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Unit 2 ph engineering_part_2_waste mgmt
1. Public health aspects of house
engineering
o Criteria of hygienic house, ventilation
engineering, code of house building,
o Merits of house engineering and its
significance in disaster
2. Housing
All places in which a group of people reside and
pursue their life goals.
- The size of settlement varies from a single
family to millions of people.
3. Social Goals Of Housing-:
a) Shelter
b) Family Life
c) Access to community facilities
d) Family participation in community life
e) Economic Stability
4. Criteria for healthful housing
тАв Provides physical protection and shelter
тАв Provides adequately for cooking, eating,
washing, and excretory functions
тАв Is designed, constructed, maintained and used
to prevent the spread of communicable diseases
тАв Provides for protection from hazards of
exposure to noise and pollution
5. Criteria for healthful housing-
тАв Is free from unsafe physical arrangements due
to construction or maintenance, and from toxic
or harmful materials
тАв Encourages personal and community
development, promotes social relationships,
reflects a regard for ecological principles and
finally promotes mental health
6. Housing Standard
The standards in Nepal
- Family income
- Family size and composition
- Standard of living, lifestyle
- Stage in life cycle
- Education and cultural factors
тАв Standard of housing varies from country to
country and from region to region.
тАв In short-there cannot be rigid, uniform standards
7. Site
- Elevated from its surroundings
- Independent access to a street of adequate width
- Away from breeding places of mosquito and flies
- Away from nuisances such as dust, smoke, smell,
excessive noise, and traffic.
- should be in pleasant surrounding
- soil should be dry and safe for founding the
structure and should be well drained.
8. Set Back
It is the open space all around the house which
allows proper ventilation and lightening
In rural areas
- should not exceed one third of total area.
In urban areas
- allowed up to two-third of total area.
- The set back should be such that there is no
obstruction of lighting and ventilation.
9. Floor
-Should be Pucca and satisfy the following
criteria-:
тАв should be impermeable
тАв must be smooth and free from cracks and
crevices
тАв it should be damp-proof
тАв the height of the plinth should be 2-3 feet(0.6 t
o 1 mtr)
10. Walls
тАв Reasonably strong
тАв Should have a low heat capacity
тАв Weather resistance
тАв Unsuitable for harbor of rats and vermin
тАв Not easily damaged
тАв Sooth ( 9 inch brick with wall plastered
smooth and colored cream or white)
11. Roof
-Should not be less than 10 feet (3 mtr) in the
absence of air-conditioning for comfort.
- should have a low heat transmittance co-
efficient
12. Rooms
- should not be less than two, at least one of
them can be closed for security
- the other may be open on one side if that side
is a private courtyard
- No. should be increased as per the family
members
14. Floor Area
- should be at least 120 sq ft for more than one
person and at least 100 sq ft for single person
- floor area per person should not be less than 50
sq mtr
16. Windows
- Every living room should be provided with at
least 2 windows and one of them should open
directly on to an open space
- the windows should be placed at a height of
more than 3 feet(1 m) above the ground in
living rooms
- windows area should be 1/5th of the floor area
doors and windows combined should have 2/5th
the floor area.
18. Kitchen
- Must have a separate kitchen
- Must be protected against dust
and smoke - adequately
lighted
- provided with water supply
- provided with a sink for
washing utensils
- fitted with arrangements for
proper drainage
19. Privy
- A sanitary privy is a must for every house,
belonging exclusively to it and readily
accessible.
20. Garbage and refuse
тАв Should be removed from the dwelling at least
daily
тАв disposed of in a sanitary manner
21. Bathing and Washing-
house should have facility for bathing and
washing belonging exclusively to it and
providing proper privacy.
Water Supply-: House should have a safe and
adequate water supply available at all times.
22. RURAL HOUSING
Minimum standard suggested-:
- There should be at least two living rooms
- Ample verandah space may be provided
- The build-up area should not exceed one-third
of total area
- There should be a separate kitchen with a paved
sink or platform for washing utensils
23. тАв The house should be provided with a sanitary latrine
тАв The window area should be at least 10% of the floor area
тАв There should be a sanitary well or a tube well within a
quarter of a ample from the house
тАв It is insanitary to keep cattle and livestock in dwelling
house.
тАв Cattle sheds should be at least 25 feet away from
dwelling houses.
