SAB 4973: HAZARDOUS WASTE TREATMENT TECHNOLOGIES

1
SAB 4973HAZARDOUS WASTE TREATMENT TECHNOLOGIES
2
Technologies

• Chemical methods
• Coagulation, flocculation, combined with
  flotation and filtration, precipitation, ion
  exchange, electroflotation, electrokinetic
  coagulation.
• Physical methods
• Membrane-filtration processes (nanofiltration,
  reverse osmosis, electrodialysis, . . .) and
  adsorption techniques.
• Biological treatments
• Biodegradation methods such as fungal
  decolorization, microbial degradation, adsorption
  by (living or dead) microbial biomass and
  bioremediation systems

3
Adsorbents

• Adsorption techniques employing solid sorbents
  are widely used to remove certain classes of
  chemical pollutants from waters, especially those
  that are practically unaffected by conventional
  biological wastewater treatments. However,
  amongst all the sorbent materials proposed,
  activated carbon is the most popular for the
  removal of pollutants from wastewater
• They must have high abrasion resistance, high
  thermal stability and small pore diameters, which
  results in higher exposed surface area and hence
  high surface capacity for adsorption.
• The adsorbents must also have a distinct pore
  structure which enables fast transport of the
  gaseous vapors.

4
Most industrial adsorbents fall into one of three
classes

• Oxygen-containing compounds Are typically
  hydrophilic and polar, including materials such
  as Silica gel and Zeolites.
• Carbon-based compounds Are typically
  hydrophobic and non-polar, including materials
  such as activated carbon and graphite.
• Polymer-based compounds - Are polar or non-polar
  functional groups in a porous polymer matrix.

5
Concept of hydrophilic and hydrophobic
6
Concept of polar and non-polar
7
Silica gel

• prepared by the coagulation of colloidal silicic
  acid results in the formation of porous and
  noncrystalline granules of different sizes. It
  shows a higher surface area as compared to
  alumina, which ranges from 250 to 900 m2/g.
• silica is expensive adsorbent
• prepared by the reaction between from sodium
  silicate and acetic acid

8
Silica gel
9
Zeolites

• natural or synthetic crystalline aluminosilicates
  which have a repeating pore network and release
  water at high temperature. Zeolites are polar in
  nature.
• Zeolites have a porous structure that can
  accommodate a wide variety of cations, such as
  Na, K, Ca2, Mg2 and others.

10
Zeolites
11
Alumina

• Aluminium oxide (Al2O3), a synthetic porous
  crystalline gel, which is available in the form
  of granules of different sizes having surface
  area ranging from 200 to 300 m2 /g
• The most common form of crystalline alumina is
  known as corundum, a octahedral crystalline.

12
Alumina
13
Activated carbon

• is the oldest adsorbent known and is usually
  prepared from coal, coconut shells, lignite, wood
  etc., using one of the two basic activation
  methods physical and chemical
• is a highly porous, amorphous solid consisting of
  micro crystallites with a graphite lattice,
  usually prepared in small pellets or a powder. It
  is non-polar and cheap. One of its main drawbacks
  is that it is reacts with oxygen at moderate
  temperatures (over 300 C).

14
Activated carbon
15
Structure of activated carbon
16
Process of producing activated carbon
17
Environmental applications

• Spill cleanup
• Groundwater remediation
• Drinking water filtration
• Air purification
• Volatile organic compounds capture from painting,
  dry cleaning, gasoline dispensing operations, and
  other processes.

18
Activated carbon is usually used in water
filtration systems.
19
Low cost activated carbon

• Chitosan
• Banana peel
• Orange peel
• Bagasse pith
• Saw dust
• Coconut shell
• Bark
• Bamboo dust

20
Biodegradation/bioremediation

• The chemical breakdown of materials by living
  organisms in environment.
• Organic material can be degraded aerobically with
  oxygen, or anaerobically, without oxygen.
• The process depends on certain microorganisms,
  such as bacteria, yeast, and fungi.

21
Biodegradation factors of polymer

• Polymer structure
• Polymer morphology
• Effects of radiation
• Molecular weight

22
Polymer structure

• Natural macromolecules, e.g. protein, cellulose,
  and starch are generally degraded in biological
  systems by hydrolysis followed by oxidation.

23
Linear structure
24
Branched structure
Amylopectin
25
Network structure
26
Biodegradability
Since most enzyme-catalyzed reactions occur in
aqueous media, the hydrophilichydrophobic
character of synthetic polymers greatly affects
their biodegradabilities. A polymer containing
both hydrophobic and hydrophilic segments seems
to have a higher biodegradability than those
polymers containing either hydrophobic or
hydrophilic structures only. the flexible
aliphatic polyesters are readily degraded by
biological systems, the more rigid aromatic
polymer compound is generally considered to be
bioinert.
27
Polymer morphology

• One of the principal differences between
  biopolymer and synthetic polymers is that
  biopolymer do not have equivalent repeating units
  along the chains.
• This regularity enhances crystallization, making
  the hydrolyzable groups inaccessible to enzymes.
  It was reasoned that synthetic polymers with long
  repeating units would be less likely to
  crystallize and thus might be biodegradable.

