PROF. A.B. GUPTADepartment OF Civil Engineering

MALAVIYA NATIONAL INSTITUTE OF TECHNOLOGY, JAIPUR

Delivered atIIT Kanpur, February 2, 2015

Disinfection of water using Chlorine, U.V., or Ozone or combinations

thereof- directions for future

Water Health   Water as direct vehicle for transmission of disease- water borne diseases

Water as habitat for vectors of disease- Malaria

Water transmitting toxic chemicals- As, F, NO3, pesticides.

Beneficial effects2

ORGANISMEXCRETED LOAD(no/g)

Champhylobacter spp. 1.00E+07Giardia lamblia 1.00E+08Entamoeba histolytica 1.00E+08Shigella spp. 1.00E+07Vibrio cholerae 1.00E+07Salmonella typhi 1.00E+08Salmonella spp. 1.00E+08E. coli (path) 1.00E+08Enteroviruses 1.00E+07Hepatitis A virus 1.00E+06Ancylostoma duodenale 1.00E+02Trichuris trichura 1.00E+03Taenia Saginata 1.00E+04Ascaris lunbricoides 1.00E+04

Human Being is

the Biggest

of Human Being3

Testing of microbiological quality of water

Routine MPN testing involves standard plating or multiple dilution tubes tests, which are time consuming and elaborate

UNICEF has supplied some quick assessment kits, which were analyzed for sensitivity in our laboratory and corroborated with “Colialert” results

Developing a kit to detect emerging pathogens

4

Colilert18

Quanti try sealer Quanti tray

5

Bacteriological H2S Strip Test medium provided by PHED

Rajasthan.

Principle Dilution preparation

9+1

Salmonella& Citrobacter

OthersSafe for drinkingNote safe for drinking 6

Bacteriological H2S Strip Test Kit provided by PHED

Rajasthan.

Principle Preparation of very close dilutions

7

Sensitivity Performance (Colilert)

Dilution Factor Table MPN value Total Coliform

count/100ml

100X Uncountable Uncountable

1000X 483.3 483000

10000X 51.9 520000

100000X 5.0 500000

1000000X <1 0

Average=501000

(Dinesh seminar 2009)

Bacteriological H2S Strip Test medium provided by PHED

Rajasthan.

Principle Dilution preparation

9+1

Salmonella& Citrobacter

OthersSafe for drinkingNote safe for drinking

Sensitivity ResultsTotalColiform count/100ml Sensitivity within 24 Hrs Sensitivity within 48Hrs

Salmonella& Citrobacter Others Salmonella& Citrobacter Others

6000 yes Yes yes yes

4800 yes Yes yes yes

3600 yes yes yes yes

2400 yes yes yes yes

1200 yes yes yes yes

600 yes yes yes yes

480 yes yes Yes yes

360 Yes yes Yes yes

240 Yes yes yes yes

120 Yes yes yes yes

60 No yes yes yes

48 No yes yes yes

36 No yes yes yes

24 No yes N.C yes

(Dinesh seminar 2009)

Cont…12 no yes no yes

6 no yes no yes

4-5 no yes no yes

3-4 no yes no yes

2-3 no no no N.C

1 no no no N.C

0 no no no N.C

0 no no no N.C

0 no no no N.C

0 no no no N.C

0 no no no N.C

0 no no no N.C

0 no no no N.C

0 no no no N.C

0 no no no N.C

0 no no no N.C

(Dinesh seminar 2009)

Bacteriological H2S Strip Test Kit provided by PHED

Rajasthan.

Principle Preparation of very close dilutions

Sensitivity Results

Total Coliform count/100ml Sensitivity within 24 Hrs Sensitivity within 48 Hrs

5000 yes yes

4000 yes yes

3000 yes yes

2000 yes yes

1000 yes yes

500 no yes

400 no yes

300 no yes

200 no yes

100 no yes

50 no yes

40 no no

(Dinesh seminar 2009)

Microbiological Analysis

Cultivation & Isolation of microbial species from water and waste water.

1. Media Preparation – Plate count agar (PCA), Potato Dextrose Agar (PDA) and Xylose desoxycholate Agar ( XLD).

2. Sterilization of media.3. Pouring plating after serial dilutions and incubating for 24

h.4. Morpho-type quantification conforming via microscopy

and gram test..

