envoiremental & pollution control

8/13/2019 Envoiremental & Pollution Control

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ENVIRONMENT &

POLLUTION CONTROL

Power Management InstituteNoida

IG/13(Restricted Circulation Only)


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CONTENTS

S.NO. TITLE Page Nos.

PART I

1. Site Selection for Thermal Power Project. 1

2.Procedure for Selection of site for Thermal Power

Project for Environmental Clearance.4

3.

Environmental Impact Assessment for Thermal Power

Project. 14

4. Air Quality Monitoring & Control. 23

5. Water Pollution & Control. 35

6. Ash Disposal System. 53

7. Ecological Aspects of Thermal Power Project. 62

8. Environmental Appraisal for Thermal Power Projects. 68

9. Environmental Guidelines for Thermal Power Plants. 89

10. Afforestation and Environmental Improvement. 98


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S.NO. TITLE Page Nos.

PART II

1. The WaterAct-1974. 1

2.The water (Prevention & Control of Pollution) Amendment Act,

1988.46

3. The Air (Prevention & Control of Pollution) Act, 1981. 60

4.The Air (Prevention & Control of Pollution) Amendment Act,

1987.

97

5. The Environmental Protection Act, 1986. 107

6. Notification under EP Rules 1986. 123

7. Effluent standards 1988. 138

8. Notification for emission standards 1989. 146

9. Notification for Ambient Noise Standards. 148

10. Notification of slack Height 1990. 150

11. Notification for Coastal Regulation Zone. 165

12. Forest Conservation Act, 1980. 178

13. Forest (Conservation) Amendment Act, 1988. 184


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PART I


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1.1. Site SelectionSite Selection ffor Thermal Power Projectsor Thermal Power Projects

INTRODUCTION

Electricity is essential to maintain and enhance our Nations social and economic well

being. Already, there are pressures on the natural resources and the pressures will

continue to grow with the steady population growth. Electric utilities want to site a plant

on land accessible by road or rail, close to a large water source that will be as near as

possible to the load centre and the coal source. The DOEn and PCBs may fear the

intrusion of the plant on the environment and its impact on ecology. The local interest

groups which want the plants power output may not for various reasons want the plantin the vicinity or on a particular location.

This dilemma could lead to delays which could greatly enlarge our Nations already

acute energy crisis.

In the past the principal factors for siting a plant were engineering and economics and all

of us were willing to accept these principles. The economics of plant location covered

mainly the plants proximity to the coal source and the distance to the load centre. Also,there had to be a suitable foundation on adequate water supply, and adequate

transportation facilities. Now, attention is being focussed on the environment. All of us

recognize the need to protect the environment and will have to orient our site selection

methodology to minimize degradation of our environment.

ENVIRONMENTAL CONSIDERATIONS

The DOEn has issued Environmental Guidelines for Thermal Power Plants.

Unfortunately, where there is water there exist either forests, or prime agricultural land,

or is in the flood plain. Further, areas close to major water sources tend to be fairly well

populated and it is not desirable to displace significant number of people. Also, officially

designated forest lands comprise of more than 30 percent of India. Thus, potential sites,

which are acceptable to DOEn, are going to be very rare. While every effort to follow the


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guidelines, is being made by utilities. DOEn should appraise the sites on a case-by-case

basis. For instance, there are large areas, which are designated as forests but have no

trees. Perhaps these areas could be considered, with adequate reforestation proposals.

Again, many of the adverse environmental Impacts can be satisfactorily mitigated by

engineering. Examples are high efficiency electrostatic precipitators for particulate

control in ambient air, and cooling towers with properly designed diffusion systems for

thermal discharge control. A site must be selected or rejected on it s specific

characteristics. And here, the role of well prepared environmental impact assessment as

a decision making tool cannot be underplayed.

SITE SELECTION METHODOLOGY

One of the problems we are facing today is that sites. for the projects being proposed

now, were identified many years ago. Environmental criteria were non-existent and

therefore, many of these sites are not acceptable today. We are, thus, placed in an

unviable position where we are trying to defend these sites as environmentally

acceptable. We will, therefore, have to start afresh.

The Central Electricity Authority (CEA) could identify general areas or States where

power plants would be required during the next 50 years. Naturally, the National Policies

and Demands would be considered during the selection of these areas or States.

When this information is available, individual utilities will be responsible for specific site

selection in these areas. The utilities will identify a team for site selection and

investigations. The team will consist of power engineers and environmental specialists at

a fairly senior level, and will involve State administrative, and DOEn/PCB officials in the

site selection process.

Survey of India topographic sheets can then be studied in detail and identify the

exclusion areas, where plants cannot be located due to engineering, economic, or

environmental reasons. Further, several potential sites can be identified on the

topographic maps for further studies.


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Available information on the potential site can then be obtained. Such information will

include geological characteristics, land use patterns, stream flow, aquifer characteristics,

water quality etc. Normally, this information is available with the different Government

agencies. A wealth of information can be had from satellite photographs, which are

available with the Indian Space Research Organization. Ahemdabad.

Based on this exercise, the potential sites are narrowed down to say five or six.

An aerial reconnaissance survey is now in order. The site selection team can view the

potential sites from low flying aircraft. While this exercise is not inexpensive to

experienced power and environmental engineers, the benefits are immediate. Two or

three of the best sites can now be selected.

At this state, field surveys and investigations can be initiated. Feasibility, including EIA

studies can be conducted and the reports prepared. This procedure will ensure the

availability of sites, acceptable from all angles, when needed. Further, the lead time

necessary for environmental clearance will be reduced by at least 18 months, even more

if the DOEn has been involved in the selection procedure.


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2.2. ProcedureProcedure ffor Selectionor Selection oof Sitef Site ffor Thermalor Thermal

Power ProjectPower Project ffor Environmentalor Environmental

ClearanceClearance

INTRODUCTION

The Ministry of Environment and Forest (MOEF) has issued Environmental Guidelines

for thermal power project in which criteria and other requirements have been

prescribed. MOEF while reviewing the FR have insisted for changing the location of sites

for some of the proposed projects due to non-adherence of some of the criteria

stipulated in the guidelines. This is resulting in delay in clearance of the projects. It is,

therefore, necessary that the following procedure is adopted while preparing the FR for

all new projects (both coal and gas) in order to avoid delay in environmental clearance.

PROJECT SITING CRITERIA OF MOEF :

(Ref. Environmental guidelines for TPP 1987 issued by MOEF)

Location of thermal power plants should be avoided within 25 kms. of the outer

peripheries of the following:

Metropolitan cities;

National parks and wild life sanctuaries; and

Economically sensitive areas like tropical forests, biosphere reserves, National Parks

and Sanctuaries, important lakes and coastal areas rich in coral formations.

In order to project the coastal areas above 500m of HTL a buffer zone of 500m should

be kept free of any TPS.


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The (chimney) should not fall with the approach funnel of the runway of the nearest

airport.

The site should be at least 500m away from Flood Plain of the Riverine Systems.

The site should also be at least 1/2 km. away from highway.

Location of TPS should be avoided in the vicinity (say 10 km) of places of

archaeological, historical, cultural, religious or tourist importance and defense

installations.

The TPS should be surrounded by an exclusion zone of 1.6 km. and located on the

leeward side of the exclusion zone with respect to the predominant wind direction.

Residential/commercial development should be regulated in the exclusion zone on the

basis of strict land use zoning.

No forest or prime agricultural land should be utilised for setting up of TPS or for ash

disposal.

PROCEDURE TO BE FOLLOWED FOR SITE SELECTION,

PREPARATION FOR FR AND EIA REPORTS.

Initially various alternative locations for the project should be selected based on the

information available from

Toposheets

Forest Map

Census Report


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INFORMATION COLLECTION

For further shortlisting of the alternative locations to meet the criteria laid down by MOEF

in their guidelines, informations are to be collected in details as indicated below. The

groups responsible and groups to be associated for identifying each of the item is

indicated. The area within 25 km. radius from the location of proposed site(s) is to be

covered under study.

Sl. No. Description Source of

Information

GroupResponsible

Group to beassociated

1. Details of MetropolitanCities

District

Collector

New Project

Group (ES)

Env. Engg.(ES)

2. Details of National

Park and Wildlife

Sanctuaries

Dist. ForestDeptt.

