Impacts on water environment

Impacts on water environment

6

Although 71% of the earth’s surface is covered by water, only a tiny fraction of the water is available to us as freshwater. About 97% of the total water available on earth is found in the oceans and is too salty for drinking or irrigation. The remaining 3% is freshwater. Of this, 2.997% is locked in ice caps or glaciers. Thus, only 0.003% of the earth’s total volume of water is easily available to us as soil moisture, groundwater, water vapor and water in lakes, streams, rivers, wetlands, and estuarine regions. In short, if the world’s water supply were only 100 L, our usable supply of freshwater would be only about 0.0003 L (one-half teaspoon). This makes water a very precious resource. The future wars in our world may well be fought over water. By the middle of this century, almost twice as many people will be trying to share the same amount of freshwater the earth has today. In the future, as freshwater becomes scarcer, the access to water resources will be an important factor in determining the economic growth of several countries around the world. When the quality or composition of water changes directly or indirectly as a result of men’s activities such that it becomes unfit for any purpose, it is said to be polluted. When a source of pollution can be readily identified because it has a definite source and place where it enters the water, it is said to come from a point source, for example, municipal and industrial discharge pipes. When a source of pollution cannot be readily identified, such as agricultural runoff and acid rain, they are said to be nonpoint sources of pollution.

6.1

Point and non point source pollution

Broadly, water pollution causes due to either point source or nonpoint source or point sources are like drainpipes, ditches, and sewer outfalls, and nonpoint sources are runoff, atmosphere deposition, etc. Water pollution may be caused by biotic and abiotic contaminants. It results from either natural sources or artificial sources (i.e., human activities). The natural phenomena, for example, drought, render water levels to decline in aquifers allowing salt water to intrude; during rains, the running water gathers silt, harmful chemicals such as fertilizers and pesticides from the soil and so on. Sewage is another major cause of water pollution. Human activities, industry, agriculture, mining, deforestation, and power generation cause water pollution. Population growth and unplanned urbanization also contribute to pollution of water. Factories and mines release large quantities of toxic chemicals, organic wastes, heavy metals, heated effluents, inert wastes, and radioactive wastes causing water pollution. Toxic chemicals/wastes are not easily degradable by biological means. DDT and mercury fall under this category. The water contaminated by them is highly poisonous and, if contacted or consumed by plants or

Environmental Impact Assessment. http://dx.doi.org/10.1016/B978-0-12-811139-0.00006-2 Copyright © 2017 BSP Books Pvt Ltd. Published by Elsevier Inc. All rights reserved.

218

Environmental Impact Assessment

animals, may prove fatal. Other examples are pesticides and herbicides that wash off from the land during rainy season into the water sources. Organic wastes refer to rotting organic matter, which generate foul smell. Examples are waste from humans, tanneries, and paper and pulp industries. These wastes, when discharged into water sources, decompose using large amounts of oxygen from water, rendering it useless. The pollution level is indicated by a parameter, biochemical oxygen demand (BOD). With oxygen depletion, some types of fish perish in these water bodies. Urban sewage is another example of organic waste, generally released into rivers, lakes, or tanks in most of the developing countries. The inert wastes such as metals, oil films, and silt settle to the bottom, if not removed, and affect plant life at the bottom of the water bodies. This is not a very serious pollution problem. The radioactive wastes are generally dumped into oceans; if proper disposal techniques are not followed, these wastes create serious pollution of oceans. This aspect is discussed later. It is estimated that many countries will have freshwater shortage by 2025. Due to water pollution, two-thirds of world population may live in water-stressed conditions. Depletion in groundwater caused by water being wasted has been alarming. Dams may ensure a year-round water supply, but much water gets evaporated, and experiences loss due to seepage. In summary, industrial units, urban centers, and farming activities are the principal sources of water pollution.

6.1.1

Major water pollutants

The following are the common types of water pollutants: Disease-causing agents: Bacteria, viruses, protozoa, and parasitic worms that enter water from domestic sewage and animal wastes. In developing countries, they are the major cause of sickness and death, prematurely killing an average of 13,700 people each day. Oxygen-demanding wastes: Organic wastes, which can be decomposed by oxygenconsuming bacteria. Large populations of bacteria supported by these wastes can deplete water of dissolved oxygen gas. Without enough oxygen, fish and other oxygen-consuming forms of aquatic life die. Water-soluble inorganic chemicals: Acids, salts, and compounds of toxic metals such as lead and mercury. Such dissolved solids can make water unfit to drink, harm fish and other aquatic life, decrease crop yields, and accelerate corrosion of equipment that uses of water. Inorganic plant nutrients: Water-soluble nitrate and phosphate compounds that can cause excessive growth of algae and other aquatic plants, which then die and decay, depleting water of dissolved oxygen and killing fish. Organic chemicals: Oil, gasoline, plastics, pesticides, cleaning solvents, detergents, and many other water soluble and insoluble chemicals that threaten human health and harm fish and other aquatic life. Sediment or suspended matter: Insoluble particles of soil and other solid inorganic and organic materials that become suspended in water and that in turns of total mass are the largest source of water pollution. Suspended particulate matter clouds the water, reduces the ability of some organisms to find food, reduces photosynthesis by aquatic plants, disrupts aquatic food webs, and carries pesticides, bacteria, and other harmful substances. Bottom sediments destroys feeding and spawning grounds of fish and clogs and fills lakes, artificial reservoirs, stream channels, and harbors.

Impacts on water environment

219

Radioactive substances: Radioisotopes that are water soluble or capable of being biologically amplified to higher concentrations as they pass through food chains and webs. Ionizing radiation from such isotopes can cause birth defects, cancer, and genetic damage. Heat: Large quantity of water is heated when it is used in the cooling towers of thermal power plants. When this hot water is discharged into the nearby water bodies, it causes an increase in its temperature. This increase in water temperature lowers dissolved oxygen content and makes aquatic organisms more vulnerable to disease, parasites, and toxic chemicals.

6.1.2

Water quality for different uses

For any water body to function adequately in satisfying the desired use, it must have corresponding degree of purity. Drinking water should be of highest purity. As the magnitude of demand for water is fast approaching the available supply, the concept of management of the quality of water is becoming as important as its quantity. Each water use has specific quality need. Therefore, to set the standard for the desire quality of a water body, it is essential to identify the uses of water in that water body. In India, the Central Pollution Control Board (CPCB) has developed a concept of designated best use. According to this, out of the several uses of water of a particular body, the use that demands highest quality is termed as designated best use. Five designated best uses have been identified. This classification helps the water quality managers and planners to set water quality targets and design suitable restoration programs for various water bodies. Tables 6.1–6.5 show the water quality standards for various uses. In India, CPCB has identified water quality requirements in terms of a few chemical characteristics, known as primary water quality criteria. Further, the Bureau of Indian Standards has also recommended water quality parameters for different uses in the standard IS 2296:1992. It is estimated that every year, 1.8 million people die due to waterborne diseases. A large part of these deaths can be indirectly attributed to improper water quality. Wastewater treatment is an important initiative that has to be taken more seriously for the betterment of the society and our future. Wastewater treatment is a process wherein the contaminants are removed from wastewater and household sewage to produce waste stream or solid waste suitable for discharge or reuse. Wastewater treatment methods are categorized into three subdivisions: physical, chemical, and biological. Effluent treatment plants (ETPs) are used by leading companies in the pharmaceutical and chemical industry to purify water and remove any toxic and nontoxic materials or chemicals from it. These plants are used by all companies for environment protection. An ETP is a plant where the treatment of industrial effluents and wastewaters is done. The ETP plants are used widely in industrial sector, for example, pharmaceutical industry, to remove the effluents from the bulk drugs. During the manufacturing process of drugs, varied effluents and contaminants are produced. The effluent treatment plants are used in the removal of high amount of organics, debris, dirt, grit, pollution, toxic, nontoxic materials, polymers, etc., from drugs and other medicated stuff. The ETP plants use evaporation and drying methods and other auxiliary techniques such as centrifuging, filtration, incineration for chemical processing, and effluent treatment.

