1. Wastewater Characteristic
1.1 Definition
Wastewater refers to the water that is contaminated by human activity. The water may be
discharged from household, agricultural activities, office and industrial wastes that are no longer
safe for human consumption. The flow of storm water and groundwater also contributes to
wastewater.
By weight, wastewater is only about 0.06% solids - dissolved or suspended materials carried in
the 99.94% water flow. The water to solids ratio is essential to transport solids through the
collection system (Drinan, Spellman 2013).
Wastewater can be classified into two types which are gray water and black water. Greywater is
water from bathroom sinks, showers, tubs, and washing machines whereas blackwater is the
waste that we flushed off from a toilet or urinal.
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1.2 Wastewater sources and general constituents
The different specific substances that comprise wastewater vary in amount or concentration,
dependent on the source.
Table 1.1 Typical Composition of Untreated Domestic Wastewater
Constituent
Abbreviation
Concentration (mg/L)
Biochemical oxygen demand
BOD5
100-300
Chemical oxygen demand
COD
250-1,000
Total dissolved solids
TDS
200-1,000
SS
100-350
TKN
20-80
TP
5-20
Suspended solids
Total Kjeldahl nitrogen
Total phosphorus (as P)
Source: (Drinan, Spellman 2013)
Human and animal wastes
Domestic wastewater contains solids and liquids discharges of humans and animals and runoff
to the environment, for example, excreta such as faecal and urine. These contribute millions of
bacteria, viruses and other organisms (some pathogenic) to the wastewater and they can
endanger public health (Drinan, Spellman 2013).
Household wastes
Residential wastewater flows may contain tissue paper, detergent, garbage, kitchen wastes and
other possible substances that may pour of flush into the sewer system (Drinan, Spellman
2013).
Industrial Wastes
Manufacturing plants in the factories usually discharge materials or fluid that is highly in toxic
into the collection system. Those materials include chemicals, acids, alkali detergents and some
other materials.
Industrial wastewater can be treated within public treatment facilities but often industries must
provide some level of treatment prior to their waste stream entering a public treatment system.
This may prevent compliance problems for the treatment facility. An industry may provide
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pretreatment to the effluent because its on-site treatment is more economical than paying
municipality fees for advanced treatment (Drinan, Spellman 2013).
Storm water runoff
During storm events, storm water runs off and takes the pollutant and contaminant on the earth
surfaces. The run-off matters may contain sand, gravel, grit as well as floor levels of water. In
the past, storm water system and sewage system were combined. However, new construction
discharges wastewater into a dual storm water and sewage system which both of them flows
into different collection systems.
Groundwater filtration
Old and improper sealed collection systems may allow groundwater to enter the system through
cracks, breaks and unsealed joints (Drinan, Spellman 2013). This may contribute large amount
of water to the wastewater flows that contain grit (Drinan, Spellman 2013).
1.3 Physical Characteristic
The presence of solids in water, level of turbidity of wastewater, color, odor and temperature are
the main concerns of the wastewater physical characteristic.
Solids
There are suspended and dissolved solids in the water we flushed off. They are in different
sizes and classified by their chemical characteristics and size distribution (Drinan, Spellman
2013). The solids consist of organic, inorganic particles and immiscible fluids. Organic matters
are mainly found in domestic water used. Whereas, Industrial wastewater contains either
organic or inorganic suspended impurities.
Turbidity
Turbidity is a measure of water clarity. It indicates the amount of material suspended in water
decreases that the passage of light through the water.
As suspended materials absorb heat, water temperature rises. Warm water thus reduces the
concentration of dissolved oxygen in the water. Some organisms can‟t survive in the warmer
water. Besides that, higher turbidity reduces the amount of light penetrate through the water,
which reduces photosynthesis and the production of the oxygen (EPA, 2012).
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Sources of turbidity can be from urban run-off, soil erosion, waste discharge from household or
factory and the excessive growth of algae.
Color
Initially, wastewater is a light brownish gray color. The flow becomes increasingly more septic
when it continuously passes through the collection systems as more anaerobic conditions
develop (Drinan, Spellman 2013). Fresh sewage color of gray will turns dark gray then to black.
Odor
As the wastewater contains various kinds of waste, it produces odor. In most urban area,
treatment plants are physically covered to prevent odors from leaving the unit processes.
However, toxic concentrations of gas will increase in these contained spaces after some time.
To overcome this problem, such units should be positively vented to wet chemical scrubbers to
prevent the buildup of toxic gas (Drinan, Spellman 2013).
Temperature
Temperature of wastewater affects how quickly and effectively chemicals dissolved and the time
for chemical reaction to take place (Drinan, Spellman 2013).
Biological wastewater treatment systems are more efficient at higher temperature as bacteria
tend to break down at high temperature. The lower the influent temperature, the more chemical
is needed for treatment (Drinan, Spellman 2013). However, summer heat increases chlorine
demand, promotes algae and microbial growth (Drinan, Spellman 2013).
