Module 6:EFFLUENT TREATMENT AND RESIDUALS MANAGEMENT

Program for North American Mobility in Higher Education

Structure of this module

This module is divided into 3 “tiers”, each with a specific goal:

Tier 1.- Basic introduction

Tier 2.- Case study of the pulp & paper sector

Tier 3.- Open-ended problem

Tier 1. Contents:

1.1. IntroductionIntroduction2.2. Industrial pollution problems.Industrial pollution problems. The petroleum industry.The petroleum industry. The pulp and paper industry.The pulp and paper industry.3.3. Programs for reducing pollution.Programs for reducing pollution.4.4. Treatment processes. Treatment processes. 5.5. Process selection.Process selection.6.6. Volume and disposal reduction. Volume and disposal reduction.

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Tier I:Tier I:Introductory Introductory conceptsconcepts

Effluent Treatment and Residuals Effluent Treatment and Residuals ManagementManagement

G o a l s:

Tier 1

To provide information about the significance of treating effluents from industry and others facilities (or sources)

To extreme the necessity of minimize pollutant concentration in the effluents and reduce the wastes production, and,

To suggest strategies to reduce pollutant wastes production and their emission to the environment

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 contaminantsFor example, Water Pollution refers to contaminants in aquatic in aquatic ecosystems (streams, lakes, etc) which render them unfit for a ecosystems (streams, lakes, etc) which render them unfit for a particular use.particular use.

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Pollutants can reach:

1. Air

2. Water

3. Solid waste

This module focuses on water pollution from industrial sources

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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:

ContaminantsContaminants Reason for importanceReason for importance

Physical suspended solids They can lead to the development of sludge deposits.

Chemical biodegradable organics

When discharged untreated to the environment, they lead to the depletion of

natural oxygen resources.

NutrientsIf discharged, they can lead to water

pollution.

HazardousBecause of their characteristics

(e.g.,toxicity, flammability) are dangerous for human health and the environment.

Heavy metalsThey can negatively impact upon

biological waste treatment processes.

Dissolved inorganic solidsThey are result of water use, and may

have to be removed if the wastewater is to be reused.

Biological pathogensCommunicable diseases can be

transmitted by the pathogenic organism in wastewater.

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Water standards

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Industrial effluent standardsParameter Mexico a USA b Canada c

Total suspended solids, (mg/l) 150150 2727 1515

BOD5, (mg/l) 2020 5656 1515

pH 5-105-10 6-96-9 6-10.56-10.5

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What is BODBOD?

By definition, BODBOD 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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Why should we minimize the use of water?

Water is such an important part of many manufacturing processes Water is such an important part of many manufacturing processes that we must consider Effluent Treatment as a part of the main that we must consider Effluent Treatment as a part of the main process because of the great amount always involved.process because of the great amount always involved.

Water is abstracted from aquifers and rivers, treated and supply to Water is abstracted from aquifers and rivers, treated and supply to industries and homes for different uses; used water is supposed industries and homes for different uses; used water is supposed to be treated and discharged again into the rivers. Most of the to be treated and discharged again into the rivers. Most of the times, this water returns to its natural environment but times, this water returns to its natural environment but unfortunately, with a greater heat content or with some unfortunately, with a greater heat content or with some substances added. substances added.

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It is also important to minimize use of water because of several reasons:

Fresh water is often scarce. High costs involved operating Fresh water is often scarce. High costs involved operating

effluent treatment plants.effluent treatment plants.

Difficult to separate all the elements that pollute water.Difficult to separate all the elements that pollute water.

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Why should we minimize the use of water?

Industrial pollution problemsIndustrial 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

to implement preventive modern technologies.

RESULTS:Ecosystems decline.Ecosystems decline.Industrialization social costs.Industrialization social costs.The increase of human diseasesThe increase of human diseases.

