Understand the science and engineering aspects of a landfill, biological treatment and thermal treatment options.

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
• Provides physical protection and shelter
• Provides adequately for cooking, eating,
washing, and excretory functions
• Is designed, constructed, maintained and used
to prevent the spread of communicable diseases
• Provides for protection from hazards of
exposure to noise and pollution

5. Criteria for healthful housing-
• Is free from unsafe physical arrangements due
to construction or maintenance, and from toxic
or harmful materials
• 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
• Standard of housing varies from country to
country and from region to region.
• 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-:
• should be impermeable
• must be smooth and free from cracks and
crevices
• it should be damp-proof
• the height of the plinth should be 2-3 feet(0.6 t
o 1 mtr)

10. Walls
• Reasonably strong
• Should have a low heat capacity
• Weather resistance
• Unsuitable for harbor of rats and vermin
• Not easily damaged
• 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

13. Person per room

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

15. Cubic Space
at least 500 c.ft per capita preferably 1000 c.ft

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.

17. Lighting
the daylight factor should exceed 1 % over half
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
• Should be removed from the dwelling at least
daily
• 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. • The house should be provided with a sanitary latrine
• The window area should be at least 10% of the floor area
• There should be a sanitary well or a tube well within a
quarter of a ample from the house
• It is insanitary to keep cattle and livestock in dwelling
house.
• Cattle sheds should be at least 25 feet away from
dwelling houses.
• A cattle shed should be open on all sides an area 8ft×4ft
is sufficient for each head of cattle
• There should be adequate arrangement for the disposal
of waste water, refuse and garbage.

24. Housing and Health
• Respiratory Infection
• Skin infection
• Rat infestation
• Arthropods
• Accidents
• Morbidity and Mortality
• Psychological effects

25. Overcrowding
• 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.
• It may promote the spread of respiratory infections
such as TB, Influenza and Diphtheria.
• 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
• Air • Light • Water • Noise • Sewage disposal
Economic
• Cost of the building • Rental levels • Taxes •
Expenditure on housing
Social
• Indicators related to prevention of disease • Indicators
related to comfort • Indicators related to mental health and
social well- being

27. Indicators related to prevention of
disease
• frequency of Inadequate sewage and garbage
collection
• Contaminated water source
• Insect borne diseases
• Overcrowding
• Accidents
• Proximity to animals
• Assess to medical facility

28. Indicators related to comfort
• Thermal comfort • Acoustic comfort • Visual
comfort • Spatial comfort
Indicators related to mental health and social
well- being
• Frequency of suicides in neighbourhood
• Neglected and abandoned youth in
neighbourhood
• 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
• 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.
• 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.