Air exposed Petri plate (PDA) INLET AREA

Air exposed Petri plate (PCA) INLET AREA

Air exposed Petri plate (PDA) near PRIMARY CLARIFIER

Air exposed Petri plate (XLD) near PRIMARY CLARIFIER

1. Introduction2. Factors Influencing Disinfection3. Common Disinfectants:4. Chlorine Disinfection5. Recent Research on chlorination6. Scope for Future

Disinfection

Disinfection is a process designed for the deliberate reduction of the number of pathogenic microorganisms. Microorganisms are destroyed or deactivated, resulting in termination of growth and reproduction

The effectiveness of disinfection is judged by analyzing for an indicator organism (total coliform bacteria)

Major factors affecting disinfection efficiency are- Kind and concentration of microorganisms in the water; presence of other constituents may impede disinfection; Temperature; Contact time; Type of disinfectant; and chemical and physical interference e.g. clumping of cells or adsorption to larger particles

Introduction

Disinfectant methods Chemical agentsIt includes:Chlorine and its compound, bromine, iodine,ozone, alcohols, dyes, soaps and manymore. Physical agentsThat can use heat, sound waves and light (UV

radiations) Mechanical meansLike chemical precipitation (New Mumbai plant),

trickling filters, activated sludge. RadiationsMajor types of radiations are electromagnetic

particle.Gamma rays can sterlize both water and wastewater.

Ozone

Ultraviolet Radiations

Chlorine

Chloramines

Chlorine Dioxide

Common Disinfectants

Comparison of common disinfectantsCharacteristic Chlorine Ozone UV radiation

Availability Low cost Moderately high cost

Moderately high cost

Homogeneity Homogenous

Homogenous No

Noncorrosive and nonstaining

Highly corrosive

Highly corrosive

No

Nontoxic to higher forms of life

Highly toxic to higher life forms

Toxic Toxic

Safety concern High Moderate Low

Solubility Stable Unstable, must be generated as used

No

CHLORINE DISINFECTION

Chlorine is the most widely used disinfectant for municipal wastewater

It destroys target organisms by oxidizing cellular material

Chlorine can be supplied in many forms, e.g. chlorine gas, hypochlorite solutions, and other chlorine compounds in solid or liquid form

Water is chlorinated by the bubbling of chlorine gas or the dissolving of chlorine compounds and their subsequent doses

Cl2 + H2O = H + Cl- + HOCl

HOCl = H+ +OCl-

Both segments of the agent are microbicides and operate by inhibiting enzymatic activity and inactivating bacteria and viruses

Chlorine Disinfection

HOCl efficiency is at least 80% greater than that of OCl-

WHO recommends a pH< 8 for appropriate disinfection

The required degree of disinfection can be achieved by varying the dose and the contact time for any chlorine disinfection system

The dose usually ranges from 5 to 20 milligrams per liter

Contd…

The effect of disinfection is determined by the pH of the water

Contd…

Reactions of chlorinewith ammonia : Ammonium ion is in equilibrium with ammonia and

hydrogen ion.NH4 + ↔ NH3 + H+

NH3 react with Cl2 or HOCl (hypochlorous acid)

NH3 + HOCl → NH2Cl (monochloramine) + H2O

NH2Cl + HOCl → NHCl2 (dichloramine) + H2O

NHCl2+ HOCl → NCl3 (Nitrogen Trichloride) + H2O

Rxns are dependent on pH , temperature , contact time , and Cl2 / NH3 ratio . Cl2 / NH3 ratio 1:1 for the formation of Monochloramine (NH2Cl) and Dichloramine (NHCl2). Further increase in mole ratio trichloramine, oxidation of part of ammonia to N2 or NO3 -.

Break Point Chlorination

More cost-effective Chlorine residual plays a important role in

disinfection Chlorine disinfection is reliable and

effective against a wide spectrum of microorganisms

Chlorine can eliminate noxious odors while disinfecting

Cont…Advantages of Chlorine

Liquid chlorine Amber in colour 1.44 times heavy as water Moderately soluble in water Use of chlorine for disinfection has been of great

importance, but important concern are also there with it.

Chlorine reaction in water

Cl2 + H2O HOCl + H+ + Cl

HOCl H+ + OCl-

Typical supply and storage of chlorine

Sodium hypochlorite (NaOCl) Solves various concerns of safety, transport,

handling Contain 12.5 to 17% available chlorine at the

time it is manufactured Cost 150 to 200% the cost of liquid chlorine Require special design consideration

Hypochlorite reaction in water

Ca(OCl)2 + 2H2O 2HOCl + Ca(OH)2

NaOCl +H2O HOCl + NaOH

Tablet Chlorinator

Calcium Hypochlorite

Sodium Hypochlorite

It depend upon the inorganic and organic impurities present in it

Excess chlorine after it reacts with ammonia forms chloramines and rest appears as free chlorine

Dose which leaves a residual of about 0.2mg/l after 10 minutes of contact period is chlorine demand of water

Cont…Doses of Chlorine

Chlorine Dose

CHLORINE DISINFECTION

ADVANTAGES• They have broad-spectrum

germicidal potency.• They show a good degree

of persistence in water distribution systems.