тАв A cattle shed should be open on all sides an area 8ft├Ч4ft
is sufficient for each head of cattle
тАв There should be adequate arrangement for the disposal
of waste water, refuse and garbage.
24. Housing and Health
тАв Respiratory Infection
тАв Skin infection
тАв Rat infestation
тАв Arthropods
тАв Accidents
тАв Morbidity and Mortality
тАв Psychological effects
25. Overcrowding
тАв It refers to the situation in which more people and
living within a single dwelling than there is space
for, so that movement is restricted, privacy
secluded, hygiene impossible, rest and sleep
difficult.
тАв It may promote the spread of respiratory infections
such as TB, Influenza and Diphtheria.
тАв Overcrowding is considered to exist if 2 person
over 9 years of age, not husband and wife , of
opposite sexes are obliged to sleep in one room
26. Indicators of Housing
Physical
тАв Air тАв Light тАв Water тАв Noise тАв Sewage disposal
Economic
тАв Cost of the building тАв Rental levels тАв Taxes тАв
Expenditure on housing
Social
тАв Indicators related to prevention of disease тАв Indicators
related to comfort тАв Indicators related to mental health and
social well- being
27. Indicators related to prevention of
disease
тАв frequency of Inadequate sewage and garbage
collection
тАв Contaminated water source
тАв Insect borne diseases
тАв Overcrowding
тАв Accidents
тАв Proximity to animals
тАв Assess to medical facility
28. Indicators related to comfort
тАв Thermal comfort тАв Acoustic comfort тАв Visual
comfort тАв Spatial comfort
Indicators related to mental health and social
well- being
тАв Frequency of suicides in neighbourhood
тАв Neglected and abandoned youth in
neighbourhood
тАв Drug abuse in neighbourhood
29. The Implementation of social goals
in housing
Govt. should:
- Introduce social housing schemes
- Establish both minimum and maximum standard
- Create financial and fiscal institutions geared to
helping low income people obtain credit for building
and improving their house.
30. Merits of house engineering and its
significance in disaster
Earthquake-resistant
structures are structures designed to protect
buildings to some or greater extent
from earthquakes.
While no structure can be entirely immune to
damage from earthquakes, the goal
of earthquake-resistant construction is to erect
structures that fare better during seismic activity
than their conventional counterparts.
31. Merits of house engineering in Nepal
тАв Nepal is facing a number of severe problems like : poor
public awareness, low literacy rate, mass poverty,
fatalistic nature of some people, difficult and
undeveloped physical infrastructure, unplanned
settlement, lack of political commitment, slow decision
making process and so on.
тАв Apart from the above the lack of cooperation and
coordination among various disaster management
related agencies and their behavior indifference,
duplication of relief works, inadequate funds and
resources and the lack of modern technology especially
early warning system have made the disaster situation
more complex.
36. Others
NHPC Minimum Requirements of Bachelor
in Public Health, Second Revision 2076 (2019)
Teaching Facilities
тАв Land, building and physical facilities
requirements are as follows:
37. тАв Land and Building: Building with adequate floor space and
sufficient land
тАв There should be minimum of four rooms for routine classes, and
three rooms for group discussion purposes. Number of classrooms
should be increased with the number of sections.
тАв The class rooms should have: тАУ Well ventilated with adequate light тАУ
0.75 sq meter space per student тАУ Appropriate desk and bench,
White board тАУ Multi-media тАУ The theory classroom should
accommodate of at least 40 students
тАв PrincipalтАЩs office room should have enough space for
visitors/faculties and for small meeting.
тАв Administration office rooms should have enough space for
administrative and financial work.
тАв Demonstration room for 20 students at a time on the basis of 1:20
teacher -student ratio for demonstration.
тАв TeachersтАЩ room with sufficient numbers of computers and printers.
38. тАв A Library should have enough space for book and studentsтАЩ study. тАУ 1
course book per 5 students must be available in library. тАУ Reference book in
each subject should be available at ratio of 1:10 students in library. тАУ
Access to HINARI or other online data bases and other related free journals
with a internet with high speed. тАУ At least 5 professional recent journals
should be available in the library. тАУ Adequate number of reference books on
each subject for teacher should also be available in library. тАУ Other related
books/dictionaries, magazines, newspapers should be made available. тАУ
Curriculum of the program must be available at office and at the library.
