Speaker:Dr. Nalini

SankararamakrishnanCentre for Environmental Science and Engineering, Indian Institute of Technology Kanpur

Water Quality Assessment for Routine Parameters, Trace Level Metals and Organics,

April 18-22, 2011

Worldwide Arsenic Contamination of Groundwater

Distribution of Arsenic Contamination of Groundwater in South Asia

Parameters West Bengal $ Bangladesh*

Total Number of Districts

Total Area (sq.m)

Total Population (Million)

WHO Arsenic Drinking Water Standard (mg/l)

Number of Districts Surveyed for Arsenic Contamination

Number of Districts Having Arsenic above 0.05 mg/l in Ground water

Area of Affected Districts

Population at Risk Potentially Exposed

Population Number of Patients Suffering from Arsenicosis

18

89,193

68

0.01

9

9

38,865

42.7

13,137

64

148,393

125

0.01

64

59

126,134

75

78,500

Few Facts About Arsenic Calamity….

As removal Well switching Shallow wells Deep wells Pond water Rain collection

New wells Surface water

Existing wells Alternative sources

Remediation Options

Safi filter @$183-kolshi filter @$5

Tube well sand filter

MaintenanceMonitoring

Bacterial growth

Pond sand filter50 families @$16 ea.

Bacteria 1/100Aquaculture

Boiling

Rainwater harverster1 family @ $160/$40 ea.

Storage-seasonality

Dug wells

SeasonalityPathogens

$50 for 150 ft

InstallationDistribution

Spatial variabilitySocial resistance

20th century Western engineering design was comparatively simple

Technical Criteria

Economic/Financial Criteria (Cost-Benefit Analysis)

Technical Financial

Environmental Awareness Added another Dimension

Technical

Economic/Financial Criteria (Cost-Benefit Analysis)

Environmental

Technical Financial

Environmental

“Engineering design for sustainable development” framework

Financial /Economic

* Low cost

* Supports local economies

* Self-sustaining

Technical

•Water quality evaluations

•WHO Guidelines

•National Standards

• Flow rate

• Use local materials

Social

• Socially acceptable

• Simple/user friendly

• Convenient

• Durable

Co-Designing/Co-evolving for Development

(an iterative process)1. Problem Awareness

Co(m)-passion, and Partnership

2. Problem Co-Definition

3. Idea Co-Generation

4. Concept Co-Evaluation

5. Field Experience, Fabrication, Experiment, Lab Work, Analysis

7. Pilot studies

6. Refined Design (Field and lab testing, multiple sites, multiple countries)

10. Reiteration

9 Scale-up

8. Implementation

Co-designing/ co-evolving

equitable and sustainable

development

Problem Co-Definition

• To design a household drinking water treatment unit to remove arsenic and pathogens;

•Technical Performance: Remove arsenic, bacteria and parasites to National Standards or WHO Guidelines;

• Water Quantity: The flow rate should be > 10 L/hour;

• Cost: The cost/unit should be < Rs. 1500. Yearly replacement parts < Rs. 200, designed for use by individuals in rural areas and urban slums who earn <Rs. 200/day;

• Socially acceptable: ease of use and maintenance by women

Alternative Water Supply Options

Surface Water Treatment This involves the treatment of surface water from ponds exclusively reserved for drinking purposes

Use of slow sand filtration system to make it safe for drinking and cooking

Taste may not be acceptable to many users

Coliforms may be present, if maintenance is poor

Construction cost is relatively high

Pond sand filter (PSF)

Alternative Water Supply Options

Small-scale Conventional Surface Water Treatment Plant

Alternative Water Supply Options

Requirements

Availability of deep aquifers separated from shallow contaminated aquifers by relatively impermeable layers.

The annular space of bore holes of the deep tubewells is required to be sealed at the level of impermeable strata to avoid percolation of arsenic contaminated water.

Dug wells can be a cost-effective option for arsenic-free groundwater.

An indigenous technology with very high social acceptance

Properly designed and protected wells (ring wells) ie. lifting water by a hand tube wells and by covering the top, they may be able to provide water of acceptable bacteriological quality.

Existing dug well waters may be used after sterilization with solar-assisted disinfection

Alternative Water Supply Options

Dug/Ring Wells

Alternative Water Supply Options

Rainwater Harvesting Basic Requirements

Adequate Rainfall-Intensity of

Rainfall-Reliability of

Rainfall

Distribution of Rainfall

Suitable Catchment area

Storage Tank

Operation and Maintenance

Alternative Water Supply OptionsRainwater Harvesting

Treatment Of Arsenic Contaminated Water

Major Treatment Processes Oxidation and Sedimentation Coagulation and Filtration

Aluminium Alum Iron salts Naturally Occurring Iron

Sorptive FiltrationActivated AluminaGranulated Ferric Hydroxide/OxideMetallic Iron/ Iron OreSynthetic Composite Active MaterialsIon Exchange