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The petroleum industryThe 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 and production:

Wastewater Solid waste Toxic pollutants

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Production wastes in the petroleum industry can be grouped broadly into 2 classes:

• 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 of underground through injection wells and it is permitted under U.S. EPA control programs.

The Petroleum Industry:

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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 includeEmissions from refineries include:

Sulfur oxides Nitrogen oxides Benzene, toluene and xylene VOC Wastewater containing BOD levels Heavy metals

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Pollution Approximate QuantitiesCooling systems 3.5-5 m3 of wastewater generated per ton of crude.

Polluted wastewater

BOD 150-250 mg/l COD 300-600 mg/lphenol 20-200 mg/loil 100-300 mg/l (desalted water)oil 5000 mg/l in tank bottombenzene 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 waste because of the heavy metals and toxic organic presence).

VOC emissions 0.5 to 6 kg/ton of crude.

Others emissionsBTX (Benzene, Toluene and Xylene) 0.75 to 6 g/ton of crude Sulfur oxides 0.2-0.6 kg/ton of crudeNitrogen oxides 0.006-0.5 kg/ton of crude

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Wastes generated:

(Pollution Prevention and Abatement Handbook World Bank Group)

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The pulp and paper industryThe pulp and paper industry

How paper is made:

Most of the raw material needed for paper manufacture is supplied Most of the raw material needed for paper manufacture is supplied by trees.by trees.

The main steps in the pulp and paper manufacture are raw material preparation, such as wood debarking, and chip making; pulp manufacturing; pulp bleaching; paper manufacturing and fiber recycling. Pulp mills and paper mills may exist separately or as integrated operations.

The characteristics of the paper (smoothness, glazed finish) are given by a process called calendering.

The paper undergo coating, whereby a thin layer of coating pigment or filler is spread onto the paper surface.

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Pulp and paper industry:Pulp and paper industry:

The pulp and paper industry has made significant steps toward conserving water and energy.

Significant water reductions are achieved through better reuse methods and by separating cooling water from process water.

The waste streams generated in this industry are best classified by their origins as show in the next slide.

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Types of waste products in the pulp Types of waste products in the pulp and paper industry:and paper industry:

Material originated in raw materials (dirt and bark with wood). Nonfiber components in wood. Contaminants in waste paper and make-up chemicals. Reaction products (dissolved wood substance from mechanical or

chemical action). Fiber fragments. By-products of chemical recovery and combustion. Fiber and nonfiber process looses and discharges of water, air

and heat.

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The pulp and paper industryThe pulp and paper industry

Water use and effluent discharges:

Liquids dischargesLiquids discharges from the process contain solids, mainly fiber, fillers, and colloidal and dissolved material. The fiber and fillers are minimized and reused. Colloidal and dissolved materials are by-products of the refining of the fibers or carried over from the pulp mill.

Discharges of dissolved material are minimized by washing the stock and displaced carryover from pulp mills and by practicing good water reuse strategies that reduce the volume and concentrations of waste in wastewater.

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Programs for reducing pollutionPrograms for reducing pollution

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Government programs for reducing pollution:

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 and providing 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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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:

1.1. Add multi-media provisions to the existing regulations.Add multi-media provisions to the existing regulations.2.2. Correct laws in other policy sectors with environmental Correct laws in other policy sectors with environmental

measures.measures.3.3. Make NEPA a stronger statute.Make NEPA a stronger statute.4.4. Make TSCA a law which can use EPA programs to control and Make TSCA a law which can use EPA programs to control and

reduce toxic substances.reduce toxic substances.5.5. Establish pollution prevention approaches.Establish pollution prevention approaches.

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Government programs for reducing pollution:

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: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 laterEnd of pipe solution to wastes and pollutants; and later Internal process modifications to reduce emissions and wastes, and eventuallyInternal process modifications to reduce emissions and wastes, and eventually Redesign products to achieve a maximum level of recycling of raw materials Redesign products to achieve a maximum level of recycling of raw materials

and minimization of wastes after the products are used.and minimization of wastes after the products are used.

