Speciation behavior of trihalomethanes formation in chlorinated waters due to the effects
of bromide is mathematically modeled by a three-tier scheme. Equations for the mole
fractions of the mono-, di-, and trihalo-intermediates at each tier level in terms of the initial
bromide to chlorine molar ratio are derived and verified by comparison with results of
other theoretical studies based on an assumption of constant bromination to chlorination
reaction reactivity ratio. It is identified that the usage of applied chlorine concentration or
available chlorine concentration for calculation of the relative initial bromide to chlorine
concentration would yield different reactivity ratio and should be used consistently. The
model equations are also tested by laboratory experiments done with source water at a
local plant. It is found that equations with an overall bromination to chlorination rate
constant ratio of 18.66 can capture the THM speciation behavior of all four tested
incubation periods well.
(NMEA) and N-nitrosodiethylamine (NDEA) are highly mutagenic compounds that are
suspected of carcinogenic activity to the human body.
The aim of the paper is the evaluation of the possibility of N-nitrosomethylethylamine and
N-nitrosodiethylamine formation as a result of the reaction of methylethylamine (MEA) or
diethylamine (DEA) respectively with chlorine in the presence of ammonia ions. The
optimal conditions of NMEA and NDEA formation were identified as a result of an
experiment carried out using different molar ratios of the substrates of reaction.
As the primary aim of the research was the evaluation of the possibility of NMEA and
NDEA formation as a result of the reaction of methylethylamine or diethylamine
respectively with chlorine in the presence of ammonia ions, a successful result obtained
after GC-LRMS analysis was fundamental to the further research. Analytes from postreaction
mixtures were concentrated, according to the modified procedure proposed by
Mitch et al., by means of liquid/liquid extraction with the usage of methylene chloride. The
N-nitrosomethylethylamine and N-nitrosodiethylamine were found in the analyzed
extracts of post-reaction mixtures. Apart from NMEA and NDEA identification, the
verification of other products with the usage of mass spectra library was also undertaken.
The results indicated that the changes in the relative ratio of the substrates influence the
concentration of NMEA and NDEA.
The obtained results revealed that NMEA and NDEA are only two of the many products
of the reaction taking place in the aqueous solution, which contained methylethylamine or
diethylamine and ammonia ions, and was disinfected with chlorine. The other identified
products are: ethyl(methyl)formamide and 3-ethyl(methyl)aminopropanenitrile. Therefore
N-nitrosomethylethylamine and N-nitrosodiethylamine can be treated as new disinfection
by-products similar to THMs, HAAs, MX or NDMA.
MX (3-Chloro-4-(Dichloromethyl)-5-Hydroxy-2(5H)-Furanone) and NDMA (N,N-dimethyl-Nnitrosoamine)
are disinfection by-products, which are formed during NOM’s and other water
containing precursors reaction with chlorine. Both, due to their potential carcinogenic and
mutagenic properties were placed on the list of potentially health hazardous disinfection byproducts.
Both of the compounds occur in drinking water at the ppt level.
An extensive review of international literature was the background of the presentation of
state of the art concerns on MX and NDMA analysis.
This paper discusses current issues with drinking water disinfection by-products (DBPs),
which include emerging (unregulated) DBPs that can be formed at greater levels with
alternative disinfectants (as compared to chlorine) and routes of human exposure (which
include inhalation and dermal exposure studies, in addition to ingestion). Health effects
driving DBP research include the recently observed reproductive/developmental effects
(including spontaneous abortion) observed in epidemiologic studies, as well as the
discrepancy between the types of cancer observed in animal studies for regulated DBPs
(mostly liver cancer) and the types of cancer observed in human epidemiologic studies
(mostly bladder cancer). Emerging DBPs discussed in this paper include iodo-acids,
bromonitromethanes, iodo-trihalomethanes (THMs), brominated forms of MX, bromoamides,
a bromopyrrole, and nitrosodimethylamine (NDMA) and other nitrosamines. Recent toxicity
studies have revealed that several of these DBPs are more genotoxic (in isolated cells) than
many of the DBPs currently regulated, and new occurrence data have revealed that many of
these DBPs can, in some cases, be present at levels comparable to regulated DBPs. Of the
alternative disinfectants, chloramination appears to increase the formation of iodo-acids,
iodo-THMs, and NDMA and other nitrosamines, relative to chlorine. Preozonation appears to
increase the formation of halonitromethanes.
The goal of this paper is an investigation into the influence of disinfection with ozone,
chlorine (Cl2) and chlorine dioxide (ClO2) on the aldehydes formation. Three types of
waters were treated with different doses of these disinfectants. The results obtained
indicate that the level of carbonyls concentration can significantly increase with the time
of Cl2 and ClO2 reaction with aldehyde precursors in treated water. There is no noticeable
correlation between quantity of aldehydes and total organic carbon (TOC) value of
disinfected water, but potential of organic by-products formation is evidently connected
with the nature of organic material. The range of productivity of aldehydes in water
treated with ClO2 or Cl2 is very similar. The productivities of aldehydes were calculated for
all investigated waters treated with different doses of oxidant and were 2 – 10 μg of
aldehydes per 1 mg TOC. Formaldehyde and acetaldehyde were the dominant carbonyl
compounds identified in water before as well as after the reaction with disinfectants.
