20111124 IEA Disinfection Seminar.ppt. Siemens Water ... Chlorine gas has an
important role to play in the disinfection process and a high degree of safety has
...
Disinfection P C Pre Conference f Workshop W k h EnviroVision 2011, IEA Annual Conference
Paresh Vora Disinfection Segment
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20111124 IEA Disinfection Seminar.ppt
Siemens Water Technologies
What are our objectives for disinfection?
Need for disinfection Reduction or elimination of pathogens, disease causing micro organisms.
Bacteria
Legionella
E-Coli E Coli
Typhoid
Viruses
Hepatitis A
Norwalk
Rotavirus
Cysts
Giardia
Cryptosporidium
Amoebic Dysentery
Zebra Mussels
Asiatic Clams
Control of biofouling that Microorganisms would affect the performance of the Microorganisms process Oxidation to create a chemical change that changes the characteristic of that contamination
Cholera
Bacteria Molluscs
Facilitate the Change colour & removal of a Reduce Toxicity d odour contaminate
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20111124 IEA Disinfection Seminar.ppt
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Water sources
Surface water
Ground water
A variety of water sources
Water reuse
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20111124 IEA Disinfection Seminar.ppt
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Factors that can influence disinfection efficiency
C Concentration t ti off pathogens th Contaminants reacting with disinfectants Concentration & dose rate of Disinfectants Available Contact Time pH & temperature
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20111124 IEA Disinfection Seminar.ppt
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Choice of chemical disinfection agents
Chlorine
AOP (Advanced Oxidation Process)
Chlorine Gas Sodium Hypochlorite yp Calcium Hypochlorite Electrochlorination
Chlorine Dioxide Oxidation Disinfection Agents ge ts
Bromine
Ozone
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20111124 IEA Disinfection Seminar.ppt
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Other Disinfectant Treatment
Ultraviolet Light
Biocides
Other Disinfectants
Physical Process (Filtration/ Membrane)
Ionizing radiation (Gamma) Protection notice / Copyright notice Page 6
20111124 IEA Disinfection Seminar.ppt
Siemens Water Technologies
The World Faces New Challenges
Resistance of certain Pathogens
New
Need to
Environmental
minimize
and Safety
disinfection by
Regulations
products
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20111124 IEA Disinfection Seminar.ppt
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Desired Disinfectant Characteristics
Effective against most known pathogens
Reasonable Cost
To be easily monitored and controlled
Multiple Barrier Approach
Provide protective Residual
Suitable for a wide range of water quality Protection notice / Copyright notice Page 8
20111124 IEA Disinfection Seminar.ppt
Siemens Water Technologies
Chlorine gas Chlorine gas has an important role to play in the disinfection process and a high degree of safety has been built into today’s chlorine gas equipment. Advantages Effective against most pathogens
Provides a residual to protect against recontamination and bio-film
Easily applied, controlled, and monitored
Strong oxidant meeting most pre-oxidation objectives
Operationally the most reliable/simple
A very cost-effective disinfectant
Disadvantages
Byproduct formation (e.g (e g THM THM’ss,))
Less effective against Cyst type organisms
Requires transport and storage of chemicals
Less effective at high pHs Protection notice / Copyright notice Page 9
20111124 IEA Disinfection Seminar.ppt
Siemens Water Technologies
Commercial Sodium Hypochlorite Advantages Is supplied as a solution and easier to handle than chlorine gas Simpler training requirements and regulations Lower equipment/installation capital cost
Disadvantages Limited shelf-life (chlorate, chlorite and bromate) Adds inorganic byproducts (chlorate Storage consideration to prevent degradation Higher chemical & Transportation costs than chlorine gas
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20111124 IEA Disinfection Seminar.ppt
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On site Generation of Hypochlorite (OSEC) On-site Advantages Simple generation of Sodium Hypochlorite by electrolysis of brine Minimal chemical storage and transport of chemicals. Stable product Simple solution feed and control Control over quality and availability C Cost: t S Salt lt / El Electric t i / ttransportt vs. costt off chemical h i l such h as H Hypochlorite hl it Chlorine Gas & their transport / safety aspects Disadvantages
