Download Environment Ecology.pdf PDF

TitleEnvironment Ecology.pdf
File Size1.5 MB
Total Pages163
Table of Contents
                            1. Environment Ecology (Merging File)
2. Ecology sample Questions
3. Answers of Sample Question
4. Ecology (UPSC Questions)
5. Answers of UPSC Question
                        
Document Text Contents
Page 1

Add : D/108, Sec-2, Noida (U.P.), Pin - 20 1301
Email id : [email protected]

Call : 09582948810, 09953007628, 0120-2440265

ECOLECOLECOLECOLECOLOGYOGYOGYOGYOGY

&&&&&

ENVIRENVIRENVIRENVIRENVIRONMENTONMENTONMENTONMENTONMENT

Page 2

Chronicle IAS Academy [2]

Page 81

Chronicle IAS Academy [81]

figure given below is a schematic representation
of the prioritized options.

i) Minimization of the amount generated by
modifying the industrial processes involved.

ii) Transfer of the waste to another industry
that can utilize it.

iii) Reprocessing of the waste to recover energy
or materials.

iv) Separation of hazardous waste from non-
hazardous waste at the source and its
subsequent concentration, which reduces the
handling, transportation and disposal costs.

v) Incineration of the waste or its treatment
to reduce the degree of hazard, and

vi) Disposal of the waste in a secure landfill,
one that is located, designed, operated and
monitored in a manner that protects life
and environment.

Let us examine the different disposal and
treatment methods currently in use.

Landfill

Landfills for the disposal of hazardous
wastes evolved from sanitary landfills.

Site Selection

The selection of a site for waste disposal is
governed by climatic, geologic and hydrological
factors. Arid conditions are favourable as little
leaching occurs. Sites made up of impermeable
material, such as clay till, are preferable because such
material retards the movement of contaminants
from the site and attenuates the effect by adsorption
and filtration. On the other hand, a site close to the
recharge zone is not suitable because the ground
water gets affected. Likewise, if the discharge flows
into a stream because of a high water table, the
ground water gets contaminated.

Design and Construction

The design and construction of a hazardous
landfill incorporates an impermeable cover, an
impermeable bottom liner, a system of drainage
pipes to collect and remove any leachate that
may accumulate, and a system of monitoring wells.

The cover prevents infiltration of
precipitation into the landfill. The bottom liner
serves to reduce the rate of leachate migration.
The leachate collection and recovery system
checks leachate migration and hydrostatic
pressure. This is accomplished by a system of

perforated pipes buried in the lower part of the
landfill, from where the liquid is pumped out.
Regular monitoring of the wells can detect, before
hand, the effects of groundwater contamination.
The NAS (National Academy of Sciences) has
decided that at least 500 years is realistic as a
period of concern for wastes in landfills.

Landfill gas generation is a major concern in
organic waste dumping. The emission rate from
landfill depends on a number of factors, such as
vapour pressure, diffusion coefficient, mass
transfer coefficient and solubility. Several control
techniques have been proposed regarding toxic
gas emission from landfills.

Wastes that are explosive or have high vapour
pressure, such as organic sludges, volatile
organic wastes and liquids, should not be
landfilled. Many types of waste should be pre-
treated to make them more innocuous and less
volatile. Gas collection device should be installed.
The site should be capped.

Hazardous wastes are now stored in separate
cells i.e. discrete storage areas, which are highly
suitable for incompatible wastes. Also, when a
cell is full, it can be quickly sealed and
revegetated. The Office of Technology
Assessment has concluded that complete
protection from migration, even for the operating
life of the fill, is probably unattainable.

Land treatment

This is a biological method in which,
hazardous wastes are deposited either on the
land or injected just beneath it and degraded
naturally by aerobic organisms. Oxygen levels
may be maintained by periodic ploughing.

Although the basic concept of land treatment
is simple, its planning and implementation are
exceedingly complex, involving an
understanding of microbiology, soil science,
chemistry, hydrology, geology and climatology.
In order for organic constituents to be suitable
for land treatment, they must degrade at a rate
faster than volatization, leaching or runoff. The
mobility, toxicity and accumulation of heavy
metals must also be considered in facility design.

Acceptable sites for landfill may also prove
most acceptable for land treatment. If bio-
degradable hazardous wastes are eliminated,
and toxic metals and other hazardous materials
immobilized in surfacial material, land treatment
could prove to be superior to landfill.

Page 82

Chronicle IAS Academy [82]

Selection of the kind of hazardous waste treated
by this technique, combined with careful site
monitoring, will reduce the danger of environmental
contamination by the biodegradable fraction of the
waste. The ultimate fate of toxic materials that
remain in the treated ground is more questionable.

Deep-well Injection

The use of injection wells for industrial waste
disposal began around 1950. In a typical
injection well, depths to the disposal zone
commonly range between 600 to 1800 m but may
by shallower or deeper.

The major difference between an injection
well and a normal well is the closed annular
space between the injection tubing and the inner
or long string casing. This space is filled with a
fluid under pressure which preserves the casing
and tubing, and which is monitored by a
pressure gauge at the surface. On completion,
the well is plugged to prevent the release of
liquids and also any change in reservoir pressure.

Underground injection of hazardous wastes
requires a very careful appraisal of factors,
including subsurface stratigraphy, lithology,
subsurface structure, fresh-water geohydrology,
extent of disposal zone area, pressure conditions
of disposal zone, density, toxicity, chemistry and
reactivity of wastes, etc.

