chapter 3; key principles of engineering and science for environmental problem

CHAPTER 3: Key Principles of Engineering and Science for

environmental problemPrepared by: Shaheen SardarBSc textile engineeringMS Textile ManagementFaisalabad, Punjab, PakistanEmail: shaheen1934@yahoo.com

COURSE TITLE: Environmental issues of textile industry

Key Principles of Engineering and Science for environmental problem

Introduction:• In this Chapter we will review following key

principles.(1) Mass and energy transfer(2) Environmental chemistry(3) Mathematics of growth(4) Risk assessment

MASS AND ENERGY TRANSFER

• Law of conservation of mass says “When chemical reactions take place, matter is neither created nor destroyed. (Though in nuclear reactions mass can be converted to energy). This law shows that pollutants have to go somewhere. We should be careful about approaches that transport them from one medium to another.

Law of conservation of mass

MASS AND ENERGY TRANSFER

• First law of thermodynamics says “Energy can neither be created nor destroyed, energy may change forms”

First law of thermodynamics

MASS AND ENERGY TRANSFER

• Second law of thermodynamics says “There will always be some waste heat. How that waste heat affects the environment is an important consideration in the study of environmental engineering and science. It is impossible to devise a machine that can convert heat to work with 100% efficiency. There will always be losses.

Second law of thermodynamics

ENVIRONMENTAL CHEMISTRY

• Almost every pollution problem that we face has a chemical basis.

• In Stoichiometry, we use law of conservation of mass to balance chemical equations.

N2 + 3H2 → 2NH3

• We use law of conservation of energy to learn something about heat absorbed or released during chemical reactions. Since energy must be conserved, we should be able to track it from beginning to end.

Law of conservation of energy

ENVIRONMENTAL CHEMISTRY

• When the rates of reaction are same in both directions, the reaction is said to have reached equilibrium.

• Organic chemistry is the chemistry of compounds of carbons.

• Nuclear chemistry is the chemistry of radioactive substances. It is the Study of the atomic nucleus, including fission and fusion reactions and their products.

Nuclear chemistry

MATHEMATICS OF GROWTH

• It is used to shed light on the number of environmental problems including population growth, resource consumption, pollution accumulation, and radioactive decay.

MATHEMATICS OF GROWTH

MATHEMATICS OF GROWTH

RISK ASSESSMENT

• Risk = Hazard x Exposure• Risk assessment is the gathering of data that

are used to relate response to dose. The data can be combined with estimates of likely human exposure to produce overall assessments of risk.

RISK ASSESSMENT

RISK ASSESSMENT

Risk management

• Risk management is the decision making about how to allocate national resources to protect public health and the environment.

Risk management

RISK ASSESSMENT

• Our concern is with the probability that exposure of some number of people to some combination of chemicals will cause some amount of response, such as cancer, reproductive failure, neurological damage, development problems, or birth defects.

• Risk assessment is usually considered to be a four step process followed by risk management.

RISK ASSESSMENTHazard identification

Dose-Response Assessment Exposure assessment

Risk characterization

Risk Management

RISK ASSESSMENT

(1) Hazard identification: • It is the process to determine whether or not

the chemicals are linked with adverse health effects.

Hazard identification

RISK ASSESSMENT

(2) Dose-Response Assessment: • Process to obtain a mathematical relationship

between the amount of a toxicant that a human is exposed to and the risk that there will be an unhealthy response to that dose.

Dose-Response Assessment

RISK ASSESSMENT

(3) Human Exposure assessment: • It is two-step process as follows; • (a) Pathways that allow toxic agents to be

transported from source to the point of contact with people must be evaluated.

• (b) An estimate must be made of the amount of contact that is likely to occur between people and those contaminants.

Human Exposure assessment

RISK ASSESSMENT

(4) Risk characterization: • It is the integration of the forgoing 3-steps,

which results in an estimate of the magnitude of the public-health problem.

• This phase determines the probability of an adverse effect to a human population by a toxic substance and outlines permissible exposure levels from which standards of exposure are set.