Ferrate - Solution to the Issue of Emergency Water Supply to the People in Flooding Areas, Tran Tien Khoi

FERRATE - SOLUTION TO THE ISSUE OF
EMERGENCY WATER SUPPLY TO THE PEOPLE IN
FLOODING AREAS
Tran Tien Khoi
Regional Center of Expertise on Education for
Sustainable Development in Southern Vietnam
International University
Vietnam National University – Hochiminh City
ttkhoi@hcmiu.edu.vn

CONTENT
 Identifying problems
 Current solutions
 Gap - Objectives
 Ferrate
 Characteristics
 Synthesis
 Application
 Method
 Results and discussion
 Perspective

MEKONG DELTA AREA
Total area : 40,000 km2
Population: 17 million

MEKONG DELTA AREA
Mekong river
systems:
• Main water
supply source
• Seasonal
flooding (August
to November)

IDENTIFYING PROBLEMS
 Centralized water supply systems can serve
only a minority of the population because of the
scattering population of this region.
 Water Treatment Plants: use surface water
(rivers)
 People have to use:
 River water with simple treatment
 Bottled water from private section (from river
water)
 Household harvested rainwater

 River water is polluted with:
 Increasing organic content,
 Residual pesticides from agriculture activities
 suspended solid (very high during flooding
season)
 domestic waste water
 and bacteria (eg. E.coli, coliform)
 More severe in flooding season

– PESTICIDE POLLUTION
 Pollution of drinking water sources with
agrochemicals is often a major threat to human and
ecosystem health in some river deltas, where
agricultural production must meet the requirements of
national food security or export aspirations.
 Chau et.al. (2015) performed a survey on the use of
different drinking water sources and their pollution
with pesticides in rural areas of the Mekong River
delta, Vietnam.


 The field work comprised both household surveys
and monitoring of 15 frequently used pesticide
active ingredients in different water sources used
for drinking:
 Surface water,
 Groundwater,
 Water at public pumping stations, water
chemically treated at household level,
harvested rainwater, and bottled water).

 The results show that despite the local differences
in the amount and frequency of pesticides applied,
pesticide pollution was ubiquitous.
 Isoprothiolane: 8.49 μg/L (max. concentration)
 Fenobucarb: 2.32 μg/L (max. concentration)
 Fipronil : 0.41 μg/L (max. concentration)
 They were detected in almost all analyzed water
samples (98 % of all surface samples contained
isoprothiolane, for instance).

 Other pesticides quantified comprised butachlor,
pretilachlor, propiconazole, hexaconazole,
difenoconazole, cypermethrin, fenoxapro-p-ethyl,
tebuconazole, trifloxystrobin, azoxystrobin,
quinalphos, and thiamethoxam.
 Among the studied water sources, concentrations
were highest in canal waters.
 Pesticide concentrations varied with cropping
season but did not diminish through the year.

 Even in harvested rainwater or purchased bottled
water, up to 12 different pesticides were detected
at concentrations exceeding the European
Commission’s parametric guideline values for
individual or total pesticides in drinking water (0.1
and 0.5 μg/L; respectively).
 The highest total pesticide concentration quantified
in bottled water samples
was 1.38 μg/L.

 Overall, they failed to identify a clean water
source in the Mekong Delta with respect to
pesticide pollution.
 It is therefore urgent to understand further and
address drinking water-related health risk issues
in the region

TRADITIONAL WATER TREATMENT TECHNOLOGY
Coagulation
(alum)
Sedimentation
Filtration
(sand filter)
Disinfection
(chlorine,
chloramine B,
Aquatab)
Preliminary treatment:
• Remove particles (SS),
colloids, color, turbidity
• Partially remove organic
content (30-50% TOC)
• Kill bacteria, pathogens
• Combine with residual TOC to
produce DBPs (eg. THM)
• Can not remove TOC,
pesticides, herbicides,
EDCs…

HOUSEHOLD WATER TREATMENT
Coagulation
(alum)
Sedimentation
Direct use
Boiled before
drinking
Preliminary treatment:
• Remove particles (SS),
colloids, color, turbidity
• Partially remove organic
content (30-50% TOC)
• Kill bacteria, pathogens
• Can not remove TOC,
pesticides, herbicides,
EDCs…

Figure 1. There needs to be an effective solution
to emergent water supply to them
(using helicopter, high speed boat?)

Figure 2. They need clean water
(Is centralized system suitable for this case?)

Figure 3. They need clean water
(Is household treatment system suitable for this case?)