Wildlife Board,MOEF

Env. Engg.

3. Details of EcologicallySensitive areas liketropical forests, biospherereserves, national parksand sanctuaries, importantlakes and coastal areas

rich in coral formations.

State ForestDeptt.

Wildlife BoardMOEF NIO,

Goa.

Env. Engg.

4. High Tide Level data forcoastal locations

State Port &Harbour Deptt.NlO Goa

New Project

Group

Env. Engg.

5. Details of existing/proposed Airports/ Airstrips

National

Airport

Authority

New Project

Group

-

6. Details of flood plain of theRiverine System

State

Cirrigarion

Deptt.

New Project

Group

-

7. Details of State Highways District

Collector

New Project

Group

-

8. Details of the followingwithin 10 km. Radius of theproposed location (s).

- - -


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8.1 Places of Archaeologicalimportance

ArchaeologicalSociety of India

New Project

Group

-

8.2 Places of HistoricalCultural Religious or

Tourist importance.

Dist.CollectorDistt. Tourist

Officer.

-do- -

8.3 Defence installation -do- -do- -

9. Broad Classification ofland in the project areawith emphasis on forestland/prime agricultural landinvolved.

District RevenueOfficer

New Project

Group

Env. Engg.

10. Approximate number ofpersons likely to beaffected and no. of houses

likely to be acquired.

District RevenueDeptt./ CensusBook & local

enquiry

Env. Engg.

11. In line with the circularissued by DOP, therepresentative of MOEFshould be requested tovisit the short listed sites.

New Project

Group

Env. Engg.

12*. Investigation andpreparation of FR

District RevenueDeptt./ CensusBook and localenquiry.

New Project

Group

Env. Engg.

13*. EIA Studies and socio-

economic survey

New Project

Group

Env. Engg.

* Note Action for these items shall normally be initiated only after the proposed site

is cleared in principle by MOEF.

Information related to a particular site needs to be collected as per Annexure-I for

Techno-Economic Evaluation and short listing of alternative locations prior to putting

upto MOEF for the in principle clearance of the project.

OTHER RELEVANT INFORMATION

In addition to information stated under item no. 3.1 to 3.5 the following data which are

often sought by MOEF during appraisal should also be collected after the location is

cleared in principle by MOEF.


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Sl.No.

Description Source ofInformation

GroupResponsible

Group to beassociated

1. Coal Linkage,Clearance andexecution statusof the linked block

Deptt. OfCoal/CoalIndia/ConcernedCoal Company

Coal Coordn.Group New projectGroup

2. Water availability andcommitment includingeffect on other downstream beneficiaries

State IrrigationDeptt./ StateGovt.

New projectGroup

-

3. NOC from StatePollution Control

Board (SPCB)

SPCBGroup

Env. Engg.

4. Site Clearance fromState Department ofEnvironment (DOEn)

StateDOEn

Env. Engg.Group

-

5. Environmentalimplication ofdedication dam.

State IrrigationDeptt.

Env. Engg.Group

New projectGroup

6. Forest Clearance(in-principle)

State ForestDeptt.

New projectGroup

Env. Engg.Group

FR GUIDELINES

Information on the Site proposed for setting up of Gas/Coal based Thermal Power

Stations.


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PROJECT:

S.No. Description Responsibility

1.0 Location details : New Project Group (ES)

1.1 State/District/Village :

1.2 Latitude / Longitude :

2.0 Approach to Site : New Project Group (ES)

2.1 Rail

a. Nearest Railhead & Distance

b. Type (B.G. / M.G.)

c. Constraints Enroute

:

:

:

2.2 Road

a. Existing highways/roads distance from

site

b. Load Carrying capacity of these

road/bridges, culverts enroutes &

physical condition

c. Constraints enroute.

:

:

:

2.3 Distance from nearest air port :

2.4 Distance from big cities, ports, power

equipment, manufacturing centres.

:

2.5 Distance from nearest airways :


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3.0 Land Availability & Use pattern : New Project Group (ES)

3.1 Extent of Land :

3.2 Type of Land (Agriculture, Barren, Forest

etc.)

:

3.3 Ownership of land :

3.4 To ascertain from local enquiries possible

earlier use of site i.e. for quarrying,

mining, agriculture etc.

:

3.5 Land Prince :

4.0 Topography :

4.1 Ground Profile & levels :

4.2 Permanent feature :

5.0 Soil Condition : New Project Group (ES)

5.1 Presence of any wells (open and/or tube)

in the site and approx. water level. Likely

ground water table in the area form local

enquiries.

:

5.2 Nature of strata anticipated whether soil

or rock is anticipated at shallow depths

:

5.3 Type of foundations adopted for

neighboring structures-both for houses

& for industrial units.

:


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5.4 Presence of black cotton soil :

5.5 Presence of Salt petre :

5.6 Information regarding major geological

fault existing through local geological

department.

:

6.0 Site Data : New Project Group (ES)

6.1 a. Land :

H.F.L. :

M.W.L. :

Flash flood condition :

Area drainage system :

Ground Water flow direction :

Forest Cover, location and type :

Existence of mines & other present

& future development activity.

:

6.2 b. Meteorological data (Monthlyaverage data for 12 monthspreferably for last 10 years)

:

Temperature (Dry bulb & wet bulb) :

Humidity :

Rain fall Intensity (Hourly) :

Run Off coeff. :

Ambient temperature :

Wind Rose :


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7.0 Water : New Project Group (ES)

7.1 Estimated circulating & consumptive

requirement for the proposed/ultimate

capacity

:

7.2 Source of circulating/consumptive water :

7.3 River/Canal water availability & quality :

7.4 Plant storage requirement/canal closure

period

:

7.5 Salient features of Dam/Barrage

existing/ to be constructed

:

7.6 G.W. / T.W. water availability & quality :

7.7 Sea Water Quality :

7.8 Type of cooling envisaged :

7.9 Conveyance System :

7.10 Proposed arrangement forintake/discharge water

:

8.0 Fuel : Coal Coordination

(For Coal Based)

8.1 Source of coal/gas : HOD/Mech.

(For Gas Based)

8.2 Availability :


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8.3 Quality :

8.4 Estimated Requirements :

8.5 Transportation arrangement

contemplated

:

9.0 General : New Project Group (ES)

9.1 Source of construction & potable water :

9.2 Source of construction power

& start up power

:

9.3 Local schedule of rates :

9.4 Labour rate

Type Wages

i. Unskilled :

ii. Semi skilled :

iii. Skilled :

9.5 Source of availability of constructionmaterial like sand, brick, stone chips,borrow earth etc.

9.6 Proximity of infrastructure facilitiesavailable hereby

a) Hospitals :

b) Schools :

c) Residential accommodation :

Note:

FR Guidelines for Gas Based Projects will be issued separately after finalisation of site

selection guideline by Department of Environment.


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3.3. Environmental Impact AssessmentEnvironmental Impact Assessment fforor

Thermal Power ProjectsThermal Power Projects

INTRODUCTION

Industrial development is essential in a developing country for the social and economic

upliftment of its people. Energy production can be considered on index of the level of

development. With the vast reserves of coal available in India, coal based thermal power

generation is a major source of energy production. They, however, carry inseparable

adverse environmental impacts. The deteriorating Environmental Quality has gained a

significant importance in India today. The biosphere is finite and the capacity to cleanse

itself although as yet imperfectly understood, seems to be limited. There has been a

growing need for integrating environmental factors into the process or planned economic

development.

The need for assessing the environmental impacts due to the operation of the power

plants has been realised and the concept of Environmental impact Assessment (EIA)

Studies is gaining momentum in our country today. The EIA criteria hinge on the

potential impacts, sensitivity and significance of the affected areas and their importance

and controvertiality in respect of local, regional and national levels. The need to protect

environment has been realized by the National Thermal Power Corporation (NTPC)

quite easy and a full fledged environmental department comprising of a multi-discipinary

team of scientists and engineers has been set up at the corporate level. Detailed EIA

studies for the upcoming and ongoing projects of NTPC are conducted by this group in-

house based on which the environmental clearances are accorded by the Department of

Environment (DOEn).