Chloroform and other bromochlorotrihalomethanes were first identified as disinfection
byproducts (DBPs) in chlorinated water in 1970s. Since then, many other DBPs have
been identified such as haloacetonitriles, haloacetaldehydes, cyanogen halides,
aldehydes, ketoacids, chlorite, bromate and other organic and inorganic compounds. Due
to their occurrence and potential health risks, the U.S.EPA promulgated the Stage I
Disinfectants and Disinfection Byproducts (D-DBP) Rule in 1998. To assist water utilities
monitoring DBPs in their finished water, the U.S. EPA published a list of approved
analytical methods under the D-DBP Rule. In 1996, the U.S. EPA also promulgated the
Information Collection Rule (ICR) to collect brackground information on DBPs and
pathogens for the Stage II D-DBP-Rule. Actually 500 DBPs are known but few have been
investigated for their quantitative occurrence and health effects. Due to the fact that their
identification and quantitation have become extremely important to drinking water
companies in order to reduce or remove their presence, other analytical methods different
from those proposed by U.S. EPA have been optimized and are now commented in this
The occurrence of THMs and HAAs, and other volatile organics in Istanbul (Turkey) and
Salerno (Italy) surface water resources was investigated by the previous and present
data obtained on raw, coagulated, pre-chlorinated, pre-ozonated water samples. The
present drinking water directives/regulations in developed countries set maximum
contaminant level (MCL) for THMs at different levels. In Italy, where the 80-85% of water
demand is supplied by groundwater, a relatively low THMs value of 30 μg l-1 was set,
however there are no HAAs and bromate limits. On the other hand, there is still no
regulation for the THMs in Turkey. The characterization of chlorinated by-products,
particularly THMs, is detailed according to raw water origin and treatment technologies
currently applied in both cities.
The formation of Disinfection By-Products (DBPs) in drinking water results from the
reaction of chlorine or other disinfectants added to the water with naturally occurring
organic materials, and has raised concerns during the last decades because these
compounds are harmful for human health. During the present work, the formation of
different categories of DBPs was investigated in four water treatment plants (WTP) using
chlorine as disinfectant, and in selected points of the distribution network of Athens,
Greece, which is supplied from these four WTP, during a period of ten years. The
concentrations of DBPs were generally low and the annual mean concentrations always
well below the regulatory limit of the European Union (EU) for the total trihalomethanes
(TTHMs). The haloacetic acids (HAAs) have not been regulated in the EU, but during this
investigation they often occurred in significant levels, sometimes exceeding the levels of
TTHMs, which highlights the importance of their monitoring in drinking water. Apart from
THMs and HAAs, several other DBPs species were detected at much lower
concentrations in the chlorinated waters: chloral hydrate, haloketones and, in a limited
number of cases, haloacetonitriles.
Chlorination has been the most widely used technology for the disinfection of drinking
water around the world. The main purpose for the disinfection of drinking water is to
protect it against microbial contamination in the distribution systems and to prevent or at
least control re-growth of microorganisms in the pipelines.
A major disadvantage of chlorination is the formation of a wide variety of halogenated
compounds from natural organic matter (Rook, 1974; Christman et al., 1983). Some of
these by-products, namely trihalomethanes, 1,2-dichloroethane, trichloro- and
tetrachloro-ethene have diverse negative effects on human health, including toxicological,
mutagenic and carcinogenic effects, as well as induction of congenital malformations and
retarded fetal growth (Boorman et al., 1999). Current regulations in Europe demand a
target of 100 μg l-1 for trihalomethanes (THMs), 3 μg l-1 for 1,2-dichloroethane, 10 μg l-1
for the sum of trichloro- and tetrachloroethene, 1 μg l-1 for benzene and include all the
prementioned compounds in the category of volatile organic compounds (VOCs).
Since September 2003, the city of Thessaloniki and its suburbs are partly supplied with
drinking water from the Thessaloniki Water Treatment Plant (TWTP), which takes raw
water from the river Aliakmonas. This study presents the regular monitoring results at the
TWTP during the period February 2004 – February 2005 for THMs and VOCs included in
the European guidelines. At the same time, parameters such as pH, temperature,
chlorine demand, total organic carbon (TOC) and contact time (tR) were monitored.
Chlorination disinfection by-products (DBPs) are formed when water is chlorinated and the
organic matter in the water reacts with chlorine to form these by-products. There have
been concerns about the potential health effects of these by-products, including cancer and
reproductive effects. Here we have reviewed the literature on reproductive health effects.
Epidemiological studies on neural tube defects, urinary tract defects and small for gestation
age/intra growth retardation have shown the most consistent statistically significant
associations with an index of DBPs, but generally the risk estimates are small. The
interpretation of the studies is not straight forward because they may not be directly
comparable because of differences in DBP mixtures, exposure categories and actually
uptake of DBPs due to differences in e.g. ingestion rates, showering, bathing, and
swimming. Only few specific DBPs have been studied and THMs have often been used as
a marker for other DBPs, since they are often routinely available. Sample sizes, and
therefore power, have at times been low, particularly when the population was split into
exposure categories. Although most studies considered some confounders, (residual)
confounding by other water contaminants or other factors related to water intake, cannot
always be excluded. Case ascertainment, for outcomes such as spontaneous abortion and
certain congenital anomalies is far from straight forward, and for the latter at times
anomalies are lumped together with different aetiology, which may be inappropriate.
Furthermore, as with many reproductive epidemiological, if the putative agent affects both
early pregnancy loss and later birth outcomes such as congenital anomalies, interpretation
of later birth outcomes may be more difficult.