32. code of house building
Refer pdf

33. घर बनाउँदा यस्तो छ नक्सा पास प्रक्रिया
स्थानीय स्वायत्त ऐन २०५५ अनुसार
आवासीय तथा व्यापाररक प्रयोजनका भवन ननर्ााण गदाा अपनाउनुपने प्रक्रिया यस्तो छ –
१. अमिनबाट बाटो वा प्रस्ताववत बाटो/जीएलडी (गाइडेड ल्यान्ड डेभलपिेन्ट) जााँच गने
२. इन्न्जननयरबाट नक्सा जााँच तथा दस्तुर ननर्ाारण गराउने
३. भवन संहिताले ननदेमित गरेअनुसारका िता पालना गरेर भूकम्पबाट सुरक्षित ककमसिले घरको नक्सा
डडजाइन भएको छ छैन भन्ने कम््युटर जााँच गराउने
४. इन्न्जननयरबाट सोको नक्सा पुनः जााँच गराउने
५. िुल्क बुझाउने (िुल्क प्रनतवगाकिट आवासीय भवनलाई रू. २५ र व्यापाररक प्रयोजनका भवनिा रू.
३५ लाग्छ ।)
६. नक्सा पुनः जााँच र िुल्क भुक्तानीको बेिोरा कम््युटरिा दताा गराउने
७. वडाबाट सन्जािन सूचना टासाँका लागग सम्बन्न्र्त वडािा नक्सा िाइल दताा गराउने
८. वडा कायाालयबाट सन्जािनको सूचना टााँस
९. सूचना टााँस गरेको १५ हदनपनछ सन्जािन वडा कायाालयका प्राववगर्कबाट स्थान ननरीिण प्रिाणणत गने
१०. वडा प्रिुख वा प्रिासकीय प्रिुखबाट ििरी ववकास ववभागिा सक्कलै िाइल पठाउने
११. वडा कायाालयबाट ल्याएको िाइल नगरपामलकाको ििरी ववकास ववभागको सम्बन्न्र्त िाटाँिा
बुझाउने तथा दताा गने
१२. सम्बन्न्र्त वडाको न्जम्िेवारी तोककएको इन्न्जननयरले िाइल जााँच गने
१३. जााँच गरेको िाइल स्वीकृ त गने अनघकारीसिि पेि गने
१४. न््लन्थ लेबल (डीपीसी)सम्िको ननिााण काया सम्पन्न गररसके पनछ सो कायाको स्थलगत जााँच िुने
१५. न््लन्थ लेबल स्थलगत जााँच ररपोटा पेिपश्चात् इन्न्जननयरबाट नक्सा जााँच गराई स्वीकृ नतका लागग
ििािाखा प्रिुख वा ववभागीय प्रिुखसिि पेि गने
१६. स्थायी नक्सा पास गरेर कम््युटरिा दताा गराउने
१७. स्थायी इजाजत पत्र प्रा्त

34. • नक्सा पास गनाका लागग आवश्यक कागजातरू
• भवनको नक्सा आवेदन िाइलिा उल्लेख भएका
कागजपत्रिरू
जस्तै
– सम्बन्न्र्त व्यन्क्तको नागररकताको प्रनतमलवप
– ककत्ता नापी नक्सा
– जग्गाको िालपोत नतरेको प्रिाणपत्रसिेत
सम्बन्न्र्त कायाालयिा पेि गनुापनेछ
– चारककल्ला स्पस्ट पाररएको कागजात

35. आवासीय भवनको नक्सा पास रुन तथा
ननर्ााण स्वीकृ नत पाउन ननम्न आधारभूत
शता सरकारले तोके को छ ।
– सडकको चौडाइ न्यूनति ६ मिटर र न्यूनति सेडब्याक सडक ककनाराबाट १.५ मिटर
छोडडएको िुनुपने
– सेटब्याक छाडेर िात्र पखााल लगाउन पाइने । पखाालको उचाइ बढीिा ४ किट र
त्योभन्दा िागथ ३ किट तारको जाली राख्न सककने
– पखााल, सेफ्टी ट्याङ्कीसिेतको नक्सा पास गनुापने
– सडकको िेत्रागर्कार र सेड ब्याकमभत्र टप, बादाली, छज्जी आहद कु नै पनन संरचनािरू
बनाउन नपाइने । भवन ननिााण िेत्रमभत्र पनन एक मिटरभन्दा बढीको टप,
बादाली, छज्जी ननकाल्न नपाइने
– ननिााण सम्पन्न प्रिाणपत्रववना भवनको बैङ्ककङ र बीिा कारोबार गना नसककने
– ३० डडग्रीभन्दा मभरालो जिीनिा भवन बनाउन नपाइने
– खानी तथा भूगभा ववभाग र न्जल्ला दैवी प्रकोप उद्र्ार समिनतले ननषेर् गरेको
स्थानिा भवन बनाउन नपाइने
– २५० वगामिटरसम्िको िेत्रिा घर बनाउाँदा २० प्रनतित र सोभन्दा बढीिा ४० प्रनतित
जिीन खाली राखेर भवन ननिााण गररनुपने
– वविानस्थलको र्ावनिागा आसपास भवन बनाउन लागगएको अवस्थािा नागररक
उड्डयन प्रागर्करणले तोके को िापदण्ड पूरा गरेको िुनुपने । र्ावनिागाको बाहिरी
सीिाबाट ५०० मिटर आसापस १७ मिटरभन्दा अग्लो भवन ननिााण गनुापदाा नागररक
उड्डयन प्रागर्करणबाट अननवाया रूपिा स्वीकृ नत मलएको िुनुपने
– उपत्यकाबाहिरका नगरपामलकािरूले ििरी ववकास िन्त्रालयले तयार पारेको भवन
ननिााणसम्बन्र्ी िागादिान २०७२ लाई पालना गनुापने

