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Industrial Wastewater
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Industrial Wastewater
The water or liquid carried waste froman industrial process
These wastes may result from anyprocess or activity of industry,manufacture, trade or business, fromthe development of any naturalresource, or from animal operations
such as feedlots, poultry houses, ordairies The term includes contaminated
storm water and leachate from solid waste facilities
Waste material (solid, gas or liquid)
generated by a commercial, industrialor nonresidential activity
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What is pollution?
Pollution means:
…changes in the physical, chemical and biological characteristics of air, land and
water
…
harms for the human and other living species, and,
…degradation of the ecosystems
...the undesirable state of the natural environment being contaminated with
harmful substances as a consequence of human activities
For example, Water Pollution refers to contaminants
in aquatic ecosystems
(streams, lakes, etc) which render them unfit for a particular use.
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Pollutants can reach:
1. Air
2. Water
3. Solid waste
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Water standards:
Drinkable
Recreation: swimming, fishing.
Irrigation
Water impurities may or may not be harmful; it depends on:
• The amounts and nature of these impurities,• The next use to which the water will be put, and
• The tolerance of these impurities for the next use.
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Types and characteristics of wastewaters:
Contaminants Reason for importance
Physical suspended solids
They can lead to the development of sludgedeposits.
Chemical biodegradable
organics
When discharged untreated to theenvironment, they lead to the depletion of
natural oxygen resources.
Nutrients
If discharged, they can lead to waterpollution.
Hazardous
Because of their characteristics(e.g.,toxicity, flammability) are dangerousfor human health and the environment.
Heavy metals
They can negatively impact upon biologicalwaste treatment processes.
Dissolved inorganic solids
They are result of water use, and may haveto be removed if the wastewater is to be
reused.
Biological pathogens
Communicable diseases can be transmittedby the pathogenic organism in wastewater.
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Water standards
Industrial effluent standards
Parameter Mexico a USA b
Canada c
Total suspended
solids, mg/l)
150 27 15
BOD5, mg/l)
20 56 15
pH 5-10 6-9 6-10.5
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What is BOD?
By definition, BOD is the quantity of oxygen required for the stabilization of the
oxidizable organic matter present over 5 days of
incubation at 20 oC; that can be explained as a measure of the oxygen required
by microbes to degrade a sample of effluent.
The organic content of the water can be estimated by the BOD.
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Biochemical Oxygen Demand (BOD)
Definition: The amount of dissolved oxygen utilized by microbes for
the biochemical oxidation of organic (carbonaceous BOD) and
inorganic (autotrophic or nitrogenous BOD)
The BOD test was developed in 1930’s. This is a five day test that measures
the amount of O2 consumed in a wastewater sample by a mixed population of
heterotrophic bacteria in the dark at 20o
C
BOD of wastewater is typically 110-440 mg/L and must be reduced to 20 mg/L
for discharge
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BOD = Di – Df
P
where:
Di = initial dissolved O2 concentration
Df = final or 5-day dissolved O2 concentration
P = volumetric fraction of wastewater
Example: 5 ml wastewater is added to a 300 ml BOD flask
P = 5 = 0.0167 Di = 8 mg/L Df = 2 mg/L300
BOD = 8 – 2 = 359 mg/L0.0167
Oxidation is usually 60-70% complete after 5 days
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Total Organic Carbon (TOC)
TOC is measured using a TOC analyzer. The sample is combusted and
organic carbon quantified using infrared detection.
Chemical Oxygen Demand (COD)
COD is measured following digestion at high temperature with strong
oxidant such as chromic acid, or sulfuric acid/potassium dichromate. The
chromate ion reacts with the COD producing a color that is measured.
If COD >> than BOD what does this mean?
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Why should we minimize the use of water?
Water is such an important part of many manufacturing processes
that we must consider Effluent Treatment as a part of the main
process because of the great amount always involved.
Water is abstracted from aquifers and rivers, treated and supply to
industries and homes for different uses; used water is supposed to
be treated and discharged again into the rivers. Most of the times,
this water returns to its natural environment but unfortunately, with
a greater heat content or with some substances added.
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Why should we minimize the use of water?
It is also important to minimize use of water because of several reasons:
Fresh water is often scarce. High costs involved operating effluent treatment plants.
Difficult to separate all the elements that pollute water.
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Industrial pollution problems
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Industrial pollution problems:
The main pollution problems are related to :
Increasing use of water for agriculture.