CURRENT EMERGENT SOLUTION
Figure 4. Carrying the water to the site by
highspeed boat: can you imagine their cost ?
• Costly
• Delayed
• Almost impossible
with strong water
flowing
• Cannot reach all
household within a
wide area
• Small capacity

Figure 5. Carrying the water to the site by
helicopter: can you imagine their cost ?
• Very costly
household with a
wide area
household in wide
area
• Risk of houses
blown up

Figure 6. VN Army mobile filtration unit
• Mobile
• Effective only after
flooding
• Can be used on
boat but less mobile

Figure 7. Carry the water to the site by simple
transportation means: can you imagine their timing
?
• Need lots of labours
• Very slow
• Effective only after
flooding

Figure 8. Chloramine B is the main chemical used
for cleaning and water treatment after flooding in
Vietnam
POST-FLOODING SOLUTIONS

POST-FLOODING SOLUTIONS
 Contaminated water is traditionally treated with
alum and chlormine B (10g Cloramin B 25%/m3)
 Simple, cheap, easy to use rồi mới cho chloramine B
 Mainly remove turbidity and disinfect the water
 Cannot remove pesticides, organic carbon and
other organic pollutants.
 Risk of forming toxic disinfection byproducts e.g
THMs (trihalomethane)

CHLORINE TABLETS
 Brand names you may recognize for this type of tablet
are Aquatabs and Rothco’s Military “Chlor-Floc“.
 NaDCC, also known as sodium dichloroisocyanurate
or sodium troclosene, is a form of chlorine used for
disinfection.
 They are available with different chlorine content (e.g.
3.5 mg to 10 g) to treat from 1 to 3000 liters at a time.
They are usually effervescent (meaning that escaping
carbon dioxide gas causes the tablets to dissolve
quickly, with a ‘fizz’), allowing the tablet to dissolve in
less than 1 minute.
 When added to water, NaDCC releases hydrochloric
acid which reacts through oxidization with
microorganisms and kills them.

IODINE TABLETS

Brand names you may recognize for this type of
tablet are Potable Aqua, Coleman,
and Coghlans.
 Iodine Tablets use iodine to purify contaminated
water.
 Most iodine purification tablets tend to leave a
funny taste to the water and some discoloration,
however vitamin C or ascorbic acid can be
added after the treatment time to improve the
taste and remove the color.
 This often comes in the form of two bottles with
two separate tablets. Iodine water treatment has
been proven to be somewhat effective against
Giardia and not effective against
Crytosporidium. (Source)

 Brand names you may recognize for this type of tablet
are Katadyn, Potable Aqua, and Aquamira.
 Even though the word “chlorine” is in the name, chlorine
dioxide is neither iodine nor chlorine.
 It uses a highly active form of oxygen to purify water so
it leaves absolutely zero taste.
 As a nice bonus the action of chlorine dioxide causes a
lot of sediment to drop out of suspension (fall to the
bottom) leaving the container of water more clear and
further improving flavor.
 While the general printed expiration date of chlorine
dioxide is four years out, if it is kept in temperature
controlled environment it can last indefinitely.
 Chlorine dioxide tablets are a good choice for those
allergic to iodine, with thyroid problems, or on
lithium. (click here to learn more about chlorine dioxide)
CHLORINE DIOXIDE TABLETS

OBJECTIVES
We need to find out an solution of emergent water
supply under harsh conditions which is:
 Simple to use
 Need no power source
 Effectively remove suspended solid
 Effectively remove organic pollutants, pesticides
 Effectively remove bacteria and pathogen
 Leave no strong odor, strange taste
(And what else?)

RESEARCH QUESTIONS
 Is ferrate applicable for emergent water supply in
this area?
 At what dose and condition?
 In what form of production?

FERRATE
 An Fe(VI) compound
 A dual-function chemical reagent (oxidation
and coagulation).
 Reaction in aqueous systems with reducing matter:
Acid
FeO4
2- + 8H+ + 3e  Fe3+ + 4H2O E=2.20 V
Neutral and weak basic
FeO4
2- + 4H2O + 3e  Fe(OH)3 + 5OH- E=0.72 V

POTASSIUM FERRATE
 A strong oxidant (Fe6+)
 A coagulant : Fe3+ is hydrolysed to form insoluble
Fe(OH)3, which will act as a coagulant.
 A disinfectant due to strong oxidising nature
 A promising multi-purpose water and waste water
treatment chemical
 Benefits from the combined effect :
 Higher water quality
 Lower operational and capital cost

FERRATE STABILITY IN AQUEOUS
CONDITIONS
Decomposition rate constant, k
7 8 9 10 11 12
0.0000
0.0005
0.0010
0.0015
0.0020
0.0025
0.0030
0.0035
0.0040
k(s
-1
)
pH
0.25 mM
][
][ 2
4
2
4 

