envoiremental & pollution control
TRANSCRIPT
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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