Dr. M.V.Ramana Murthy

&Dr. M.A.Atmanand,

Ministry of Earth Sciences

• Rivers in

spate,

Submerged

flyovers ,

Airport, Roads

and Settlements

Dec., 2015 Floods that paralyzed Chennai – Some snapshots

Coastal Flooding –information

lacunae

No data on

• Vulnerable areas

• Extent of flooding

• Low lying areas

• No warning system

Early Warning System for forecasting Coastal Floods

MoES ( NCMRWF, IMD and NCCR) has

developed Urban Flood Warning System

integrating the Numerical models of

Weather (Precipitation),

Hydrology (Catchment),

Hydraulic ( River),

Hydrodynamic (Tide and Storm

Surge )

and Urban Drainage/overland flow.

Web Based Decision Support System is

put into operation for Greater Chennai

Corporation (GCC) in association with

TN State Disaster Management Unit by

integrating Topography

(DEM)/Bathymetry,

population/infrastructure and

administrative information.

Similar System is being developed by

MoES for Mumbai with network of

observatories. It will be extended to

other cities in the country.

Water demand, Population growth, Over exploitation of resources

Climatic change and variability

Land use, Catchment areas for Refill / Reservoirs

Water quality , Pollution

Natural /Chemical / Biological Impurities

Sea Water Ingression

Contamination by Industrial / Domestic Waste

Poverty and economic policy

Water resource Management

International waters / Sociological issues

Water Scenario: Challenges

Source: 'India's Water Future to 2025-2050’,International Water Management Institute; Datamonitor; ’Dreaming With BRICs: The Path to 2050’,GoldmanSachs Global Economics Paper No:99;Population Division, Department of Economic and Social Affairs, United Nations: ’Sustainable Technology Options forReuse of Wastewater', Central Pollution Control Board; 'Urban and Rural Areas 2007’,Population Division, Department of Economic and Social Affairs,United Nations; 'India's Water Resources,Availabliity,Needs and Management:21st Century', German Coastal Engineering Research Council

Source: Sustainable technology options for Reuse of Wastewater', Central Pollution Control Board; 'Wastewater management and Reuse for Agriculture andAquaculture in India’, CSE Conference on Health and Environment 2006; Wastewater reuse and Recycling Systems: A perspective into India and Australia',International Water Management Institute

Source: 'Corporate initiatives for Water Conservation and Waste Water Management’ India Water portal; 'Higher Incomes for farmers in India’s KarnatakaWatershed', World Bank; 'Rain Water Harvesting Catches on in Chennai', The Hindu Business Line; 'Agricultural Engineering', Government of Tamil Nadu; ’SeaWater Reverse Osmosis Plant to be Established in Chennai', Andhra News; ‘BARC Builds Barge-mounted Plant to Produce Safe Drinking Water', Live Mint;'Garland of Hope: River-linking as a Solution to Water Crisis ‘,The Times of India

Source: ‘India’s Water future to 2025-2050:Business as usual Scenario and Deviations’, International Water Management Institute; India Census 2001;’WaterPoverty in Urban India: A Study of major Cities’, Jamia Millia Islamia;’ Troubled Waters', Development Alternatives;’ Dreamings with BRIC’s: The Path to2025’,Goldman Sachs,2003;’Urban and Rural Areas 2007’,United Nations; ’Water Supply-The Indian Scenario’, IEA India ;’Status Of Water Treatment Plants InIndia', Central Pollution Control Board; Population Division of the Department of Economic and Social Affairs of the United Nations Secretariat

On 18 June 2019, the city's reservoirs ran dry, leaving the city in severe crisis

Chennai population : 8.24 million (2011 census)

As the city lacks a perennial water source, catering the water requirements of the population has remained an arduous task.

Although three rivers flow through the city,

Chennai relies on North East Monson to

replenish its water reservoirs since therivers are polluted with sewage.

With the increase in population and

depleting ground water the city often

grapples with acute water supply

shortages.

Chennai Water Crisis

Chennai is entirely dependent on ground water resources to meet its water needs.

Ground water resources in Chennai are replenished by rain water and the city's average rainfall is 1,276 mm.

Chennai receives about 985 million liters per day (mld) from various sources against the required amount of 1,200 mld. This demand is expected to rise to 2,100 mld by 2031.

Water to the city's residents is being supplied from desalination plants at Nemelliand Minjur; aquifers in Neyveli, Minjur and Panchetty;

There is a canal to tap into excess water from the Krishna basin (as part of the Telugu Ganga project) and Cauvery (Veeranam project).

There are four reservoirs in the city, namely, Red Hills, Cholavaram, Poondi and Chembarambakkam, with a combined capacity of 11,057 mcft.