More complex than gas or bulk hypochlorite
Requires higher level of maintenance
Higher capital cost
(although various financial schemes in place) Protection notice / Copyright notice Page 11
20111124 IEA Disinfection Seminar.ppt
Siemens Water Technologies
Chlorine Dioxide Advantages 1. Highly effective effective disinfectant & oxidant 2. Effective from pH 2.0 – 10.0 3. Does not react with ammonia or bromides 4. Does not chlorinate organics to produce THM’s & THAA’s 5. Effective at low dosage rate:
Potable Water: ~ 0.5 to 1.5 PPM to raw incoming surface water
Potable Water: ~ 0.2 0 2 to 0 0.4 4 PPM to distribution system
Wastewater:
~ 2.0 to 5.0 PPM
Controls viruses, algae, bacteria, fungi and protozoa Includes cryptosporidium, giardia, e-coli, salmonella, chlorea, mollusks Disadvantages 1. Handling of chemicals 2. Process not widely understood Protection notice / Copyright notice Page 12
20111124 IEA Disinfection Seminar.ppt
Siemens Water Technologies
UV Disinfection Advantages
Non chemical approach to disinfection. Effective against a wide variety of microorganisms, viruses, bacteria, fungi and protozoans. protozoans
UV is a proven method for effectively treating Cryptosporidium and Giardia Reduces the risks and hazards associated with on-site storage, handling and transportation of chlorine and other toxic or hazardous chemicals
Requires a shorter contact time when compared to other disinfectants Does not effect the aesthetic qqualityy of the water ((T & O))
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20111124 IEA Disinfection Seminar.ppt
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UV Disinfection Limitations
N residual No id l protection t ti ffor di distribution t ib ti system t ((municipal i i ld drinking i ki water) t ) Not effective as a preoxidant, for taste and odor control High doses required for some viruses, e.g. adenovirus Not effective if large particles are present
Waste Water installation
Drinking Water installation Protection notice / Copyright notice
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20111124 IEA Disinfection Seminar.ppt
Siemens Water Technologies
Chlorination – Automation Example
CAN –Easy Easy Connectivity
Improve control by “trimming” chemical feed after the chlorine contact tank Protection notice / Copyright notice Page 15
20111124 IEA Disinfection Seminar.ppt
Siemens Water Technologies
Chlorination – Dechlorination Automation Example
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20111124 IEA Disinfection Seminar.ppt
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Distribution system monitoring Effective distribution monitoring
Battery powered analyzer that measures: Chlorine Æ Chloroclam Temperature } P Pressure }H Hydroclam d l Conductivity } Turbidity } Connects to hydrants or to a ‘T’ on the main Options to provide remote outputs Protection notice / Copyright notice Page 17
20111124 IEA Disinfection Seminar.ppt
Siemens Water Technologies
Gas Chlorination Example – Small Capacity
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20111124 IEA Disinfection Seminar.ppt
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Gas Chlorination Example – Large Capacity 1/2
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20111124 IEA Disinfection Seminar.ppt
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Gas Chlorination Example – Large Capacity 2/2
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20111124 IEA Disinfection Seminar.ppt
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Hypochlorite Dosing / Electrochlorination Example – 1/2
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20111124 IEA Disinfection Seminar.ppt
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Hypochlorite Dosing / Electrochlorination Example – 2/2
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20111124 IEA Disinfection Seminar.ppt
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On-Site On Site Hypochlorite Generation Chemistry
NaCl + H2O + Electricity 3.5 kg Salt (NaCl)
+
Water
+
4.5 kWh electricity
NaOCl + H2
=
1 kg of chlorine equivalent;125 litres lit off 0 0.8% 8% sodium hypochlorite
+ 612 litres waste hydrogen Protection notice / Copyright notice Page 23
20111124 IEA Disinfection Seminar.ppt
Siemens Water Technologies
On-Site On Site Hypochlorite Generation Process
WATER
UPSTREAM
CORE
WATER
CHILLER
SOFTENER
OR HEATER
BRINE
SALT
ELECTROLYZER
PREP TANK
DOWNSTREAM
BLOWER
HYPOCHLORITE TANK
AIR
H2 GAS