220

Table 6.1

Environmental Impact Assessment

Criteria in using of water for various purposes

Designated best use

Class

Criteria

Drinking water source without conventional treatment but after disinfection

A

1. Total coliform organism MPN/ 100 mL shall be 50 or less 2. pH between 6.5 and 8.5 3. Dissolved oxygen 6 mg/L or more 4. Biochemical oxygen demand 5 days 20°C, 2 mg/L or less

Outdoor bathing (organized)

B

1. Total coliform organism MPN/ 100 mL shall be 500 or less 2. pH between 6.5 and 8.5 3. Dissolved oxygen 5 mg/L or more 4. Biochemical oxygen demand 5 days 20°C, 3 mg/L or less

Drinking water source after conventional treatment and disinfection

C

1. Total coliform organism MPN/ 100 mL shall be 5000 or less 2. pH between 6 and 9 3. Dissolved oxygen 4 mg/L or more 4. Biochemical oxygen demand 5 days 20°C, 3 mg/L or less

Propagation of wild life and fisheries

D

1. 2. 3. 4.

Irrigation, industrial cooling, controlled waste disposal

E

1. pH between 6.0 and 8.5 2. Electric conductivity at 25°C micro mhos/cm, maximum of 2250 3. Sodium absorption ratio max. 26 4. Boron max. 2 mg/L

Below E

Not meeting any of the A, B, C, D, and E criteria

pH between 6.5 and 8.5 Dissolved oxygen 4 mg/L or more Free ammonia (as N) Biochemical oxygen demand 5 days 20°C, 2 mg/L or less

Table 6.2 A color coding frequently used to depict the quality of water on maps Blue water Green water White water Brown or gray water

This water can be directly used for drinking, industrial use, etc. Water contained in soil and plants is termed as green water Atmospheric moisture is white water Various grades of wastewater are shown by brown or gray color

Impacts on water environment

Table 6.3

221

Water quality standards in India Designated best use

Characteristics

A

B

C

D

E

Dissolved oxygen (DO) mg/L, min Biochemical oxygen demand (BOD)mg/L, max Total coliform organisms MPN/100 mL, max pH value Color, Hazen units, max Odor Taste Total dissolved solids, mg/L, max Total hardness (as CaCO3), mg/L, max Calcium hardness (as CaCO3), mg/L, max Magnesium hardness (as CaCO3), mg/L, max Copper (as Cu), mg/L, max Iron (as Fe), mg/L, max Manganese (as Mn), mg/L, max Chlorides (as Cu), mg/L, max Sulfates (as SO4), mg/L, max Nitrates (as NO3), mg/L, max Fluorides (as F), mg/L, max Phenolic compounds (as C2H5OH), mg/L, max Mercury (as Hg), mg/L, max Cadmium (as Cd), mg/L, max Selenium (as Se), mg/L, max Arsenic (as As), mg/L, max

6

5

4

4

–

2

3

3

–

–

50

500

5000

–

–

6.0–9.0 300 – 1500

6.5–8.5 – – – –

6.0–8.5 – – – 2100

Source: IS 2296:1992.

6.5–8.5 6.5–8.5 10 300 Unobjectionable Tasteless – 500 – 200

–

–

–

–

200

–

–

–

–

200

–

–

–

–

1.5 0.3 0.5

– – –

1.5 0.5 –

– – –

– – –

250

–

600

–

600

400

–

400

–

1000

20

–

50

–

–

1.5 0.002

1.5 0.005

1.5 0.005

– –

– –

0.001

–

–

–

–

0.01

–

0.01

–

–

0.01

–

0.05

–

–

0.05

0.2

0.2

222

Table 6.4

Environmental Impact Assessment

Indian standard specifications for drinking water IS 10500

S. no.

Parameter

Requirement desirable limit

1.

Color

5

2.

Turbidity

10

3.

pH

6.5–8.5

4. 5. 6.

Total hardness Calcium as Ca Magnesium as Mg Copper as Cu Iron Manganese Chlorides Sulfates Nitrates Fluoride

300 75 30

Phenols Mercury Cadmium Selenium Arsenic Cyanide Lead Zinc Anionic detergents (MBAS) Chromium as Cr+6 Poly nuclear aromatic hydrocarbons Mineral oil Residual free chlorine Pesticides Radioactive

0.001 0.001 0.01 0.01 0.05 0.05 0.1 5.0 0.2

May be relaxed up to 1.5 May be extended up to 1 May be extended up to 0.5 May be extended up to 1000 May be extended up to 400 No relaxation If the limit is below 0.6, water should be rejected; max. limit is extended to 1.5 May be relaxed up to 0.002 No relaxation No relaxation No relaxation No relaxation No relaxation No relaxation May be extended up to 10.0 May be relaxed up to 1

0.05

No relaxation

0.01 0.2

May be relaxed up to 0.03 Applicable only when water is chlorinated

7. 8. 9. 10. 11. 12. 13.

14. 15. 16. 17. 18. 19. 20. 21. 22.

23. 24.

25. 26. 27. 28.

0.05 0.3 0.1 250 150 45 0.6–1.2

Absent

Remarks May be extended up to 50 if toxic substances are suspected May be relaxed up to 25 in the absence of alternate May be relaxed up to 9.2 in the absence of alternate May be extended up to 600 May be extended up to 200 May be extended up to 100

Impacts on water environment

223

Table 6.5 Drinking water specification IS 10500, 1992 (Reaffirmed 1993) tolerance limits

S. no

Parameter

IS 10500 requirement (desirable limit)

Undesirable effect outside the desirable limit

IS 10500 permissible limit in the absence of alternate source

Essential characteristics 1.

pH

6.5–8.5

2.

Color (Hazen units), maximum Odor Taste Turbidity, NTU, max

5

3. 4. 5.

Unobjectionable Agreeable 5

Beyond this range, the water will affect the mucous membrane and/or water supply system Above 5, consumer acceptance decreases

No relaxation

Above 5, consumer acceptance decreases

10

Encrustation in water supply structure and adverse effects on domestic use Beyond this limit, taste and appearance are affected; has adverse effect on domestic uses and water supply structures and promotes iron bacteria Beyond this limit, taste, corrosion, and palatability are affected Beyond this palatability

600

Decreases and may cause gastrointestinal irritation

2000

25

Following results are expressed in mg/L 6.

Total hardness as CaCO3, max

300

7.

Iron as Fe, max

0.30

8.

Chlorides as Cl, max

250

9.

Residual, free Chlorine, min

0.20

1.0

1000

Desirable characteristics 10.

Dissolved solids, max

500

Continued

224

Table 6.5

Environmental Impact Assessment

Continued

IS 10500 requirement (desirable limit)

S. no

Parameter

11.

Calcium as Ca, max

75

12.

Magnesium as Mg, max Copper as Cu, max

30

14.

Manganese as Mn, max

0.1

15.

Sulfate as SO4, max

200

16.

Nitrates as NO3

45

17.

Fluoride, max

1.0

18.

Phenolic compounds as C6H5OH, max Mercury as Hg, max Cadmium as Cd, max Selenium as Se, max

0.001

13.

19. 20. 21.

0.05

0.001 0.01 0.01

Undesirable effect outside the desirable limit

IS 10500 permissible limit in the absence of alternate source

Encrustation in water supply structure and adverse effects on domestic use –

200

Astringent taste, discoloration and corrosion of pipes, fitting and utensils will be caused beyond this Beyond this limit, taste and appearance are affected; has adverse effect on domestic uses and water supply structures Beyond this, causes gastrointentional irritation when magnesium or sodium is present Beyond this, methemoglobinemia takes place Fluoride may be kept as low as possible. High fluoride may cause fluorosis Beyond this, it may cause objectionable taste and odor Beyond this, the water becomes toxic Beyond this, the water becomes toxic Beyond this, the water becomes toxic

1.5

100

0.3

400

100

1.5

0.002

No relaxation No relaxation No relaxation

Impacts on water environment

Table 6.5

225

Continued

IS 10500 requirement (desirable limit)

S. no

Parameter

22.

