ENVIRONMENTAL SCIENCE AND ENGINEERING
Environmental engineering is the application of science and engineering principles to protect and
utilise natural resources, control environmental pollution, improve environmental quality to enable
healthy ecosystems and comfortable habitation of humans. This helps to increased awareness of the
importance of intact, functioning ecological and social systems will stimulate new requests by citizens
and policy-makers for timely, credible information about environmental changes.
Types of Environment
1. Natural Environment – encompasses all living and nonliving things occuring naturally in the
area.
2. Built Environment – refers to the human-made surroundings that provide the setting for human
activity(e.g. buildings, parks, cities and supporting infrastructure such as transport, water supply
and energy supply)
Lesson 2: ECOSYSTEM
Ecosystem is a community of living (biotic) organisms in conjunction with the nonliving components
(abiotic) of the environment, interacting as a system.
ENERGY FLOW
Energy flow also called “calorific flow”. This refers to the flow of energy through a food chain.
TROPIC LEVEL (Food level)
Based on the way to get food, organisms are classified as:
1. Producers (autotrophs) - typically plants or algae that do not usually eat other organisms, but
pull nutrients from the soil or the ocean and manufacture their own food using photosynthesis
powered by solar energy.
2. Consumers (heterotrophs) – organisms that cannot manufacture their own food and need to
consume other organisms.
• Herbivores – animals that eat primary producers
• Carnivores – animals that eat other animals
• Omnivores – animals that eat both plants and other animals.
3. Decomposers (Detritivore) – break down dead plants and animals and their wastes as energy
and nutrients into the ecosystem for recycling such as bacteria and fungi.
TROPIC LEVEL
CLASSIFICATION OF CONSUMERS
1. PRIMARY CONSUMERS - A consumers that absorb most of the stored energy in the plant
through digestion, and transform it into the form of energy they need through
respiration.
2. SECONDARY CONSUMERS - A consumers that absorb the energy embodied in the
primary consumers through the process of digestion.
NUTRIENTS CYCLES (BIOGEOCHEMICAL CYCLES)
Nutrients cycles is the movement and exchange of organic and inorganic matter back into the
production of living matter. Nutrient cycle is part of a closed system and these chemicals are recycled
and replenished constantly instead of being lost. This involved micros nutrients (iron, copper, sodium,
etc.) and macros nutrients ( carbon, nitrogen, oxygen, phosphorus and sulphur, etc.). Some key macros
nutrients are described because they play an essential role in ecosystems.
TWO (2) BASIC TYPES OF BIOGEOCHEMICAL CYLES:
1. GASEOUS NUTRIENT CYCLES – main source of nutrients are in atmosphere and the oceans. The
gases which are most important for life such as nitrogen, oxygen, and carbon dioxide. 2.
SEDIMENTARY NUTRIENT CYCLE – main source of nutrients are in soil, rocks and minerals. They are
regarded as less ideal cycles since they take a long time to complete their circulation. This is because
nutritional elements may become trapped in the reservoir pool during recycling taking a long time
to emerge and continue circulation.
OXYGEN CYCLE
Oxygen is a colorless, odorless and tasteless gas. Oxygen is the most important element of the
human body, makes up about 65% of the mass of the human body. Oxygen cycle is a biogeochemical
cycle which the movement of matter through the biotic and the abiotic spheres of the ecosystem. The
main driving factor of the oxygen cycle is the process of photosynthesis.
Oxygen cycle is interconnected with the carbon dioxide. Through photosynthesis, plants convert the
energy from the sun and water into carbohydrates and oxygen. The autotrophs uses carbon dioxide,
water and sunlight to produce food and releases oxygen to the atmosphere. The animals then breathe in
the oxygen and breathe out carbon dioxide that is needed again by the plants in manufacturing food.
Decaying matters release carbon dioxide that also used by the plants for photosynthetic process. During
daytime, plants convert carbon dioxide into oxygen while during nightime plants convert oxygen into
carbon dioxide to maintain their metabolism.