The increase of aqueous effluent to receiving water.
Population growth. Industrial products and services.
The mental, technical, financial, regulatory and institutional barriers toimplement preventive modern technologies.
RESULTS:Ecosystems decline.
Industrialization social costs.
The increase of human diseases.
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The petroleum industry
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The Petroleum Industry:
Crude oil refining operations involve extracting useful petroleum products from
crude oil. Crude oil contains fractions of napthas, gasoline, gas oils, diesel fuel,
asphalt, jet fuel and lubrication fuels.
Large quantities of production wastes are produced during exploration andproduction:
Wastewater
Solid waste
Toxic pollutants
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The Petroleum Industry:
Production wastes in the petroleum industry can be grouped broadly into 2classes:
• Wastes related to drilling including chemical additives: treatment and disposal
of oil drilling wastes takes place either on or off the drilling site.
• Wastes related to oil production, primarily produced water:
The volume of produced water exceeds the volume of drilled wastes.
If environmental quality standards are not exceeded the remainder may be
discharged to surface waters. The majority of produced water is disposed ofunderground through injection wells and it is permitted under U.S. EPAcontrol programs.
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What is refinery effluent?
Petroleum refineries use large volumes of water in their processes.
The wastewater contains hazardous chemicals:
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Refinery wastes:
Emissions from refineries include:
Sulphur oxides
Nitrogen oxides
Benzene, toluene and xylene
VOC
Wastewater containing BOD levels
Heavy metals
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Pollution Approximate Quantities
Cooling systems 3.5-5 m3 of wastewater generated per ton of crude.
Polluted wastewater
BOD 150-250 mg/l
COD 300-600 mg/l
phenol 20-200 mg/l
oil 100-300 mg/l (desalted water)
oil 5000 mg/l in tank bottom
benzene 1-100 mg/lheavy metals 0.1-100 mg/l
Solid waste and sludge
3 to 5 kg per ton of crude (80 % should be considered as hazardous wastebecause of the heavy metals and toxic organic presence).
VOC emissions 0.5 to 6 kg/ton of crude.
Others emissions
BTX (Benzene, Toluene and Xylene) 0.75 to 6 g/ton of crudeSulphur oxides 0.2-0.6 kg/ton of crudeNitrogen oxides 0.006-0.5 kg/ton of crude
Wastes generated:
(Pollution Prevention and Abatement Handbook World Bank Group)
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Programs for reducing pollution
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Government programs for reducingpollution:
For sustainable development, governmental pollution prevention programs can
best counteract the pressure to invest in “end of pipe” pollution solutions
by demonstrating the economic and environmental benefits of a source
reduction approach, making technical information available andproviding technical assistance.
EPA has been working with industry and government representing
environmental, community and work force issues to prevent pollution at
the source prior to “end of pipe” treatment.
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Government programs for reducingpollution:
Laws such as NEPA, TCSA, CAAA and PPA remain outside the scope of most
pollution control work. The following options were suggested for USEPA for
moving forward interaction in the US:
1. Add multi-media provisions to the existing regulations.
2. Correct laws in other policy sectors with environmental measures.
3. Make NEPA a stronger statute.
4. Make TSCA a law which can use EPA programs to control and reduce toxic
substances.
5. Establish pollution prevention approaches.
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Programs for reducing pollution:
Manufacturers could implement a variety of
improved management procedures
that would aid pollution reduction:
Environmental audits. Identify (inventory) and correct problems (strategies to achieve
reductions) that generate wastes.
Regular preventive maintenance. Inspection, maintenance and replacement of
equipment.
Material handling and storage. Emissions of hazardous material must be avoided. There
should be labels of all containers and first aid recommendations.
Employee training. Well informed employees are better able to make valuable waste
reduction suggestion.
Operating manual and record keeping. Good facility documentation: process
procedures, control parameters, hazards and operator responsibilities.
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Environmental programs:
Some industries may see no difference between end of pipe pollution control and a front end
pollution prevention control.
The importance is that those industries may not go beyond the first stage of waste reduction.
As the environmental concern deepens, industries have to move further up the production chain:
End of pipe solution to wastes and pollutants; and later
Internal process modifications to reduce emissions and wastes, and eventually
Redesign products to achieve a maximum level of recycling of raw materials andminimization of wastes after the products are used.
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Some measurements to save water:
Keep water effluent streams separated.