36. Others
NHPC Minimum Requirements of Bachelor
in Public Health, Second Revision 2076 (2019)
Teaching Facilities
• Land, building and physical facilities
requirements are as follows:

37. • Land and Building: Building with adequate floor space and
sufficient land
• 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.
• The class rooms should have: – Well ventilated with adequate light –
0.75 sq meter space per student – Appropriate desk and bench,
White board – Multi-media – The theory classroom should
accommodate of at least 40 students
• Principal’s office room should have enough space for
visitors/faculties and for small meeting.
• Administration office rooms should have enough space for
administrative and financial work.
• Demonstration room for 20 students at a time on the basis of 1:20
teacher -student ratio for demonstration.
• Teachers’ room with sufficient numbers of computers and printers.

38. • A Library should have enough space for book and students’ study. – 1
course book per 5 students must be available in library. – Reference book in
each subject should be available at ratio of 1:10 students in library. –
Access to HINARI or other online data bases and other related free journals
with a internet with high speed. – At least 5 professional recent journals
should be available in the library. – Adequate number of reference books on
each subject for teacher should also be available in library. – Other related
books/dictionaries, magazines, newspapers should be made available. –
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. – Sufficient Computer, printer, photocopy
machine, email – internet facilities should be made available.
• For computer class, there should be one computer per two students and a
separate computer classroom should be available.
• Audio-visual aid equipment should be available for classroom.
• Toilet at a ratio of 1:10 for working staffs and students (male/female
separate).
• Multipurpose hall (at least 200-person accommodation with essential
facilities) should be available.

39. Facilities for Other Activities
• An outdoors athletic ground
• Indoor games
• Provision of vehicles for field activities
• Parking space- faculties, staffs and students
• Space for student welfare with counseling
services
• Students’ hostel (Male and Female separate) is
preferable
• 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 – 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. • Per head- 135 litre/per capita/day for personal
hygiene and needs.
• 60% of waste are domestic wastes.
• As of June 2013, about 86% of the population
had access to basic services of drinking water
supply and about 11% of country’s 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
• By 2017- Up to 2035 MW hydropower electricity
is developed to meet the projected domestic
demand at base case scenario, excluding export.
• Fifty per cent of households are supplied with
INPS electricity, 12% by isolated (micro and
small) hydro systems and 3% by alternative
energy.
• Per capita electricity consumption of 160 KWh is
achieved.

44. By 2027
• Up to 4,000 MW of hydropower is developed
to meet the projected domestic demand at base
case scenario, excluding export.
• 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.
• 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
“substances 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 law”
Disposal means
“any operation which may lead to resource recovery,
recycling, reclamation, direct re-use or alternative uses (Annex
IVB of the Basel convention)”

46. Basel Convention
• 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.
• The Convention was opened for signature on 22nd March 1989, and
entered into force on 5 May 1992.