Demand and Supply of Water in chennai

The failure of northeast monsoon in 2018 and pre-monsoon showers in 2019 have caused depletion of the already over-exploited lakes.

The Poondi reservoir has a capacity of 3,231 mcft

The Chembarambakkamreservoir has a capacity of 3,645 mcft.

2018 2019

2018 2019

Present Scenario : As on June 2019

The Chennai city has network of about 650water bodies including major lakes, pondsand storage tanks has been destroyed. Thecurrent number stands at around 27,according to the NIDM study.

Total area of 19 major lakes in the CMAhas nearly halved from 1, 130 hectares toabout 645 hectares.

This is the overall capacity of water bodiesin the city to contain excess rain water hasreduced.

Cause I : Disappearing water bodies

Extent of Water bodies as mapped from

Toposheet and Pre and Post flood

satellite data

SOI Toposheet(1975) : 105.5 sq.kmPre-flood Sat data (6.10.2015) : 35.4 sq.kmPost-flood Sat data (10.2.2016) : 105.7 sq.km

Cause I : Disappearing water bodies

Water bodies

Topo

sheet

[1976]

6-Oct-

15

10-Jan-

16

%

Change

Ambattur

Lake 1.68 1.41 1.3

22.62%

Chembaramba

kkam Lake 20.54 8.52 19.71

4.04%

Cholavaram

Lake 6.54 1 6.2

5.19%

Korattur Lake 1.96 1.57 1.68 14.28%

Porur Lake 1.17 0.09 0.75 35.89%

Puzhal Lake 19.54 3.94 19.06 2.45%

Retteri Lake 1.47 0.82 1.07 27.21%

Velachery

Lake 0.95 0.08 0.16

83.15%

Cause II : Tampering of recharge structures

Tampering of recharge structures like lakes, tanks , ponds and wetlands is one reason attributed to the water crisis in Chennai.

Cause III : Fractured flood sink

Pallikaranai is a freshwater marsh inthe city of Chennai and is home toseveral rare/ endangered andthreatened species.

Pallikaranai used to cover an area of50 sq km but it has now been reducedto a tenth of its size. 90% of themarshland has been lost toconstruction of IT corridors, gatedcommunities, garbage dumps andsewage treatment plants.

A survey conducted by Care EarthTrust in the early 2000s revealed thatthe marsh had shrunk by almost 90percent--from close to 6000 hectaresto barely 600 hectares--over a 50-yearperiod.

Fractured flood sink - Temporal changes in Pallikaranai marsh (1990-2016)

Dump yard

Chennai’s Water Crisis:Five-point solution

Improving storage of surface water

Efficient implementation of rainwater harvesting

Recharging groundwater

Protection of flood plains, lakes and wetlands

Desalination plants

According to the records of the Water Resources Department, only 19 of the 29 major

waterbodies in the city's periphery can be restored.

Nine lakes cannot be rejuvenated owing to encroachments, including those in

Valasaravakkam, Virugambakkam, Maduravoyal etc.

Once rejuvenated completely, the remaining lakes will have a combined storage

capacity of 1,000 million cubic feet (mcft).

In addition, if the four primary reservoirs are desilted by a metre, an additional water

volume of about 500 mcft can be stored.

It is estimated that as many as 3,600 tanks in and around the Chennai metro area

(covering the whole of Kancheepuram and Tiruvallur districts), if properly preserved

and networked, can provide five times the quantum of water that the city needs in

normal times. Water harnessed through these tanks is estimated to be about 80,000

million cubic feet (TMC).

Solution I :Improving storage of surface water

19

DESALINATION TECHNOLOGIES

Thermal Desalination

1. Multi effect distillation / Multi stage flashing

2. Low Temperature Thermal Desalination

3. Solar based Desalination

Membrane Desalination

1. Sea water reverse osmosis

2. Electro dialysis

Desalination

Natural Way

LTTD Desalination at

Union Territory of Lakshadweep

LTTD ProcessVertical Temp profile across Ocean

•Temperature differences between the surface (28o– 30o) and deep sea

water(10-12o) at the Islands used

•Under vacuum condition, warm (surface) sea water is evaporated and it is condensed using the deep sea cold water resulting in pure fresh water

• Major components are Marine Structure, Plant Building and Deep sea submarine pipeline

Desalination Low Temperature Thermal Desalination uses two water

bodies where in warmer water is evaporated at low

pressures and the colder water is used in condensing

the colder water to obtain high quality drinking water.

The applicability of the technique is site specific.