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Some measurements to save water:

Keep water effluent streams separated.Keep water effluent streams separated. Reuse water as close to source as possible.Reuse water as close to source as possible. Recycling whenever it is possible.Recycling whenever it is possible. Better control of usage with automated systems.Better control of usage with automated systems. Checking and control of leaks.Checking and control of leaks. When buying new equipment, evaluate water-efficiency When buying new equipment, evaluate water-efficiency

models including accessories.models including accessories. Reducing the quantities of chemicals so that the amount Reducing the quantities of chemicals so that the amount

of dilution water will be reduced.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 It is not only possible but necessary to reuse wastewater of a process stream before it leaves the plant accomplished by piping, diluting stream before it leaves the plant accomplished by piping, diluting or treating some of the effluents before using them again.or treating some of the effluents before using them again.

Some plants are now using closed systems, so that there are no Some plants are now using closed systems, so that there are no water discharges.water discharges.

Zero discharges has been practiced in locations where water is Zero discharges has been practiced in locations where water is scarce, and may involve technologies for removing suspended and scarce, and may involve technologies for removing suspended and dissolved solids.dissolved solids.

Complete demineralization is relatively expensive, however, in some Complete demineralization is relatively expensive, however, in some cases wastewater discharges can be reduced significantly with cases wastewater discharges can be reduced significantly with other less expensive technologies.other less expensive technologies.

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Treatment processesTreatment 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 treatment program should give us are listed below:

Overview of a new or existent problem.Overview of a new or existent problem. Lab study of all system and water composition.Lab study of all system and water composition. Submit a proposal.Submit a proposal. Program implementation.Program implementation. Monitoring to optimize.Monitoring to optimize. Use of modern treatment techniques.Use of modern treatment techniques.

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Program under controlProgram under control

Treatment Program

New or Problem System

PlantStudy

LabStudy

Proposal ImplementProgram

Follow-up

New ProductTechnology

Systemundercontrol

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Wastewater treatment processes:

Wastes are generated by every industrial enterprise, and this wastes can either be liquids or solids.

Wastewater treatment can be divided into three stages:

1.1. Primary treatmentPrimary treatment that uses physical operations to remove free oil and/or suspended solids.

2.2. Secondary treatmentSecondary treatment to remove dissolved contaminants through chemical or biological action, and

3.3. Tertiary treatmentTertiary 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, the microorganisms and solids suspended are allowed to settle.

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Treatments…

The tertiary treatment remove specific residuals. By filtration, suspended colloidal solids can be removed; adsorption removes organics by granular activated carbon (GAC); and chemical oxidation also removes organic compounds.

Tertiary systems have to treat great amounts of wastewater, so they are expensive.

When streams rich in heavy metals, pesticides or other substances that may pass through primary treatment and inhibit biological treatment are present, in-plant treatments are necessary.

Precipitation, activated carbon adsorption, chemical oxidation, air or steam stripping, wet air oxidation, ion exchange, reverse osmosis are some of the methods 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.

1.1. RecirculationRecirculation. 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.

2.2. SegregationSegregation. Clean streams are separated for direct discharge.3.3. DisposalDisposal. In many cases, the total discharge BOD and suspended solids

can be reduced by removal of residue in semidry state for disposal.4.4. ReductionReduction. The use of automatic cutoffs can reduce the wastewater

volume.5.5. SubstitutionSubstitution. The substitution of chemical additives of a lower

pollutional effect in processing operations.

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.

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Wastewater treatment processes:Wastewater treatment processes:

Process selectionProcess selection

Figure 1. Conceptual treatment program for organic and toxic industrial wastewater

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Organic streams

Streams containingheavy metals

Mineral streams

Source controlSource controlFigure 3.Figure 3.