Saturated Brine 26%
POWER
TRANSFORMER
DOSING
RECTIFIER
EQUIPMENT
HYPO
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20111124 IEA Disinfection Seminar.ppt
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Chlorinedioxide Generation – Precursor Chemicals Produced from one of two precursors Sodium chlorate (NaClO3) Sodium S di chlorite hl it (N (NaClO ClO2) Chemistry is either… Acid conversion using mineral or organic acids Conversion involving chlorine in some form: gaseous chlorine; aqueous chlorine; sodium hypochlorite plus acid to produce chlorine in the generator
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20111124 IEA Disinfection Seminar.ppt
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Chlorinedioxide Generation – Chemistry Options Acid Chlorite – Liquid Phase 5 NaClO2 + 4 HCl --> 4 ClO2 + 5 NaCl + 2H2O Actual conversion of chlorite - Lower Aqueous Chlorine Chlorite – Liquid Phase 2 NaClO2 + Cl2Æ 2 ClO2 + 2 NaCl Actual conversion of chlorite - Low Molecular Chlorine Chlorite – Vapour Phase 2 NaClO2 + Cl2Æ 2 ClO2 + 2 NaCl Actual conversion of chlorite – High Acid Hypochlorite Chlorite – Vapour Phase 2 NaClO2 + NaOCl + 2 HCl Æ 2 ClO2 + 3NaCl + H2O Actual conversion of chlorite – High Protection notice / Copyright notice Page 26
20111124 IEA Disinfection Seminar.ppt
Siemens Water Technologies
2 Chemical Vapour Phase Generation Eductor
H2O
ClO2 Reaction Column
Chlorite
Chlorine
2 Chemical Systems “Vapor Vapor Phase Phase” Cl2 and 25% Sodium Chlorite (or acid – chlorite system with larger reaction column and pH control) Protection notice / Copyright notice Page 27
20111124 IEA Disinfection Seminar.ppt
Siemens Water Technologies
Comparision Vapour - Liquid Phase Chemistry: 2 Chemical “Vapor Phase” chlorine gas / chlorite - Simplest p and most efficient chlorite process p 2NaClO2
+
Cl2
2ClO2
+
2NaCl
•
Maximum theoretical yield = 100%
•
Practical yyield = 95-98%
•
Molar conversion efficiency from chlorite = 95-98%
•
One mole sodium chlorite goes to 1 mole chlorine dioxide
Chemistry: Ch i t 2 Ch Chemical i l “HCl – Chlorite” Chl it ” process 5 NaClO2 + 4 HCL -> 4 CLO2 + 5 NaCl + 2 H20
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•
Maximum theoretical yield = 100%
•
P ti l yield Practical i ld = 60 tto 80%
•
Maximum theoretical molar conversion efficiency = 80%
•
5 moles sodium chlorite -> 4 moles CLO2
•
20% more sodium chlorite required to produce 1 lb CLO2
•
pH of reaction must be driven to 3.0 to 3.5
•
Rx is temp dependent
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20111124 IEA Disinfection Seminar.ppt
Siemens Water Technologies
3 Chemical Vapour Phase Generation
Eductor
ClO2
H2O Reaction C l Column
Chlorite
Cl2 Formation
Bleach
Acid
3 Chemical Systems p Phase” In-situ Cl2 and 25% Sodium Chlorite “Vapor Protection notice / Copyright notice Page 29
20111124 IEA Disinfection Seminar.ppt
Siemens Water Technologies
Comparision Vapour - Liquid Phase Chemistry: 3 Chemical “Vapor Phase” - Generation of chlorine in situ - Instantaneous two step reaction (1) NaOCl
+
2HCl
(2) 2NaClO2 + Cl2
Æ
Cl2 + NaCl + H2O
Æ
2ClO2 + 2NaCl
Maximum theoretical yield = 100% Practical yield = 95-98% Molar conversion efficiencyy = 95-98% ((from sodium chlorite)) Advantages of Vapour phase technology Gives most effective conversion of chlorite to ClO2 Low chemical costs relative to others Instantaneous generation under vacuum Little or no acid contaminant (little pH depression). Inherently safe, vacuum driven Protection notice / Copyright notice Page 30
20111124 IEA Disinfection Seminar.ppt
Siemens Water Technologies
Chlorine dioxide Example
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20111124 IEA Disinfection Seminar.ppt
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Ultraviolet Systems - Example
VR / VE - Vertical Channel Mounted
HR / HE - Horizontal Channel Mounted
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20111124 IEA Disinfection Seminar.ppt
Siemens Water Technologies
Summary
The disinfectant should be chosen to suit the application
Each one of the disinfectants has its advantages & disadvantages
Analysers,controllers Analysers controllers & automation are now an essential part of the process
A multiple barrier approach provides a cost effective solution with added security of disinfection
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20111124 IEA Disinfection Seminar.ppt
Siemens Water Technologies
Thank you for your attention!
[email protected] Protection notice / Copyright notice Page 34
20111124 IEA Disinfection Seminar.ppt
Siemens Water Technologies