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Escola Superior de Tecnologia e Gestão (ESTG) >
Artigos em Revista Internacional (ESTG) >
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http://hdl.handle.net/10314/3881
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Título: | Factorial analysis of the trihalomethane formation in the reaction of colloidal, hydrophobic, and transphilic fractions of DOM with free chlorine |
Autores: | Platikanov, Stefan Tauler, Roma Rodrigues, Pedro M.S.M. Antunes, Maria Cristina G. Pereira, Dilson Esteves da Silva, Joaquim C. G. |
Palavras Chave: | Factorial analysis Response surface methodology Chlorine water disinfection Colloidal Hydrophobic Transphilic Trihalomethanes formation Disinfection by products |
Data: | 25-Apr-2010 |
Editora: | Environmental Science and Pollution Research |
Resumo: | Background, aim, and scope This study focuses on the
factors that affect trihalomethane (THMs) formation when
dissolved organic matter (DOM) fractions (colloidal,
hydrophobic, and transphilic fractions) in aqueous solutions
were disinfected with chlorine.
Materials and methods DOM fractions were isolated and
fractionated from filtered lake water and were characterized
by elemental analysis. The investigation involved a screening
Placket-Burman factorial analysis design of five factors
(DOM concentration, chlorine dose, temperature, pH, and
bromide concentration) and a Box-Behnken design for a
detailed assessment of the three most important factor effects
(DOM concentration, chlorine dose, and temperature).
Results The results showed that colloidal fraction has a
relatively low contribution to THM formation; transphilic
fraction was responsible for about 50% of the chloroform
generation, and the hydrophobic fraction was the most
important to the brominated THM formation.
Discussion When colloidal and hydrophobic fraction solutions
were disinfected, the most significant factors were
the following: higher DOM fraction concentration led to
higher THM concentration, an increase of pH corresponded
to higher concentration levels of chloroform and reduced
bromoform, higher levels of chlorine dose and temperature
produced a rise in the total THM formation, especially of
the chlorinated THMs; higher bromide concentration generates
higher concentrations of brominated THMs. Moreover,
linear models were implemented and response surface
plots were obtained for the four THM concentrations and
their total sum in the disinfection solution as a function of
the DOM concentration, chlorine dose, and temperature.
Overall, results indicated that THM formation models were
very complex due to individual factor effects and significant
interactions among the factors.
Conclusions In order to reduce the concentration of THMs
in drinking water, DOM concentrations must be reduced in
the water prior to the disinfection. Fractionation of DOM,
together with an elemental analysis of the fractions, is
important issue in the revealing of the quality and quantity
characteristics of DOM. Systematic study composed from
DOM fraction investigation and factorial analysis of the
responsible parameters in the THM formation reaction can,
after an evaluation of the adjustment of the models with the
reality, serves well for the evaluation of the spatial and
temporal variability in the THM formation in dependence
of DOM. However, taking into consideration the natural
complexity of DOM, different operations and a strict
control of them (like coagulation/flocculation and filtration) has to be used to quantitatively remove DOM from the raw
water.
Recommendations and perspectives Assuming that this
study represents a local case study, similar experiments
can be easily applied and will supply with relevant
information every local water treatment plant meeting
problems with THM formation. The coagulation/flocculation
and the filtration stages are the main mechanisms to
remove DOM, particularly the colloidal DOM fraction.
With the objective to minimize THMs generation, different
unit operation designed to quantitatively remove DOM
from water must be optimized. |
URI: | http://hdl.handle.net/10314/3881 |
Aparece nas Colecções: | Artigos em Revista Internacional (ESTG)
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Ficheiros deste Registo:
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Environ_Sci_Pollut_Res (2010).pdf | | 521Kb | Adobe PDF | Ver/Abrir | |
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