THE EIA

An Environmental Impact is any alteration of environmental conditions or creation of

new environmental conditions adverse or beneficial caused or induced by the action


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under consideration. The objective of the EIA is to define the existing conditions and

then to identify and quantity the alterations due to the proposed project are fairly easy to

define but the environmental costs another matter. Again, the benefits occur in one

region while the costs are usually in a completely different region or regions. When one

takes into account the power plant, the coal mines, the transmission and transportation

condors the several components of the environment: physical, biological, socio

economic political, etc. the task at hand is, indeed, herculean.

A brief description of the scope and contents of EIAs that are being prepared by NTPC,

with the facit approval of the DOEn, is presented.

SCOPE AND CONTENTS

The EIA studies consist of literature research, field studies and impact assessment. The

areas of studies are Land Use, Water Use, Socio-economics, Soils, Hydrology, Water

Quality Meteorology and Air Quality Terrestrial and Aquatic Ecology and Noise. The four

basic stages of the study are:

Determination of baseline conditions or defining the existing environment in the

areas identified :

Establishing the relevant features of the power plant that are likely to have an impact

on the environment :

Assessing the impacts on the identified areas of environment due to the construction

and operation of the power plant; and

Identifying the mitigatory measure necessary to limit the adverse environmental

impacts to within acceptable levels.

The assessment process is reiterative. The basic design of the plant and environmental

protection devices have to be identified and impacts assessed. In case, the impacts are

not acceptable the designs have to be revised and the impacts reassessed. This

process continues until an acceptable situation is arrived at.


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BASELINE STUDIES

The objectives of this stage of the EIA studies are to define the existing environmental

conditions. Normally an area falling within a 10 km radius of the project is studied in

detail, while the area falling within a 50 km radius is examined for major features. A lot of

information is available from local government agencies and universities. Revenue

records, census reports, the irrigation Department, Forest Department, Inland Fisheries,

the India Meteorological Department, etc. have to be collected and collated. Once this

data is analysed information gaps are identified and a field sampling programme

designed and implemented. The field studies span over a period of one year to

accommodate seasonal variations. A brief scope of the different areas of study follows.

Land Use

Land Use Pattern and the trend is identified with respect to agricultural land grazing,

mining, forests, human settlements, etc. Annual crop yields are collected.

Archoeological, historical, and cultural sites are identified.

Water Use

Existing surface and ground water, used for irrigation, industry, cattle and household

use, recreation and drinking use are identified.

Socio-Economics

A study of the exiting population, migration patterns, socio-economic characteristics,

sources of livelihood and levels, existing infrastructure etc. is carried out.

Soils

Significant soil parameters with respect to their agricultural and forest potential as well

as their physical and chemical properties relating to ground water hydrology are

identified.


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Hydrology

Existing hydrological data for both surface and ground water is determined. This

includes identification of aquifers and their characteristics. A water budget of the area is

prepared.

Water Quali ty

A sampling network for both surface and ground water characteristic is designed.

Parameters to be measured are in accordance with international drinking water

standards. Temperature and dissolved oxygen profiles of major surface water bodies are

established.

Meteorology

Background meteorological data from the nearest India Meteorological Department

(IMD) stations are collected for the past decade. Parameters of interest are temperature,

pressure, relative humidity wind speed and direction, atmospheric stability (inversion

data), evaporation rates, rainfall, cloud cover and solar intensity. In additional, rainfall

characteristics are identified. In some cases it may become necessary to install an on

site meteorological observatory.

Air Quali ty

A monitoring network for ambient air quality is designed. Twenty four hour sampling for

sulphur dioxide, oxides of nitrogen and suspended particulate matter is conducted at

several locations at regular intervals. Stock emissions are characterized at existing

industries.

Ecology

Terrestrial:The flora and founa (including avifauna) in the study area is characterised.

Rare and endangered species in the area, nesting, feeding and migrating patterns,

density and diversity of species is determined.


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Aquatic: The ecology of major water bodies is thoroughly investigated. The water

bodies are characterised for trophic status, chemical and thermal pollution, primary

productivity, and densities of plankton, invertebrates, fish and aquatic plants.

Noise

Sensitive areas and activities are identified. A noise monitoring survey is conducted to

characterise the noise environment of sensitive areas.

Power Plant Features

This stage involves the finalization of the conceptual design of the power plant including

the environmental protection devices, such as the flue gas cleaning, waste water

treatment facilities, etc. The emissions and effluents from the plant are then

characterised. Other factors, such as, coal handling, transmission corridors, layout of

plant, ash disposal area, housing colony, cooling systems, etc. are defined.

It is worthwhile to emphasis that the EIA document is a regulatory requirement. Any

revision of the design concepts defined may change the assessed impacts. Therefore,

all revisions in concepts need reassessment of the impacts and theoretically, have to be

approved by the DOEn.

Impact Ass essment

This is the most crucial stage and unfortunately, also the most subjective. In many of

the areas of study the impacts can not be quantified. Further, the environmental

conditions in any area are constantly changing. Therefore, the changes due to the power

plant will be in addition to the changes that would have occurred even without the power

plant. However, knowledge gained from experience and research all over the world,

coupled with theoretical and empirical models developed enable trained scientists

and engineers to assess the impacts to a fair degree of accuracy. Again, the degree

of accuracy is different for the different areas. While some models, are fairly easily

validated others such as, ecological models, take many yeas of continuous monitoring.


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Much remains to be known in the field of environmental impact assessment.

Essentially, air quality models using historical meteorological data, terrain conditions,

and emission data predict the increments of the pollutants. This, when superimposed on

the baseline air quality data give the predicted air quality n the different sectors

surrounding the plant. Similarly, water quality impacts are determined through effluent

characterisation and receiving body baseline data. With the impacts on the air and water

environments defined the consequential impacts on the terrestrial and aquatic

ecosystems are predicted. Essentially these impacts are due to the pollution generated

by the plant. Most socioeconomic impacts, however, are not related to pollution.

Different techniques are used to predict socioeconomic impacts. Wherever possible, the

impacts are quantified. Various attempts have been made to develop cost benefit

models for EIAs. To date, no consensus has been reached on the validity of these

models due to some of the difficulties expressed in section 20.

Mitigative Measu res

Mitigative measures are the steps taken to minimize the adverse impacts. Once the

adverse impacts are identified, alternative measures are evaluated and the most

appropriate ones are identified for implementation. Mitigative measures are normally

site-specific.

Monitor ing Plans

A post-commissioning environmental monitoring pan is normally included in the EIA

Selected environmental parameters are monitored at regular intervals during the life of

the plant. This monitoring serves several purposes.

Demonstrates compliance with environmental regulations and standards.

Serves as an early warning system. and

Information gained can be used to validate and refine assessment techniques.


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The monitoring plan is designed to comply with regulatory requirements and other site-

specific baseline environmental conditions.

NTPC APPROACH TOWARDS EIA/EMP

The basic methodology adopted by NTPC for conducting the EIA studies has been

explained in section 3 above. A lot more is done at NTPC to ensure the protection of

environment to the extent possible. The process towards environmental protection starts

at the site selection stage itself. The site is selected, based on the guidelines issued by

the Department of Environment. One of the very effective means of site selection is

through the use of Satellite imageries. The satellite photographs through LANDSAT are

available since 1974. The French Satellite SPOT gives a detailed account of the vegetal

cover barren and follow land, rocky exposures, crop pattern and surface water

conditions, of present and past. A detailed computer analysis gives the crop yields and

ground water conditions as well.

The baseline data collection involves a significant amount of instrumentation. The air

samples are collected through High Volume Samplers. The collected air samples gives

an idea of the ground level concentration of SPM, SOX, NOX, and CO. The water

sample collected is analysed through various instruments. The catonic composition is

determined through AAS with Carbon Rod Atomiser (CRA) and cold vapour

attachments. The anionic parameters are determined through colorometric analysis (UV-

VZ) spectrophotometer) and ion stripping electrodes. The seaiments and soils are

studied through conventional analytical techniques and XRD and XRF instrumentation.

For detailed studies Electron Scanning for Chemical Analysis (ESCA), Scanning

Electron Microscope (SEM), Transmission Electronic Microscope (TEM) etc. can also be

used.

