Disinfection-Siemens

Disinfection P C Pre Conference f Workshop W k h EnviroVision 2011, IEA Annual Conference

Paresh Vora Disinfection Segment

For internal use only / Copyright © Siemens AG 2006. All rights reserved. Protection notice / Copyright notice Page 1

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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Water sources

Surface water

Ground water

A variety of water sources

Water reuse




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




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




Other Disinfectant Treatment

Ultraviolet Light

Biocides

Other Disinfectants

Physical Process (Filtration/ Membrane)

Ionizing radiation (Gamma) Protection notice / Copyright notice Page 6



The World Faces New Challenges

Resistance of certain Pathogens

New

Need to

Environmental

minimize

and Safety

disinfection by

Regulations

products




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



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



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




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



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



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))




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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Chlorination – Automation Example

CAN –Easy Easy Connectivity

Improve control by “trimming” chemical feed after the chlorine contact tank Protection notice / Copyright notice Page 15



Chlorination – Dechlorination Automation Example




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



Gas Chlorination Example – Small Capacity




Gas Chlorination Example – Large Capacity 1/2




Gas Chlorination Example – Large Capacity 2/2




Hypochlorite Dosing / Electrochlorination Example – 1/2




Hypochlorite Dosing / Electrochlorination Example – 2/2




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



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




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




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



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



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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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



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



Chlorine dioxide Example




Ultraviolet Systems - Example

VR / VE - Vertical Channel Mounted

HR / HE - Horizontal Channel Mounted




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




Thank you for your attention!

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