Using Huwa-san as Alternative
Disinfecting Agent for Water
Treatment
Presented
by
Yaser Hagag Mohamed
Greater Cairo Drinking Water Company (CGWC)
Introduction
 Chlorination is widely used in several countries to
ensure a safe drinking water. The chlorine reacts with
natural organic matter forming disinfection byproducts
which have been related to the occurrence of cancer,
growth retardation, spontaneous abortion, and
congenital cardiac defects.
 It is a non-selective oxidant, and therefore reacts
with both organic and inorganic chemical species in
water, as well as functioning as an antimicrobial agent.
 Chlorine, added to water in the form of
hypochlorous acid/hypochlorite ion or as chlorine gas,
is still the most widely used and most cost-effective
disinfectant worldwide.
 The chlorine reacts with natural organic matter to
form disinfection by products. The higher the organic
load of chlorinated water, the more disinfection
byproducts will be formed. However, the amount of
disinfection byproducts generated not only depends on
the concentration of natural organic matter but also on
the total algae count. So many studies were directed to
search for alternative safe disinfecting agents.
 Huwa-San was produced as a disinfectant for
biofilm removal. The previous study was restricted to
evaluate with respect of Huwa-San capacity to remove
the biofilm on pipe systems of drinking water. It is
based on silver stabilised hydrogen peroxide.
 The treatment with Huwa-San showed a strong
decrease in density of the microorganisms. This
required a higher dose rate of chemicals and it
depends completely on important factors as the
concentration of Huwa-San ; contact time and mode of
treatment which may be static or in circulation.
 It is highly effective against gram negative and
gram positive, aerobic and anaerobic, spore forming
and non spore forming pathogenic and saprophytic
bacteria. It will not impart taste or taint or smell to
water or any substrate to which it is applied and it is
characterized that there is no by-products. So, the
present experiment was directed to study Huwa-San as
alternative disinfecting agent during water treatment.
Aim of the work
The current experiment aims to search for new
disinfecting agent without formation of byproducts to replace the chlorine. The study was
carried out at all the levels.
Materials and Methods
Nile Sample
Nile water samples were taken from water intake
throughout the fustat water treatment plant.
Jar test
This test was carried out using different concentrations
of disinfecting agent at constant coagulating agent (30
ppm Al2(SO4)3).
Disinfecting agent
Nile water samples were dosed with disinfecting agent at
six different concentrations including 2, 3, 4, 5, 6 and 7
ml. These concentrations were prepared from solution
with concentration (1 % - 10 mg L-1).
The disinfecting agents which were under study
 Chlorine
The chlorine residues were measured by the DPD
colorimetric method.
 Huwa-san
There was no free chlorine to be measured.
Measurements
Chemical measurements by titrimetric method
 Hardness
The total and calcium hardness were measured in water matrix by
titration against EDTA depending on type of indicator.
 Chlorides
Chloride in the water samples determined by using Argentometric
method by titration against silver nitrate in presence of potassium
chromate.
 Alkalinity
Alkalinity is the acid neutralizing capacity. It used to determine
alkalinity of carbonate, bicarbonate and hydroxyl content by titration
against sulfuric acid in presence of methyl orange as indicator.
Chemical measurements by electrode
 Dissolved Oxygen (D.O)
The DO gave indication to measure the oxygen needed for all oxidation,
nitrification and decomposition processes.
 pH
The pH value gave indication to concentration of the hydrogen ions
(H+) obtained as a result of dissociation or hydrolysis process.
 Conductivity
The conductivity value gave indication to concentration of the minerals
in the water matrix and hence ability of the aqueous solution to carry
electric current.
Chemical measurements by photometric techniques
 Turbidity
The turbidity value gave indication to small and large particles scattered
throughout the matrix.
 Sulfates
Sulphate concentration in the water samples were determined by
Turbidimetric method after precipitation of sulphate ions as crystals of
barium sulphate.
 Heavy metals
Aluminium and iron were measured spectrophotometrically at specific
wave lengths after certain processing.
Microbiological examination
 The total coliform occurred and fecal coliform were
detected total and fecal coliform membrane filter
procedure.
 The pour plate method occurred to compare the
disinfecting effect of chlorine and huwa-san at the same
doses on the microbial growth.
 The total algae count (TAC) measured using counting
cell. The low magnification method is the most suitable
method for the plankton counting.
Results and Discussion
- There was free residual chlorine obtained as a
result of water disinfection by chlorine. There was
no residual chlorine in case of huwa-San.
- There was direct relation between the chlorine dose
added during the treatment and concentration of the
residual
Fig. : Chart showing values of residual chlorine after water disinfection
by chlorination at the doses 2, 3, 4, 5, 6 and 7 ppm.