47. The definition…………
• 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
• Any garbage or refuse (Municipal Solid Waste)
• Sludge from a wastewater treatment plant, water supply
treatment plant, or air pollution control facility
• Other discarded material
• 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

50. Sources of Wastes
Households
Commerce and Industry

51. Generation & Collection of KMC
• Waste Generation 0.3 kg/p/day
• Total domestic waste gen. App. 246 ton/day
• Commercial waste (12%)app. 30 ton/day
• Street Waste (12%) app. 30 ton/day
• Total Generation 335 ton/day
• Collection 306 ton/day
• About 70% waste are organic
Source: Environment Mgt. Department, 2014

52. Landfill – concept, site selection
criteria, design and operation
52

53. 53
Source: WASTE INCINERATION (2010) and AFRICAN DEVELOPMENT BANK (2002)
Source: SUSANA on Flickr 2009

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
• Open Dump:
– Waste is discharge open without any management
• Basic Landfill:
– Waste is discharged in a pit and covered every day
• Engineered Landfill:
– Liner, cover, leachate treatment and gas extraction (energy
production or flared)
• Bioreactor Landfill:
– 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 layer avoids spreading of
waste, pathogens, odour
Gas extraction well  control and
reuse of biogas (mainly CO2 and
CH4) for energy production
Liner system  avoids a
contamination of ground water
Leachate system  collection and
treatment of fluid effluent
Groundwater monitoring  on-
going information about the
groundwater quality

59. Basic Landfill (Emergency Landfill)(HARVEY et al. 2002)
• Pit should be
backfilled with
excavated soil every
day.
• Site should be agreed
with local population
and authorities.
• Site should be fenced.
• At least 1 km
downwind from the
nearest dwellings.
59
Source: HARVEY et al. (2002)

60. Engineered Landfill (UNEP 2002)
• The capacity is planned and the site is chosen
based on an environmental risk assessment
study.
• Gas is flared or used for energy production.
60
Source: UNEP (2002)

61. Bioreactor Landfill (WM 2004)
61
• Acceleration of biologic decomposition (organic fraction).
• Promoting conditions necessary for the microorganisms (moisture
content).
• Liquids must be added (leachate, stormwater, sewerage sludge).
• Gas is collected to produce
electrical energy.
• Design includes liner, cover,
leachate system, groundwater
monitoring.
• 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
• Requires dedicated operators.
• Waste has to be covered each day.
• Proper leachate management.
• Cover must be resistant to erosion.
• Once capacity is reached, the bottom (cover layer) has to be
controlled regularly to avoid toxic effluents/emissions.
• Bioreactor landfills require a more complex set of O&M.

65. •Advantages:
– An effective disposal
method if well-managed.
– A sanitary disposal method
if managed effectively.
– Energy production and fast
degradation if designed as a
bioreactor landfill.
Disadvantages:
• Fills up quickly if waste is not reduced
and reusable waste is not collected
separately and recycled.
• A reasonable large area required.
• Risk of groundwater contamination if not
sealed correctly or the liner system is
damaged.
• High costs for high-tech landfills.
• If the management is bad, there is a risk
that the landfill degenerates into an
open dump.
• 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.

68. Biological treatment - composting and anaerobic
digestion, design and operation

69. Step by step process

71. 1. STAGE ONE: SCREENING
• Screening is the first stage of the wastewater
treatment process.
• 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.
• Special equipment is also used to remove grit
that gets washed into the sewer.

76. 2. STAGE TWO: PRIMARY TREATMENT
• This involves the separation of organic solid
matter (or human waste) from the
wastewater.
• This is done by putting the wastewater into
large settlement tanks for the solids to sink to
the bottom of the tank.
• The settled solids are called ‘sludge’.

77. • 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.
• The rest of the water is then moved to the
Secondary treatment.

83. 3. STAGE THREE: SECONDARY
TREATMENT
• The water, at this stage, is put into large
rectangular tanks.
• These are called aeration lanes.
• Air is pumped into the water to encourage
bacteria to break down the tiny bits of sludge
that escaped the sludge scrapping process.

86. 4. STAGE FOUR: FINAL TREATMENT
• Next, the ‘almost’ treated wastewater is passed
through a settlement tank.
• 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. • The water at this stage is almost free from
harmful substances and chemicals.
• The water is allowed to flow over a wall where
it is filtered through a bed of sand to remove
any additional particles.

