The document discusses the process of chlorination in water treatment, detailing its advantages and disadvantages, particularly the formation of trihalomethanes (THMs) which can be harmful to human health. It also covers perchlorate contamination and its health effects, including links to cancer and reproductive issues. Recommendations for reducing THM formation and managing organic material in water are provided, including the use of alternative disinfection methods.

1. Trihalomethanes
(THMs)
BAGHDAD UNIVERSITY
SANITARY ENGINEERING DEPARTMENT
M.SC. STUDENT : MARWA MOHAMMED

2.  the process of adding chlorine (Cl
2) or hypochlorite to water. This method
is used to kill certain bacteria and other
microbes in tap water as chlorine is
highly toxic. In particular, chlorination
is used to prevent the spread
of waterborne diseases such
as cholera, dysentery, and typhoid.
Chlorination

3. Chlorination
1- The process is economical and cheap .
2- It is harmless to human beings
.
3- It is reliable and effective .
4- Residual chlorine can be maintained in the water.
5- Easy to apply and ease to measure .

4. Disadvantages of Chlorination
* Formation of Trihalomethanes (THMs) , such
as carcinogen chloroform (CHCL3) .
* To avoid the formation of THMs , water
should be removed of organic impurities as
much as possible before chlorination .

5. Percolate
A perchlorate is the name for a chemical compound
containing the perchlorate ion, ClO−The preponderance
of perchlorates are produced commercially
Perchlorate salts are mainly used for propellants,
exploiting properties as powerful oxidizing agents.
Perchlorate contamination in the environment has been
extensively studied as it has effects on human health.
Perchlorate has been linked to its negative influence on
the thyroid gland

6. Most perchlorates are colorless solids that are soluble
in water. Four perchlorates are of primary
commercial interest: ammonium perchlorate
(NH4ClO4), perchloric acid (HClO4), potassium
perchlorate (KClO4), and sodium perchlorate
(NaClO4). Perchlorate is the anion resulting from the
dissociation of perchloric acid and its salts upon their
dissolution in water. Many perchlorate salts are
soluble in non-aqueous solutions.

7. The THMs forming
When chlorine is added to water with organic
material, such as algae, river weeds, and decaying
leaves, THMs are formed. Residual chlorine
molecules react with this harmless organic material
to form a group of chlorinated chemical compounds,
THMs. They are tasteless and odorless, but harmful
and potentially toxic. The quantity of byproducts
formed is determined by several factors, such as the
amount and type of organic material present in
water, temperature, pH, chlorine dosage, contact
time available for chlorine, and bromide
concentration in the water.

8. The THMs forming

9. The organic matter in water mainly
consists of
1- humic substance, which is
the organic portion of soil
that remains after prolonged
microbial decomposition
formed by the decay of
leaves, wood, and other
vegetable matter
2- fulvic acid, which is a water
soluble substance of low
molecular weight that is
derived from humus .

10. Trihalomethanes (THMs)
THMs are a class of chemical compounds derived from
methane (CH4) in which 3 of the 4 H atoms have been
replaced by halogens Possibilities in drinking water
include CHCl2Br, CHClBr2 and CHBr3. But the most
prevalent is chloroform, CHCl3 .

11. The Oxidation of chlorine
+7+5+3+1-1
Chlorine
oxidation
state
perchlo
rate
Chlorat
e
chlori
te
hypoch
lorite
chlorid
e
Name
ClO−4ClO−3ClO-2
ClO−Cl-Formula
Structure

12. The byproduct concentration is mainly determined by the
amount of organic material in the source water. Water facilities
that draw water from surface water (lakes, rivers, and reservoirs)
produce water with higher levels of THMs than facilities with
groundwater (wells and springs) as their source of water. THM
concentrations range from 0.030 to 0.150 milligrams per liter
(mg/l) in surface water and 0.001 to 0.010 mg/l in groundwater.
The distribution of these four compounds varies with bromide
concentration in water. EPA is currently regulating THMs for
small communities as part of the Microbial/ Disinfection and
Disinfection Byproducts (M/DBP) Rules. Under these rules the
allowable THM concentrations are 0.080 mg/l of THMs .
The levels that THMs Present in water

13. exposure to THMs may pose an increased risk of cancer.
Two THMs, chloroform and dibromochloromethane, are
carcinogens; and another THM, bromodichloromethane,
has been identified as a mutagen, which alters DNA.
Mutagens are considered to affect the genetics of future
generations in addition to being carcinogenic. THMs may
be responsible for reproductive problems and miscarriage.
some study found a miscarriage rate of 15.7 percent for
women who drank five or more glasses of cold water
containing more than 0.075 mg/l THM, compared to a
miscarriage rate of 9.5 percent for women with low THM
exposure. In addition to these risks, THMs are linked to
bladder cancer, heart, lungs, kidney, liver, and central
nervous system damage .
The Health Effects of THMs

14. The Health Effects of THMs
THMS
Compound Adverse effects
CHCL3 Cancer, liver, kidney and adversely affect the
process of reproduction.
CHCLBr2 The kidney affects the nervous system, liver,
kidney and reproduction.
CHCL2Br Cancer, liver, kidney and affects the process
of reproduction
CHBr2 Cancer, nervous system, liver, kidney

15. The earlier THM regulations only applied to larger systems (those serving more
than 10,000 people). EPA, keeping the following factors in mind, believed that
exempting smaller systems would not negatively affect the health of small
community people because :
The THMs Regulation
a) The majority of smaller systems use groundwater as their source .
b) Small systems usually use less detention time and hence less
contact time .
c) Lack of required professional expertise to control the THMs and
the necessity of disinfection .
d) Small systems often use less chlorine .

16. Cleanup
There have been many attempts to eliminate
perchlorate contamination. Current
remediation technologies for perchlorate
have negative downsides of high costs and
difficulty in operation. Thus, there have
been interests in developing systems that
would offer economic and green alternatives.

17. Drinking water systems can reduce THM formation in
several ways. How to best treat and dispose of the
residual waste materials that result from wastewater
treatment processes (sewage sludge and domestic
septage, for example) is a hot topic in many small
communities. By managing these wastes as biosolids
in accordance with federal, state, and local
regulations, communities often can cost-effectively
recycle and beneficially apply these wastes to improve
soils or to rehabilitate land damaged by mining or
other industries
The THMs Reducing systems

18. Recommendations No.1
a) Reduce the organic material before hlorinating the water.
Treatment techniques, such as coagulation, sedimentation,
and filtration can remove most of the organic materials.
However, activated carbon can be used to remove greater
amounts of organic material than can be removed by other
techniques.
b) Optimize chlorine usage.
c) Change the point of chlorine addition in the treatment
series. If the point of chlorine addition is moved to a location
after sedimentation or filtration, THM production can be
reduced as these processes remove parts of the organic matter.

19. Recommendations No.2
d) Use alternative disinfection methods. Using a mixture
of chlorine and ammonia (chloramine) reduces THM
formation. Chloramine also disinfects, but doesn’t form
THMs. Ozone can be used along with chlorine and
chloramine. Chlorine dioxide is another alternative. The
combination of disinfectants not only reduces the
formation of THMs, but also maintains the residual
concentration in the distribution system. But changing
the disinfectant may alter the whole treatment process
and might affect the removal of other contaminants.
e) Other methods: These include filtration, aeration,
boiling, distillation, commercial home treatment systems
or filters, nanofiltration, activated . carbon filtering, or
leaving tap water standing in a pitcher in the fridge
overnight.

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