5.stabilisation and solidification

8/13/2019 5.Stabilisation and Solidification

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LEARNINGOUTCOMES

At the end of lectures of week 6 student will

Be able to identify the mechanism of

solidification and stabilization

Able to describe the technology and perform

analysis on solidification

Know the way stabilization was implement at

field


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TOPICOFDISCUSSION

Introduction

Mechanisms

Technology

Performance Anaysis

Field implementation


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INTRODUCTION

Stabilisation and solidification are intended primarily to

reduce the mobility of waste constituents.

Widely applied in management of hazardous waste.

Categorize as physicochemical process Objectives:

To reduce the waste toxicity and mobility, and

To improve the engineering properties of the

stabilized materials.


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STABILISATIONStabilisation is a process where additives

(reagents) are mixed with waste to minimize

the rate of contaminant migration from the

waste and reduce the toxicity (hazardous

nature) of the waste. Improve the handling and physical characteristics of the

waste

Decrease the surface area across which transfer or loss of

contaminants can occur

Limit the solubility of any pollutants contained in the waste

Reduce the toxicity of the contaminants


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SOLIDIFICATIONSolidification is a process employing additives by

which the physical nature of the waste is altered during

the process (i.e. its strength, compressibility, and/or

permeability).

Sufficient quantities of solidifying are added to hw to

result in a solidified mass of materials.

Resulting in strength increase, decreases

compressibility, and decreases permeability of the

waste.


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APPLICATION

Three major areas of application for stabilization

technologies are:

Industrial Waste - The treatment of industrial wastessuch as sludges,

Land disposal the treatment of waste prior to secure

landfill disposal, and

Site remediation

the treatment of contaminated landwhere large quantities of soil containing contaminants

are found.


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MECHANISMS

Can consist one or more of the following mechanism:

Macroencapsulation

Microencapsulation

Adsorption Absorption

Precipitation

Detoxification


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TECHNOLOGY

Cement-Based Stabilisation/Solidification

Portland cement is the most common stabilisation agent

used.

It is mixed with the waste in predetermined proportions

and water is added.

Best suited for inorganic wastes ~ heavy metals

Not suitable for organic mater because;

Interfere with hydration process

Reduce final strength Not easily stabilized

Advantages:

well known technology

Low cost


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Pozzolanic Stabilisation/solidification

A pozzolanic is not cementation on its own but form

cementitious compounds when combined with lime

(CaO) and water (H2O).

The most common pozzolans are fly ash from coal-firedpower plant, kiln dust from lime or cement kilns and

blast furnace slack.

TECHNOLOGY


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Thermoplastic Stabilisation/Solidification

Thermoplastic are substances that exhibits plastic

behavior at elevated temperatures.

In contaminated media treatment applications, they are

used in microencapsulation in which the thermoplasticoccupies pore spaces among waste/soil particles.

TECHNOLOGY


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PERFORMANCEANALYSISFORSTABILIZED/SOLIDIFIEDWASTES

Usually need to be analyzed with respect to their

durability and the associated potential for release of

contaminants into environment.

Leachability is the release of contaminants from waste

matrix into the aqueous phase and the exit of these

contaminants from the bounding surfaces of the waste

mass.

Several factors influence contaminant leachability from a

stabilized matrix.


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FACTORINFLUENCECONTAMINANT

LEACHABILITY

Surface area of the waste

Contaminants leachability increase with the specific

surface of particulate media.

The specific surface is the ratio of total available surface

area to the waste mass volume of weigh.

Agitation Technique and Equipment

In lab test, agitation is necessary to accelerate the

attainment of equilibrium between solid samples and

leachant.

*Leachant the fluid to which the contaminants are

leached.


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FACTORINFLUENCECONTAMINANT

LEACHABILITY

Characteristics of the Leachant

The pH of the leachant affect contaminant leachability

because of their controls on the solubility of compounds

within the waste matrix.

Leachant/Waste Volumetric Ratio

The higher the leachant/waste volumetrics ratio, the

higher is the total mass of contaminants released for a

given time interval.


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IN-DRUMMIXINGALTERNATIVES

Objective: to improve the physical characteristics of

drummed hazardous wastes prior to land disposal,

containers of toxic and hazardous liquids and

sludge.

Has been used extensively

The drum serves as:

Mixing vessel

Shipment container

Process involves:

Addition of the chemical reagent

Mixing by a top-entering mixing table.

May be performed remotely by robot.


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IN-SITUMIXINGALTERNATIVES

Widely employed method

Frequently uses commonly available construction

equipment to accomplish the mixing process.

Can minimize the handling of the waste Examples:

By using modified auger with mixing blades

Jet grouting

Advantages: Smaller equipment with ability to work near buildings

and buried utilities

Low vibration - quite


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PLANTMIXINGALTERNATIVES

Employs mechanical mixer ~ batch or continuous

processes

Agents are added and blended during the process

Treated materials then are placed in their ultimatedisposal area.

Continuous process can provide significantly

improve control over the mix proportions and the

thoroughness of blending.

The blended material is then transported for

disposal

5.stabilisation and solidification

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