0.05

24.

Arsenic as As, max Cyanide as CN, max Lead as Pb, max

25.

Zinc as Zn, max

5

26.

Anionic detergents as MBAS, max Chromium as Cr6 +, max Polynuclear aromatic hydrocarbons as PAH, max Mineral oil, max

0.2

Pesticides, max Radioactive materials: (a) α emitters Bq/1, max, and (b) β emitters Pci/1, max Alkalinity, max

Absent –

33.

Aluminum as Al, max

0.03

34.

Boron, max

1

23.

27. 28.

29.

30. 31.

32.

0.05 0.05

0.05 –

0.01

200

Undesirable effect outside the desirable limit

IS 10500 permissible limit in the absence of alternate source

Beyond this, the water becomes toxic Beyond this, the water becomes toxic Beyond this, the water becomes toxic Beyond this limit, it can cause astringent taste and an opalescence in water Beyond this limit, it can cause a light froth in water May be carcinogenic above this limit May be carcinogenic

No relaxation

Beyond this limit, undesirable taste and odor after chlorination take place Toxic –

0.03

Beyond this limit, taste becomes unpleasant Cumulative effect is reported to cause dementia –

No relaxation No relaxation 15

1.0

No relaxation –

0.001 0.11

600

0.2

5

226

6.2

Environmental Impact Assessment

Impact concerns

Many types of projects, plans, programs, or policies have impact implications for the surface-water environment features like rivers, lakes, estuaries, and oceans. Effects can be represented by quantity and/or quality changes, and these changes can, in turn, have aquatic faunal or floral species and aquatic ecosystem implications. Examples of projects that create impact concerns for the water environment include the following: 1. Industrial plants or power plants withdrawing surface and groundwater for use as cooling water 2. Power plants discharging heated wastewater from their cooling cycles 3. Industries discharging process wastewaters from either routine operations. Also discharges wastewater as a result of accidents and spills 4. Municipal wastewater treatment plants discharging primary-, secondary-, or tertiarytreated wastewaters 5. Dredging projects in rivers, harbors, estuaries, and/or coastal areas where turbidity increased and releases of sediment contaminants may occur 6. Projects involving “fill” or creation of “fast lands” along rivers, lakes, estuaries, and coastal areas 7. Surface mining projects with resultant changes in surface-water hydrology and nonpoint pollution 8. Construction of dams for purposes of water supply, flood control, and/or hydropower production 9. River channelization projects for flow improvements 10. Deforestation and agricultural development resulting in nonpoint source pollution associated with nutrients and pesticides and irrigation projects leading to return flows laden with nutrients and pesticides 11. Commercial hazardous waste disposal sites, and/or sanitary landfills, with resultant runoff water and nonpoint source pollution 12. Tourism projects adjacent to estuaries or coastal areas, with concerns related to bacterial pollution

An additional issue of potential concern is the transboundary nature of surface-water system. For example, rivers can flow from region to region within a country or from one country to another. Impacts caused by projects in one location may be experienced in distant locations. Therefore, surface-water impact studies may need to address the implications of projects in a transboundary or transnational context. This is particularly important in that the major effects of projects are often experienced downstream.

6.3 6.3.1

Surface-water quantity and quality Surface water quantity

When considering surface-water quantity and quality, it is important to understand the processes that create bodies of surface water, namely, rivers, streams, lakes, and the like. Surface water is replenished by rainfall (or snowfall) that ends up in runoff and by groundwater that discharges into it, as shown in Fig. 6.1. Rainfall can infiltrate the subsurface, intercepted by foliage (initial abstraction), or result in runoff. It may

Impacts on water environment

227

Fig. 6.1 Hydrologic cycle.

subsequently evapotranspirate (evaporate naturally or through vegetative growth), enters the groundwater, and/or results in surface-water flow. The runoff flows downgradient usually from a higher to a lower elevation into creeks, streams, lakes and rivers, and eventually into the oceans unless it evaporates, infiltrates the subsurface, or is withdrawn along the way. The rainfall that infiltrates the subsurface and becomes groundwater may discharge into a surface water at some other locations. In this case, the surface water is referred to as a receiving stream, and the discharging groundwater is referred to as base flow. Base flow accounts for the flow in streams, rivers, and so on, between rainfall-runoff events. Once the rainfall has reached the oceans (or anytime between), evaporation can return the runoff to the atmosphere for a future rainfall event (likely at some other location), and the cycle starts over again; thus, the system is referred to as the hydrologic cycle. Fig. 6.1 demonstrates the cycle of both surfacewater and groundwater hydrology. Because of the dynamic nature of both the quantity- and quality-influencing processes, natural variations occur in the flow and quality characteristics, respectively.

6.3.2

Surface-water quality parameters

Surface water comprises rainfall, runoff, base flow, and so on. Each of these inputs to the surface-water system can contribute natural compounds of relevance to water quality. For example, rainfall in highly industrialized regions may consist of acidic precipitation that is introduced to the surface water; runoff may bring with it natural organics, sediments, and so on; and base flow may have elevated levels of hardness

228

Environmental Impact Assessment

Total solids

Dissolved solids

Suspended solids

Volatile suspended solids

Fixed suspended solids

Volatile dissolved solids

Fixed dissolved solids

Fig. 6.2 Relationships of various solid tests used for water quality characterization.

from the flow of the water through the subsurface. Human activities may increase the concentration of existing compounds in a surface water or may cause additional compounds to enter the surface water. For example, discharge of wastewater (treated or otherwise) greatly adds to the organic loading of the surface water and clearing of land (for construction, farming, etc.) that can result in increased erosion and sediment load in the surface water. Thus, it is important to recognize the natural (background) quality of surface waters and the existing impacts of human activities on this water quality. “Surface-water pollution” can be defined in a number of ways. However, most definitions address excessive concentrations of particular substances for sufficient periods of time to cause identifiable effects. “Water quality” can be defined in terms of the physical, chemical, and biological characterization of the water. Physical parameters include color, odor, temperature, solids (residues), turbidity, oil content, and grease content. Each physical parameter can be broken down into subcategories. For example, the characterization of solids can be further subdivided into suspended and dissolved solids (size and settleability) and organic (volatile) and inorganic (fixed) fractions. Fig. 6.2 depicts a hierarchy of different solid tests. Chemical parameters associated with the organic content of water include biochemical oxygen demand (BOD), chemical oxygen demand (COD), total organic carbon (TOC), and total oxygen demand (TOD). It should be noted that BOD is a measure of the organics present in the water; it is determined by measuring the oxygen necessary to biostabilize the organics (oxygen equivalent of the biodegradable organics present). A BOD response curve is shown in Fig. 6.3. Inorganic chemical parameters include salinity, hardness, pH, acidity, alkalinity, and the presence of substances including iron, manganese, chlorides, sulfates, sulfides, heavy metals (mercury, lead, chromium, copper, and zinc), nitrogen (organic, ammonia, nitrite, and nitrate), and phosphorus. Biological properties include bacteriologic parameters such as coliforms, fecal coliforms, specific pathogens, and viruses. Table 6.6 provides an overview of various types and sources of water quality characteristics.

Impacts on water environment

229

300

First stage BOD = 175 ppm 150

Ult. carbonaceous demand

BOD, mg/L

200

250 − 175

250

NOD = 75 ppm

Second stage BOD = 250 ppm

100

50

0

2

4

6

8

10

12 14 16 Time, days NOD = nitrogenous oxygen demand

18

20

22

24

Fig. 6.3 BOD response curve.

