Topic 6 - Hazardous Waste

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CHAPTER 6

HAZARDOUS WASTE

MANAGEMENT

PSA/JKA/CHIA/CC604 1

DEFINITION OF HAZARDOUS WASTE

Hazardous waste is a waste with properties that make it potentially dangerous or harmful to human health or the environment.

Hazardous wastes can be liquids, solids, or contained gases.

Most hazardous wastes are from industrial processes.

Major generators – metal finishing, chemical, petrochemical, printing and packaging industries.


CHARACTERISTICS OF HAZARDOUS

WASTE CHARACTERISTIC EXPLANATION EXAMPLE

1. Reactive • Unstable under normal conditions.

• Can cause explosions or release toxic fumes,

gases, or vapour when heated, compressed,

or mixed with water., air or other materials.

• lithium-sulfur

batteries

• Unused

explosives

2. Ignitability • Wastes can create fires under certain

conditions

• Undergo spontaneously combustible

• Have a flash point less than 60 °C (140 °F).

• Waste oil

• Used solvent

3. Corrosive • Corrosive wastes are acids or bases that are

capable of corroding metal containers, such

as storage tanks, drums, and barrels

• Produce acidic or alkaline solutions. (has a

pH ≤ 2 or pH ≥ 12.5)

• Batteries Acid


CHARACTERISTICS OF HAZARDOUS

WASTE CHARACTERISTIC EXPLANATION EXAMPLE

4. Toxicity • Harmful or fatal when ingested or absorbed

(e.g., containing mercury, lead, etc.).

• When toxic wastes are land disposed,

contaminated liquid may leach from the

waste and pollute ground water.

• Chemical

solution

5. Infectious

Waste/

Medical

Waste

• Generated during the diagnosis, treatment,

or immunization of human beings or animals

or in research activities in these fields or in

the production or testing of biological.

• Sharp

• Soiled waste

• Swab/bandage

• Body fluid

6. Radioactive

Waste

• A waste product containing radioactive

material

• Usually the product of a nuclear process

such as nuclear fission, though industries not

directly connected to the nuclear power

industry may also produce radioactive waste.

• Radioactive

material

• X-ray


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SYMBOLS OF HAZARDOUS WASTE


SOURCES OF HAZARDOUS WASTE

Industrial manufacturers of chemical

products

Petroleum industry

Electronics sector

Industrial metal

Paper industry

Hospital waste

Scheduled wastes from the house


SOURCES OF HAZARDOUS WASTE


EFFECTS OF HAZARDOUS WASTE

To Human :

Inhalation, absorption into the skin, ingestion or

wound.

Temporary impact as dizziness, headache and

nausea.

Permanent effects such as cancer, disability and

cause of death.

These effects can occur either instantly or gradualty.


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To Environment :

The main effects of air, water and soil vary

according to the quantity of waste.

To Property :

Damage (corrosive) personal and public properties

due to danger of fire and explosion at disposal site.

It can also cause harm through heat and smoke,

open fire, flying debris, fire and explosions that

procedure harmful substances in the atmosphera.



To Security :

Knowledge of the rules and safety measures are

important to a person directly involved in the

management and operation of scheduled waste.

Site safety plan is need to implement the policies

and procedures to protect workers and the public

from potential harm.


ENVIRONMENTAL QUALITY ACT 1974

Malaysia has developed a comprehensive set of legal provisions related to the management of toxic and hazardous wastes.

The regulation is based on the cradle to grave principle.

A facility which generates, stores, transports, treats or disposes scheduled wastes is subject to the following main regulations:

◦ Environmental Quality (Scheduled Wastes) Regulations 2005 (Amendment) 2007

◦ Environmental Quality (Prescribed Conveyance) (Scheduled Wastes) Order 2005

◦ Environmental Quality (Prescribed Premises) (Scheduled Wastes Treatment and Disposal Facilities) (Amendment) Order 2006

◦ Environmental Quality (Prescribed Premises) (Scheduled Waste Treatment and Disposal Facilities) (Amendment) Regulations 2006



http://www.ohs.unsw.edu.au/ohs_waste/Hazardous_Waste_Disposal_Pictogram.pdf

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METHOD OF HAZARDOUS WASTE

PROCESSING

1. Incineration

2. Ion-Exchange

3. Neutralization

4. Precipitation

5. Oxidation-Reduction


1. INCINERATION

CONCEPT :

Waste storage and feed preparation.

Combustion in a furnace, producing hot gases and a

bottom ash residue for disposal.

Gas temperature reduction, frequently involving heat

recovery via steam generation.

Treatment of the cooled gas to remove air pollutants, and

disposal of residuals from this treatment process.

Dispersion of the treated gas to the atmosphere through an

induced-draft fan and stack.


1. INCINERATION

ADVANTAGES :

Minimum of land is needed compared to the dimensions of waste

disposal sites.

The weight of the waste is reduced to 25% of the initial value.

The waste volume is reduced to almost 10% of the initial value.