Fig. : Chart showing comparison between chlorination and huwa-san at
the doses 2, 3, 4, 5, 6 and 7 ppm on the dissolved oxygen
- The chlorination decreased D.O. while the huwasan increased it in a dose dependent manner.
- There is no simple correlation between adding
chlorine and dissolved oxygen.
- The hydrogen peroxide molecule contains one extra
oxygen atom, compared to the more stable water
molecule. The bond between the two oxygen atoms,
the so-called peroxide bond, is broken while two HO radicals are formed.
Fig. : Chart showing comparison between chlorination and huwa-san at
the doses 2, 3, 4, 5, 6 and 7 ppm on the conductivity value.
Fig. : Chart showing comparison between chlorination and huwa-san at
the doses 2, 3, 4, 5, 6 and 7 ppm on the pH value.
Fig. : Chart showing comparison between chlorination and huwa-san at
the doses 2, 3, 4, 5, 6 and 7 ppm on the turbidity value.
- The turbidity value showed that the disinfection by
both of chlorination and huwa-san has the same effect
on the turbidity value. This may refer to decreasing the
total particle counts.
- The Turbidity in water is the reduction of
transparency due to the presence of particulate matter
such as clay or silt, finely divided organic matter,
plankton or other microscopic organisms. These cause
light to be scattered and absorbed rather than
transmitted in straight lines through the sample.
Fig. : Chart showing comparison between chlorination and huwa-san at
the doses 2, 3, 4, 5, 6 and 7 ppm on the total hardness.
Fig. : Chart showing comparison between chlorination and huwa-san at
the doses 2, 3, 4, 5, 6 and 7 ppm on the magnesium hardness.
- The chlorination increased the total and calcium
hardness due to maintaining the minerals soluble in the
chloride forms and this caused increase in the total
hardness. The disinfection by huwa-san has no
obvious effect on the total and calcium hardness at any
dose.
- The disinfection by the two ways changed Mg
hardness in a dose independent manner. This because
magnesium compounds are much more soluble than
their calcium counterparts so the concentrations of
magnesium are extremely high.
Fig. : Chart showing comparison between chlorination and huwa-san at
the doses 2, 3, 4, 5, 6 and 7 ppm on the chlorides.
- The chlorination increased the chlorides directly with
increasing the chlorine dose in a dose dependent
manner.
- The disinfection with huwa-san has no any effect on
concentration of the chlorides. This may be due to
involving of chlorine in formation of byproducts as
chloroform which caused elevation of the chlorides.
Fig. : Chart showing comparison between chlorination and huwa-san at
the doses 2, 3, 4, 5, 6 and 7 ppm on the chlorides.
Fig. : Chart showing comparison between chlorination and huwa-san at
the doses 2, 3, 4, 5, 6 and 7 ppm on the Alkalinity.
- The chlorination at the doses 6 and 7 ppm decreased
alkalinity obviously giving indication to normal role of
chlorine in the treatment process while the disinfection
with huwa-san maintained the alkalinity level due to
the presence of hydroxyl group which contributed in
maintaining the alkalinity level.
Fig. : Chart showing comparison between chlorination and huwa-san at
the doses 2, 3, 4, 5, 6 and 7 ppm on Aluminium measured by
spectrophotometric method.
Fig. : Chart showing comparison between chlorination and huwa-san at
the doses 2, 3, 4, 5, 6 and 7 ppm on Iron measured by spectrophotometric
method.
- It was found that the disinfection by chlorine and
huwa-san caused decrease in Al and Fe in a dose
independent manner. Both of chlorine and huwa-san
caused deposition of Al and Fe as AlCl3, FeCl3,
Al(OH)3 and Fe(OH)3.
- The disinfection by chlorine at the doses 6 and 7 ppm
showed more effect on Al than huwa-san. Huwa-san
was more effective in decreasing iron concentration
during treatment than chlorine. Rate of iron deposition
in form of Fe(OH)3 was more rapid than that in form
of FeCl3.
Fig. : Chart showing comparison between chlorination and huwa-san at
the doses 2, 3, 4, 5, 6 and 7 ppm on the Total Algae Count.
Table : Effect of chlorination and huwa-san at the doses 2, 3, 4, 5, 6 and 7
ppm on the total and fecal coliform, plate count and total algae count.
- The microbiological data showed that both of
chlorine and huwa-san have the same disinfecting
effect at the same doses on all the parameters (total,
fecal coliform, TAC and protozoa living in fresh
water).
- Both of chlorine and huwa-san decreased the TAC
obviously in a dose independent manner.
- The pour plate method confirmed that the chlorine is
more effective than huwa-san against the bacterial
growth. It was found that the chlorine inhibit the
bacterial growth completely at any chlorine dose while
the huwa-san at the dose 10 µl decreased the bacterial
growth from 5000 to 2000 colony forming unit. The
other huwa-san doses (15, 20, 25, 30 and 40 µl) have
the same effect as chlorine.