EqualizationEqualizationNeutralizationNeutralization

Oil/grease removalOil/grease removalSuspended solidsSuspended solids

Biological treatmentBiological 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 of hazardous 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 heavy metals/volatile organics

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Priority pollutantsscan andbioassay

Fedbatch

reactor

Long-termbiodegradation

Prioritypollutantsscan andbioassay

Equalizedsample

Air or steam stripping

Chemical oxidationreduction

Precipitation

Sourcetreatment

Granularactivated

carbon

Powderactivated

carbon

Reverseosmosis

Ionexchange

Nondegradable/ toxic

Degradable

VOC/NH3

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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IonIonexchangeexchange

FiltrationFiltration

PrecipitationPrecipitation

OxidationOxidationreductionreduction

PolymericPolymericresinsresins

GranularGranularcarboncarbon

adsorptionadsorption

AnaerobicAnaerobictreatmenttreatment

Wet air Wet air oxidationoxidation

ChemicalChemicaloxidationoxidation

ReverseReverseosmosisosmosis

Air or steamAir or steamstrippingstripping

ProcessProcesswastewaterwastewater

HeavyHeavymetalsmetals

Organic Organic chemicalschemicals

VolatileVolatileorganicsorganicsammoniaammonia

To dischargeTo dischargerecycle or recycle or treatmenttreatmentIf 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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Sedimentation:Sedimentation:

Reduce solids by at least 50%, with proportional reduce of BOD. Addition of chemicals to assist settlement by coagulating particles or

chemical precipitation can be essential. Can have acceptable discharge standards with regular desludging

without a secondary treatment. Primary tanks are desludged at intervals of between 8 and 24 hours. Secondary settlement follows any form of biological aeration or

filtration to produce an effluent low in solids. Particularly demanding discharge consents may dictate a tertiary

treatment to remove solids and BOD by a further 50%.

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Flotation: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:Flotation:

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General diagram for flotation methods:

Coagulation:Coagulation:

Paperboards wastes can be effectively coagulated with low dosages of alum. Silica or polyelectrolyte will aid in the formation of a rapid settling floc.

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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Precipitation:Precipitation:

Chemical precipitation in wastewater treatment involves the addition of chemicals to alter the physical and chemical state of dissolved and suspended material and to facilitate their removal. It is usually combined with coagulation, flocculation, separation.

Principle: Dissolved compounds, for instance heavy metal ions, are brought into their insoluble hydroxides by pH increase through dosing of lime or NaOH. Using coagulation, flocculation techniques these small hydroxide nuclei become larger flocs for separation. With proper precipitants these flocs also serve as entrapment for other dissolved (organic) compounds; a form of co-precipitation.

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Chemical precipitation

Chemical precipitation in wastewater treatment involves the addition of chemicals to alter the physical and chemical state of dissolved and suspended material and to facilitate their removal. It is usually combined with coagulation – flocculation – separation.

Principle

Dissolved compounds, for instance heavy metal ions, are brought into their insoluble hydroxides by pH increase through dosing of lime or NaOH. Using coagulation, flocculation techniques these small hydroxide nuclei become larger flocs for separation. With proper precipitants these flocs also serve as entrapment for other dissolved (organic) compounds ; a form of co-precipitation.

Chemical precipitation

Chemical precipitation in wastewater treatment involves the addition of chemicals to alter the physical and chemical state of dissolved and suspended material and to facilitate their removal. It is usually combined with coagulation – flocculation – separation.

Principle

Dissolved compounds, for instance heavy metal ions, are brought into their insoluble hydroxides by pH increase through dosing of lime or NaOH. Using coagulation, flocculation techniques these small hydroxide nuclei become larger flocs for separation. With proper precipitants these flocs also serve as entrapment for other dissolved (organic) compounds ; a form of co-precipitation.

