ERT 319
Industrial Waste Treatment
Semester 1 2012/2013
Huzairy Hassan
School of Bioprocess Engineering
UniMAP
Landfill & Incineration
Waste Treatment
Systems
LANDFILL
Introduction
- A landfill site (also known as tip, dump, rubbish
dump or dumping ground) is a site for the disposal
of waste materials by burial and is the oldest form of
waste treatment.
- Historically, landfills have been the most common
methods of organized waste disposal and remain so
in many places around the world.
- In Europe, follows EC Waste Landfill Directive (1999).
- Major advantages:
•
•
Waste landfill is low cost compared with other disposal
options and the fact that a wide variety of wastes are
suitable for landfill.
Collection & utilization of landfill gas as a fuel for energy
generation.
• However, landfill achieves a lower conversion of the wastes
into energy with about one-third less energy recovery per tonne
from landfill gas than incineration.
• This is due to the conversion of the organic materials in the
waste into non-combustible gases and leachate and general
losses from the system.
- Disadvantages:
 Older sites of landfill – still under current use or have
long been disused, were constructed before the
environmental impacts of leachate and landfill gas were
realized.
- now, sources of pollution with uncontrolled leakage.
- landfill gas can be hazardous, ex. largest component,
methane can reach explosive concentrations, and also
is a ‘greenhouse gas’, which has about 30 times the
effect of CO2.
- constructed close to housing areas, and some have
been built on disused landfill sites.
Site Selection and Assessment
- Depends on a wide range of criteria, including the
proximity (closeness) of the sites to the source of waste
generation, the suitability of access roads, the impact on
the local environment of site operations and the
geological and hydrogeological stability of the site.
-  the chosen sites will have no significant impact on
environment.
- Location requirements:
- The distance from the boundary of the site to residential areas,
waterways, and other agricultural or urban sites.
- The operator should report on the geological and
hydrogeological conditions of the area and the risks of hazards
such as flooding, landslides and avalanches (large mass slides, flood).
- levels of water and air quality.
Considerations for Landfills
1) Final landform profile – dictates after-use of the site, waste
capacity, and settlement of the site after completion and landscaping.
2) Site capacity
3) Waste density – typical range: 0.4 – 1.00 tonnes/m3
4) Settlement:
– due to physical rearrangement of wastes soon after emplacement.
- typical long term settlement for municipal solid wastes: 15-20
% reduction.
- can take place over 50 years, but the major settlement (up to
90%) occurs within first 5 years of the final emplacement of
wastes.
- involves 3 stages:
a) Initial compression: virtually instantaneous and due to
compaction of the void space and particles caused by
compression of overlying waste and the compaction vehicles.
b) Primary compression: due to dissipation of pore water and
gases from the void space and usually takes around 30 days.
c) Secondary compression: may take many years, due to waste
creep and biodegradation processes of wastes which produce
leachate and landfill gas thus, reduce mass and volume.
5) Material requirements – clay, sand, gravel and soil.
6) Drainage – drainage of rainwater on the site is required to
ensure that excessive water does not infiltrate the waste directly
or from run-off from surrounding areas
7) Operational practice
Types of Waste Landfilled
1) Hazardous waste: waste which is dangerous or difficult to
keep, treat or dispose of and may contain substances which are
corrosive, toxic, reactive, carcinogenic, infectious, irritant, toxic to
human and environment.
2) Non-hazardous waste: includes municipal solid wastes, and
wide range of industrial wastes, such as organic and inorganic
materials provided that they are non-hazardous  and
biodegradable.
3) Inert waste: waste that does not undergo any significant
physical, chemical or biological transformations  do not pose a
significant environemntal risk, not endanger surface / ground
water, no reactivity. Ex: bricks, glass, tiles and ceramic, concrete,
stones, etc.
Landfill Design and Engineering
- Key to design: barrier system at the base, sides and cap of the
waste landfill.
- Barrier liner system – from natural or synthetic materials – for
protection of surrounding soil and groundwater.
 To provide sufficient permeability and thickness requirements
at least equivalent to the following:
1) For hazardous waste landfill sites, hydraulic conductivity
(permeability) of ≤ 1.0 x 10-9 m/s, and liner material thickness
of ≥ 5m.
2) For non-hazardous waste landfill sites, hydraulic conductivity of
≤ 1.0 x 10-9 m/s, and liner material thickness of ≥ 1m.
3) For inert waste landfill sites, hydraulic conductivity of ≤ 1.0 x 10-9
m/s, and liner materialthickness of ≥ 1m.
Landfill liner materials
1) Natural clay – un-joined rocks composed of clay minerals
formed as breakdown products from weathering of preexisting rocks.
2) Bentonite-enhanced soils
3) Geosynthetic clay liners
4) Flexible membrane liners
Landfill Liner Systems
1) Single Liner System
- Suitable for low-risk wastes in sites where escape of
leachate poses negligible risk of contamination.
- Comprises of primary barrier consisting of a layer of
clay, bentonite-enhanced soil or hydraulic asphalt
- Above and below primary liner or barrier would be a
separation/protection layer of geotextile material, (ex:
non-woven, needlepunch fabrics-polyester /
polypropylene fiber  acts as a protective layer and
filter for fine suspended solids.
- Between the waste and separation/protection layer
would be a leachate collection system consisting of a
series of drainpipes or drainage layer.
- Beneath the liner, may be a groundwater collection
system.
Typical liner materials used in landfill liner systems
Process operating in waste landfills
Hydrogeological requirements for sustainable landfill design
Landfill Leachate
- Leachate represents the water which passes through the
waste from precipitation, and water generated from the
waste within the landfill site, resulting in a liquid
containing suspended solids, soluble components of the
wastes and products from the degradation of the waste by
various microorganisms.
- Associated with malodorous smell, due to presence of
organic acids.
- Composts of highly variable concentrations of wide range
of components such as salts, halogenated organic
compounds, trace metals, organic compounds (high
ammonia, etc).
Characteristics / categories of landfill leachate:
1) Dissolved organic material (quantifies as COD and TOC),
volatile fatty acids and fluvic and humic-like material.
2) Inorganic macro-components including Ca, Mg, Na, K,
Ammonium, Fe, Mn, Cl, Sulphate, and Bicarbonate compounds.
3) Heavy metals such as Cd, Cr, Cu, Pb, Ni, Zn compounds.
4) XOC which are compounds not degraded by organisms in the
environment and include aromatic hydrocarbons, pesticides,
plasticizers, chlorinated aliphatic compounds, etc. (originated
from household and industrial chemicals, present in low
concentrations)
Energy Recovery from Landfill Gas
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