Reuse water as close to source as possible.
Recycling whenever it is possible.
Better control of usage with automated systems.
Checking and control of leaks.
When buying new equipment, evaluate water-efficiency models
including accessories.
Reducing the quantities of chemicals so that the amount of dilution
water will be reduced.
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Reusing water:
It is not only possible but necessary to reuse wastewater of a process stream before
it leaves the plant accomplished by piping, diluting or treating some of the
effluents before using them again.
Some plants are now using closed systems, so that there are no water discharges.Zero discharges has been practiced in locations where water is scarce, and may
involve technologies for removing suspended and dissolved solids.
Complete demineralization is relatively expensive, however, in some cases
wastewater discharges can be reduced significantly with other less expensive
technologies.
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Treatment processes
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Expectations of a water treatment program:
The expectations from a water treatment program should be integrated to include
all aspects of the program, from the proposal through to the implementation
stages.
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Treatment Program
As we will see in the next diagram, the expectations that a good treatmentprogram should give us are listed below:
Overview of a new or existent problem.
Lab study of all system and water composition.
Submit a proposal.
Program implementation.
Monitoring to optimize.
Use of modern treatment techniques.
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Program under control
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Treatment Program
New orProblem
System
PlantStudy
LabStudy
Proposal Implement
Program
Follow-up
New ProductTechnology
Systemundercontrol
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Wastewater treatment processes:
Wastes are generated by every industrial enterprise, and this wastes can either beliquids or solids.
Wastewater treatment can be divided into three stages: 1. Primary treatment that uses physical operations to remove free oil and/or
suspended solids.
2. Secondary treatment to remove dissolved contaminants through chemical
or biological action, and
3. Tertiary treatment for the removal of residual contaminants.
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Separation order
This list shows how separation is carried out:
Primary treatment
• Sedimentation
• Aeration
Secondary treatment
Tertiary treatment
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Treatments…
Primary treatment prepares the wastewater for biological treatment. Large
solids are removed by screening, and grit. Equalization in a mixing basin, levels
out the flows variation and concentrations. Neutralization, where required,
follows equalization. Oils, greases and suspended solids are removed by
flotation, sedimentation of filtration.
Secondary treatment is a biological degradation of soluble organic compounds
from input levels of 50- 1000 mg/l BOD or greater to effluent levels under 15
mg/l. Aerobic treatment in an open vessel is done. After biotreatment, themicroorganisms and solids suspended are allowed to settle.
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Treatments…
The tertiary treatment remove specific residuals. By filtration, suspendedcolloidal solids can be removed; adsorption removes organics by granularactivated carbon (GAC); and chemical oxidation also removes organiccompounds.
Tertiary systems have to treat great amounts of wastewater, so they areexpensive.
When streams rich in heavy metals, pesticides or other substances that may passthrough primary treatment and inhibit biological treatment are present, in-
plant treatmentsare necessary.Precipitation, activated carbon adsorption, chemical oxidation, air or steam
stripping, wet air oxidation, ion exchange, reverse osmosis are some of themethods useful when in-plant treatments are to be used.
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The tertiary treatment…
Tertiary treatment is a polishing step. Its importance is that rather than have to
find solutions at the end of pipe, where primary and secondary treatments are
used to, it is possible to minimize some toxics or hazardous components in the
process before they are combined with other less “hazardous”.
Biological treatment usually produces a ’30/20’ effluent with no more than 30
mg/l suspended solids and 20 mg/l BOD.
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Tertiary treatment
However, river flows have decreased owing to drought conditions. In these
circumstances, new limits are imposed on the quality of the final effluent. The
treatment processes beyond the secondary treatment to achieve the required limits
in the process are well known as tertiary treatments.
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In plant treatment
Before end of pipe wastewater treatment, a program of waste minimization
should be initiated.
1. Recirculation. In the paper board industry, white water from a paper
machine can be put through a save all to remove the pulp and fiber and
recycled to various points in the process. 2. Segregation. Clean streams are separated for direct discharge.
3. Disposal . In many cases, the total discharge BOD and suspended solids
can be reduced by removal of residue in semidry state for disposal.
4. Reduction. The use of automatic cutoffs can reduce the wastewater
volume. 5. Substitution. The substitution of chemical additives of a lower pollutional
effect in processing operations.
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.