The flue gas, which is containing heavy metals and other harmful

substances after the incineration process, is cleaned and emitted

through the stack in environmentally friendly form.

Incineration plants can be located close to residential areas,

By using the ashes for environmentally appropriate construction, low

costs are provided and furthermore the need for landfill capacity is

reduced.

Can be used as a renewable energy source


1. INCINERATION

DISADVANTAGES :

The air pollution controls required in incineration

plants are extremely expensive.

Energy, produced by means of waste incineration is

not likely to be practical for small communities.

The extremely high technical standards of the plants

require skilled workers, which leads to the facts that

rather high wages have to be paid.

The residues from the flue gas cleaning can

contaminate the environment if they aren’t handled


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2. ION EXCHANGE

CONCEPT :


2. ION EXCHANGE

CONCEPT :

Ion exchange is the process through which ions in solution are

transferred to a solid matrix which, in turn releases ions of a

different type but of the same polarity.

In other words the ions in solutions are replaced by different ions

originally present in the solid.

During ion exchange the ions being exchanged are reversibly

removed from the wastewater and transferred to the ion

exchanger.

This means that ion exchange is a physical separation process

in which the ions exchanged are not chemically altered.


2. ION EXCHANGE

CONCEPT :

Since the chemical characteristics of the ions exchanged are not

modified the use of ion exchange in wastewater treatment is

associated with the removal of hazardous ionic material(s) from

the wastewater and its transfer to the ion exchanger.

Since the ion exchanger only collects the hazardous material the

spent exchanger must be treated at the end of a cycle .

Typically this involves the regeneration of the ion exchanger by

contacting the spent exchanger with a concentrated solution of

an ion (such as H+ or OH-) which can replace the ions adsorbed

on the exchanger during the treatment process.

This results in the generation of a spent regenerating solution

containing the waste ions in a concentrated form.


2. ION EXCHANGE

ADVANTAGES :

Capability of handling and separating components from dilute

wastes.

Possibility of concentrating pollutants.

Capability of handling hazardous wastes.

Possibility of recovery expensive materials from waste (e.g.,

precious metals).

Possibility of regenerating ion exchanger.

Possibility of recycling components present in the waste and/or

regenerating chemicals.


http://en.citizendium.org/wiki/File:Ion_Exchange.PNG

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2. ION EXCHANGE

DISADVANTAGES :

Limitation on the concentration in the effluent to be treated.

In general, lack of selectivity against specific target ions.

Susceptibility to fouling by organic substances present in the

wastewater.


3. NEUTRALIZATION

CONCEPT :

Corrosive acid when neutralized (remember this corrosive is one of the factors of

hazardous wastes) with basic substance becomes no longer corrosive/ non

hazardous.

PH adjustment; pH is a very important factor in the creation of hazardous waste.

So by adjusting this important factor the waste can be neutralized and becomes

nonhazardous.

The most common neutralizing chemicals are:

◦ Acids :

Sulfuric Acid(H2SO4)

Carbon Dioxide (CO2) - which converts in water to Carbonic Acid (H2CO3)

Hydrochloric Acid (HCl) Phosphoric Acid (H3PO4)

Nitric Acid (HNO3)

◦ Bases:

Caustic (NaOH) – also known as Caustic Soda

Calcium Hydroxide (CaOH2)

Calcium Carbonate (CaCO3) – also known as Lime or Limestone

Ammonium Hydroxide (NH4OH) PSA/JKA/CHIA/CC604 22

3. NEUTRALIZATION

ADVANTAGES :

Reduce the level of a waste's corrosivity.

Lime is least expensive and is widely used for treating acidic

wastes.

Can used CO2 that it is often readily available in the exhaust gas

from any combustion process at the treatment site.


3. NEUTRALIZATION

DISADVANTAGES :

The reagent itself is highly corrosive to skin and material.

Some reagent are not strong base however is less reactive and

more expensive.

Must have special precaution to handle reagent.

Low reactivity will increase the process time.


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4. PRECIPITATION

CONCEPT :

Particularly useful for converting hazardous heavy metals to a less mobile,

insoluble form.

During the chemical precipitation of hazardous waste streams, a soluble

hazardous species is removed from the solution by the addition of a precipitating

reagent; an insoluble compound subsequently forms that contains the hazardous

constituents.

The precipitate is removed from the solution using a physical separation

technique such as sedimentation or filtration.

Coagulants or flocculants may be added to the mixture to enhance the separation

of the precipitate from the soluble phase.

Examples of common inorganic coagulants are aluminum sulfate (alum),

(Al2(SO4)3·18H2O) and ferric sulfate (Fe2(SO4)3).

Precipitation processes are typically geared toward the removal of dissolved

inorganic ions.


4. PRECIPITATION

CONCEPT :

A number of counter anions are suitable for reaction with the metal. These anions

vary widely in terms of rate of reaction, inherent toxicity, and cost. A common

means of precipitating soluble metal ions is by hydroxide formation.