 FeOk
dt
FeOd

 A large number of investigations on the oxidation of
ferrate have been reported : strong, selective
oxidant
 Ammonia, cyanide, anilines, hydrogen sulphide
 Alcohols, amino-acids, carboxylic, phenol
 8 mg/L dose of ferrate could remove 99.9% total
coliform and 97% total bacteria (Waite, 1979)
 remove more turbidity from model colloidal systems
Fe(III) and Fe(II) salts (Waite and Gray, 1984)
 Enhance the removal of algae by alum coagulation;
reduce alum dosage (Ma and Liu, 2002)
APPLICATION OF FERRATE IN WATER AND WASTE
WATER TREATMENT

FERRATE SYNTHESIS
Basically, there are 3 methods for the synthesis of
ferrate :
 The dry oxidation method : iron oxide containing
minerals are heated under strongly alkaline conditions
with oxygen supplement
The electro-chemical method : iron or alloy is oxidized.
in the electrolyte solution of NaOH/ KOH
 The wet oxidation method : an iron(III) salt is oxidised
under strongly alkaline conditions using either
hypochlorite or chlorine as an oxdising agent

LABSCALE FERRATE PREPARATION
Wet oxidation method: oxidation ferric nitrate with
hypochlorite
Generating chlorine :
KMnO4 + 8 HCl  MnCl2 + 5/2 Cl2 + 4H2O + KCl
Bubbling the chlorine gas through a potassium
hydroxide solution to form hypochlorite solution:
Cl2 + 2KOH  KClO + KCl + H2O
Oxidising ferric nitrate with hypochlorite :
2Fe3+ + 3OCl- + 10OH- 2FeO4
2- + 3Cl- + 5H2O
 Ferrate purity : 90 – 95% (solid phase)

EXPERIMENTAL METHODS AND MATERIALS
• Surface water taken from Hau river – Mekong river
branch
•Buffer solutions: pH adjustment with HCl and NaOH
Parameter Unit Value
pH - 7.0 – 7.4
TSS mg/L 164
Turbidity NTU 109
Color Pt-Co 0.34
UV254 - abs cm-1 0.0436
CODMn mg/L 19.7
TOC mg/L 7.59
Fe mg/L 0.77
Coliforms MPN/100ml 29.104

RESULTS: TURBIDITY REMOVAL
0
10
20
30
40
50
60
70
80
90
100
0.25 0.5 0.75 2.5 5 7.5 10
Turbidityremoval(%)
Ferrate dose (mgFe/L)
pH 5 pH 6 pH 7 pH 8 pH 9
Low
coagulation
performance
due to
restabilization

RESULTS: ORGANIC REMOVAL
0
10
20
30
40
50
60
70
80
90
100
0.25 0.5 0.75 2.5 5 7.5 10
TOCremoval%
Ferrate dosage as mgFe/L
pH 5 pH 6 pH 7 pH 8 pH 9

RESULTS: EFFECTS OF PH
3.58 5.41 7.84
51.96
82.43
85.74 86.89
0
10
20
30
40
50
60
70
80
90
100
0.25 0.5 0.75 2.5 5 7.5 10
RemovalEfficiency(%)
Ferrate dose as mgFe/L
pH = 5
Turbidity
1.76 3.72 2.43
17.84
31.42 31.62
42.64
0
10
20
30
40
50
60
70
80
90
100
0.25 0.5 0.75 2.5 5 7.5 10
Removalefficiency(%)
Ferrate dose as mgFe/LpH =7
• Oxidation effect : higher
• Coagulation effect: lower
• Oxidation effect : lower
• Coagulation effect: higher
TOC

RESULTS: DISINFECTION
0
20
40
60
80
100
120
0.25 0.5 0.75 2.5 5 7.5 10
Coliformsdeactivation(%)
Ferrate dose as mgFe/L
pH 5
pH 6
pH 7
pH 8
pH 9

CONCLUSION
 Ferrate is a promising water treatment agent for
emergent water supply to people in flooding region,
due to:
 Its simple use :all in one stage
 Kill all coliform (bacteria) up to 4 log
 Remove 80% turbidity and 42% TOC at pH 7
 Coupled with a simple sand-filter, treated water
meets VN standard for drinking water.
 Effectively degrade pesticides, herbicides…
(anticipated)

ACKNOWDGMENT
This research is funded by Vietnam National
University HoChiMinh City (VNU-HCM) under grant
number C2015-20-32

 Thank you very much for your listening!

Ferrate - Solution to the Issue of Emergency Water Supply to the People in Flooding Areas, Tran Tien Khoi

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