Industrial Wastewater

7/24/2019 Industrial Wastewater

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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



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



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.



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.



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



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.



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



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



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?



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.



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



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:



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)



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



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



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)



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.



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)



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:



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



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:



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)



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



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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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

Industrial Wastewater

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