Example :

Zn2+ + 2OH- = Zn(OH)2

Hydroxide ion source can be a common alkali such as NaOH, Na2CO3, or

(Ca(OH)2).

When reacted with such alkalis, most metal ions will produce basic salt

precipitates. Lime addition is the most common reagent for the precipitation of

metals as hydroxides and basic salts.

Sodium carbonate is used to form hydroxide precipitates (Cr(OH)3), carbonates

(CdCO3), or basic carbonate salts (2PbCO3·Pb(OH)2) (Manahan, 1994). The

carbonate anion produces hydroxide as a result of hydrolysis with water:

CO32-+ H2O =HCO3

- + OH-

The carbonate anion subsequently reacts with the metal. PSA/JKA/CHIA/CC604 26

4. PRECIPITATION

ADVANTAGES :

Can remove organic and inorganic contaminant

Efficient and easy implement

DISADVANTAGES :

Sludge require further treatment

Precipitation with heavy metal sulfide can produce a toxic gas

Require power and high cost


5. OXIDATION-REDUCTION

CONCEPT :

The earliest view of oxidation and reduction is that of adding

oxygen to form an oxide (oxidation) or removing oxygen

(reduction). They always occur together.

One important chemical redox treatment involves the oxidation of

cyanide wastes from metal finishing industry, using chlorine in

alkali solution.

In this reaction CN- is first converted to less toxic cyanide.

Further chlorination oxidizes the cyanide to simple carbon dioxide

and nitrogen gas.

Example:

NaCN+Cl2+2NaOH = NaCNO+2NaCl+H2O

NaCNO + 3Cl2+4NaOH = 2CO2 +N2 + 6NaCl +2H2O PSA/JKA/CHIA/CC604 28

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CONCEPT :

Another important redox treatment process is the reduction of

hexavalent chromium Cr (VI) to trivalent chromium Cr (III) in large

electroplating operations.

Sulfur dioxide is used as the reducing agent and the reactions

are as follows :

3SO2+ H2O = 3 H2SO3

2CrO3+2H2SO3 = Cr2(SO4)3 + 3H2O

A large variety of oxidisable contaminants in waste water and

sludges are oxidized by ozone which can be generated on site by

an electrical discharge through dry air or oxygen.



ADVANTAGES :

The use of chemical oxidation and reduction can be quite safe.

The greatest advantages are the rapid treatment time and the ability to treat contaminants present at high concentrations.

It is effective on a diverse group of contaminants. Common contaminants treated by chemical oxidation are amines, phenols, chlorophenols, cyanides, halogenated aliphatic compounds, and certain pesticides in liquid waste streams.



DISADVANTAGES :

Pottential hazard including corrosive and highly reactive oxidant.

Not only react with the target contaminants but also with substances found in the soil that can be readily oxidized. In the case of ozone, ozone can react with water and decompose to oxygen.

Oxygen production can lead to serious problems such as the development of high pressures below the ground surface and possible explosions.

Control of pH, temperature, and contact time is important to ensure the desired extent of oxidation. PSA/JKA/CHIA/CC604 31

METHOD OF HAZARDOUS WASTE

DISPOSAL

Disposal is the intentional placement of hazardous waste into the water, air or into the land where by the waste can safely re-enter the environment.

Disposal must have adequate liability coverage

for both emergencies (spills, explosions) and long term damage.

Methods of hazardous waste disposal : 1. Secure Landfill

2. Underground Injection

3. Incineration


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1. SECURE LANDFILL


1. SECURE LANDFILL

ADVANTAGES :

Compared to incineration, it’s more cheaper.

Skilled labour is not required.

No residue or by product, hence no further disposal.

DISADVANTAGES :

Need a large space of land.

Need proper leachate piping system, treatment plant and liner installation requirement.

Need a monitoring well to check the groundwater quality.

Adverse weather condition has effect the work progress.


2. UNDERGROUND INJECTION


2. UNDERGROUND INJECTION

ADVANTAGES :

Safe method if sites are chosen carefully

Waste can be retrieved if problem develop

Just need a small space of ground land

Easy to do

Low cost

DISADVANTAGES :

Leaks or spills at surface

Leaks from corrosion of well casting

Existing fractures or earthquakes can allow wastes to escape into groundwater

Encourage waste production PSA/JKA/CHIA/CC604 36

http://www.sott.net/image/image/s5/105744/full/article_2163265_13BD38C2000005.jpg

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3. INCINERATION


3. INCINERATION

ADVANTAGES :

Most hygienic method

Complete destruction of pathogens

Mo odour trouble

Heat generated may be used for steam power

Clinkers producted may be used for road construction.

Less space required

Adverse weather condition has not effect

DISADVANTAGES :

Large initial expense

Care and attention required otherwise incomplete combustion will increase air pollution

Residues required to be disposed which require money

Large no of vehicle required for transportation PSA/JKA/CHIA/CC604 38


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Topic 6 - Hazardous Waste