Furniture like table, chair, open rack, must be available in the library as per
required standard and quantity. тАУ Sufficient Computer, printer, photocopy
machine, email тАУ internet facilities should be made available.
тАв For computer class, there should be one computer per two students and a
separate computer classroom should be available.
тАв Audio-visual aid equipment should be available for classroom.
тАв Toilet at a ratio of 1:10 for working staffs and students (male/female
separate).
тАв Multipurpose hall (at least 200-person accommodation with essential
facilities) should be available.
39. Facilities for Other Activities
тАв An outdoors athletic ground
тАв Indoor games
тАв Provision of vehicles for field activities
тАв Parking space- faculties, staffs and students
тАв Space for student welfare with counseling
services
тАв StudentsтАЩ hostel (Male and Female separate) is
preferable
тАв Canteen with safe drinking water, hygienic
kitchen and dining hall
40. Term Paper Preparation
Group 1: Demonstration of modern types of toilet
(engineering of sanitary disposal system)
Group 2: Urban health clinic and its engineering of water,
toilet and waste.
Group 3: Implementation of code of house development
of your own house or rent house where you are living now
(health home, sanitation aspects, disaster aspects of
security concern of house.
Group 4: Think and plan your future house a/c to
Engineering layout/sketch of public health engineering
(land fill site, preparation guideline and healthy house and
city.
41. Waste management engineering
The current generation rates for major waste streams,
collection and potential recycling options.
Solid waste engineering options
- Landfill тАУ concept, site selection criteria, design and
operation
- Biological treatment - composting and anaerobic
digestion, design and operation
- Thermal treatment - combustion, pyrolysis and
gasification, design and operation
- Emission control - flue gas cleaning systems, odour
control, leachate management and bioaerosol control
42. тАв Per head- 135 litre/per capita/day for personal
hygiene and needs.
тАв 60% of waste are domestic wastes.
тАв As of June 2013, about 86% of the population
had access to basic services of drinking water
supply and about 11% of countryтАЩs population
had access to safe drinking water supply
services. Likewise, about 62% of the
population had access to basic sanitary
services as of June 2013 (NPC, 2014).
43. Water engineering
тАв By 2017- Up to 2035 MW hydropower electricity
is developed to meet the projected domestic
demand at base case scenario, excluding export.
тАв Fifty per cent of households are supplied with
INPS electricity, 12% by isolated (micro and
small) hydro systems and 3% by alternative
energy.
тАв Per capita electricity consumption of 160 KWh is
achieved.
44. By 2027
тАв Up to 4,000 MW of hydropower is developed
to meet the projected domestic demand at base
case scenario, excluding export.
тАв Seventy-five per cent of the households are
supplied with INPS electricity, 20% by
isolated (micro and small) hydro systems and
5% by alternative energy.
тАв Per capita electricity consumption of over 400
KWh is achieved.
45. What are Wastes?
Waste (also known as rubbish, trash, refuse, garbage, junk,
litter, and ort) is unwanted or useless materials. In biology,
waste is any of the many unwanted substances or toxins that are
expelled from living organisms, metabolic waste; such as urea
and sweat.
Basel Convention Definition of Wastes
тАЬsubstances or objects which are disposed of or are intended to
be disposed of or are required to be disposed of by the
provisions of the lawтАЭ
Disposal means
тАЬany operation which may lead to resource recovery,
recycling, reclamation, direct re-use or alternative uses (Annex
IVB of the Basel convention)тАЭ
46. Basel Convention
тАв The Basel Convention on the Control of Transboundary Movements of
Hazardous Wastes and Their Disposal, usually known simply as Basel
Convention, is an international treaty that was designed to reduce the
movements of hazardous waste between nations, specially to prevent
transfer of hazardous waste from developed to less developed countries
(LDCs). It does not, however, address the movement of radioactive waste.
The convention is also intended to minimize the amount and toxicity of
wastes generated, to ensure their environmentally sound management as
closely as possible to the source of generation, and to assist LDCs in
environmentally sound management of the hazardous and other wastes they
generate.
тАв The Convention was opened for signature on 22nd March 1989, and
entered into force on 5 May 1992.