In evaluating surface-water pollution impacts associated with the construction and operation of a potential project, two main sources of water pollutants should be considered: nonpoint and point. Nonpoint sources are also referred to as “area” or “diffuse” sources. “Nonpoint pollutants” refer to those substances that can be introduced into receiving waters as a result of urban area, industrial area, or rural runoff, for example, sediment, pesticides, or nitrates entering a surface water because of runoff from agricultural farms. Point sources are related to specific discharges from municipalities or industrial complexes, for example, organics or metals entering a surface water as a result of wastewater discharge from a manufacturing plant. In a given body of surface water, nonpoint source pollution can be a significant contributor to the total pollutant loading, particularly with regard to nutrients and pesticides. Fig. 6.4 illustrates the relationship between land usage and these pollution sources relative to the resulting quality of receiving waters.

6.3.3

Surface water contaminant and their impacts

Some general characteristics of nonpoint source pollution are as follows (Novotny and Chesters, 1981): 1. Nonpoint source discharges enter surface waters in a diffuse manner and at intermittent intervals that are related mostly to the occurrence of meteorological events. 2. Pollution arises over an extensive area of land and is in transit overland before it reaches surface waters.

Table 6.6 Physical, chemical, and biological water quality characteristics and their sources Characteristics

Sources

Physical properties Color Odor Solids Temperature

Domestic and industrial wastes, natural decay of organic materials Decomposing wastewater, industrial wastes Domestic water supply, domestic and industrial wastes, soil erosion, inflow/infiltration Domestic and industrial wastes

Chemical constituents Organic Carbohydrates Fats, oils, and grease Pesticides Phenols Proteins Priority pollutants Surfactants Volatile organic compounds Others Inorganic Alkalinity Chlorides Heavy metals Nitrogen pH Phosphorus Priority pollutants Sulfur

Domestic, commercial, Domestic, commercial, Agricultural wastes Industrial wastes Domestic, commercial, Domestic, commercial, Domestic, commercial, Domestic, commercial,

and industrial wastes and industrial wastes

and industrial and industrial and industrial and industrial

wastes wastes wastes wastes

Natural decay of organic materials Domestic wastes, domestic water supply, groundwater infiltration Domestic wastes, domestic water supply, groundwater infiltration Industrial wastes Domestic, commercial, and industrial wastes Domestic, commercial, and industrial wastes Domestic, commercial, and industrial wastes; natural runoff Domestic, commercial, and industrial wastes Domestic water supply, domestic, commercial, and industrial wastes

Gases Hydrogen sulfide Methane Oxygen

Decomposition of domestic wastes Decomposition of domestic wastes Domestic water supply, surface-water infiltration

Biological constituents Animals Plants

Decomposition of domestic wastes Decomposition of domestic wastes

Protists Eubacteria Archaebacteria Viruses

Domestic wastes, surface-water infiltration, treatment plants Domestic wastes, surface-water infiltration, treatment plants Domestic wastes

Source: Metcalf and Eddy, 1991. Wastewater Engineering-Treatment, Disposal and Reuse, third ed. McGraw-Hill Book Company, New York.

Impacts on water environment

231 Land use determinants

Population and economic growth

Private market forces

Public services and facilities

Land use regulation

Natural features and constraints

Land use pattern

• Form • Density • Use mix • Open space • Land conversion rate Water quality impacts of land use

Loss of natural ground cover and disturbance of environmentally sensitive areas

Withdrawal of surface and groundwater

Net change of stream flow

Domestic waste loads

Constructionrelated sediment loads

Urban runoff loads

Industrial waste loads

Stream enlargement and erosion

Total nonpoint load

Water quality standards and effluent limitations

Quantity and quality of discharge

Water quality management practices

Quantity and quality of receiving water prior to discharge

Resulting quality of receiving waters

Silvaculture mining and agriculture runoff loads

Total point load

Land disposal wastewater reuse

Fig. 6.4 Schematic diagram of the land use/water quality relationship (Shubinski and Tierney, 1973). 3. Nonpoint source discharges generally cannot be monitored at the point of origin, and the exact source is difficult or impossible to trace. 4. Elimination or control of these pollutants must be directed at specific sites. 5. In general, the most effective and economical controls are land management techniques that are conservation practices in rural zones and architectural or hydrologic control in urban zones.

The effects of pollution sources on receiving water quality are manifold and dependent upon the type and concentration of pollutants (Nemerow and Dasgupta, 1991). Soluble organics, as represented by high BOD wastes, cause depletion of oxygen in the surface water. This can result in fish kills, undesirable aquatic life, and undesirable odors. Even trace quantities of certain organics may cause undesirable taste and odors, and certain organics may be biomagnified in the aquatic food chain.

232

Environmental Impact Assessment

Suspended solids decrease water clarity and hinder photosynthetic processes; if solids settle and form sludge deposits, changes in benthic ecosystems result. Color, turbidity, oils, and floating materials are of concern because of their aesthetic undesirability and possible influence on water clarity and photosynthetic processes. Excessive nitrogen and phosphorus can lead to algal overgrowth, with concomitant water treatment problems resulting from algae decay and interferences with treatment processes. Chlorides cause a salty taste to be imparted to water, and, in sufficient concentration, limitations on water usage can occur. Acids, alkalis, and toxic substances have the potential for causing fish kills and creating other imbalances in stream ecosystems. Thermal discharges can also cause imbalances and reductions in stream waste assimilative capacity. Stratified flows from thermal discharges minimize normal mixing patterns in receiving streams and reservoirs. Table 6.7 provides an overview of important surface-water contaminants and their impacts. Table 6.7

Important surface-water contaminants and their impacts

Contaminants

Reason for importance

Suspended solids

Suspended solids can lead to the development of sludge deposits and anaerobic conditions when untreated wastewater is discharged in the aquatic environment Composed principally of proteins, carbohydrates, and fats: biodegradable organics are measured most commonly in terms of biochemical oxygen demand (BOD) and chemical oxygen demand (COD). If discharged untreated to the environment, their biological stabilization can lead to the depletion of natural oxygen resources and to the development of septic conditions Communicable diseases can be transmitted by the pathogenic organisms in wastewater Both nitrogen and phosphorus, along with carbon, are essential nutrients for growth. When discharged to the aquatic environment, these nutrients can lead to the growth of undesirable aquatic life. When discharged in excessive amounts on land, they can also lead to the pollution of groundwater Organic and inorganic compounds selected on the basis of their known or suspected carcinogenicity, mutagenicity, teratogenicity, or high acute toxicity. Many of these compounds are found in wastewater These organics tend to resist conventional methods of wastewater treatment. Typical examples include surfactants, phenols, and agricultural pesticides Heavy metals are usually added to wastewater from commercial and industrial activities and may have to be removed if the wastewater is to be reused Inorganic constituents such as calcium, sodium, and sulfate are added to the original domestic water supply as a result of water use and may have to be removed if the wastewater is to be reused

Biodegradable organics

Pathogens Nutrients

Priority pollutants Refractory organics Heavy metals

Dissolved inorganics

Source: Metcalf and Eddy, 1991. Wastewater Engineering-Treatment, Disposal and Reuse, third ed. McGraw-Hill Book Company, New York, p. 58.