For environmental study of the Singrauli area, NTPC deployed SODAR equipment for

upper air data. The use of sophisticated instrumentation helps in predicting the impact of

an action on the dynamic environment more precisely. When one talks of environmental

protection normally the general understanding is that air quality and water quality are

major components. One tends to forget that man is the vital component of the eco-

system, and no consideration was given till recently towards the people affected by the


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development activities. For the construction of any Super Thermal Power Plant, a large

area of land has to be acquired with the consequent displacement of a substantial

number of people. The approach of the authorities earlier was to pay cash compensation

for the land acquired. Most of the people being illiterate and ignorant had no means of

knowing how to invest this money for long term gains. Often this money was squandered

for material gains and within short time their economic condition was worse off as

compared to their original status. NTPC is making all efforts in consultation with the state

Government to evolve workable and practical rehabilitation plans for the displaced

persons. Training and other avenues of employment are created so that the displaced

persons have a regular source of income leading to socio-economic contentment

amongst the people. NTPC philosophy is that social contentment of people in the area

plays a vital role in the overall well being of the project.\

Adequate care is taken to avoid acquisition of forest land. The adverse impacts of

deforestation are evident to all of us. Where it is not possible to avoid acquisition of

forest land, compensatory afforestation schemes are formulated and implemented.

Besides, a general afforestation programme in and around the plant, township and ash

disposal areas is designed and implemented. This not only acts as protection measures

for air pollution but also contributes to the increase in the forest cover of the country. Of

late, schemes for reclamation of abandoned ash ponds through afforestation have been

developed and are being executed in all our projects. To sum up, The EIA supported by

various environment management programmes, helps in the overall protection of the

environment, and leads to an ecologically sound industrial development. This is the

approach of NTPC towards environmental protection.

CONCLUSION

The importance of overall environmental protection and the role of EIA towards

achieving this goal has been realised in our country today. The Government has enacted

various laws and acts to ensure this. A beginning has been made in the right direction,

but a lot more needs to be done.

Environmental impact information is costly, it requires scarce resources, such as, time,

money and skilled manpower. Costs are immediate and specific to the decision makers


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while benefits of impact assessment are likely to be realized only in the long run

accruing to the public. Thus, from a project proponents view, EIAs are difficult to justify.

However, the EIA process is a powerful tool in the integrated development programme

of the country and is perhaps a too important to be left on the meagre resources of

project proponents alone.

In view of the scanty experience and a definite shortage of trained professional expertise

in the country perhaps the DOEn could bring together teams of competent impact

assessment professionals in many different areas to conduct EIAs for programme and

regional planning. This would not only give direction to the national environmental

objectives but would also make individual project EIAs easier to prepare and assess and

contribute to the expansion of the available expertise.


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4.4. Air Quality MonitoringAir Quality Monitoring aand Controlnd Control

INTRODUCTION

Thermal Power generation accounts for a major percentage of total power generation in

the country. Natural gas, Oil and coal are fuels used in thermal power stations. Gas firing

results in the least pollution problems. Indian coal presents serious problem owing to

high ash content (20%-50%) and relatively more moisture. Air pollution is one of the

inevitable consequences of coal-based generation. Although efforts are being made to

develop alternate sources of energy, the relatively slower pace of development makes

coal a major source of energy in the country at present. The coal-based energy hasassumed greater significance and importance in view of the enormous coal reserves in

India and its role in the countrys plan to achieve economic self-reliance. The natural

sources are of importance in understanding the global background of air impurities and

natural mechanisms of assimilation. The biosphere is finite and the capacity to cleanse

itself although as yet imperfectly understood. Seems to be limited.

In the world today, sampling procedures for pollution measurement and instrumentation

are so oriented as to meet better accuracy, greater sensitivity to reduced pollutantconcentrations more capability for continuous measurement and increased reliability. A

number of engineering designs are formulated to control pollution through efficient

combustion, removal through sorbent: injection and fluidized-bed techniques. NTPC has

taken a lead in the country so far as environmental management is concerned and has

infrastructural facilities for impact assessment studies in detail. Attempts to anticipate

and mitigate environmental problems take root at the planning stage itself. The air

quality and control program adopted by NTPC does meet the presently laid out ambient

and emission standards of pollution control board.

The link between national economic strategy and technological development on the one

hand the emergence of new environmental thinking on the other hand is what is know

popularly known as THE ENTERPRISE CULTURE


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PRESENT SCENARIO

SOURCES OF AIR POLLUTION

The sources of air pollution in the Thermal Power Plant are mainly stack, coal handling

plant and ash disposal areas. Even though, the prime importance is presently given to

stack emission control, measures to check fugitive dust emission from the latter two

areas are progressively gaining equal importance.

The air quality monitoring and control is briefly discussed under the following heads:

Ambient air quality measurements

Ambient and Emission Standards

Prediction Methodology

Post-monitoring

Mitigatory Measures

Harmful effects of pollutions.

AMBIENT AIR QUALITY MEASUREMENTS

The primary objective of this monitoring is determine the background pollution level. The

background air quality measurements are carried out presently by the R & D

department. The monitoring sites for this purpose are governed by the accessibility,

meteorological conditions and the local surroundings (topography). Generally, the

sampling is done at 4-12 m above the ground level to avoid interferences of trees,

building etc. The three and twelve month data is included in the interim and detailed

environmental impact assessment reports respectively.

The sampling locations are jointly identified by the environmental engineering and R&D

departments in the field, based on the above criteria. The monthly measurements for

SPM, SO2 & NOx on 8 hourly average basis are carried out in the field for all locations.

The samples thus collected are analyzed in the laboratory for determining the

concentrations of SPM, SO2 and NOx.


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AMBIENT AND EMISSION STANDARDS

The Government of India in recent years has become increasingly conscious of the

environmental crisis engulfing the country while recognizing the importance of

maintaining and restoring the wholesomeness of air environment and controlling

pollution. It has enacted the Air Act, 1981 and Environment Act, 1986. The ambient

and emission standards in India for thermal power plants are presented in Tables 1&2

respectively.

PREDICTION METHODOLOGY

The knowledge on meteorological characteristics of the study area is important as the

transport and diffusion of the pollutants in the atmosphere is governed by them. The

primary meteorological factors (wind speed, wind direction and stability) are responsible

for dispersion and diffusion whereas secondary factors (temperature, relative humidity,

precipitation and pressure) have also a role in the transmission of air pollutants, though

indirectly. The background meteorological data from the nearest India Meteorological

Deptt. (IMD) station for the past 5-10 years is collected and analyzed.

The climatological charts are prepared for temperature, rainfall, relative humidity and

wind roses based on the above data. The plant characteristics pertaining to coal/gas

consumption, sulphur/nitrogen content, stack diameter, flue gas temperature and volume

flow rate are incorporated in the computer modeling for SO2/NOx predictions (Long

term). The ground level concentration (glc) of pollutants on seasonal and annual basis

for different stability classes are worked out with the help of an appropriate Gaussian

Dispersion Model. The long-term concentration values are computed at 1 km intervals in

the 16 geographical directions upto 20 kms from the plant. As the purpose is to predict

long terms concentrations emanating from the plant, a single source emission is being

considered. Worst-case consumption are incorporated for the very same purpose. The

climatological data collected from the IMD is normally assumed to be representative of

the site meteorological regime and are incorporated into the model.


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The isopleths prepared based on the computer results indicated the zone and direction

of the likely affected area around the project. The predicted concentrations are

incremental values to the existing background level. The short term concentrations,

similarly, are worked out based on an appropriate Gaussian Dispersion Model.

POST MONITORING

The monthly monitoring of ambient air quality around the operating projects is being

carried out by the Chemistry group. The measurements are carried out at selected

locations around the power project in the core area. The locations chosen for ambient

monitoring in the area of likely impact are well suited for continued monitoring.

Regular monitoring of stack emissions from the operating units is similarly being

conducted by the project. This is done by means of a stack sampler for emission levels

of particulate matter, SO2 and NOx once a month. The maintenance of ESP is given

high priority to ensure compliance with standards for particulate emission.

