الفهرس 
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Abstract
Water, (especially drinking water) pollution with organics and bacteriological species constitutes a dangerous environmental problem that increased in the last decades due to industrial, agricultural and domestic wastes which are drained into surface water without sufficient treatmentWater is the most common element on the earth’s
surface. It makes up the hydrosphere. Its volume is estimated at
1370 million cubic kilometers. The volume of fresh water
distributed between rivers, lakes and ground water is
considered to be between 500,000 and one million cubic
kilometers. The volume of polar ice caps represents 25 million
cubic kilometers of fresh water. Finally, there are 50,000 cubic
kilometers of water in the atmosphere in the form of vapour
and clouds. Annual evaporation is about 500,000 cubic
kilometers yearly [1].Above all, however, water is essential for biological life.
It is the major component of living matter. On the average, it
accounts for 80% of its composition. In higher animals, the
percentage of water is between 60 and 70%. In marine
organisms, such as jelly-fish and certain algae, the proportions
reach extremes of 98% [1].
Due to human activities these limited water sources are
exposed to pollution.The most important sources of water pollution are urban
(wastewaters containing metabolic wastes from domestic
activities and that resulting from urban structures) and
industrial residues. The main waste load of urban residues is
organic (mostly non-toxic and relatively biodegradable) while
the other type (the industrial residue) may contain a complex or
toxic organic and inorganic composition depending on the
category of industry [2].
Although these industries are useful and vital to human
life, they introduce waste products to the environment. The
pollutants may be degradable or non-degradable [3].
In addition, a wide spectrum of compounds transform to
more dangerous substances during the traditional drinking
water disinfection process, especially by chlorine. Chlorinealso can react with natural organic matter (NOM) in fresh
water. NOM are defined as a complex matrix of organic
materials present in all natural waters. As a result of the
interactions between the hydrological cycle and the biosphere
and geosphere, the water sources used for drinking water
purposes generally contain NOM. The amount, character and
properties of NOM differ considerably in water of different
origins and depend on the biogeochemical cycles of the
surrounding environments [4]Moreover, the range of organic components of NOM
may vary also on the same location seasonally [5], due to for
example rainfall event, snowmelt runoff, floods or droughts.
The mixture of organic compounds of NOM is divided into
hydrophilic and hydrophobic fractions with resins [5, 6]. The
hydrophilic fractions of NOM are composed mostly of
aliphatic carbon and nitrogenous compounds, such as
carboxylic acids, carbohydrates and proteins. Hydrophobic
NOM primarily consists of humic and fulvic acids (humic
substances) and is rich in aromatic carbon, phenolic structures
and conjugated double bonds [4, 6]. As a result, NOM affects
potable water quality by contributing to annoying color, taste,
and odor problems and as a carrier of metals and hydrophobic
organic chemicals. In addition, NOM is responsible for the
majority of the coagulant and disinfectant use in watertreatment. It has a tendency to interfere with removal of other
contaminants. Furthermore, it is responsible for fouling of
membranes, contributes to corrosion and acts as a substrate for
bacterial growth in the distribution system [7].
Also, NOM has been noted to be the major contributor to
the disinfection by-product (DBP) formation. DBPs have
become a focus of attention in water treatment, since they have
been reported to have adverse health effects [8]More than 600 compounds of DBPs have been
identified, among which trihalomethanes (THMs) and
haloacetic acids (HAAs) are the most common which were
specified from United States Enviromental Protection Agency
(USEPA) to increase the risk of cancer [9, 10].
Because of the possible public health effects, the
USEPA as well as Egyptian regulation has set a maximum
contaminant level of about 0.1 mg/L (100 ppb) for
trihalomethanes in drinking water [10,11].
Once THMs are formed, they are very difficult to
remove. Therefore, the best way to keep THM levels low is to
prevent their formation by the removal of organics before
chlorination [4].