Other techniques for desalination are Reverse Osmosis,

Multi Stage Flashing and Multi Effect Distillation

Islands with availability of 400m depth for cold water

within 1 km distance and Coastal Thermal Power Plants

discharging huge amounts of hot water into nearby sea

are suitable for LTTD. For mainland applications an

offshore floating plant would be required.

23

Kavaratti Island, UTL

RO plant Bitra

Parabolic Solar

Collectors

MED System

Solar Desalination

LTTD PLANTS TAKEN UP BY MOES-NIOT

Completed• 2005: Kavaratti Plant – 100 m3/day• 2007: Barge Mounted Plant - 1000 m3/day• 2009: Power Plant Based LTTD – 150 m3/day• 2013: Solar MED 35 m3/day (Cond. design by NIOT)• 2011: Agatti and Minicoy Plants – 100 m3/day

Underway• 2 x 1000m3/day: Power Plant based Plant in

Tuticorin (Design Stage, fabrication to commence)• 10000 m3/day Offshore Plant (DPR Stage)• 6 x 150m3/day: Plants in Lakshadweep Islands

(Under Progress)

Agatti-2011

NCTPS -2009 Off Chennai - 2007 Kavaratti -2005

Minicoy-2011

Coral/sand stone rock in HTL

Underwater pictures Agatti / Androth

AgattiAndroth

DESALINATION: PROCESS Ocean Thermal Gradient: The temperature of water decreases

with an increase in depth.

Low Temperature Thermal Desalination (LTTD)

The temperature difference is utilized to produce potable water by

evaporating surface sea water at low pressures and condensing the resultant fresh vapour with deep sea cold water.

26

Components: Flash Chamber, Condenser, Sea Water Pumps, Vacuum System, Cold Water Pipe, Marine structures like sump, Bridge and Plant Building.

Desalination plant

1000m

Cold water pipe

400m

LagoonReef

Typical Island profile

LTTD plant at Agatti

Minicoy LTTD plant

Completed LTTD Plants at UT LakshadweepLTTD plants each with fresh water generation capacity of 100 m3/day were established at Agatti

(July 2011), Minicoy (April 2011) and Kavaratti (May 2005). Six more plants under construction at

Amini, Androth, Chetlat, Kadamat, Kalpeni and Kiltan islands.

SumpPlant building

Approach trestleInstallation of Deep Sea

Cold Water Pipe

230m (approx.)700m (approx.)

400m (appro

x.)

Agatti Desalination plant

Major components: Marine Structures (Sump, Approach Bridge, and Plant Building) Submarine Cold Water

Pipe: ~ 1000m long HDPE pipeline with attachments;

Process Equipment (Flash Chamber, Condenser, Seawater Pumps, Vacuum System, Plant Piping )

AGATTI PLANT

Sump with Sea Water Pumps

Plant BuildingWith Equipment

Bridge for Access, Piping and Power

BreakerRegion

Shallow Water Region

Control Room

Typical conditions in the Breaker Region of the Site

Side view of the Plant

KILTENCHETLET

KADAMAT

AMINI

KALPENI

ANDROTH

A 35000 liters per day capacity is installed atRamanathpuram, TN, in 1400 m2 area with apower requirement of 26 kW.

Concentrates Solar Energy with Linear FresnelType Collectors for Heating / EvaporatingSeawater

Multistage Desalination of the sea water Features: 6 stage multi effect

desalination (MED) system forDesalination

Components: Pumps for maintaining theflows; vacuum system for maintaining therequired pressure in the system;Instrumentation for the plant

Advantages / Disadvantages for remote islands• Effective utilization of the solar heat for only

6 hours during the day• Periodical cleaning Essential to ensure

efficiency

EVAPORATOR

FLASH CHAMBER

CONDENSER

COLOUR CODE

BRINE PUMP

MAIN SEA WATER PUMP

DISTILLATE PUMP

DM RECYCLEPUMP

VACUUM SYSTEM

BRINE

SEA WATER

STEAM

DISTILLATE

DISTILLATE OUTLET

BRINE REJECT

SEA WATER INLET

SOLAR PANEL

Solar Desalination System - A Schematic

Parabolic Solar Collectors MED System

A view of the Desalination Plant a Ramanathapuram

Solar Assisted LTTD Plant Installed at Ramanathapuram, TN

Schematic of Solar desalination plant

Solar Thermal Distillation Plant of 10 m³/day capacityhas been commissioned by IIT Madras with thefunding of MoES under TRB.

Intake caisson with pumping system for supplying seawater to the MED plant has been commissioned byNIOT.