MITIGATORY MEASURES

Electrostatic precipitators (ESP) of high efficiency are installed to control particulate

emission from the plant. The ESP efficiency limiting emissions below 150mg/Nm3 was in

practice before the enactment of the standards. However, their efficiency is reiterated to

limit the outlet emission to 100mg/Nm3 in the project subsequently. The tall stacks

facilitate wider dispersion of the gaseous emission as there are no standards for the

same in India. In addition, the efficient boiler design helps in controlling the NOx

emissions.

The fugitive dust from coal handling area is controlled by sprinkling water. The blanket of

water maintained continuously over the ash pond area similarly checks fugitive emission.

The extensive plantation in and around the plant area and township acts as sink for

pollutants.


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HARMFUL EFFECT OF POLLUTANTS

The fugitive dust emissions from coal handling and ash disposal area are stable

pollutants that accumulate in the environment through deposition on surfaces of

materials and plants. This reduces visibility in the atmosphere and solar radiation. Their

deposition on leaf surface and accumulation in the soil medium affects vegetation. The

particulate concentration in the environment results in changes of solar radiation,

decrease in chlorophyll level and interruption in gaseous exchange. The alterations in

pH induced by the dust and other physico-chemical properties of soil disturb the plant

growth.

The studies on the effect of SO2on vegetation is of recent origin. The SO2 and NOX

concentrations in the environment cause foliar injury, micromorphological changes and

changes in growth and productivity. It is not their direct effect on entities that warrant

concern.

These are the primary input reactions of intricate series of photochemical reactions

which produce irritants and oxidants.

Dust concentration in the ambient air result in numerous health problems such as

Pneumoconiosis, nervous weakness, and bronchitis leading cancer among humans. The

gaseous emissions lead to increased mortality, impairment of mental functions, etc.

FUTURE PLAN

The rapid expansion program envisaged by NTPC will lead to the emphasis on the

multisource emissions unlike the present single source. It will, therefore, be ideal to set

up permanent meteorological and air quality stations at the projects in order to achieve a

better air quality monitoring and control for the future.

The procurement of equipment and establishment of the above stations should be the

responsibility of the project personnel. The meteorological station with the equipment

enlisted an Annexure-I will generate the data on not only primary parameters but also


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the secondary parameters which are so vital in understanding the air quality around the

projects. This would enable NTPC to maintain meteorological data of the particular

location instead of banking on the data accumulated from the nearest IMD station.

The air quality station with continuous monitoring equipment (Annexure-II) should be

located in the downwind direction based on the computer predictions. An Automatic Dust

Sampler for continuous monitoring of Suspended Particulate Matter (SPM) will be

extremely useful in the air quality station.

The Correlation Spectrophotometer is a unique all weather portable remote sensing

electrochemical device for stack monitoring. Its sensitivity to even cloudy and rainy

conditions makes it more efficient than the High Volume Sampler that is presently

employed.

There are practically, no FGD plants at power stations in India to date. However, with

rapid industrialization and the concentration of power generation activities and other

diverse industries in certain areas, these have been growing concern about SO2levels.

The space for FGD plants is being provided in the new projects. In case the continuous

motoring warrant higher concentrations than the stipulated values, FGD will have to be

provided.

In fact, very stringent NOxemission standards are under active consideration in many of

the European countries, USA and Japan. It can be seen from emission standards (Table

3) that they are much lower compared to SO2.

The injection of Ammonia into high temperature flue in the range of 850 deg.-1200oC in

oil/gas fired power plants in Japan is believed to remove 65-90% NO x. This process is

known popularly as Selective Catalytic Reduction (SCR).

Both soil and vegetation of an ecosystem remove atmospheric contaminants through a

variety of natural mechanisms. In the Extensive afforestation program proposed for

plant, township and green belt zones, a number of species with high air pollution

tolerance index are included to act as sink for pollutant absorption. Similar exercise

around the ash disposal area right from the beginning will serve to check fugitive dust


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emissions. A humble beginning on reclamation of abandoned ash ponds has already

been made at NTPC.

CONCLUSION

Pollution is not a static phenomenon but a dynamic one. There is a direct relationship

between development processes and pollution generation. Although NTPC has realized

this fact and has taken initiative in establishing an environmental group to address on

such sensitive matters, we cannot afford to be complacent. More emphasis has to be

laid on monitoring aspects through sophisticated instruments at all our projects Steps

have been taken in framing a more realistic and workable monitoring program, results

can only come out through serious implementation by the project authorities.

There is always a scope for improvement in the techniques of air pollution control and

the environmental group has a mojor role in keeping NTPC abreast of the latest

developments so that pollution due to this very important source in thermal power can be

minimized if not completely mitigated/removed.


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TABL E 1

AMBIENT AIR QUALITY STANDARDS

Area Category Concentration Microgrammes per metre cube

SPM SO2 CO NOx

A Industrial &mixed-use

500 120 5000 120

B Residential& Rural

200 80 2000 80

C Sensitive 100 30 1000 30

TABL E 2

EMISSION STANDARDS FOR THERMAL POWER PLANT (INDIA)

PARTICULATE

Boiler Size Old New (after 1979) Protected Area

Less than 200 MW 600 mg/Nm

3

350 mg/Nm

3

150 mg/Nm

3

200 MW and above 150 mg/Nm3 150 mg/Nm3

SULPHUR DIOXIDE

Boiler Size Stack Height

200 MW and more to less than 500 MW 200 metres

500 MW and More 275 metres

Less than 200 MW H=14 (Q)0.3

Q = Sulphur dioxide emission in kg/hr

H = Stack height in metres


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TABL E 3

EMISSION STANDARDS FOR TPP (COAL FIRED)

FOR DIFFERENT COUNTRIES

Country SPM SO2 NOx CO

(mg/Nm3of effluent gas)

Australia 250 - 2500 500

Denmark 150 - - -

Federal Republic ofGermany

100(Lignite coal)

2845 - 250

150(Hard coal)

Italy - 2000 - -

Japan

Urban 200 500 767 -Rural 400 2500 - -

U.K. 115 - - -

U.S.A. 45 1900 950 -

AIR QUALITY

(PRESENT SCENARIO)

ENVIRONMENTAL IMPACT ASSESSMENT

Collection of meteorological data for 5-10 years.

Field measurements of background pollution Ambient Air Quality : Monthly

measurement

Interim Report - 3 months data

Detailed - 12 months data


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AIR QUALITY

(FUTURE PLAN)

METEOROLOGICAL OBSERVATORY STATION

Equipment required for the station:

Wind Vane Aneroid Barometer

Dry & Wet Bulb Thermometer Cup Counter Anemometer

Open Pan Evapometer Rain Gauge

Sunshine Recorder

Procurement and implementation

(Responsibility Project Authorities)

AIR QUALITY STATION

To be located in the down wind direction based on computer results with the

following equipment for continuous monitoring :

Ultraviolet AnalyserElectrochemical Analyser

Pulsed Fluorescent Analyser

Chemiluminescent Analyser

Automatic Dust Sampler

Air Quality Monitoring is to be done once a week for 24 hours on 8 hourly

average basis as per CPCB regulation.

STACK MONITORING

Continuous monitoring through Barringer Correlation spectrophotomer.


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ASH DISPOSAL AREA

Afforestation with suitable species to primarily check dust emission.


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5.5. Water PollutionWater Pollution aand Controlnd Control

INTRODUCTION

The power generation industry uses large quantities of water. In India, water pollution

caused by thermal power plants is not considered to be significant and takes a second

place when compared to air pollution.

An overview of water management techniques for coal-fired power plants is presented in

this paper. Topics discussed include environmental regulations, water requirements,

wastewater generated, treatment requirements, and technologies for total reuse. As anexample, a water management plan for a typical 4x210 MW generating station is also

presented.