Heavy Metals Removal:

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HEAVY METALS REMOVAL TECHNOLOGIESConventional precipitation

HydroxideSulfide

carbonatecoprecipitation

Enhanced precipitationDimethyl thio carbamateDiethyl thio carbamate

Trimercapto-s-triazine, trisodium saltOther methods

Ion exchangeAdsorption

Recovery opportunitiesIon exchangeMembranes

Electrolytic techniques

The Biological Treatment

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Influentwastewater

Physical and chemical treatment BiodegradableBiodegradable High

strengthAnaerobictreatment

Discharge PACTPACT Inhibitory

Nondegradable fraction

Polishedeffluent

Dispersedgrowth system

Complete mixsystem

Readilydegradable

Nitrogenremovalrequired Fixed

Growth system

Discharge

DischargeDischarge

Intermittentprocess

Nitrification/ Denitrification

system

Plugflow system

Selectorsystem

Polished effluent

HighHighstrengthstrength

Yes Yes

Yes

Yes

Yes

YesYes

No

No

No

No No No

No

(Eckenfelder, 2000)

When biological When biological

treatment is treatment is

needed, there needed, there

are several are several

options:options:

The biological treatmentThe biological treatment: typical operating parameters and dimensions

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Treatment method Mode of operation Degree of

treatment Land requirements Equipment Remarks

LagoonIntermittent or continuous

discharge; facultative or anaerobic

IntermediateEarth 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 of organics

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

filter

Continuous application; may employ effluent recycle

Intermediate or high, depending on

loading

225-1400 ft /(million gal/d)

Plastic packing 20-40 ft deep

Pretreatment before POTW or activated

sludge plant

RBC Multistage continuous Intermediate or high Plastic disks Solids 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 Advanced wastewater treatment is defined as the processes that remove more pollutants from wastewater than the conventional treatments. This more pollutants from wastewater than the conventional treatments. This term may be applied usually as tertiary treatment, but most of their goals term may be applied usually as tertiary treatment, but most of their goals are to remove nitrogen, phosphorus, and suspended solids.are to remove nitrogen, phosphorus, and suspended solids.

Advanced treatments include: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 reductionVolume 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 wastesReuse of treated wastewater and wastes Treatment modifications to reduce solid residuesTreatment modifications to reduce solid residues Segregated treatments to reduce hazardous waste mixturesSegregated treatments to reduce hazardous waste mixtures Incineration to reduce waste volume and to render a hazardous Incineration to reduce waste volume and to render a hazardous

waste nonhazardous.waste nonhazardous.

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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 significant reduction 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

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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Reduction of waste production and disposal volumes

A waste management diagram…

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Wastedisposal

Wastetreatment

Wasterecycle

Upgradeoperation

Redesignprocess

Substituteraw material

Increasing Effectivenessof waste management

Multiple choice questionsMultiple choice questions

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Tier 1: Quiz

1.1. What is pollution?What is pollution?

a) Pollution refers to harmful environmental contaminants and to the act or process of polluting the environment.

b) Any undesirable change in the characteristics of the air, water, soil or food that can affect the health called pollution.

c) Unwanted chemicals or other materials found in the environment. Pollutants can harm human health, the environment, and property.

d) All of the above.

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2.2. What is BOD?What is BOD?

a) The quantity of oxygen required for the stabilization of the oxidizable organic matter present over 7 days of incubation at 20 oF.

b) An empirical test used for measuring waste, evaluating the measure of the oxygen required by microbes to degrade a sample of effluent.

c) A test used to evaluate the quantity of oxygen present in the stream.

d) The quantity of oxygen required to develop a biochemical test.

Tier 1: Quiz

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3.3. Why is it important to reduce hazardous contaminants?Why is it important to reduce hazardous contaminants?

a) Because if discharged, they can lead to water pollution.

b) Because of its radioactive characteristics, its effects on human health and development of cancer.

c) Communicable diseases can be transmitted when in contact to them.

d) Because of their dangerous characteristics for human health and the environment.

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Tier 1: Quiz

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Tier 1: Quiz