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Wastewater treatment processes:
Process selection
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Figure 1. Conceptual treatment program fororganic and toxic industrial wastewater
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Organicstreams
Streams containing
heavy metals
Mineralstreams
Source control
Figure 3.
Equalization
NeutralizationOil/grease removal
Suspended solids
Biological treatment
Final disposal
Biodegradable volatile
Toxic and/or
nonbiodegradable
To define the wastewater treatment problems, a preliminary analysis should be carried out:
For wastewaters containing nontoxic organics, process design criteria can be obtained from lab studies.
(Eckenfelder, 2000)
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Source treatment:
Source reduction is any activity that reduces or eliminates the generation ofhazardous wastes at the source
The fundamental goal is to enact changes in consumption, use and waste
generation patterns associated with products
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Source treatment:
Source treatments involves different definitions of source reduction, but the
general consensus appears to be that include any in-plant actions to reduce
the quantity or the toxicity of the waste at the source.
Examples include equipment modification, design and operations changes of
the process and products and substitution of raw materials.
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Figure 2. Laboratory studies for heavymetals/volatile organics
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Prioritypollutants
scan and
bioassay
Fed
batch
reactor
Long-term
biodegradation
Priority
pollutants
scan and
bioassay
Equalized
sample
Air or steam
strippingChemical
oxidation
reduction
Precipitation
Source
treatment
Granular
activated
carbon
Powder
activated
carbon
Reverse
osmosis
Ion
exchange
Nondegradable/ toxic
Degradable
VOC/NH 3
Heavy metals
Priority pollutants/toxic
TDS/inorganics
start
(Eckenfelder, 2000)
When toxic and nontoxic organics and
inorganics are present, it is necessary to
evaluate the existence of heavy metals or
volatile organics.
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Figure 3. Treatment of toxic wastewater:In-plant treatment
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Ion
exchange
Filtration
Precipitation
Oxidation
reduction
Polymeric
resins
Granular
carbon
adsorption
Anaerobic
treatment
Wet air
oxidation
Chemical
oxidation
Reverse
osmosis
Air or steam
stripping
Process
wastewater
Heavy
metals
Organic
chemicals
Volatile
organics
ammonia
To discharge
recycle or
treatmentIf the wastewater is
nonbiodegradable or toxic, it
should be considered source
treatment or in-plant
modification.
(Eckenfelder, 2000)
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Methods for suspended solids removal
Sedimentation is the more common technique in wastewater treatment
because it involves little mechanical equipment and it is very stable to operate.
However, there are some situations where flotation is a better choice.
Flotation is a good technique for solids removal when the density difference
between water and the solids is marginal, or the solids have a high fat or oil
content.
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Methods for suspended solids removal
Coagulation is employed for removal of waste materials in suspended or
colloidal form. Colloids are particles within the size range of 1 nm to 0.1 nm, do
not settle out on standing and can not be removed by conventional physical
treatment processes.
Precipitation. In the water treatment, the precipitation process is used for
softening (removal of the hardness caused by calcium and magnesium) and
removal of iron and manganese.
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Flotation:
Dissolved air flotation, which is a common technique. This technique basically
consists on injecting an aqueous stream containing dissolved air into the
wastewater . The dissolved air forms bubbles when it comes out of solution
and carries suspended particles, which tend to concentrate at the bubble
wastewater interface, to the surface, where they form an emulsion.
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Flotation:
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General diagram for flotation methods:
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Coagulation:
Paperboards wastes can be effectively coagulated with low dosages of alum. Silica
or polyelectrolyte will aid in the formation of a rapid settling f loc.
Wastes that contain emulsified oil can also be clarified by coagulation.
For effective coagulation, alkalinity should first be added, . After addition of alkali
and coagulant, a rapid mixing is recommended.