EFFLUENT REGULATIONS

The Central Board for the Prevention and Control of water Pollution is the agency

responsible for formulating effluent regulations for various industries. Normally, the state

pollution Control Boards adopt and enforce the effluent regulations. The states may,

however, adopt regulations that are more stringent than those recommended by the

Central Board. In May, 1986, the Central Board issued the Minimal National Standards

(MINAS)for thermal power plants in their Comprehensive Industry Document Series

(COINDS/21/86). These standards prescribe the minimum standards for wastewaters

discharged from condenser cooling, boiler blow down, cooling tower blow down and ash

ponds for thermal power plants. The relevant standards are reproduced as appendix-I. In

addition, several States have adopted the Bureau of Indian Standards Tolerance Limits

for Industrial Effluents, IS: 2490 (Part-I), 1981. The limits for industrial effluents into

inland surface waters are reproduced in Table-I, All new industries are required to obtain

a Consent Order from the concerned State Board prior to commencing operations.


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Demineral ized Water System

In todays boilers, it is critical that the feed water be of the highest quality. Concentration

of total solids in the fed water is usually less than 0.15 mg/1. In order to maintain boiler

water quality, demineralize trains are utilized for the feed water, and the condensate. A

small quantity of make-up feed water is required to compensate for boiler blow down and

other losses. In addition, demineralize water is used for initial filling and periodic

chemical cleaning of the boiler. At the reference plant, average water requirements for

the demineralizers are 160 m3/hr. which includes regeneration water requirements.

Ash Transpor t

A major water requirement at coal-fired power plant is for ash transport. Fly ash is

collected, dry, at the electrostatic precipitators. Bottom ash is collected at the bottom ash

hoppers. The ash is conveyed, hydraulically, to the ash slurry pump house and then to

the ash disposal area in slurry form. At our reference plant the average water required

for ash transport is 3200 m3/hr.

Miscel laneous

Other water requirements at a power plant are for pump bearings and sealing, air

conditioning and ventilation, coal dust suppression, service and drinking water, etc.

Normally surface water sources have varying amounts of suspended solids and are not

suitable for the above requirements without treatment. Pretreatment, in the form of

flocculation and clarification, is usually provided. Average requirements for pretreatment

water at our reference plant are 896 m3/hr., which includes the input requirement for the

demineralize water system.


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WATER MANAGEMENT TECHNIQUES

Condens er Cool ing

Power Engineers prefer to use once-through condenser cooling wherever feasible. This

is because of operational efficiency of once through cooling when compared with a

recirculating system. This, however, presents two problems. One is a regulatory one.

While condensers are normally designed for a temperature increase of between 8 and

10 C in the effluent, the MINAS regulations required that the temperature of the effluents

be no more than 5 C above the intake water temperature. Further, ISI guidelines specify

that the receiving water body temperature may not exceed 40 C. This implies that in

future condensers for once-through cooling will have to be designed for a water

temperature rise of 5 C, which in turn implies additional costs and substantial quantities

of additional water.

Normally condenser-cooling water is chlorinated to prevent biological fouling of the

condensers. It is essential to carry out optimization studies so that chlorination is carried

out at the minimum levels necessary. Chlorination should be for a few hours per day per

unit and for one unit at a time. This is to minimize the free available chlorine

concentrations in the final effluent.

Thermal Pol lut ion

The other problem with once-through cooling is thermal pollution. Large quantities of

hot water discharged into a natural water body (river, lake, or sea) affect the physical,

chemical, and biological characteristics of the receiving water bodies. Changes also

occur in metabolism, reproduction, and development rates of many organisms. These

changes result in a change in the structure of the aquatic ecosystem. Another possible

impact of the thermal discharges on the aquatic community is due to thermal shocks,

that is a rapid change in temperature caused during start-up and shut down of the

stations. Of course, for a multi-unit station this possibility is reduced.

Again, not all the changes that may occur due to thermal discharges are detrimental.

Sometimes, the heated discharges may prove to be beneficial to certain commercial


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species. It is, therefore, all the more important to be able to predict the impacts of the

heated discharges on the natural water bodies. Impact assessment studies are normally

conducted to predict the impacts.

Preliminary assessments have to be made during the site selection stage, so that sites,

where significant adverse impacts are probable, can be avoided. In some cases, many

of the adverse impacts may be mitigated by proper design. Such mitigating measures

include modifications in the design of discharge structures to enable rapid mixing and

smaller mixing zones. In extreme cases, it may become necessary to utilize cooling

towers to reduce the thermal discharges in to natural water bodies.

Cool ing Towers

Significant reductions in the withdrawal of surface waters can be achieved by the use of

a recirculating condenser cooling system. The heated water cooled in evaporative

cooling towers and recirculated. The evaporation rate is dependent on plant design and

meteorological conditions. For example, had cooling towers been used at our reference

plant, the annual average evaporation losses would be in the order of 2400 m3/hr.

The circulating cooling water chemistry has to be studied carefully to maintain the

desired water quality. Ideally, the water should neither be corrosive nor be scale-forming.

The water quality is normally maintained by blowing down a certain portion of the

circulating water. Make-up water is required to replace the water lost through

evaporation, blow down, and drift. Cooling tower drift is the water lost in the form of

droplets escaping along with the evaporative losses. However, now-a-days cooling tower

drift losses are controlled to be minimal and can be ignored for the purposes of these

calculations.

A study of the make-up water chemistry enables the selection of an optimum cycles of

concentration for cooling towers. Some treatment in the form of corrosion inhibitors or

acias may become necessary. A biocide, normally chlorine, is usually necessary to

control biological fouling. However, all efforts should be made to avoid chemical

additions and minimize chlorination.


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Drastic reductions in both make-up and blow down water quantities may be achieved by

increasing the cycles of concentration in the cooling tower. Cycles of concentration is

defined as the ratio of the concentration of total solids in the re-circulating water to the

concentration of total solids in the make-up water. Assuming a fresh water intake,

concentration factors between three and five are fairly common. A re-circulating cooling

system, as an alternative to once-through cooling for our reference plant, along with

variations in make-up and blow down quantity for different cycles of concentration is

present in Figure-II.

Blow down quality is a function of the make-up water quality and the concentration

factor. Residual chlorine concentrations should be kept at a minimum. This is

accomplished by chlorinating for short intervals and not blowing down while chlorinating.

Cooling tower blow down can be reused for ash transport.

Demineral ized Water System s

Discharges from the demineralized water system are boiler blowdown, demineralizer

regeneration wasters and periodic boiler cleaning wastes.

Boi ler Blowdown

Boiler blowdown is usually high quality water and quantities are small. The blowdown

may be alkaline and may require neutralization prior to reuse or discharge.

Demineral ization Regeneration Wastes

Demineralization regeneration wastes are usually high in dissolved and suspended

solids and show wide variations in pH. The concentrations of various parameters in the

regeneration wastes are about five to seven times the concentrations in the input water.

Sodium and sulphate or chloride ions from the regeneration chemicals are also added. A

degree of self-neutralization can be achieved by detention in holding basins.

Neutralization may be required.


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Boi ler Cleaning Wastes

Boiler and other metal cleaning wastes are generated periodically by routine

maintenance chemical cleaning operations. Frequencies may vary from twice a year to

once in five years. Total waste volume per cleaning period may be in the order of two to

three times one boiler fill or around 1000m3. These wastes are high in suspended solids,

iron and sometimes copper, and normally require sedimentation and chemical

precipitation of dissolved iron and copper. Normally, metal cleaning wastes are retained

in holding basins for treatment at low rates.

Reuse of demineralizer wastes after treatment is feasible, however, the intermittent

nature of these wastes makes reuse difficult unless space is available for storage for

long periods.

Ash Transpor t

Ash transport water normally picks up dissolved solids from ash. In addition, depending

on the design and operator of the ash pond, large quantities of suspended solids may be

present. Wide variations in pH of the ash transport water have also been observed. The

range of concentrations of the various parameters of ash transport waters, monitored by

the National Thermal Power Corporation at its operating stations is presented in Table-II.

It may be noted that the data available for Indian stations is very limited. Extensive

monitoring of ash pond discharges at different power stations in India is necessary

before an adequate database is built up and proper predictions can be made.

The normal method of ash disposal in India has been transport in slurry form of the fly

ash and bottom ash to lowlying areas, preferably barren, in the vicinity of the plant.

Natural depressions are utilized where possible otherwise dykes are built surrounding

the area. Recirculation of ash transport water is not practiced. The overflow from the ash

pond is discharged into a surface water body. More often than not, the ash ponds and

the overflow structures are poorly designed and result in substantial carry over of the

ash, thus seriously degrading the natural water bodies. The possibility of water pollution

arising out of trace elements in the ash transport water and leachates was seldom

considered.