47. The definitionтАжтАжтАжтАж
тАв Produced by the United Nations Statistics Division
(U.N.S.D.):
"Wastes are materials that are not prime products (that is
products produced for the market) for which the generator has
no further use in terms of his/her own purposes of production,
transformation or consumption, and of which he/she wants to
dispose. Wastes may be generated during the extraction of raw
materials, the processing of raw materials into intermediate
and final products, the consumption of final products, and
other human activities. Residuals recycled or reused at the
place of generation are excluded."
48. Kinds of Wastes
Solid wastes: wastes in solid forms, domestic, commercial and
industrial wastes
Examples: plastics, styrofoam containers, bottles,
cans, papers, scrap iron, and other trash
Liquid Wastes: wastes in liquid form
Examples: domestic washings, chemicals, oils, waste
water from ponds, manufacturing industries
and other sources
49. According to EPA regulations, SOLID WASTE is
тАв Any garbage or refuse (Municipal Solid Waste)
тАв Sludge from a wastewater treatment plant, water supply
treatment plant, or air pollution control facility
тАв Other discarded material
тАв Solid, liquid, semi-solid, or contained gaseous material
from industrial, commercial, mining, and agricultural
operations, and from community activities
http://www.epa.gov/epaoswer/osw/basifact.htm#solidwaste
54. 54
Source: WASTE INCINERATION (2010) and AFRICAN DEVELOPMENT BANK (2002)
Source: SUSANA on Flickr 2009
Landfilling is the least
preferred method in the
hierarchy of integrated
solid waste management.
55. Is a Landfill an Open Dump?
55
Source: SUSANA on Flickr 2009
56. Is a Landfill an Open Dump?
56
Source: SUSANA on Flickr 2009
It is not an open dump, it is an
engineered facility in order to
protect the environment and
human health!
Source: LATROBE CITY COUNCIL (2005)
57. Types of Landfills
тАв Open Dump:
тАУ Waste is discharge open without any management
тАв Basic Landfill:
тАУ Waste is discharged in a pit and covered every day
тАв Engineered Landfill:
тАУ Liner, cover, leachate treatment and gas extraction (energy
production or flared)
тАв Bioreactor Landfill:
тАУ Acceleration of decomposition and creation of a conditions for
microbiological activities -> produced gas is used for energy
production.
57
58. Engineered Landfills in Contrast to
Open Dumps
58
Source: LATROBE CITY COUNCIL (2005)
Cover layerяАв avoids spreading of
waste, pathogens, odour
Gas extraction well яАв control and
reuse of biogas (mainly CO2 and
CH4) for energy production
Liner system яАв avoids a
contamination of ground water
Leachate system яАв collection and
treatment of fluid effluent
Groundwater monitoring яАв on-
going information about the
groundwater quality
59. Basic Landfill (Emergency Landfill)(HARVEY et al. 2002)
тАв Pit should be
backfilled with
excavated soil every
day.
тАв Site should be agreed
with local population
and authorities.
тАв Site should be fenced.
тАв At least 1 km
downwind from the
nearest dwellings.
59
Source: HARVEY et al. (2002)
60. Engineered Landfill (UNEP 2002)
тАв The capacity is planned and the site is chosen
based on an environmental risk assessment
study.
тАв Gas is flared or used for energy production.
60
Source: UNEP (2002)
61. Bioreactor Landfill (WM 2004)
61
тАв Acceleration of biologic decomposition (organic fraction).
тАв Promoting conditions necessary for the microorganisms (moisture
content).
тАв Liquids must be added (leachate, stormwater, sewerage sludge).
тАв Gas is collected to produce
electrical energy.
тАв Design includes liner, cover,
leachate system, groundwater
monitoring.
тАв Systems: aerobic, anaerobic,
aerobic-anaerobic, facultative
(to control high ammonia
concentration).
Source: WM (2004)
62. Treatment and Health Aspect
62
Open Dump
Basic Landfill
Engineered Landfill
Bioreactor Landfill
healthandenvironmentalprotection
63. Treatment and Health Aspect
63
Open Dump slow decomposition; spreading of waste,
pathogens and odour; no liner, no cover
Basic Landfill better decomposition; cover avoids
spreading of waste and breeding of insects;
leaching may occur
Engineered Landfill advanced decomposition; cover; liner;
leachate, stormwater and gas management
Bioreactor Landfill acceleration of decomposition; cover;
liner; leachate and stormwater
management; energy production
64. 64
Operation and Maintenance
тАв Requires dedicated operators.