Membrane FiltrationNano FiltrationReverse Osmosis

Arsenic Removal Processes Based On Oxidation

Arsenite[As(III) ] Arsenate [As(V)]

Oxidizing AgentsOxygen (Air), Ozone, Free chlorine, Hypochlorite, Permanganate, Hydrogen Peroxide and Fulton's Reagent(H2O2/Fe2+)

Oxidizing Reactions H3AsO3 + ½O2 = H2AsO4-+ 2 H+

H3AsO3+ HClO = HAsO4--+ Cl-+ 3H+

3H3AsO3 + 2KMnO4 = 3HAsO4--+ 2MnO2++ 2K++ 4H+

+ H2O

Arsenic Removal Processes Based On Oxidation

In situ remediation

Iron oxide for In situ remediation Altering Geochemical conditions which favour the reduction of arsenic concentration in groundwaters

Iron oxide is the most important phase for arsenic removal in groundwater

Approach involves withdrawing iron-rich groundwater, oxidizing Fe2+ to Fe3+ by introducing oxygen (or KMnO4) followed by injection

Above process converts As(III) to As(V) and sorption of As(V) on ferric oxyhydroxide removes arsenic from groundwater

Few field trials have been reported

Arsenic Removal Processes Based On Oxidation

In situ remediation

Nitrate for In-situ remediationNitrate suppresses iron oxyhydroxide reduction by bacteria

Nitrate can oxidise Fe(II) to Fe (III) under anoxic conditions

Presence of nitrate (in groundwaters) this can lead to low arsenic concentrations.

Field studies have shown that nitrate injection into groundwaters, leads to the decrease in arsenic concentration

Guidelines/Standards (WHO: 45 mg/L, BIS: 50 mg/L) for nitrate in potable water is health based. Hence concentration should be within permissible limits, when used for in situ remediation.

Arsenic Removal Processes Based On Oxidation

In situ remediation

Sulphate for In-situ remediationPresence of sulphate in groundwater could stimulate sulphate-reducing bacteria, leading to the formation of sulphide

Sulphide combines with dissolved iron and arsenic, promoting iron/arsenic-sulphide precipitation

It is generally observed that arsenic-rich groundwaters have low sulphate concentration

It is proposed that this sulfate limitation is the reason for high dissolved arsenic.

It has been suggested that addition of sulfate is a low-cost treatment approach for low sulfate groundwater

Arsenic Removal Processes Based On Oxidation

SORAS FilterMethod uses irradiation of water with sunlight in PET or other UV-A transparent bottles to reduce arsenic levels in drinking water.

Method is based on photochemical oxidation of As (III) followed by precipitation or filtration of As (V) adsorbed on Fe(III) oxides .

The goals of the SORAS To work without addition of Fe (II,III) salts when the naturally present iron is above 5 mg/L.

To increase the efficiency of the As (III) oxidation at pH 7.0 – 8.0 with locally available materials

To conduct the treatment in closed and easily available PET bottles.

Arsenic Removal Based On Coagulation -Filtration

Principles

Precipitation: Formation of insoluble compounds.

Coprecipitation: Incorporation of soluble arsenic species

into a growing metal hydroxide phase;

Adsorption: Electrostatic binding of soluble arsenic to external surfaces of the insoluble metal hydroxide

Filtration: Separation of precipitates by filtration through a medium.

Arsenic Removal Based On Coagulation -Filtration

Aluminum Sulfate ( Alum)

Al2(SO4)3.18H2O = 2Al+++ + 3SO4++ + 18H2O

Al+++ + 6H2O = 2Al(OH)3+ 6H+

H2AsO4-+ Al(OH)3= Al-As (complex) + Others

Relative Affinity

PO4> SeO3> AsO4> AsO3>> SiO4> SO2> F > B(OH)3

Arsenic Removal Based On Coagulation -Filtration

Bucket Treatment Unit

Developed by the DPHE-Danida Project and improved by the Bangladesh University of Engineering and Technology (BUET) Based on coagulation, coprecipitation, and adsorption processes Chemicals are mixed manually with arsenic contaminated water in the upper red bucket by vigorous stirring with a wooden stick and then flocculated by gentle stirring for about 90 seconds. The mixed water is allowed to settle and then flow into the lower green bucket and water is collected through a sand filter installed in the lower bucket. Found to be very effective in removing iron, manganese, phosphate, and silica along with arsenic.

Arsenic Removal Based On Coagulation -Filtration

Stevens Institute Technology Filter

The Stevens Institute technology also uses two buckets, one to mix chemicals (iron coagulant and hypochloride) supplied in packets and the other to separate flocs using the processes of sedimentation and filtration The second bucket has an inner bucket with slits on the sides to help sedimentation and keep the filter sand bed in place.

The chemicals form visible large flocs when mixed (by stirring with a stick).

Clean water is collected through a plastic pipe fitted with an outlet covered with a cloth filter to prevent the entry of sand.