Impacts on water environment

6.4

233

Groundwater quantity and quality

Groundwater quantity concerns are typically related to groundwater in connection with its availability. The study of developable groundwater resources in relation to water supply needs involves the consideration of hydrogeologic factors and quality characteristics. If groundwater is withdrawn at a rate greater than its natural replenishment rate, then the depth to groundwater increases, and the resource is “mined.” In addition, excessive usage of groundwater in coastal areas can cause saltwater intrusion (this problem can also occur in inland states where freshwater-bearing zones are underlain by saline aquifers). Finally, because of the hydraulic influences, the relationship between shallow, alluvial aquifers and the flow of surface streams and rivers may need to be explored. Groundwater quality concerns other than inorganic quality issues, primarily focused on chlorides, have been increasing within the last decade. This increased attention is a result of greater emphasis upon hazardous waste sites across the globe and the realization that many global environmental problems may also have implications for groundwater resources, including the potential influence of acid. Table 6.8 shows the possible sources of groundwater contamination. Some of the important issues to be considered in understanding the identification, prediction, and assessment of impacts on water environment, more specifically, groundwater regime, are listed below (Canter, 1986): 1. Descriptions should be assembled on groundwater systems in the study area, indicating whether they are confined or unconfined, with the obvious pollution relevance being that unconfined groundwater systems tend to be more susceptible to groundwater contamination. Of particular importance would be the description of karst aquifer systems, since these areas can exhibit unique and rapid groundwater flow patterns. 2. Many areas are characterized by the presence of multiple groundwater systems; accordingly, it would be appropriate to describe those geographic areas characterized by multiple aquifer systems. 3. If information exists on the quantitative aspects of the groundwater resource in terms of potentially useable supplies, which could be extracted, it should be summarized. 4. Information should be summarized on the uses of groundwater within the study area, with a more detailed study of this subject to be conducted later. 5. A description of the relationships between local groundwater systems and surface streams, lakes, estuaries, or coastal areas may be important, since mutual quantitative or qualitative influences can occur. 6. Groundwater pollution vulnerability is associated with whether or not the project area is in a recharge zone for a given groundwater systems; thus, this should be determined because there is greater pollution potential if in recharge zone. (It should be noted that for confined aquifer systems, the recharge area may be located distances away from the actual segment of the groundwater system being used for the purpose of water supply.) 7. Depth to groundwater is a fundamental parameter that could be identified, with the pertinent issue being that the greater the depth of groundwater, the greater the degree of natural protection. 8. Unsaturated zone permeability should be described. Here, the “unsaturated zone” refers to that segment of the subsurface environment between the land surface and the water table of an unconfined aquifer system. The unsaturated zone permeability can influence the

234

Table 6.8

Environmental Impact Assessment

Possible sources of groundwater contamination

Category I—Sources designed to discharge substance Subsurface percolation (e.g., septic tanks and cesspools) Injection wells Hazardous waste Nonhazardous waste (e.g., brine disposal and drainage) Nonwaste (e.g., enhanced recovery, artificial recharge, solution mining, and in situ mining) Land application Wastewater (e.g., spray irrigation) Wastewater by-products (e.g., sludge) Hazardous waste Nonhazardous waste Category II—Source designed to store, treat, and/or dispose of substances, discharge through unplanned release Landfills Industrial hazardous waste Industrial nonhazardous waste Municipal sanitary Open dumps, including illegal dumping (waste) Residential (for local) disposal (waste) Surface impoundments Hazardous waste Nonhazardous waste Waste tailings Waste piles Hazardous waste Nonhazardous waste Materials stockpiles (nonwaste) Graveyards Animal burial Above-ground storage tanks Hazardous waste Nonhazardous waste Nonwaste Underground storage links Containers Hazardous waste Nonhazardous waste Nonwaste Open burning and detonation sites Radioactive disposal sites Category III—Sources designed to retain substances during transport or transmission Pipelines Hazardous waste Nonhazardous waste Nonwaste

Impacts on water environment

Table 6.8

235

Continued

Material transport and transfer operations Hazardous waste Nonhazardous waste Nonwaste Category IV—Sources discharging substances as a consequence of other planned activities Irrigation practices (e.g., return flow) Pesticide applications Fertilizer applications Animal feeding operations Deicing salt applications Urban runoff Percolation of atmospheric pollutants Mining and mine drainage Surface mine-related Underground mine-related Category V—Source providing conduit or inducing through altered flow patterns Production wells Oil (and gas) wells Geothermal and heat recovery wells Water supply wells Other wells (nonwaste) Monitoring wells Exploration wells Construction excavation Category VI—Naturally occurring sources whose discharge is created and/or exacerbated by human activity Groundwater-surface-water interactions Natural leaching Saltwater intrusion/brackish water upcoming (or intrusion of other poor-quality natural water) Source: Canter (1986).

attenuation of contaminants as they move away from a source of pollution and toward the groundwater system. 9. Aquifer transmissivity should be described. This parameter represents information on the water-carrying capacity of the groundwater system. 10. Any existing data on groundwater quality should be summarized. If no such data exist, it may be necessary to appropriately plan and conduct a groundwater monitoring program. In some unique cases, the quality data may need to be described in terms of aquatic ecosystems.

Describing groundwater quality may be difficult because most historical data on groundwater quality have tend to focus on inorganic constituents such as chlorides,

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while essentially minimal information is available on bacteriologic or organic quality of groundwater systems. Furthermore, because of the slow rate of movement of most groundwater systems and the possibility of incomplete mixing, there can be considerably incomplete mixing, and there can be considerable variations in groundwater quality, both spatially and vertically, in a given study area.

6.5

Impacts study approach

Water environment comprises of all surface-water bodies like rivers, lakes, estuaries, ponds, coastal, zones, and ocean. Groundwater regimes also are taken under water environment. The approach is mainly based on the 10-step model (Chapter 3) and is flexible that can be adapted to various project types by modification. The steps involved in the approach are as follows: 1. 2. 3. 4. 5. 6.

Identification of water quantity/quality impacts of proposed project Preparation of description of existing water environment Procurement of relevant water quantity/quality standards Impact prediction Assessment of impact significance Identification and incorporation of mitigation measures

6.5.1

Identification of water quantity/quality impacts

The first step is to determine the features of the proposed project, the need for the project, and the potential alternatives that either have been or could be considered. Key information relative to the proposed project includes (1) the type of project and how it functions or operates in a technical context, particularly with regard to water usage and wastewater generation, or to the creation of changes in water quantity or quality; (2) the proposed location of the project; (3) the time period required for project construction; (4) the potential environmental outputs from the project during its operations phase, including information relative to water usage and water pollutant emissions and waste generation and disposal needs; (5) the identified need for the proposed project, in particular, location; and (6) any alternatives that have been considered, with generic alternatives for factors including site location, project size, project design features and pollution control measures, and project timing relative to construction and operational phases. The focus of this step is on identifying potential impacts of the subject project. This early qualitative identification of anticipated impact can help in refining subsequent steps; for example, it can aid in describing the affected environment and in calculating potential impact. Several methods have been developed as aids for identifying generic impacts related to the project type being analyzed; one approach makes use of simple interaction matrices by preparing an impact matrix that depicts various land-use changes and their consequences on selected hydrologic parameters. This matrix indicated that both positive and negative effects might occur either at the site of the land-use change

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237

(development) or downstream of the development. Additional methods for impact identification, such as networks and simple and descriptive checklists, are also useful for identification of impacts. Identifying potential impacts may require the delineation of the quantities of water usage, the types and quantities of potential water pollutants to be utilized or generated during the project, and/or the activities that will alter the amount and quality of runoff. The materials utilized during the project may contaminate surface water during storage as the result of precipitation-runoff events. Materials that are disposed off during the project may contaminate surface water if not properly managed. Materials that may result in surface-water contamination include fuels and oils, preservatives, bituminous products, insecticides, fertilizers, various other chemicals, and solid and liquid wastes. Quality characteristics of industrial wastes vary considerably depending upon the types of industry. A useful parameter in describing industrial wastes is population equivalent: PE ¼

ðAÞðBÞð8:34Þ 0:17

where PE ¼ population equivalent based on organic constituents in industrial waste; A ¼ industrial waste flow, mgd; B ¼ industrial waste BOD, mg/L; 0.17—lb BOD per person/day. A similar type of population equivalent calculation could be made for suspended solids, nutrients, and other pertinent constituents. To express all waste loadings on a similar basis, population equivalent calculations can be made for various pollutants from both point and nonpoint sources (MoEF) 2010.