тАв Waste has to be covered each day.
тАв Proper leachate management.
тАв Cover must be resistant to erosion.
тАв Once capacity is reached, the bottom (cover layer) has to be
controlled regularly to avoid toxic effluents/emissions.
тАв Bioreactor landfills require a more complex set of O&M.
65. тАвAdvantages:
тАУ An effective disposal
method if well-managed.
тАУ A sanitary disposal method
if managed effectively.
тАУ Energy production and fast
degradation if designed as a
bioreactor landfill.
Disadvantages:
тАв Fills up quickly if waste is not reduced
and reusable waste is not collected
separately and recycled.
тАв A reasonable large area required.
тАв Risk of groundwater contamination if not
sealed correctly or the liner system is
damaged.
тАв High costs for high-tech landfills.
тАв If the management is bad, there is a risk
that the landfill degenerates into an
open dump.
тАв After the end of disposal the landfill
needs still O&M and monitoring for the
next 50 to 100 years.
65
66. A landfill site at Bancharedanda on the border of Nuwakot and
Dhading districts for sustainable waste management in
Kathmandu Valley.
67. The Valley produces an average of 1,000 tonnes
of garbage daily, and nearly 70 per cent of them
are disposed in Okharpauwa Sisdole Landfill
Site developed with the support of JICA.
A study conducted by JICA in 2005 had
suggested that around 350 tonnes of waste could
be disposed of in the landfill site daily for
another 23 years.
71. 1. STAGE ONE: SCREENING
тАв Screening is the first stage of the wastewater
treatment process.
тАв Screening removes large objects like, diapers,
nappies, sanitary items, cotton buds, face
wipes and even broken bottles, bottle tops,
plastics and rags that may block or damage
equipment.
тАв Special equipment is also used to remove grit
that gets washed into the sewer.
72.
73.
74.
75.
76. 2. STAGE TWO: PRIMARY TREATMENT
тАв This involves the separation of organic solid
matter (or human waste) from the
wastewater.
тАв This is done by putting the wastewater into
large settlement tanks for the solids to sink to
the bottom of the tank.
тАв The settled solids are called тАШsludgeтАЩ.
77. тАв At the bottom of these circular tanks, large
scrappers continuously scrape the floor of the
tank and push the sludge towards the center
where it is pumped away for further
treatment.
тАв The rest of the water is then moved to the
Secondary treatment.
78.
79.
80.
81.
82.
83. 3. STAGE THREE: SECONDARY
TREATMENT
тАв The water, at this stage, is put into large
rectangular tanks.
тАв These are called aeration lanes.
тАв Air is pumped into the water to encourage
bacteria to break down the tiny bits of sludge
that escaped the sludge scrapping process.
84.
85.
86. 4. STAGE FOUR: FINAL TREATMENT
тАв Next, the тАШalmostтАЩ treated wastewater is passed
through a settlement tank.
тАв Here, more sludge is formed at the bottom of
the tank from the settling of the bacterial
action. Again, the sludge is scraped and
collected for treatment.
87. тАв The water at this stage is almost free from
harmful substances and chemicals.
тАв The water is allowed to flow over a wall where
it is filtered through a bed of sand to remove
any additional particles.
96. Thermal Processing of Solid Wastes
тАЬit can be defined as the conversion of wastes into gaseous,
liquid and solid production, with or without energy
valorization.тАЭ
Thermal processes with respect to air
requirements:
яБ╢combustion
яБ╢gasification
яБ╢pyrolysis
97. Thermal Processing of Solid Wastes
тАв Combustion is occurred by stoichiometric
amount of oxygen or excess air.
тАв Gasification is the partial combustion of
materials, thus materials convert to
combustible gases (such as carbon monoxide,
hydrogen, and gaseous hydrocarbons).
тАв Pyrolysis can be defined as destructive
distillation; materials are combusted with
absence of oxygen.
99. Combustion Systems
Combustion systems (Incinerators) are involves
the application of combustion processes under
controlled conditions to convert waste
materials to inert mineral ash and gases. Types
of incinerators;
тАв Fixed-Hearth Incinerators
тАв Rotary Kiln Incinerators
тАв Refuse Derived Fuel Incinerators
тАв Fluidized Bed Incinerator
100. Pyrolysis
тАв Pyrolysis recycling is a non combustion heat
treatment that chemically decomposes waste
material by applying heat (directly or indirectly)
to the waste material in an oxygen free
environment.