Arsenic Removal Based On Coagulation -Filtration

Designed and installed by the All India Institute of Hygiene and Public Health (AIIH&PH)

Principles of arsenic removal by alum coagulation, sedimentation, and filtration have been employed in this compact unit

Effective in removing 90% of the arsenic from tubewell water.Treatment process involves the addition of sodium

hypochloride and aluminium alum in diluted form, mixing, flocculation, sedimentation, and upflow filtration in a compact unit.

Arsenic Removal Unit Attached to Tubewell

Aresenic Removal By Sorptive Filtration

Activated Alumina BUET Activated Alumina, [Bangladesh] Alcan Enhanced Activated Alumina [Bangladesh & India] Apyron Arsenic Treatment Unit [Bangladesh & India] Oxides India (Catalyst) Pvt. [India] RPM Marketing Pvt. [India]

Granular Ferric Hydroxide, [Bangladesh & India]

Iron Coated Sand/Brick Chips, [ Bangladesh ]

Iron Fillings (Metallic Iron), [ Bangladesh, Nepal ]

Red Hematite, Fe2O3( Public Health Eng. Dept), [ India ]

Ion-Exchange, & Bucket of Resins [ Bangladesh & India ]

Composite Sorptive Media [ Bangladesh & India ]

Aresenic Removal By Sorptive Filtration

BUET Activated Alumina

[ Activated Alumina ]

Developed by Bangladesh University of Engineering and Technology.

Based on the oxidation of As (III) to As (V) removal of iron and subsequent adsorption of arsenic onto activated alumina.

Chemicals are added to raw water in 25 L plastic bowl for oxidation of As (III) to As (V) and from precipitation.

Co-precipitation and adsorption of arsenic occur during these operations

Filtration unit consists of 20 cm deep sand layer in 22 L plastic bucket.

Adsorption unit is a plastic pipe of 37 cm diameter having activated alumina depth of 22 cm.

Arsenic Removal By Sorptive Filtration Million Dollar Prize!!!!!

It is based on passive coagulation with iron filings and/or adsorption onto sand matrix.

Developed in 1999 and designed modified in 2001.

Consists of three 18 L clay or 3 buckets (called SONO filters) contains 2 Kg of coarse sand and 3 Kg of iron filing on the top.

The middle chamber contents 2 Kg of coarse sand and 1 Kg of wood charcoal.

Top and second pitcher have small holes in the bottom to facilate draining of water from one pitcher to other.

Accepted by users in Bangladesh.

Sono3-Kalshi[ Iron Fillings]

Aresenic Removal By Sorptive Filtration

Based on adsorption of arsenic onto the candle material.

Candle is made from chemical mixture of lateral soil, ferric oxide, manganese dioxide, aluminium hydroxide and mesoporous silica.

Comprises of two concrete buckets of different sizes placed one above the other.

The permissible candle removes bacteria also plot sock studies showed the arsenic removal was not very satisfactory

SAFI Filter

Work Carried out at IIT Kanpur

Obtained as a waste from Marine Industry Bio degradable, Bio compatible, Antimicrobial Properties –

For water treatment applications Could be functionalized with various groups for selective

applications Presence of amino and carboxyl groups – excellent

complexation with heavy metals Could be used in various forms like flakes, granules, fibres

etc.

Flakes Granules Fibers

Novel Bio Sorbents

Domestic Filter Units to remove Arsenic

Advantages:

• Able to Remove Both As(III) and As(V)

•Could be operated at neutral pH

•Ideal for Rural Setting

•A very High absorption capacity (20 times more than AA)

• Able to remove arsenic down to WHO standards of 0.01 mg/l!!!

Advantages and Disadvantages

Stage 1: All Sources are safe, arsenic is below 10 ppb

Actions:

To create awareness about the arsenic among the community and benefits of safe water and its consumption

To develop faith on the drinking water taken from hand pumps / habitations and advice not to cross the village for collecting water from other village as there may be arsenic in excess in water source

Stage 3: Water source marginally contaminated (10 – 25 ppb)

Actions:

To carry out health survey with trained doctors and proper assessment of population at risk.

To stop drinking contaminated water and try to use alternate source of water.

Nutritious and protein rich foods may help people with arsenicosis.

Stage 2: Safe and unsafe water sources co-exist

Actions:

As per ATF (Arsenic Task Force, Uttar Pradesh), an initial measure arsenic-safe hand pumps will be marked blue and arsenic contaminated hand pump will be marked red (work completed in district Ballia, UP)

To use Safe source for water consumption

To use unsafe source for other purpose

Stage 4: Water sources highly contaminated

Actions:

To compile information of hydro-geochemical aspects, rainfall, terrain and population.

Digging tube well deeper meaningful if the deeper aquifer has safe water.Harvesting rain water to consider if rain fall is adequate.Bringing safe water from a distance to consider if economically viable.If arsenic filters is the choice, community installation, hand pump attachment and /or domestic filter may be adopted.

Actions for Arsenic Mitigation

Thanks