OXYGEN CYCLE
CARBON CYCLE
Carbon is the basic building block element of large molecules necessary of life. The source of carbon
for plants is the carbon dioxide in the atmosphere and dissolved carbon dioxide in water. Carbon also
occurs in the earth’s crust as carbonate rocks such as limestones. Volcanos can return carbon dioxide to
the air and water during eruptions. The carbon is converted from carbon dioxide into sugars by green
plants and into organic molecules by photosynthesis. From there, the carbon is transferred through
ingestion along the food chains to herbivores and carnivores. At each stage part of the carbon stored in
the complex food molecules is broken down is cycled back as carbon dioxide to the air and water. The
remaining carbon is returned to the air and water when organisms die and decay.
Three (3) ways returning carbon atom to the pools of carbon dioxide in the air and water:
1. Respiration – nearly all living organisms, including plants engage in circular respiration. 2.
Combustion – there’s a release of carbon atom when fossil fuels are burned 3. Erosion – marine
organisms the shells of dead organisms form sediments which is limestone.
CARBON CYCLE
NITROGEN CYCLE
The atmosphere is about 78% nitrogen gas. However, most organisms are unable to use it in
this form. Organisms need nitrogen and phosphorus to build proteins and nucleic acids. The
process combining nitrogen with hydrogen to form ammonia is called Nitrogen fixation.
Nitrogen cycle is a complex process with four stages:
1. ASSIMILATION – the absorption and incorporation of nitrogen into organic components by
plants.
2. AMMONIFICATION – it is the production of ammonia by bacteria during the decay of organic
matter. It occurs when plants or animals dies or excretes waste. Decomposers such as
bacteria and fungi first break down the proteins in the organic matter.
3. NITRIFICATION – the production of nitrate from ammonia also known as nitrogen fixation.
The conversion of ammonium salts to nitrites and the further conversion of nitrites to
nitrates is through Oxidation (as by bacteria). Oxidation is the loss or gain of electron during
a reaction by a molecule, atom or ion. Oxidation occurs when the oxidation state of a
molecule, atom or ion increased.
4. DENTRIFICATION – it is the conversion of nitrate to nitrogen gas.
PHOSPHORUS CYCLE
Phosphorus cycle circulates through rocks, water, soil sediments and organisms in a
cycle. Phosphorus forms a significant part of the structural framework of DNA and RNA.
Humans contain 80% of phosphorus in teeth and bones. Rain and weathering cause
phosphate ions and other minerals to be released from rocks throughout time.
MINERALISATION PROCESS:
Inorganic phosphate is taken up by plants from the soil. It is the passed to animals, that is
herbivores and then carnivores. When plants or animals dies, it decomposes releasing
organic phosphate in soil to inorganic forms of phosphorus that can make organic forms of
phosphate available to plants in the soil. Bacteria that break down organic materials.
Phosphorus from the soil can end up in streams and eventually, the oceans. It can be
absorbed into sediments over time once it reaches that location.
SULPHUR CYCLE
The majority of the world’s sulphur is bound up in rocks and salts or buried deep within
oceanic sediments. Both natural and human sources contribute to its presence in the
atmosphere. In natural sources are due to volcanic eruptions, water evaporation and
decomposing organisms. In human sources, primarily due to industrial activities that
generate large amount of sulfur dioxide (SO2) and hydrogen sulfide (H2S). Sulfur dioxide
(SO2) reacts both in oxygen and water. In Oxygen, Sulfur dioxide (SO2) reacts to form sulfur
trioxide gas (SO3), or other chemicals in the atmosphere to produce sulfur salts, when it
reaches the atmosphere. While in water, Sulfur dioxide (SO2) to form Sulfuric acid.
SULFUR CYCLE
References:
1. Mackenzie L. Davis, PhD, P.E, BCEE and David A. Cornwell, “ Introduction to Environmental
Engineering, 5th ed.” (2013), McGraw-Hill Companies,Inc.
2. Dawei Han, PhD, “ Concise Environmental Engineering” (2012), Bookboon.com 3.
James R. Pfafflin and Edward N. Ziegler, “Encyclopedia of Environmental Science and
Engineering, 5th ed.” (2006), Taylor & Francis Group, LLC, CRC Press
4. Michael Allaby, “Basics of Environmental Science, 2nd ed.” (2000), Taylor & Francis e-library