тАв It is an endothermic reaction and requires an input
of energy, which is typically applied indirectly
through the walls of the reactor in which the
waste material is placed for treatment.
101. Gasification
the thermo-chemical conversion of a solid or liquid
carbon-based material (feedstock) into a
combustible gaseous product (combustible gas).
тАв Direct gasification occurs when an oxidant
gasification agent is used to partially oxidize the
feedstock.
тАв Indirect gasification occurs without an oxidizing
agent and needs an external energy source.
103. Emission control
- flue gas cleaning systems,
- odour control,
- leachate management and
- bioaerosol control
104. Flue gas often refers to the combustion exhaust gas produced
at power plant. These gases are treated as pollutants. Flue gas
may contain oxides of carbon, nitrogen, and sulphur as well as
fly-ash, other pollutants, and water vapour.
Flue gas is the by-product of combustion, normally vented
through long pipes known as flues, which exhaust gases from
fireplaces, ovens, furnaces, boilers or steam generators.
Large amounts of flue gases are generated around the world on
a daily basis, with heavy industry and the power industry in
particular being responsible for a large percentage of the total
generated. These gases are also created by wood fires and
vehicle exhaust.
105. One of the greatest contemporary challenges is
to ensure air quality. Flue gas cleaning plants for
power stations and industrial facilities contribute
a significant part to this process by complying
with the most stringent environmental standards
providing processes for long-term efficiency and
cost-effective use.
107. The gas cleaning systems can be divided as follows:
1. Removal of particles or dust collection.
тАв Fabric filters
тАв Sand Band
тАв Electrostatic precipitators
2. Removal of water soluble gases: SO2, HCl, HF and NH3 Flue
тАв Gas Desulphurisation
тАв Wet scrubbing
тАв Dry scrubbing
тАв Spray absorption
3. Separation of heavy metals and very toxic substances like Dioxin and
Mercury (Hg)..
Activated carbon dosing
4. Removal of NOx (mainly NO)
Denitrification`
108. I. DUST REMOVAL
Electrostatic precipitators
The function of dust separation in an electrostatic precipitator is
based on an electrical field built up between the discharge
electrodes, which is kept at a high voltage, and the earthed
collecting electrodes. the principle includes charging the
particles, separating them from the gas in an electrostatic field to
a collector and remove the dust layer by dry or wet methods.
This separation principle can remove even fine dust particles
from gas very well in the electrostatic precipitator which is
particularly protective of the environment
109. Advantages of Electrostatic precipitators
тАв High dust separation
Efficiencies of over 99.95%
тАв Low clean gas dust content
of < 10mg/Nm3
тАв Low service and
maintenance cost
тАв Electrostatic precipitators
are particularly important
for product recovery, as
they make a valuable
contribution to resource
110. Fabric Filter
Fabric Filter (FF), also known as
Bag(house)filter, Fibrous filter.
These are most common adhesion separator, has
a large area of woven or needled fabric from
which the flue gas has to flow through.
During passage, the particles are removed by
deflection (mass forces), interception, diffusion
(adhesion forces) and electrical forces.
111. Advantages of fabric filter
тАв High dust separation
efficiencies of over
99.95%
тАв Simultaneous separation of
gaseous pollutants
possible
тАв Large variety of
applications in all sectors
112. Sand bed filter
тАв Sand bed filters also use mass forces for removal of
particles.
тАв When the particles are deflected during passage through the
sand bed they stick on the surface and are collected. The
particle cut diameter for a well designed sand bed filter is
around one 1 m and it can then remove the main part of the
coarse particles.
тАв The fractional efficiency curve is normally steep so the
removal of particles smaller than one 1 m is limited. A sand
bed filter is robust and can stand extreme conditions.
тАв By introducing electrostatic fields in the sand bed the
removal of small harmful particles can be improved.
113. Flue gas Desulphurization
Flue-gas desulfurization (FGD) is a set of
technologies used to remove Sulphur
dioxide (SO2) from exhaust gases of
power plants and from the emissions of
other sulphur oxide emitting processes.
