Biological methods of waste disposal. mujahid hussain

Mujahid Hussain (12)
Department of botany, University of Sargodha
6/15/2017 1
Mujahid Hussain (M.Phil Botany) Department of Botany, University
of Sargodha. (mujahid.hussain7877@gmail.com)

Waste:
“Waste is any substance which is discarded after primary
use, or it is worthless, defective and of no use”.
Examples include municipal solid waste (household trash/refuse),
hazardous waste, wastewater (such as sewage), radioactive waste,
and others.
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Waste Disposal:
“Waste management or Waste disposal is all the activities and
actions required to manage waste from its inception to its final
disposal”.This includes collection, transport, treatment and disposal
of waste together with monitoring and regulation.
 The term normally relates to all kinds of waste. Waste
management is intended to reduce adverse effects of waste
on health, the environment or aesthetics.
 Waste management practices are not uniform among countries
(developed and developing nations); regions (urban and rural area),
and sectors (residential and industrial).
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Methods of Waste Disposal:
 Physical Methods
 Biological Methods
 Chemical Methods
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Biological Methods:
 Composting
 Anaerobic Digestion
 Bio drying
 Mechanical Biological Treatment
 Microbial Fuel Cell
 Phytoremediation
 Biofiltration
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Composting
“Composting is transformation of organic material (plant
matter) through decomposition into a soil- like material called
compost”.
Invertebrates (insects & earthworms) & microorganisms (bacteria
& fungi) help in this transformation.
e.g. Grass clippings, Leaves, Food scraps
Compost
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Microorganisms:
 Bacteria- The most numerous of all the microorganisms found in
compost.
 Actinobacteria- Necessary for breaking down paper products such as
newspaper, bark, etc.
 Fungi- Molds and yeast help break down materials that bacteria cannot,
especially lignin in woody material.
 Protozoa- Help consume bacteria, fungi and micro organic particulates.
 Rotifers- Rotifers help control populations of bacteria and small
protozoans.
 In addition, earthworms not only ingest partly composted material, but
also continually re-create aeration and drainage tunnels as they move
through the compost.
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Process:
 At the simplest level, the process of composting requires making
a heap of wetted organic matter known as green waste (leaves, food
waste) and waiting for the materials to break down
into humus after a period of weeks or months.
 Modern, methodical composting is a multi-step, closely
monitored process with measured inputs of water, air, and carbon-
and nitrogen-rich materials.
 The decomposition process is aided by shredding the plant
matter, adding water and ensuring proper aeration by regularly
turning the mixture.
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 Worms and fungi further break up the material.
 Bacteria requiring oxygen to function (aerobic bacteria) and
fungi manage the chemical process by converting the inputs into
heat, carbon dioxide and ammonium.
 The ammonium (NH4) is the form of nitrogen used by plants.
When available ammonium is not used by plants it is further
converted by bacteria into nitrates (NO3) through the process
of nitrification.
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Advantages of Composting:
 Compost is rich in nutrients. It is used
in gardens, landscaping, horticulture, and agriculture.
 The compost itself is beneficial for the land in many ways,
including as a soil conditioner, a fertilizer, addition of vital
humus or humic acids, and as a natural pesticide for soil.
 In ecosystems, compost is useful for erosion control, land and
stream reclamation, wetland construction, and as landfill cover.
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Anaerobic Digestion
“Anaerobic digestion is a collection of processes by
which microorganisms break down biodegradable material in the
absence of oxygen”.
 The process is used for industrial or domestic purposes to manage
waste or to produce fuels.
 Much of the fermentation used industrially to produce food and
drink products, as well as home fermentation, uses anaerobic
digestion.
 Anaerobic digestion occurs naturally in some soils, lake and
oceanic basin sediments, where it is usually referred to as "anaerobic
activity".
 This is the source of marsh gas methane as discovered by Volta in
1776.
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4 steps in Anaerobic Conversion
Remember: this is not a complete
conversion -
some organic matter will remain
(digestate)
Note that biogas is a mixture – not
only the useful CH4
Depending on the substrate there
can be other gases too.
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Process:
 The digestion process begins with bacterial hydrolysis of the
input materials. Insoluble organic polymers, such
as carbohydrates, are broken down to soluble derivatives that
become available for other bacteria.
 Acidogenic bacteria then convert the sugars and amino
acids into carbon dioxide, hydrogen, ammonia, and organic acids.