6.5.2

Description of existing water environment

The second step is mainly focused on describing existing environment—a condition of water environment. Pertinent data include water quantity and quality identifying unique pollution problems, highlighting key climatological information, conducting baseline monitoring, and summarizing information on point and nonpoint pollution sources and on water users and uses. Broadly, water environment would be described in terms of raw water availability, water quality, surface-water bodies around the project site, and groundwater status like water table, local aquifer storage capacity, specific yield, specific retention, water-level depth and fluctuations, coastal aquifers, and wastewater discharges.

Water quantity-quality Information should be assembled on both the quantity (flow variations) and quality of the surface water in the river reach of concern, and potentially, in relevant downstream reaches. The quality emphasis should be on those water pollutants expected to be emitted during the construction and operational phases of the project. If possible, consideration should be given to historical trends in surface-water quantity and quality

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characteristics in the study area. Information for a given geographic area may already have been collected and may be available in one or more computerized databases. A summary of existing information on quantity and quality for the pertinent surface water and groundwater should be developed. When data are incomplete or not normally distributed, nonparametric testing of water quality time-series data has been suggested as a means of identifying and analyzing trends (Hipel, 1988). One approach for summarizing baseline quality-quantity information is through the use of environmental indices like water quality index (WQI) (Anji Reddy, 2009) and its development (Ott, 1978). Multivariate statistical techniques have been used to aggregate water quality parameters into an index that permits examination of the effects and impacts. Water quality standards can be used to interpret assembled data. Since water quality standards vary according to the specific beneficial uses assigned for particular streams or stream segments, it is necessary to evaluate existing water quality relative to various standards. The identification of any unique pollution problems that have occurred in the project study area is a prerequisite if one is to adequately describe the environmental setting, to indicate a familiarity with the area and establish credibility, and to focus on environmentally sensitive parameters for “fatal flaws.” Examples of unique pollution problems that should be identified include fish kills, excessive algal growth, and thermal discharges causing stratified flow. Many sources can be used to obtain information on unique pollution problems. Local and state water resource agencies constitute one source, conservation groups, and others. Local newspapers can also provide historical documentation of pollution concerns. Certain climatological factors—such as precipitations, evaporation, and air temperature—are important for predicting and assessing water quality impacts. The primary sources of information include local and state water resources departments. Precipitation information will be useful for addressing hydraulic balances (flows), delineating acid rainfall, evaluating nonpoint sources of pollution, and scheduling construction. Evaporation information, including the loss of water from impoundments, is also relevant to hydraulic balances. Air temperature can be related to water temperature and thus, in turn, to water quality modeling; in addition, this information may be necessary for construction scheduling. It may be necessary to plan and conduct specific baseline flow and quality studies to collect original background data. Such data can be used to detect impacts caused by the following: (1) pollutants that are difficult to identify chemically or characterize toxicologically, (2) complex or unanticipated exposures from spills, and (3) habitat degradation due to channelization, sedimentation, or historical contamination.

6.5.3

Water quantity-quality standards

To determine the severity of the impacts that may result from a project, it is necessary to make use of institutional measures for determining impact significance; water quantity and quality standards of India are examples of these measures. Thus, determination of the specific requirements for a given water will require contacting concerned government departments in one or several regions, states, and/or countries with

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jurisdiction for that surface water. The intended use of the surface water will also affect the standards to be applied for that surface water, with use as a drinking water supply typically resulting in the most stringent standards. Effluent limitations regulating the permissible quality of discharged wastewater from domestic and industrial sources may also be pertinent, along with regulations concerning nonpoint discharges from industrial areas. In some cases, there may be limitations on the amount and timing of water usage from a given body of water. Water quality management policies may also be pertinent. These conditions need to be considered in interpreting existing quality-quantity and in impact calculations and their resultant interpretation. In addition, it may be necessary to consider low-flow requirements for the maintenance of the aquatic ecosystem. One of the approaches that can be used for identifying and procuring institutional information is scoping. Contacts with regulatory agencies and other interested publics can aid in the identification of pertinent institutional information. This information can primarily serve two functions: (1) as an aid in the interpretation of existing quality and/or quantity conditions relative to the environment and (2) as a basis for interpreting the anticipated quality and/or quantity impacts of the resultant project. In the complete absence of water quantity-quantity and aquatic ecosystem standards, it might be appropriate to utilize generic criteria or standards developed for nearby geographic areas.

6.5.4

Impact prediction

“Impact prediction” basically refers to the quantification (or, at least, the qualitative description), where possible, of the anticipated impacts of the proposed project on various water environment factors. Depending upon the particular impact, technically demanding mathematical models might be required for prediction. Other approaches include the conduction of laboratory testing, such as leachate testing for dredged material and for solid or hazardous waste materials or sludges (Deeley and Canter, 1986). Still, other laboratory studies might be appropriate (Canter et al., 1990). Other techniques include the use of look-alike or analogous information on actual impacts from similar types of projects in other similar geographic locations. Finally, environmental indexing methods such as the WQI or other types of systematic techniques for relatively addressing anticipated impacts can also be considered. It is desirable to quantify as many impacts as possible, because, in doing so, it has been frequently determined that the concerns related to anticipated changes are not as great as they would appear to be in the event of nonquantification. Also, if anticipated impacts are quantified, it would be appropriate to use specific numerical standards as the basis for interpretation (assessment) of the anticipated changes existing habitat conditions by assigning values is easier than determining the actual fish population. It is also easier to predict the changes in habitat conditions that will be produced by a proposed water-extraction project (Brookes, 1988). Numerous aquatic productivity models are available for use in impact studies. Several other methods may be relevant to the prediction of water quantity-quality impacts. Examples include (1) frequency distribution of decreased quality and

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Environmental Impact Assessment

quantity; (2) effects of sedimentation on the stream-bottom ecosystem; (3) fate of nutrients by incorporation into biomass; (4) reconcentration of metals, pesticides, or radionuclides into the food web; (5) chemical precipitation or oxidation-reduction of inorganic chemicals; and (6) anticipated distance downstream of decreased water quality and the implications for water users and related raw water quality requirements. Table 5.7 shows the impact prediction tools for water impacts due to any type of project.

6.5.5

Assessment of impacts

The next activity is impact assessment. The terminology used here in “assessment” refers to the interpretation of the significance of anticipated changes related to the proposed project. Impact interpretation can be based upon the systematic application of a definition of “significance.” For some types of anticipated impacts, there are specific numerical standards or criteria that can be used as a basis for impact interpretation. Examples include the application of water quality standards and wastewater discharge standards (effluent limitations) from particular facilities. Professional judgment can also be used in evaluating the percentage changes from baseline conditions in terms of pollutant loading and selected parameters or water quality index; such changes could be anticipated during both the construction and operational phases of a project. Another example is the application of professional judgment in the context of assessing impacts related to the biological environment; for example, the biological scientist in the study team would render judgments as to the applicability of various laws and the potential significance of the loss of particular habitats, including wetland areas.

6.5.6

Impacts mitigation measures

The next activity is that of identifying and evaluating potential impact mitigation measures. Mitigation measures may need to be added to the project proposal to make it acceptable. These mitigation measures might consist of decreasing the magnitude of the surface-water impacts or including features that will compensate for the surface-water impacts. The specific mitigation measures will be dependent upon the particular project type and location; however, examples of some things that could be considered as mitigation or control measures, depending on the type of project, are listed below: 1. Decrease surface-water usage and wastewater generation through the promotion of water conservation and wastewater treatment and reuse. Pretreat wastewaters prior to discharging into receptor. 2. Minimize erosion during the construction and operational phases of the project; this could be facilitated by the use of on-site sediment retention basins and by planting rapidly growing vegetation. 3. In projects involving the use of agricultural chemicals, consider measures that could be used to better plan the timing of chemical applications, the rate of application, and the extent of

Impacts on water environment

4. 5.