The FGD technology is based on a
chemical reaction that occurs when the
warm exhaust gases come into contact
with limestone.
This reaction removes 92% of the
sulphur dioxide from the flue gas and
converts the limestone into Calcium
Sulphite
114. Depending on the upstream plant, FGD can be
done by these ways:
Wet scrubbing
тАв The exhaust gases of combustion may contain substances considered
harmful to the environment, and the scrubber may remove or neutralize
those.
тАв A wet scrubber is used for cleaning fuel gas containing various pollutants
and dust particles.
тАв Wet scrubbing works via the contact of target compounds or particulate
matter with the scrubbing solution. Solutions may simply be water (for
dust) or solutions of reagents that specifically target certain compounds.
тАв Fuel gas can also contain water-soluble toxic or corrosive gases like
hydrochloric acid (HCl) or ammonia (NH3 ). These can be removed very
well by a wet scrubber.
тАв Removal efficiency of pollutants is improved by increasing residence time
in the. Wet scrubbers may increase the proportion of water in the gas.
115. Dry scrubbing
A dry or semi-dry scrubbing system, unlike the wet
scrubber, does not saturate the flue gas stream that is
being treated with moisture. In some cases no
moisture is added, while in others only the amount
of moisture that can be evaporated in the flue gas
without condensing is added. Therefore, dry
scrubbers generally do not have a stack steam plume
or wastewater handling/disposal requirements.
Dry scrubbing systems are used to remove acid
gases (such as SO2 and HCl) primarily from
combustion sources.
116. SPRAY ABSORBER
тАв In spray absorption system untreated flue gas is introduced into a
spray dryer absorber module and contacts with a fine spray of lime
slurry/reagent.
тАв The pollutants SO2 , SO3 , HCI and HF are rapidly absorbed,
converted into the reaction products and removed by the downstream
particle collector (fabric filter or electrostatic precipitator).
тАв The dry spray absorption technology is a low capital investment, low
O&M cost, low auxiliary power consumption, less space requirement,
simple structure and high availability.
тАв This technology is mature enough that numerous absorbers have been
installed and successfully operated in the power stations worldwide.
117. Denitrification - last exit for greenhouse gases
тАв Anthropogenic nitrogen oxide emissions from
combustion processes are one factor responsible
for ozone destruction in the stratosphere.
тАв NOx- production from nitrogen in the air can take
place if there are very high temperatures (>1200 -
1300┬░C) in the furnace.
тАв The NOx comprises normally > 95% NO.
тАв In 1984, the introduction of large-scale
denitrification technology in Germany
downstream of steam generators established the
first steps towards countering this problem.
118. Activated carbon filters
The activated carbon filter is used for
precision cleaning and it is a safety
system should one of the upstream
flue gas cleaning stages fail.
The activated carbon filter is a
universal separation stage for nearly
all pollutants to be separated from
the exhaust gas
122. Natural Bioaerosols
тАв Clearance mechanisms
тАв Allergic reactions
- hay fever 10 % of children in
German health survey
- 5 % of children in German
environmental survey sensitised to
Alternaria alternata
123. Man-made Bioaerosols
Legionella in aerosols from showers pools/spas and
cooling towers
Health risks: lung inflammation, death
Very high bioaerosol concentrations at work places
Health risks: problems with lung and mucous
membranes: - ODTS (organic dust toxic syndrome
e.g. humidifier fever) - EEA (extrinsic allergic
alveolitis e.g. farmer`s lung) - MMI (mucous
membrane irritation) - chronical bronchitis
124. тАв Elevated concentrations in the environment
тАв Indoor Air: Damp and mouldy buildings
тАв Health risks: - allergic reactions - upper
respiratory tract symptoms - cough, wheeze -
asthma exacerbation - unspecific health
problems?
125. Treatment of Leachate (SAтАЩAT 2006)
125
Without proper cleaning, leachate will cause environmental problems. Potential
methods for treatment:
тАвRecirculation of leachate through the landfill
тАвDisposal off-site to sewer for treatment as an admixture with domestic sewage
тАвPhysical-chemical treatment
тАвMembrane filtration
тАвReverse osmosis
тАвAnaerobic biological treatment
тАвAerobic biological treatment
тАвConstructed wetlands
Design of a vertical flow constructed wetland. Source: MOREL &
DIENER (2006)