Change search
ReferencesLink to record
Permanent link

Direct link
Use of GAC after enhanced coagulation for the removal of natural organic matter from water for purification
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
2009 (English)In: Water Science and Technology: Water Supply, ISSN 1606-9749, Vol. 9, no 2, 173-180 p.Article in journal (Refereed) Published
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.

Place, publisher, year, edition, pages
2009. Vol. 9, no 2, 173-180 p.
Keyword [en]
colour ratio, enhanced coagulation, granular activated carbon, natural organic matter
National Category
Chemical Engineering
URN: urn:nbn:se:kth:diva-29562DOI: 10.2166/ws.2009.292ScopusID: 2-s2.0-74949102944OAI: diva2:395807
QC 20110208Available from: 2011-02-08 Created: 2011-02-08 Last updated: 2011-02-15Bibliographically 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

Open Access in DiVA

No full text

Other links

Publisher's full textScopus

Search in DiVA

By author/editor
García, IndianaMoreno, Luis
By organisation
Chemical Engineering
In the same journal
Water Science and Technology: Water Supply
Chemical Engineering

Search outside of DiVA

GoogleGoogle Scholar
The number of downloads is the sum of all downloads of full texts. It may include eg previous versions that are now no longer available

Altmetric score

Total: 42 hits
ReferencesLink to record
Permanent link

Direct link