6. 7. 8.

241

such applications in an effort to minimize erosion and chemical transport to surface-water systems. Manage nonpoint source pollution through the application of best management practices (BMPs). Consider alternative wastewater treatment schemes to achieve treatment goals in a costeffective manner. For point sources, the treatment schemes could include primary, secondary, and/or tertiary processes involving physical, biological, and/or chemical principles of pollutant removal. For thermal effluents, the use of cooling ponds or towers might be appropriate. Use discharge credit trading within watersheds to enable the trading off permitted pollution credits between parties responsible for both point and nonpoint source discharges. Consider project operational modes that would minimize detrimental impacts. Use techniques such as sediment removal and macrophyte (weed) harvesting for restoring lakes and reservoirs from water quality deterioration and eutrophication.

6.6

Wastewater management

In an industrial estate (IE), wastewater will be generated from various industries. The main advantage of industries to be located within the IE is the common treatment facility. The wastewater generated from various industries is managed by a common effluent treatment plant (CETP) within the IE. The common effluent treatment plant becomes one of the basic amenities that is offered to the industries by an IE. The feasible approaches in the wastewater management through a CETP are listed below. A classical example of CETP is also presented in this section of the chapter. The feasible approach in establishing such common facilities is described as preliminary treatment at individual level to meet influent limits of a common treatment facility, common/combined treatment facility for further treatment, and recycling of treated waters for beneficial uses or disposal through marine outfall.

6.6.1 l

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Advantages of CETP

Homogenization of wastewater. Relatively better hydraulic stability. Advantage through scale of operation. Professional control over treatment can be affordable. Offers great relief to small units, which are of main concern in terms of treatment. Eliminates multiple discharges in the area and provides opportunity for better management of wastewater, i.e., proper treatment and disposal. Inventorization of industries and pollution loads (hydraulic loading, organic loading, inorganic loading, toxicity factor, heavy metal, etc.). Characterization of effluents (predominantly organic, predominantly inorganic mixed, etc.). Choice of technologies (treatability, cost-effective operation and maintenance, mode of disposal, resilience to absorb shock loads, recovery, renovation, and recycling options). Mode of transport to carry effluent from industry to CETP (open channels, pipes, tankers, and a combination of these). Norms for effective functioning of CETPs.

242 l

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Environmental Impact Assessment

Major industries to lead the cooperatives. Norms for influent quality. CETP shall have the power to reject the effluent that does not meet the influent quality. Manifestation systems. Guidelines for individual industries to pretreat effluent so as to meet the norms for discharge in to CETP. Issuing consent to CETP based on its disposal specificity. Issuing consent to individual industries as per acceptable inlet concentration of CETP.

6.6.2

Liquid effluents

The maximum effluent levels presented in Table 6.9 should be achieved by discharges from common effluent treatment units. Common effluent treatment units should be designed to handle the characteristics and loading of wastewaters generated from the IE. In some cases, different types of treatment units will be needed to handle different types of wastewaters. For example, chemical precipitation units may be required to handle toxic metallic wastewaters and biological treatment units for handling organic wastewaters.

Table 6.9

Effluents from IEs

Parameters

Maximum value units

pH BOD COD TSS

6–9 50 250 50 (20 if toxic metals are present at significant metals) 10 0.1

Oil and grease Cadmium Chromium Hexavalent Copper Lead Nickel Zinc Phenol AOX Benzene Benzo(a)pyrene Sulfide Temperature increase

0.1 0.5 0.1 0.5 2 0.5 1 0.05 0.05 1 3°C

Source: Pollution Prevention and Abatement Handbook 1998: Toward Cleaner Production, The World Bank Group Washington, D.C. 1999. http://documents.worldbank.org/.

Impacts on water environment

6.6.3

243

Wastewater collection

Many different industries generate wastewater streams that contain organic compounds. Nearly all of these streams undergo collection, contaminant treatment, and/or storage operations before they are finally discharged into either a receiving body of water or a municipal treatment plant for further treatment. There are many types of wastewater collection systems. In general, a collection system is located at or near the point of wastewater generation and is designed to receive one or more wastewater streams and then to direct these streams to treat and/or storage systems. A typical industrial waste water collection system may include drains, manholes, trenches, junction boxes, sumps, lift stations, tankers, and/or weirs. Wastewater streams from different points throughout the industrial facility normally enter the collection system through individual drains or trenches connected to a main sewer line. The drains and trenches are usually open to the atmosphere. Junction boxes, sumps, trenches, lift stations, and weirs will be located at points requiring wastewater transport from one area or treatment process to another. As the arrangement of collection system components is facility-specific, the order in which the collection system descriptions are presented is somewhat arbitrary. Wastewater streams normally are introduced into the collection system through individual or area drains, which can be open to the atmosphere or sealed to prevent wastewater contact with the atmosphere. In industry, individual drains may be dedicated to a single source or piece of equipment. Area drains will serve several sources and are located centrally among the sources or pieces of equipment that they serve. Manholes into sewer lines permit service, inspection, and cleaning of a line. They may be located where sewer lines intersect or where there is a significant change in direction, grade, or sewer line diameter. Trenches can be used to transport industrial wastewater from point of generation to collection units such as junction boxes and lift station, from one process area of an industrial facility to another or from one treatment unit to another. Trenches are likely to be either open or covered with a safety grating. Junction boxes typically serve several process sewer lines, which meet at the junction box to combine multiple wastewater streams into one. Junction boxes normally are sized to suit the total flow rate of the entering streams. Sumps are used typically for collection and equalization of wastewater flow from trenches or sewer lines before treatment or storage. They are usually quiescent and open to the atmosphere. Lift stations are usually the last collection unit before the treatment system, accepting wastewater from one or several sewer lines. Their main function is to lift the collected wastewater to a treatment and/or storage system, usually by pumping or by the use of a hydraulic lift, such as a screw. Weirs can act as open channel dams, or they can be used to discharge cleaner effluent from a settling basin, such as a clarifier. When used as a dam, the weir’s face is normally aligned perpendicular to the bed and walls of the channel. Water from the channel usually flows over the weir and falls to the receiving body of water. In some cases, the water may pass through a notch or opening in the weir face. Weir height, generally the distance of the waterfalls, is usually no more than 2 m (6 ft). A typical clarifier weir is designed to allow settled

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Environmental Impact Assessment

wastewater to overflow to the next treatment process. The weir is generally placed around the perimeter of the settling basin, but it can also be toward the middle. Clarifier weir height is usually only about 0.1 m (4 in.).

6.6.4

Wastewater treatment

Industrial wastewater operations can range from pretreatment to full-scale treatment processes. In a typical pretreatment facility, process and/or sanitary wastewater or stormwater runoff is collected, equalized, neutralized, and then discharged to a municipal wastewater plant, also known as a publicly owned treatment works (POTWs), where it is then typically treated further by biodegradation. Wastewater treatment can be divided into four major categories or steps based on design, operation, and application. l

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Preliminary treatment: It involves a number of unit processes to eliminate undesirable characteristics of wastewater. Processes include the use of screen sand grates for removal of large particles and communitors for grinding of coarse solids and preaeration for odor control and some removal of grease. Primary treatment: It involves removal of readily settable solids prior to biological treatment. Sedimentation chambers are the main units involved, but various auxiliary processes such as floatation, flocculation, and fine screening may also be used. Secondary treatment: It Involves purification of wastewater primarily by decomposition of suspended and dissolved organic matter by microbial action. A number of processes are available, but land treatment, activated sludge process, or biological filtration methods are mainly used. Auxiliary/tertiary treatment: This mainly includes large number of physical and chemical treatment processes that can be used before or after the biological treatment to meet the treatment objectives.

Design of the actual treatment system for a CETP involves selection of alternative processes based on the ability of individual treatment processes to remove specific waste constituents.