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The disposal of ash in ponds with supernatant discharge into natural bodies can be

environmentally acceptable, provided that the supernatant meets the discharge criteria.

The pond and overflow must be properly designed such that suspended solids carry

over is minimal. The impact of the supernatant on surface water bodies must be

assessed. Further, ground water contamination from the leachates has be to studied.

Leachates may be controlled through the use of clay liners if necessary. Neutralization of

the supernatant may also be necessary. The ash pond has to be operated so as to

maintain a blanket of water over the ash of all times to prevent fugitive dust emissions.

In developed countries, most power plants utilize a pneumatic fly ash transport system

with the fly ash being disposed in landfills. This, however, requires careful management

to prevent fugitive dust. Bottom ash can also be conveyed by conveyors, yielding an

essentially dry product for disposal. Normally, a recirculating bottom ash transport

system is utilized. The water is recycled either from the ash pond or from ash dewatering

bins. Recirculating bottom ash systems usually require a small blowdown to minimize

sealing. The blowdown may be discharged after suspended solids removal and if

necessary, neutralization. Make-up water will be required to compensate for the

blowdown and other loses. A zero blowdown bottom ash sluice system can also be

designed by incorporating sidestream softening.

Thus, while it is environmentally feasible to use a once-through ash transport system,

substantial water savings can be achieved by utilizing a dry or recirculating ash transport

system. Contamination of natural water bodies is also minimized through the use of

these dry or recirculating systems.

Thus, while it is environmentally feasible to use a once-through ash transport system,

substantial waste savings can b achieved by utilizing a dry or recirculting ash transport

system. Contamination of natural water bodies is also minimized through the use of

these dry or recirculating systems.

Miscellaneous

Sanitary Wastes


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Sanitary wastes are normally treated in oxidation ponds or in small extended aeration

package plants.

Floor and A rea Drains

Miscellaneous plant drains usually contain suspended solids, oil and grease, detergents,

etc. Normally these wastes are collected and routed through oil separators and

sedimentation basins.

Rainfal l Runo ff

Rainfall runoff from coal storage and handling areas is high in suspended solids. The pH

of the runoff may vary over a wide range. Other paved areas at the plant may also

generate contaminated runoff. Oil storage and handling area runoff is likely to contain oil

and grease.

All such areas need to be identified and runoff collection systems designed. Normally, a

sedimentation basin is provided to store a one in ten year, 24 hour storm. Oil separator

must be provided for runoff contaminated with oil. Neutralization facilities may also have

to be provided.

REFERENCE STATION WATER MANGEMENT PLAN

The objective of a water management is to optimize the use of plant water resources

while satisfying environmental requirements. The water management plan must :

Be cost effective

Meet applicable regulations

Be environmentally acceptable

Maximize water reuse within the plant


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Minimize water intake and discharge

Be technically feasible

The water management plan selected for the reference station is an attempt in this

direction. The major constraint in India has been the acceptability of water management

plans by power engineers. This was primarily because of a lack of awareness of the

benefits and costs. As such water reuse within the plant is minimal. However, the plan

presented is environmentally acceptable and similar systems are, in fact, being

implemented at our power stations.

The influent sources of water are surface water and rain water. The points of discharge

are condenser cooling water, ash pond overflow, and sedimentation basin discharge.

Depending on the physical location of these discharges they may be combined. The only

recycling of water is the utilization of the condenser cooling water for ash sluicing.

The wastewater treatment facilities incorporated are as follows. The demineralization

system wastes are drained to a flow equalization and holding tank for temporary storage.

The holding tank is sized to hold the wastes generated by one complete cycle of boiler

clearing for one unit. From the holding tank the wastes are treated in a clariflocculator

where chemical precipitation of iron is achieved. Effluent from the clariflocculator is

discharged into the sedimentation basin.

Miscellaneous wastes from various plant drains etc., will be directed to the

sedimentation basin through oil separators. Plant sanitary wastes are treated in an

extended aeration package plant prior to discharge into the sedimentation basin.

Wastewater discharges from the pretreatment plant, coal handling area, and rainfall

runoff from the coal storage are will also drain to the sedimentation basin. This basin is

sized to provide 24 hours detention to the once-in-ten year storm water runoff from the

coal storage area. The discharge from the sedimentation basin will be to the surface

water body.

The final pH of the sedimentation basin effluent and the ash pond overflow can not be

predicted. It is, therefore, necessary to plan for the neutralization of these effluents.

Once the plant goes into operation, neutralization facilities can be provided, if necessary.


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WATER MANAGEMENT

Water management is an important aspect of power plant design. A water and waste

management study should be conducted during the early phases of a project. Close

cooperation with other disciplines is essential to the formulation of a sound water

management plan. The degree of water pollution control measures to be implemented

are highly site specific and overall environmental impacts must be assessed.

Ground water pollution is a special concern. Leachates from coal and ash may often

contain unacceptable concentrations of toxic substances. Potential impacts on ground

water aquifiers should be evaluated. It may be necessary to provide impervious liners,

natural or artificial, under the coal storage areas and ash disposal sites. A ground water

monitoring programme may also be desirable.

Another potential source of discharge of toxic pollutants into surface water is the ash

ponds. Fly ash contains several trace elements and depending on the water

characteristics toxic quantities may be discharged into the environment. It is almost

impossible to predict concentrations of toxic pollutants in the discharge. Therefore, these

discharges must be closely monitored. This is also true for rainfall runoff from coal

storage areas.

SUMMARY

We have discussed some concepts of water management for coal-fired power plants.

Today power plants can and are being operated without degrading water resources.

Similar advances have been made in the fields of air and land pollution control.

Substantial progress has also been made in other areas of water reuse, such as reuse

of treated municipal wastewater for cooling tower make-up and utilization of heated

discharges from power plants. It is our responsibility to continue to seek new and better

methods of cool water reuse.


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TABL E 1

TOLERANCE LIMITS FOR INDUSTRIAL EFFLUENTS INTO INLAND SURFACE

WATERS

Sl. Characteristic Tolerance limit in mg/1

No. (Except where noted)

1. Suspended solids 100

2. Dissolved solids (inorganic) 2100

3. pH value (Standard Unit) 5.5 to 9.0

4. Temperature, degree C Shall not exceed 40 in any

section of the steam with in

15 metres downstream from

the effluent outlet.

5. Oil and Grease 10

6. Total residual chlorine 1

7. Ammonical nitrogen (as N) 50

8. Total Kjeldhal nitrogen (as N) 100

9. Free ammonia (as NH3) 5

10. Biochemical oxygen, demand

(5 days at 20 C) 30

11. Chemical oxygen demand 250

12. Arsenic (as As) 0.2


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13. Mercury (as Hg) 0.01

14. Lead (as Pb) 0.1

15. Cadium (as Cd) 2

16. Hexavalent Chromium (as Cr+6) 0.1

17. Total Chromium (as Cr) 2

18. Copper (as Cu) 3

19. Zinc (as Zn) 5

20. Selenium (as Se) 0.05

21. Nickel (as Ni) 3

22. Boron (as B) 2

23. Percent sodium -

24 Residual sodium carbonate -

25. Cyanide (as CN) 0.2

26. Chloride (as Cl) 1000

27. Fluoride (as F) 2.0

28. Dissolved phosphates (as P) 5

29. Sulphate (as SO4) 1000


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9. Sodium (Na) 6.00 to 50.00