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Heavy Metals Removal:
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HEAVY METALS REMOVAL TECHNOLOGIES
onventional precipitation
Hydroxide
Sulfide
carbonate
coprecipitationEnhanced precipitation
Dimethyl thio carbamate
Diethyl thio carbamate
Trimercapto-s-triazine, trisodium salt
Other methods
Ion exchange
Adsorption
Recovery opportunities
Ion exchange
Membranes
Electrolytic techniques
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The Biological Treatment
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Influent
wastewater
Physical and
chemical treatment Biodegradable
High
strength
Anaerobic
treatment
Discharge PACTInhibitory
Nondegradable
fraction
Polished
effluent
Dispersed
growth system
Complete mix
system
Readily
degradable
Nitrogenremoval
required Fixed
Growth system
Discharge
DischargeDischarge
Intermittent
process
Nitrification/
Denitrification
system
Plug
flow system
Selector
systemPolished
effluent
High
strength
Yes Yes
Yes
Yes
Yes
Yes Yes
No
No
No
No No No
No
(Eckenfelder, 2000)
When biological
treatment is
needed, there are
several options:
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The biological treatment: typical operatingparameters and dimensions
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Treatment
methodMode of operation
Degree of
treatmentLand requirements Equipment Remarks
Lagoon
Intermittent or continuous
discharge; facultative or
anaerobicIntermediate
Earth dug; 10-60 days’
retention
Odor control
frequently required
Activated
lagoons
Completely mixed or facultative
continuous basins
High in summer;
less in winter
Earth basin, 8-16 ft
deep, 8-16
acres/(million gal/d)
Pier-mounted or
floating surface
aerators or
subsurface diffusers
Solids separation in
lagoon; periodic
dewatering and sludge
removal
Activated
sludge
Completely mixed or plug flow;
sludge recycle
> 90% removal oforganics
Earth or concrete basin; 12p20 ft deep;
75000-350000ft3/(million
gal/d)
Diffused or
mechanical aerators;
clarifier for sludge
separation and
recycle
Excess sludge
dewatered and
disposed of
Trickling filterContinuous application; may
employ effluent recycle
Intermediate or
high, depending on
loading
225-1400 ft /(milliongal/d)
Plastic packing 20-
40 ft deep
Pretreatment before
POTW or activated
sludge plant
RBC Multistage continuous Intermediate or high Plastic disksSolids separation
required
Anaerobic
Complete mix with recycle;
upflow or downflow filter,
fluidized bed; upflow sludge
blanket
Intermediate
Gas collection
required;
pretreatment before
POTW or activated
sludge plant
Spray
irrigation
Intermittent application of
waste
Complete; water
percolation into
groundwater and
runoff to stream
40-300 gal/(min.acre)
Aluminum irrigation
pipe and spray
nozzles; movable for
relocation
Solids separation
required; salt content
in waste limited
(Eckenfelder, 2000)
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Advanced wastewater treatments
Advanced wastewater treatment is defined as the processes that remove more pollutants
from wastewater than the conventional treatments. This term may be applied usually as
tertiary treatment, but most of their goals are to remove nitrogen, phosphorus, and
suspended solids.
Advanced treatments include: Chemical coagulation of wastewater
Granular media filters
Ultrafiltration
Nanofiltration
Wedge-wire screens
Microscreening
Diatomaceous earth filters
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Volume and disposal reduction
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Volume reduction
Volume reduction can be used to reduce treatment cost and to reduce handling
and disposal costs for residues remaining after treatment. Volume reduction
can be accomplished by using a variety of methods:
Reuse of treated wastewater and wastes
Treatment modifications to reduce solid residues
Segregated treatments to reduce hazardous waste mixtures
Incineration to reduce waste volume and to render a hazardous wastenonhazardous.
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Reduction of waste production and disposal volumes
Simple dewatering: the sludge is discharged into a series of tanks and allowed to
settle. Top water can then be decanted. This method reduce the volume of
sludge for disposal.
Composting: the material is mechanically turned at intervals, force aerated and
often contained in a building where heat losses, odor and water content can be
controlled.
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Digestion: is the slow degeneration of the organic content of sludge by obligate
anaerobic bacteria to simpler compounds- carbon dioxide, water and anions
(nitrate, sulphate, phosphate).
Digestion is one of the few sludge treatment processes in which a significantreduction of pathogens is possible.
The digestor gas produced is 65-70% methane, 30-34% carbon dioxide, and traces
of sulphur compounds. The collected gas is burnt in a boiler to keep the
digestor warm and the excess put to further heating or power generation
purposes.
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Reduction of waste production and disposal volumes
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Reduction of waste production and disposal volumes
Incineration: its main advantages lie in the complete destruction of organic
compounds, the ash being inert and usually less than 25% of the original
sludge volume.
Most incinerators are of the fluidized bed variety.
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A waste management diagram…
Wastedisposal
Waste
treatment
Waste
recycle
Upgrade
operation
Redesign
process
Substituteraw material
Increasing Effectiveness
of waste management
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