An ideal disposal reservoir has a thick,
porous and permeable blanket of sandstone
underlying an entire basin and confined from
above and below by impermeable beds. A waste
that is lighter than the interstitial water would
be effectively contained in an anticline. In
contrast, a fluid denser than the interstitial water
would be best contained in a syncline.

Another important factor in underground
disposal is the selection of an injection pressure
high enough to displace the interstitial fluids
with the waste but is not so high that the
containing impermeable beds are fractured.

Incineration

The safest and most effective alternative to
land-based disposal of hazardous wastes is
incineration. This process is widely used in
Europe, chiefly in Germany.

About 240 facilities in the US incinerate 17
million metric tonnes of waste. Another 3-5
million metric tonnes are burned in industrial
boilers and 3, 50,000 metric tonnes by other
means like cement kilns.

Many incinerators have been shut down as
they failed to meet air pollution standards. To
obtain a permit for an incinerator, the company
must demonstrate a removal efficiency of 99.99 per
cent for PCBs and 9.99 per cent for other pollutants.

Many organic

toxic wastes are broken down to

harmless CO2 and H
2
O at high temperatures. Small

amounts of HCl, SO
2
, dioxins etc, may be produced

depending on the efficiency of the incinerator. These
can be removed using special equipment.

The effectiveness of incineration depends
upon temperature, turbulence and residence
time. PCBs can be incinerated with 99.99 per
cent efficiency at 750° C. The chief breakdown
product, hexachlorobenzene (HCB), decomposes
after 800° C and persists at low levels even at
1000° C. Fine particulate matter, metal aerosols
and hydrogen halide gases that escape
incineration also pose a problem. New methods
like ionizing wet scrubbers, supersonic steam
injection and electrostatic precipitation will lead
to an increased treatment of these wastes.

A new experimental method involves heating
a mixture of water and organic wastes to 400°C
at high pressure. Air is passed through this
mixture. All organic compounds, including
dioxins, break into water and CO

2
. High

incinerator temperatures result in an increased
emission of heavy metals. An increase in vapour
pressure of cadmium, copper, lead and
chromium with temperature, has been shown.

Incineration at sea: This is attractive because
of its low cost, roughly half that of incineration
on land. Interest in sea disposal began in the early
1970s when Volvanus-I went into operation in
the North Sea. The largest amount to be
incinerated was 1.5 million gallons of PCB in the
Gulf of Mexico. To date, incineration at sea can
be described as a cheap and effective method.

Other treatment methods

In many instances, these methods are still
under development and are not presently cost
effective. Heavy metals, if not recycled, poses a
potentially long-term toxicologic problem for
waste disposal. They can be solidified into
granular form, mixed with cement-based grouts
and pumped into underground disposal caverns.

Thermoplastic techniques using poly-
ethylene, paraffins and bitumen are popular as
the wastes are tightly bound and the leaching
rate is low due to the water resistant media.

Page 162

Ecology

C
H
R
O

N
I
C
L
E

I
A
S

A
C
A
D
E
M

Y

4

(b) 2 and 3 only

(c) 2, 3 and 4 only

(d) 1, 2, 3 and 4

23. The "Red Data Books" published by the In-
ternational Union for Conservation of Nature
and Natural Resources (IUCN) contain lists
of
1. Endemic plant and animal species present

in the biodiversity hotspots,

2. Threatened plant and animal species.

3. Protected sites for conservation of nature
and natural resources in various countries.

Select the correct answer using the codes given
below:
(a) 1 and 3

(b) 2 only

(c) 2 and 3

(d) 3 only

24. Human activities in the recent past have
caused the increased concentration of carbon
dioxide in the atmosphere, but a lot of it does
not remain in the lower atmosphere because
of
1. its escape into the outer stratosphere.

2. the photosynthesis by phyto-plankton in the
oceans.

3. the trapping of air in the polar ice caps.

Which of the statements given above is/are
correct?
(a) 1 and 2

(b) 2 only

(c) 2 and 3

(d) 3 only

25. In the context of ecosystem productivity, ma-
rine upwelling zones are important as they
increase the marine productivity by bringing
the
1. decomposer microorganisms to the surface.

2. nutrients to the surface.

3. bottom-dwelling organisms to- the surface.

Which of the statements given above is/are
correct?
(a) 1 and 2

(b) 2 only

(c) 2 and 3

(d) 3 only

���

Page 163

C
H

R
C
H

R
C
H

R
C
H

R
C
H

R
O

N
IC

L
E

O
N

IC
L
E

O
N

IC
L
E

O
N

IC
L
E

O
N

IC
L
E


IA

S



IA

S



IA

S



IA

S



IA

S

AAAAA
C
A
D
E
M

Y

C
A
D
E
M

Y

C
A
D
E
M

Y

C
A
D
E
M

Y

C
A
D
E
M

Y

Ecology 1

1 (a)

2 (a)

3 (a)

4 (d)

5 (c)

6 (a)

7 (b)

8 (c)

9 (a)

10 (a)

11 (a)

12 (b)

13 (d)

CHRONICLE
IAS ACADEMY
A CIVIL SERVICES CHRONICLE INITIATIVE

ECOLOGY (UPSC QUESTIONS)
(ANSWERS)

14 (c)

15 (c)

16 (a)

17 (d)

18 (d)

19 (a)

20 (b)

21 (b)

22 (c)

23 (b)

24 (b)

25 (b)

���

Similer Documents