10. Arsenic (As) 0.002 to 0.05

11. Cadmium (Cd) 0.0006 to 0.01

12. Chromium (Hexavalent Cr) 0.005 to 0.05

13. Copper (Cu) 0.0005 to 0.1

14. Lead (Pb) 0.02 to 0.1

15. Manganese (Mn) 0.003 to 0.6

16. Mercury (Hg) 0.001

17. Selenium (Se) 0.005

18. Zinc (Zn) 0.01 to 0.14

19. Cyanides (CN) 0.003

20. Detergents (As MEAS) 0.6 to 0.8

21. Phenolic compounds (As Phenol) 0.001

22. Total Hardness (As CaCO3) 76 to 300

23. Total Dissolved Solids 120 to 956

24. pH (Standard Units) 7.4 to 11.5


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Appendix 1

MINIMAL NATIONAL STANDARDS

THERMAL POWER PLANT

COMPREHENSIVE INDUSTRY DOCUMENT SERIES

COINDS/21/1986

CENTRAL BOARD FOR THE PREVENTION

AND CONTROL OF WATER POLLUTION

NEW DELHI

TABLE 3.1

MINIMAL NATIONAL STANDARDS FOR CONDENSER COOLING WATERS

(Once-through cooling system)

Parameters Maximum limiting concentration

pH 6.5 8.5

Temperature Not more than 5 C higher than the

intake water temperature

Free available Chlorine 0.5 mg/1


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TABLE 3.2

MINIMAL NATIONAL STANDARDS FOR BOILER BLOWDOWNS

Parameters Maximum limiting concentration (mg/1)

Suspended solids 100.0

Oil and grease 20.0

Copper (total) 1.0

Iron (total) 1.0

MINIMAL NATIONAL STANDARDS FOR COOLING TOWER BOWDOWN

Parameters Maximum limiting concentration (mg/1)

Free available chlorine 0.5

Zinc 1.0

Chromium total 0.2

Phosphate 5.0

Other corrosion inhibiting Limit to be established on case

Materialscase by case basis


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6.6. Ash Disposal SystemAsh Disposal System

INTRODUCTION

Thermal power is still the major source of power all over the world. In India, more than

55% of power generation is from coal fired power plants. The present trend suggests

that coal will continue to be the major source of power generation in the foreseeable

future. Ash is a major byproduct of coal combustion. In India, where coal made available

for power generation is very high in ash content, the disposal of ash is beginning to be a

major issue. In addition, current ash disposal practices in India are, to say the least,

rather haphazard. This has led to severe environmental issues related to ash disposal,and guidelines for disposal site selection, and guidelines for disposal site selector, and

design of disposal facilities.

ASH CHARACTERISTICS

The products generated due to coal combustion, can be classified into three categories

(a) bottom ash, (b) fly ash, (c) gases and vapours, Bottom ash is that part of the

residue which is fused into particles, heavy enough to overcome the buoyancy of the

furnace gas stream, and is collected at the bottom of the furnace. Fly ash is the portion

which gets entrained in the gas stream, and is carried out of the boiler. The amounts of

fly ash and bottom ash generated depend upon the combustion process and coal

characteristics. About 50 to 80% of the ash produced, by weight, is fly ash. The grain

size distribution of fly ash is the most important physical characteristic, which influences

its disposal or use. More than 50% of the particles, by weight, collected through

Electrostatic Precipitators (ESP) are finer than 5 micron. A typical fly ash sample

contains 26 to 51% fine sand, 45 to 70% salt, and 1 to 20% clay.

The most interesting components of fly ash cenospheres. These are tiny particles,

ranging between 20 and 200 microns, filled with gaseous oxides of carbon and nitrogen.

The gas filled particles remain suspended for long periods, leading to environmental


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ASH EXTRACTION SYSTEMS

At thermal power plants, the bottom and fly ash extracted is normally mixed with water

and the slurry transported to the ash disposal area. This is generally known as the wet

disposal system. However, with the advancements in the field of ash disposal, the NTPC

has adopted a dry disposal system for ash at one of its upcoming plants, where it was

considered to be environmentally advantageous. A brief description of the various

systems is given below.

Bottom Handl ing System

The two most commonly employed systems for bottom ash extraction are : i) Continuous

Bottom Ash Extraction by Submerged Scrapper Conveyor, and ii) Intermittent Bottom

Ash Extraction by means of Jet Pumps. In the former bottom ash falls into a, water

quenched, dry type, refractory lined, bottom ash hopper provided below the furnace. The

hopper which has a storage capacity of 2 to 4 hours acts as a transition chute under

normal operation for transfer of spray quenched bottom ash to the water bath provided

under it. The water bath is provided with a continuously moving scrapper chain conveyor

for transferring the ash to the clinker grinder. The crushed ash from the clinker grinder

ferring the ash to the clinker grinder. The crushed ash from the clinker grinder is

conveyed to the pumping station, either through high pressure water jets, or through a

transfer sump in the boiler area. In the intermittent extraction system, the ash is collected

in a refractory lined hopper provided below the boiler furnace. The hopper has a capacity

of around 12 hours, and is provided with a number of ash slurry outlets. Each of these

outlets is provided with a hydraulically operated feed gate, as clinker grinder and a jet

pump. The slurry is conveyed to the pumping station through pipelines.

Fly Ash Handl ing System

A hydrosluicing system is adopted for fly ash transport. Ash collected in the hoppers of

the ESPs drops continuously through vertical pipes connected to the flushing apparatus,

and is continuously slurried for transport through pipes to the pumping station.


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SITE SELECTION

Since a sizable portion of land required for a power station is for ash disposal, basically

the criteria that govern the site selection for the power station are also applicable in the

case of a site for ash disposal. Once an area has been identified for a power station from

engineering and environmental considerations, the choice of an ash disposal area is

limited. Ideally, the ash disposal site should be clayey, with a low water table, and with

the minimum quantity of earthwork necessary. Of course, the selected area must neither

be forest land, nor be prime agricultural. Obviously, the chances of finding an ideal site

are rather remote. Therefore, detailed investigations must be conducted so as to enable

appropriate engineering of the disposal contamination of ground water.

SITE INVESTIGATIONS

The intent of the field and laboratory investigations is to define site conditions and to

determine the quantities and engineering properties of the various substrata at the site.

This information is used to design an effective seal for the pond, as well as stable

confining dykes. A general discussion follows.

ENGINEERING CONSIDERATIONS

Nearness to the plant to reduce capital cost.

Availability of suitable land for ash pipe corridor. As far as possible this should be in a

straight line and on level ground or gradually sloping ground.

The ideal shape of the land is circular to minimize dyke length. The land should be

regular, without any narrow projections.

The ideal site is a valley or a natural depression. This would minimize earthwork for the

ash dykes.


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The ground level of the disposal area should be lower than that of the main plant area.

This would be minimize pumping costs.

ENVIRONMENTAL CONSIDERATIONS

Geological Considerat ions

A weathered terrain is preferred over a youthful topography. The clay minerals are the

end product of weathering. The clays are low permeability materials and hence bedrock

seepage of the ash water is minimum. Fresh igneous or metamorphic terrains are to be

avoided as large-scale contamination of water regime through joints, fissures, etc. may

take place.

Hydrological Considerat ions

A thorough study of the sub surface hydrology is necessary for ash pond siting and

design to predict and mitigate ground water contamination.

General Cons ideration

The land selected should be free from agriculture and habitation as far as practicable, so

that related socio-economic problems are minimized.

MULTILAGOON CONCEPT

A relatively new concept of wet ash disposal, that is multilagoons, is now being adopted

by NTPC. Since the total land requirements for ash disposal is high, the identified area is

divided into 3 or more parts again. These parts are developed and used in a phased

manner. Thus, disturbance to the land is limited. Further, as each area is filled, it can be

reclaimed through vegetation. The multilagoon concept is especially suitable in forested

areas, where deforestation is kept at a minimum.


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MONITORING PROGRAMME

A monitoring programme should be included in the design of a wet disposal facility. The

instrumentation should monitor changes in around water elevation and quality as well as

averment of soil structures. The primary purpose of the programme is to provide early

warning to potential problems. A secondary benefit is that the information obtained can

be used in future designs.

A network of piezometers installed prior to construction can establish the baseline

ground water conditions. Additional piezometers installed near the downstream toe of

the dykes, measure the seepage through the dykes during operation. The frequency of

readings may be tapered in case a consistent trend is established Water quantity

samples may be obtained from selected piezometers to assess impacts on ground water

quality. Surface monuments may be placed at critical point along the dyke to monitor

settlement and horizontal movement. The monuments are surveyed at regular intervals.

CONCLUSION

The disposal of ash generated from thermal power stations and its utilization needs

considerable attention, especially in vie

envoiremental & pollution control

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