These bacteria convert these resulting organic acids into acetic
acid, along with additional ammonia, hydrogen, and carbon
dioxide.
 Finally, methanogens convert these products to methane and
carbon dioxide.
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AnaerobicDigester
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Applications:
 Waste and wastewater treatment.
 Reduces the emission of landfill gas into the atmosphere.
 Power generation.
 Fertilizer and soil conditioner.
 Cooking gas.
 Vehicle fuel.
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Bio drying
“Bio drying is the process by which biodegradable waste is
rapidly heated through initial stages of composting to remove moisture
from a waste stream and hence reduce its overall weight.”
 The major portion of biological heat is utilized to evaporate surface
and bound water associated with the mixed sludge. This heat
generation assists in reducing the moisture content of the biomass
without the need for supplementary fossil fuels, and with minimal
electricity consumption.
 It can take as little as 8 days to dry waste in this manner. This
enables reduced costs of disposal if landfill is charged on a cost per
tonne basis.
 Bio drying may be used as part of the production process
for refuse-derived fuels..
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Mechanical Biological Treatment
“A mechanical biological treatment (MBT) system is a type of
waste processing facility that combines a sorting facility with a
form of biological treatment such as composting or anaerobic
digestion”.
 MBT plants are designed to process mixed household waste as
well as commercial and industrial wastes.
 This system enables the recovery of materials contained within
the mixed waste or produce a Refuse-derived fuel that can be
used for the generation of power.
• Mechanical Sorting
• Biological Processing
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Advantages:
 Renewable fuel (biogas) leading to renewable power.
 Recovered recyclable materials such as metals, paper,
plastics, glass etc.
 Digestate - an organic fertilizer and soil improver.
 Residual unusable materials prepared for their final safe.
treatment (e.g. incineration or gasification) and/or landfill.
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Microbial Fuel Cell (MFC)
“A microbial fuel cell (MFC), or biological fuel cell, is a bio-
electrochemical system that drives an electric current by using bacteria
and mimicking bacterial interactions found in nature.”
 MFCs are used in water treatment to harvest energy
utilizing anaerobic digestion.
 They also derive energy directly from certain plants. This
configuration is known as a plant microbial fuel cell. Possible plants
include reed sweetgrass, cordgrass, rice, tomatoes and algae.
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Phytoremediation
“The process of removing contamination from soil or water using
potential plants”.
 The plant potential to uptake, accumulate and degradation of
contaminants vary from plant to plant.
 This technology has many advantages, beneficial in that way because it is
inexpensive, natural, conserves soil resources and has no secondary
contaminations and enhances the soil quality and productivity.
 Phytoremediation can be performed by following different methods:
1. Phytoextraction
2. Phytostabilization
3. Phytovolatilization
4. Phytotransformation
5. Phytostimulation/Rhizodegradation
6. Rhizofilteration
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Biofiltration
“Biofiltration is a pollution control technique using
a bioreactor containing living material to capture and
biologically degrade pollutants”.
Common uses include processing waste water, capturing
harmful chemicals or silt from surface runoff, and micro
biotic oxidation of contaminants in air.
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Process:
 A biofilter is a bed of media on which microorganisms attach and
grow to form a biological layer called biofilm. Generally, the
biofilm is formed by a community of different microorganisms
(bacteria, fungi, yeast, etc.), macro-organisms (protozoa, worms,
insect’s larvae, etc.) and extracellular polymeric substances.
 Water to be treated can be applied continuously over the media,
via upflow or downflow. Typically, a biofilter has two or three
phases, depending on the feeding strategy (percolating or
submerged biofilter):
 a solid phase (media);
 a liquid phase (water);
 a gaseous phase (air).
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 Organic matter and other water components diffuse into the
biofilm where the treatment occurs, mostly by biodegradation.
Biofiltration processes are usually aerobic, which means that
microorganisms require oxygen for their metabolism. Oxygen can
be supplied to the biofilm with water flow.
 Microorganisms' activity is a key-factor of the process
performance. The main influencing factors are the water
composition, the biofilter hydraulic loading, the type of media, the
feeding strategy (percolation or submerged media), the age of the
biofilm, temperature, aeration, etc.
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Thank You 
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Biological methods of waste disposal. mujahid hussain

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