Intake seawater systemIntake caisson

Solar Desalination at Kanyakumari

Plant capacity (m3/day)

Collectorarea (m2)

Water requirement (m3/day)

Surface area condensation (m2)

0.05 10 1 0.4

1 100 20 4

10 600 200 32

100 5000 2000 400

1MLD Barge Mounted LTTD Plant

Plant Components

A View of the Barge and its mooring

Pipe Tow

For mainland applications, the necessary depth for the availability of 10 – 12o Cwater is at 40 – 50 km from shore. HDPE pipe of length 600 m was towed,upended connected at the bottom of the barge at 1000 m water depth.

Deepest SPM in Indian water and for the first time in the country synthetic ropeswere used for such a mooring.Fresh water with TDS 10 ppm was obtained through indigenously designed andfabricated flash chamber and condenser.

10 MLD OFFSHORE DESALINATION PLANT Requirements : • Depth of at least 1000 meters• Distance at least 20 – 25 km from shore• Requires a large size stable weather platform for housing plant • a large cold water conduit and station keeping / mooring for the plat form• Long and higher dia pipeline required for pumping water• Very complex and challenging

Preparation of detailed project report using an industrial partner is in advanced stage of completion. In-house activities for power optimization, and detailed analysis of offshore components are also in progress.

Configuration as in DPR

In-house design configuration

• LTTD can be adopted in coastal thermal power plants where large quantity of water is drawn from the sea for cooling the condensers and later rejected back into the sea as hot water causing extensive thermal pollution.

• Power plants need De-mineralized water that is produced from local supply through RO process

• Thus, the LTTD method in Power Plants can serve two purposes –(1) generation of fresh water, thereby reducing the load on external sources. (2) reducing temperature of reject water thereby reducing the load on the

cooling tower

• NIOT successfully Demonstrated Condenser Reject based LTTD in North Chennai Thermal Power Station.

LTTD Using Condenser Reject Water (waste heat) in Power Plants

Typical CONFIGURATION OF A DESALINATION PLANT Working with POWER PLANT Condenser Reject Water

2 x 1 MLD capacity LTTD Plant in Coastal Thermal Power Plant

Establishment of Waste Heat Recovery LTTD plant using an industrialpartner for 2 modules each of 1 MLD capacity at Tuticorin ThermalPower Station (TTPS) premises.

Out of 2 modules, 1 module to produce drinking water of TDS : 100 – 200ppm, and othermodule to produce boiler qualitywater of TDS : < 2 ppm.

RFP is in progress for the award of the Work.

Overall layout of the plant

Outfall

2 modules(Flash chamber with condenser)

Cold water pumps

Warm water pumps

Power plant reject water

pipes

Parameter Desirable limit

Permissible limit

LTTD Water at Agatti

LTTD Water at NCTPS Plant

Color 5 hazen 25 hazen OK OK

Odour Unobjec-tionable

Unobjec-tionable

OK OK

Taste Unobjec-tionable

Unobjec-tionable

OK OK

pH 6.5 8.5 7-8 6.54

TDS (PPM) 500 2000 180 24

Chloride (PPM) 250 1000 90 12

Total Hardness (PPM)

300 600 100 4

Total Coli form (MPN)

- 10 Not Detected <2

COMPARISON OF WATER QUALITY WITH DRINKING WATER

NORMS

LTTD - Advantages

No pretreatment of feed water required.

Assured consistent quality water fit for drinking as per WHO standards.

Operational simplicity and easy maintenance.

No external energy for evaporating the sea water

Assurance of constant cold water temperature source

Reduces the thermal pollution when used in the process industries

Air Conditioning if on land

Cold water which is being discharged to the sea can be used to

run an air conditioning system.

Aquaculture – Land or Offshore

Deep sea water is rich in nutrients and can be used cultivate

marine life.

LTTD - CHALLENGES

• Large volumes of water are to be handled

• Low temperature differences leading to low efficiencies makes

design of thermal components challenging with available market

components.

• Power optimization required for low operation costs

• Design of structures and cold water intake pipe complex in island

scenario.

• Design of all weather floating platform and cold water conduit

never attempted before and very complex.

• Transportation of fresh water to shore never tried before and

needs designs adapted from oil industry.

• Capital cost intensive since components have to have long life in

seawater environment.

CONCLUSIONS Water Management Techniques to be implemented

Protection of Lakes and Water Bodies

Desilting of Lakes and Water Bodies

Rain Water Harvesting

Environmentally friendly Desalination Technology

Even though LTTD plants have been established at various places, still

more research has to be conducted to meet the challenges such as

increasing the thermodynamic efficiency especially in design of higher

capacity offshore / power plant based desalination plant.

Future plans : Implementation of OTEC / other renewable energy

sources such as solar / wave to make the desalination system self

sufficient.

41

THANKS FOR KIND ATTENTION