• Their easily measurable residual properties can be monitored in water networks after treatment and/or delivery to users

• This method is economic and cost-effective

DISADVANTAGES• The chlorine residual, even

at low concentrations, is toxic to aquatic life and may require dechlorination

• All forms of chlorine are highly corrosive and toxic. Thus, storage, shipping, and handling pose a risk

• Chlorine oxidizes certain types of organic matter, creating more hazardous compounds DPBs

Dechlorination

Chlorination used for destruction of harmful organisms

But many organic constituents in waste water interfere with chlorine to form toxic compounds…THMs and HAAs

So to minimize this effect dechlorination is required

During spread of diseases or ceertain specific conditions super chlorination may be practiced requiring dechlorination before supplying water (UK example…algal cells)

ULTRAVIOLET (UV) DISINFECTION

An Ultraviolet (UV) disinfection system transfers electromagnetic energy from a mercury arc lamp to an organism's genetic material (DNA and RNA)

When UV radiation penetrates the cell wall of an organism, it destroys the cell's ability to reproduce

The effectiveness of a UV disinfection system depends on the characteristics of the wastewater, the intensity of UV radiation, the amount of time the microorganisms are exposed to the radiation, and the reactor configuration

UV DISINFECTION UNIT

UV DISINFECTION

UV Disinfection

UV DISINFECTION

ADVANTAGES

Effective at inactivating most viruses, spores, cysts

It is a physical process rather chemical hence eliminates the need to handle, transport, or store toxic/ corrosive chemicals.

No residual that can be harmful to humans or aquatic life.

shorter contact time compared to other disinfectants

DISADVANTAGES Low dosage may not

effectively inactivate some viruses, spores, and cysts.

Re-vegetation of microbes in case of partial exposure

Preventive maintenance important to control fouling of tubes.

Turbidity and TSS in the wastewater can render UV disinfection ineffective

Ozone Disinfection

O3 a gas, must be generated on-site

Bubbled into a basin (or pipeline) with treated effluent

Great disinfectant!

No residual…ozone degrades to oxygen, O2

Costs More, Need equipment and electricity

Ozone chemistry

O3 + H2O HO3+ + OH-

HO3+ + OH- 2HO2

O3 + HO2 HO + 2O2

HO + HO2 H2O + O2

Free radicals HO and HO2 have greatoxidizing power and are activeforms in disinfection process.

Ozone Disinfection

Flow DiagramOzone Generation

Ozonation: +/-

Advantages: rapid reaction rate,

dissolved ozone half-life only 0-15 sec (Bullock et al., 1997);

few harmful reaction by-products in freshwater; oxygen is produced as a reaction end-product.

Disadvantages: ozone is dangerous to humans and fish.

Ozone Supports Water Treatment

directly oxidizes NO2- to NO3

- ; helps remove color & dissolved organic matter:

breaks non-biodegradable compounds into smaller & more biodegradable compounds;

helps remove dissolved & fine particulate matter precipitates dissolved organic molecules, micro-flocculates fine particulate matter, improving solids removal by settling, filtration, or

flotation.

Maintaining Ozone Residual

Sometimes difficult to maintain ozone residual for a given contact time due to ozone demand of water. dissolved ozone has a half-life of only 0-15 sec in

recirc systems (Bullock et al., 1997); Ozone demand of relatively clean surface water

supplies can range from 2-10 mg/L!

During disinfection, chlorine may react with NOM in the raw water, resulting in the formation of various DBPs such as THMs & HAAs. These THMs have some adverse health effects, in particular cancer & reproductive disorder.

Hence, disinfection methods using only chlorine are not totally safe and have some environmental consequences.

Application of a single technology is not recommended and a hybrid system such as using U.V. or Ozone after chlorination can be beneficial to carry out disinfection studies in better ways by reducing the chances of formation of carcinogenic compounds and reducing the use of high doses of chlorine against the remaining resistant bacteria

Disinfection…

Pathogenic bacteria count (per100ml) removal profile for chlorine dose of 20 ppm (Dinesh et al., 2011)

Contd…Efficacy of chlorine against different pathogens

present in sewage

Chlorine Disinfection limitation…

Figure 1: Total Coliform count (per 100ml) removal profile for chlorine dose of 5 ppm & 17.5 ppm (Dinesh et al., 2011)

Thank You