95. Thermal treatment
- combustion,
- pyrolysis and
- gasification, design and operation

96. Thermal Processing of Solid Wastes
“it can be defined as the conversion of wastes into gaseous,
liquid and solid production, with or without energy
valorization.”
Thermal processes with respect to air
requirements:
combustion
gasification
pyrolysis

97. Thermal Processing of Solid Wastes
• Combustion is occurred by stoichiometric
amount of oxygen or excess air.
• Gasification is the partial combustion of
materials, thus materials convert to
combustible gases (such as carbon monoxide,
hydrogen, and gaseous hydrocarbons).
• Pyrolysis can be defined as destructive
distillation; materials are combusted with
absence of oxygen.

98. Thermal Conversion Processes and Products

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;
• Fixed-Hearth Incinerators
• Rotary Kiln Incinerators
• Refuse Derived Fuel Incinerators
• Fluidized Bed Incinerator

100. Pyrolysis
• 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.
• 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).
• Direct gasification occurs when an oxidant
gasification agent is used to partially oxidize the
feedstock.
• Indirect gasification occurs without an oxidizing
agent and needs an external energy source.

102. Gasification Processes

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.

106. Components of flue gas

107. The gas cleaning systems can be divided as follows:
1. Removal of particles or dust collection.
• Fabric filters
• Sand Band
• Electrostatic precipitators
2. Removal of water soluble gases: SO2, HCl, HF and NH3 Flue
• Gas Desulphurisation
• Wet scrubbing
• Dry scrubbing
• 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
• High dust separation
Efficiencies of over 99.95%
• Low clean gas dust content
of < 10mg/Nm3
• Low service and
maintenance cost
• 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
• High dust separation
efficiencies of over
99.95%
• Simultaneous separation of
gaseous pollutants
possible
• Large variety of
applications in all sectors

112. Sand bed filter
• Sand bed filters also use mass forces for removal of
particles.
• 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.
• 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.
• 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
• The exhaust gases of combustion may contain substances considered
harmful to the environment, and the scrubber may remove or neutralize
those.
• A wet scrubber is used for cleaning fuel gas containing various pollutants
and dust particles.
• 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.
• 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.
• 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
• 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.
• 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).
• 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.
• 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
• Anthropogenic nitrogen oxide emissions from
combustion processes are one factor responsible
for ozone destruction in the stratosphere.
• NOx- production from nitrogen in the air can take
place if there are very high temperatures (>1200 -
1300°C) in the furnace.
• The NOx comprises normally > 95% NO.
• 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

119. Bioaerosol control
Aerosols
• Very small (nm to µm) solid particles or liquid
droplets dispersed in air (gas)

120. Bioaerosols
Aerosols containing particles or substances of
biological origin e.g.:
- pollen from plants (10-100 µm)
- microorganisms: bacteria, fungi (1-10 µm)
- viruses (10-100 nm)
- parts of microorganisms/plants
- microbial substances (e.g. endotoxin, mycotoxin)
- substances from of animals (cat, dog, mite,
cockroach)

121. Natural Bioaerosols
Pollen Part of the life cycle of plants
Spores Part of the life cycle of fungi

122. Natural Bioaerosols
• Clearance mechanisms
• 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. • Elevated concentrations in the environment
• Indoor Air: Damp and mouldy buildings
• Health risks: - allergic reactions - upper
respiratory tract symptoms - cough, wheeze -
asthma exacerbation - unspecific health
problems?

125. Treatment of Leachate (SA’AT 2006)
125
Without proper cleaning, leachate will cause environmental problems. Potential
methods for treatment:
•Recirculation of leachate through the landfill
•Disposal off-site to sewer for treatment as an admixture with domestic sewage
•Physical-chemical treatment
•Membrane filtration
•Reverse osmosis
•Anaerobic biological treatment
•Aerobic biological treatment
•Constructed wetlands
Design of a vertical flow constructed wetland. Source: MOREL &
DIENER (2006)

126. Thank you