6.7

Common effluent treatment plant—Case study

APIIC has awarded the establishment of a common effluent treatment plant (CETP) of 8.0 MLD capacity in four modules to M/s Indwa Technologies Pvt. Ltd on build, own, and operate (BOO) basis for industrial parks at Mallapur and Nacharam that are adjacent to each other and are among the oldest industrial estates in the state. Industrial park (IP) Mallapur is spread over an area of about 80 ha and has about 200 industrial units, of which 50 are chemical units. The IP Nacharam is spread over an area of 280 ha, and there are 340 industrial units in this IP, of which about 20 are chemical units. Indwa Technologies has prepared a detailed report, and JNTU has examined the techno-economic clearance (EC) and consent for establishment (CFE) for the proposed CETP. Construction of the first module of 2.0 MLD of the CETP has been taken up by the developer M/s Indwa Technologies Pvt. Ltd. The environmental clearance (EC) and

Impacts on water environment

245

CFE obtained from APPCB in the 3.16 acres land allotted by APIIC Ltd in IP Mallapur for the purpose of establishment of CETP. The construction of guard pond and pipeline from the outlet of CETP to outlet of STP at Nallacheruvu has been taken up by industries through their special-purpose vehicle (SPV), Mana Effluent Treatment Limited (METL), and APIIC. The construction of pipelines from CETP, Nacharam and Mallapur to the STP, Nallacheruvu has not commenced yet as there is some technical, physical, and social problems along the alignment of the proposed pipeline. This may be resolved through the deliberations among stakeholders, government officials of line departments, and other people involved in the process.

6.7.1

The treatment plant

The proposed scheme consists of primary, secondary, and tertiary treatment. The treatment scheme is derived to ensure not only low operating cost but also lesser operational controls and easier operation and maintenance of the CETP for producing consistent results to control the water pollution.

Primary treatment Primary treatment processes are mainly physical components, namely, grit chambers and coarse screens. The simplest grit chambers use gravity to remove grit and dirt, which consist largely of mineral particles that need to be removed before biological treatment. Coarse screens, typically bars or woven wire, strain out large solids. The primary treatment operations consist of two screening units for retaining coarse matter. Both the screens shall be with manual raking system. The wastewater is then taken to a grit chamber for retaining grit. Following this, the free-floating oil and grease in the wastewater shall be removed in an oil and grease trap with 20 min detention time. Free-floating oil and grease collected in the tank shall be periodically removed and disposed off. The wastewater is then collected in an equalization tank for attenuation of variation in waste flow rate and characteristics. Equalization basins mix influent wastewater to reduce the variations in concentrations of wastewater constituents and are also used with potentially toxic wastewaters to l

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discharge effluent to treatment processes at a uniform rate, leveling out the effect of peak and minimum flows; mix smaller volumes of concentrated wastes with larger volumes at lower concentrations; control pH to prevent fluctuations that could upset the efficiency of treatment system units by mixing acid and alkaline wastes. Air shall be bubbled in the equalization tank for mixing, to avoid solids from settling and to avoid development of anaerobic conditions. Equalization tank shall cater to 1 day detention time. From this stage, the treatment at the CETP shall be at uniform, flow rate of about 100 m3/h.

Secondary treatment Biological treatment processes are used primarily for secondary treatment and use microbial action to decompose suspended and dissolved organic matter in wastewater. Most biological treatment processes are aerobic, in which carbon provides the energy

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source for aerobic respiration, with carbon dioxide and water being the main by-products. The secondary treatment consists of a flash-mixing tank wherein chemicals are added for coagulation and pH adjustment. The flash-mixing tank is provided with a flash mixer device for homogenous mixing of chemicals and wastewater. Chemical preparation and feeding tanks are provided with agitators for preparation and feeding of chemicals required for treatment. For dosing of chemicals in a regulated manner, dosing pumps are proposed. Following chemical coagulation, the wastewater is taken to a flocculation tank for flocculation. For flocculation, a slow speed flocculator is provided. The wastewater is then taken to a tube deck settling tank for effective solid-liquid separation. Sludge collected in the tube deck settling tank shall be sent to sludge sump for onward handling of sludge. Supernatant, i.e., overflow from the tube deck settling tank, shall be subjected to biochemical oxidation in a series of aeration tanks. The aeration system shall be an attached growth fluidized bioreactor. Media providing very high surface area per unit volume shall be provided in the aeration tank for immobilizing the microbes. Air for aeration shall be provided by means of blowers connected to air grid and diffusers. The system operates as an extended aeration system. The system has the following advantages: l

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Smaller foot print area. Ease in operation and maintenance. Operator skills required are minimal. Less susceptible to upset conditions (shock loading, power failure, etc.). Lower energy requirements. No clogging or chocking of the media.

Following biochemical oxidation, the wastewater from the aeration tank is taken to a tube deck (secondary settling tank) for solid-liquid separation. The sludge collected in the hopper bottom of the settling tank is periodically withdrawn and sent to sludge sump for onward handling of sludge. Note: Nutrients for supplementing nitrogen and phosphorus shall be added for maintaining the desired BOD/N/P ratio at biochemical treatment by adding urea and DAP. Sludge from the grit trap, primary tube deck, and secondary tube deck following aeration tank shall be blended in the sludge sump and fed to sludge thickener. The thickened sludge shall be fed to decanter for dewatering. Dewatered sludge shall be applied onto sludge filter press/centrifuge. Supernatant from the thickener, decanted liquor from the decanter, and underflow from the sludge filter press/centrifuge shall be fed back at the first stage biochemical treatment.

Tertiary treatment Overflow from the secondary tube deck following the aeration tank shall be subjected to tertiary treatment to enable treated wastewater to be fit to recycle for purposes like cooling water, vehicle and floor washing, and gardening. For this, after secondary

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247

treatment, it is proposed to go for chemical oxidation followed by pressure sand filtration and activated carbon adsorption.

Disposal of treated wastewater The treated wastewater is expected to have BOD in the range of 5–10 mg/L, COD in the range of 80–100 mg/L, suspended solids less than 10 mg/L, and TDS below 1500 mg/L. These levels are within discharge standards for disposal into inland surface water. The treated wastewater, which does not meet the standards, will be recycled back to CETP for treatment until the characteristics of treated wastewater meet the standards and compliance with the MoEF/CPCB standards.

6.7.2

Cost of CETP and subsidy

The wastewater collection system within the IPs Nacharam and Mallapur and the disposal facilities for the treated wastewater are being provided by APIIC. The developer is to meet the costs of the CETP and collect user charges from the industrial units for treating their wastewaters (Fig. 6.5). The treatment plant consists of civil works and electromechanical items. The units will be interconnected through necessary piping and valves. The plant will be provided with illumination, cabling, and instrumentation. Office, laboratory facilities, staff quarters/dormitory, internal roads, drains, compound walls, etc. are to be provided. The capital cost of the 2.0 MLD CETP module is estimated as Rs. 576 lakhs and consists of the components given in Table 6.10.

Fig. 6.5 CETP of Nacharam-Mallapur industrial state.

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Environmental Impact Assessment

Table 6.10

Breakup of capital cost of 2.0 MLD treatment plant

S. no.

Item

Cost (Rs. lakhs)

1. 2. 3. 4. 5. 6. 7. 8.

Land Survey, designs, and investigations Civil works Mechanical works Interconnecting pipes and valves Electric works Instrumentation, illumination, and cabling Office building, laboratory, and ancillary works Total

Nominal lease 16 195 165 85 65 20 30 576

As an encouragement for setting up of CETP and to reduce financial burden on the industrial units, the APllC and Ministry of Environment and Forests (MoEF), Government of India, have sanctioned subsidies. The central subsidy is 25%, and the state subsidy is 25%. The developer has made arrangements with Corporation Bank for 30% of the project cost, and the remaining 20% cost is being met by the developer.