Science and Technology: Water Supply, ISSN 1606-9749, Vol. 12, no 1, 1-10 p.Article in journal (Refereed) Published
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.

Place, publisher, year, edition, pages
2012. Vol. 12, no 1, 1-10 p.
Keyword [en]
aluminium sulphate, chitosan, coagulation, fractioning, natural organic matter, nitrogen compounds
National Category
Chemical Sciences
URN: urn:nbn:se:kth:diva-29743DOI: 10.2166/ws.2011.111ISI: 000327748300001ScopusID: 2-s2.0-84861050650OAI: diva2:397390
Sida - Swedish International Development Cooperation Agency

QC 20110214. Updated from submitted to published, 20120315

Available from: 2011-02-14 Created: 2011-02-14 Last updated: 2014-01-10Bibliographically approved
In thesis
1. Removal of Natural Organic Matter to reduce the presence of Trihalomethanes in drinking water
Open this publication in new window or tab >>Removal of Natural Organic Matter to reduce the presence of Trihalomethanes in drinking water
2011 (English)Doctoral 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.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2011. 80 p.
Trita-CHE-Report, ISSN 1654-1081 ; 2011:8
National Category
Environmental Sciences
urn:nbn:se:kth:diva-29759 (URN)978-91-7415-856-4 (ISBN)
Public defence
2011-02-18, K2, Teknikringen 28, entréplan, KTH, Stockholm, 10:00 (English)
QC 20110215Available from: 2011-02-15 Created: 2011-02-15 Last updated: 2011-02-15Bibliographically approved

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