28
Effects of radiation

• Photolysis with UV light and the ?-ray
  irradiation of polymers generate radicals and/or
  ions that often lead to cleavage and
  crosslinking. Oxidation also occurs, complicating
  the situation, since exposure to light is seldom
  in the absence of oxygen.

29
Molecular weight

• Low molecular weight hydrocarbons, however, can
  be degraded by microbes.
• Plastics remain relatively immune to microbial
  attack as long as their molecular weight remains
  high.

30
Aerobic biodegradation pathways of aromatic
compounds in bacteria and fungi
31
Anaerobic biodegradation of benzoate
32
Methods of biodegradation

• Under appropriate conditions of moisture,
  temperature, and oxygen availability,
  biodegradation is a relatively rapid process
• Two types of microorganisms are of particular
  interest in the biodegradation of natural and
  synthetic polymers bacteria and fungi.

33
Bacteria
34
Shape of bacteria
35
(No Transcript)
36
(No Transcript)
37
Mushroom
38
Type of fungi for biodegradation

• White rot mushroom
• Brown rot mushroom
• Soft rot mushroom

39
White rot mushroom

• White rot fungi can degrade all cell wall
  components, including lignin. They often cause a
  bleaching of normal wood coloration. Their
  ability to metabolize large amounts of lignin in
  wood is unique among microorganisms.

40
(No Transcript)
41
Brown rot mushroom

• Brown-rot mushroom depolymerase cellulose rapidly
  during incipient stages of wood colonization.
  Considerable losses in wood strength occur very
  early in the decay process, often before decay
  characteristics are visually evident.

42
Brown-rot mushroom commonly cause decay in living
trees, downed timber and wood used in buildings.
Cell wall carbohydrates are degraded extensively
during decay leaving a modified, lignin-rich
substrate .
Scanning electron micrograph of brown-rotted
wood. Only slight pressure causes the wood cell
walls to crumble into minute fragments.
43
Soft rot fungi

• Fungi that cause soft-rot are taxonomically
  classified in the subdivisions, Ascomycota and
  Deuteromycota.
• However, soft rots can occur in dry environments
  and may be macroscopically similar to brown rot.

44
Soft rot in wood often appears brown and can be
confused with decay caused by brown rot fungi.
Soft rot is different from other types of wood
decay. Chains of cavities are produced inside the
cell wall. This micrograph taken of a section
from soft-rotted wood and viewed with a light
microscope shows cavities within the cell walls.
45
Two distinct types of soft rot are currently
recognized.

• Type 1 is characterized by longitudinal cavities
  formed within the secondary wall of wood cells
  and
• Type 2 used to describe an erosion of the entire
  secondary wall. The middle lamella is not
  degraded (in contrast to cell wall erosion by
  white-rot fungi), but may be modified in advanced
  stages of decay.

46
Different of white and brown rot

• White rot fungi, found in the wood of deciduous
  trees, first attack the lignin of wood. Once the
  lignin is digested, the fungi destroy cellulose
  and other major parts of cells. The partially
  decayed wood with residual cellulose is off-white
  in color, hence the name "white rot fungi." Brown
  rot fungi, found in conifers, damage the
  cellulose first but do very little, if any,
  damage to the lignin. The name "brown rot fungi"
  came about because infected wood becomes dark
  reddish-brown to golden in color.

47
White Rot mushroom Degradation System

• Three types of extracellular enzymes are produced
  by white rot fungi that are non-selective yet
  effective in attacking lignin.  These are often
  referred to as Lignin Modifying Enzymes
  (LMEs)/ligninolytic enzymes, and they are Lignin
  Peroxidase (LiP), Manganese-Dependent Peroxidase
  (MnP) and Laccase (Lac).

48
Lignin peroxidase

• LiP  Not all white rot fungi produce LiP, but it
  is a key component for the fungi that are being
  investigated for use. 
• LiP oxidises methoxyl groups on aromatic rings
  (R-O-CH3), and can work on substrates with quite
  high redox potentials.

49
Manganese peroxidase

• MnP is another enzymes containing peroxidase, and
  uses H2O2 to catalyse oxidation of Mn² to Mn³,
  this in turn oxidises phenolic substrates. 
• Although similar in action to LiP, it does not
  have the same ability to oxidize substances with
  higher redox potentials.

50
Laccase

• Laccase is a multi copper oxidase which has the
  ability to oxidise phenolic compounds.  In the
  presence of oxygen, it converts phenolic
  compounds into quinone radicals and then further
  converts them to quinones.  It also produces some
  co-substrates which can be useful for
  degradation.

51
(No Transcript)
52
(No Transcript)
53
(No Transcript)
54
(No Transcript)
55
(No Transcript)
56
(No Transcript)
57
(No Transcript)
58
(No Transcript)
59
(No Transcript)
60
(No Transcript)
61
(No Transcript)
62
(No Transcript)
63
(No Transcript)
64
(No Transcript)
65
(No Transcript)