1.4 Chemical Characteristic
Chemicals in the wastewater such as total dissolved solids (TDS), metals, organics, and
nutrients may affect its composition and pH rating.
Total dissolved solids
Total dissolved solid (TDS) is also known as the residue that remains in the water after the
filtration and evaporation process. TDS is also a measure of the amount of material dissolved in
water.
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High concentrations of TDS reduce water clarity, contribute to a decrease in photosynthesis,
combine with toxic compounds and heavy metals in the water, and lead to an increase in water
temperature (Murphy, 2007).
Factors that affect the amount of total dissolved solids including:
i. Geology and Soil in the Watershed
ii. Urban Runoff
iii. Fertilizer Runoff
iv. Wastewater and Septic System Effluent
vi. Soil Erosion
vii. Decaying Plants and Animals
Metals
High concentrations of dissolved metals are mainly found in industrial wastewater as a result of
their manufacturing processes. Heavy metals are harmful to human‟s body and the
environment. It must be removed to achieve a high water quality level.
High concentration of metals will kill microorganisms during the activated sludge process.
Metals are removed by chemical treatment, though that doesn‟t end the metals toxicity problem
for waste stream processing.
Industrial wastes with high levels of toxic metals or organic
substances can contaminate sewage biosolids, thereby limiting biosolids disposal options and
raising disposal costs (Drinan, Spellman 2013).
Organics
The microorganisms that rely on microbial decomposition consume dissolved oxygen in water.
This process is called biochemical oxygen demand (BOD). BOD is defined as the amount of
oxygen required by aerobic microorganisms to decompose the organic matter in measured
amount of water, keep at 68 °F (20 °C) over a 5-day incubation period. Without continuous
oxygen replacement, dissolved oxygen levels decrease until the cycle fails as the microbes
used up the oxygen available to consume and decompose the organics (Drinan, Spellman
2013).
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The presence of organic matters in wastewater includes proteins, lipids, carbohydrates, and
detergents. And about 30% of it is non-biodegradable (Drinan, Spellman 2013).
Table 1.2 summary of various type of organic matter in wastewater
Types of organic matters
The content of organic
in wastewater
matters
Proteins
Amino
Acids,
Explanation
Carbon, The
greater
mass
Hydrogen, Oxygen, Sulphur, wastewater
Phosphorous, Nitrogen
of
biosolids
material is made up of solids,
or coated with protein so that
it reacts as protein would.
Lipids
Fats, Oils, Waxes
Lipids are soluble in organic
solvents (ether, ethanol, and
acetone,
but
marginally
water soluble.
Food Wastes
Lipids, Fats (compounds of Fats
that
alcohol and glycerol), Oils, wastes
Greases
found
are
in
very
food
stable
organic compounds, and do
not easily decompose.
Grease
High
amounts
reduce
the
of
grease
efficiency
of
filters, nozzles, and sand
beds. Grease adheres to the
walls of sedimentation tank,
where it decomposes and
form scum.
Carbohydrates
Soluble: Sugars, Cellulose
Insoluble:
Starch,
Fibers
Lower organisms (bacteria)
Wood use
carbohydrates
to
synthesize fats and proteins,
as well for energy.
Detergents
Detergents
are
slightly
soluble in water and cause
foaming
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when
outfall
in
effluent into surface waters.
Detergents
reduce
the
oxygen uptake in biological
processes.
Source: (Drinan, Spellman 2013)
Inorganics
Table 1.2 summary of various type of organic matter in wastewater
Types of inorganics matters in
Descriptions
wastewater
pH (hydrogen ion concentration)
pH indicates the intensity of acidity or
alkalinity in wastewater and affects biological
and
chemical
reactions.
Increased
pH
increases the contact time needed for
chlorine disinfection.
Chlorides
Chloride is the major inorganic constituent in
wastewater. It does not cause any harmful
effects on public health.
Nutrients (Nitrogen and Phosphorous)
Nutrients are essential to the reproduction
and growth of plants and animals.
Excessive nitrate concentrations in drinking
water will endanger both human‟s health and
animal infants.
Phosphorus released into drinking water
supplies as little effect on human health but
too much phosphorus in water supply will
contribute
to
algae
bloom
and
lake
eutrophication.
Others
Sulphur, toxic inorganic compounds, heavy
metals.
Source: (Drinan, Spellman 2013)
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1.5 Biological Characteristic
Biological characteristic of wastewater is defined by the levels of bacteria, viruses, and
microscopic animals present. Human wastes infected with disease can produce harmful
pathogenic organisms in the water that enter the sewage (Drinan, Spellman 2013).
Bacteria
Bacteria are microorganisms that are too small to see with naked eyes. They are fundamental to
several wastewater treatment unit processes, especially those responsible for degradation of
organic matter (Drinan, Spellman 2013). However, these bacteria must be controlled as the
excessive growth of some species ordinarily useful bacteria (such as Sphaerotilus natans-a
filamentous organism) may reduce the treatment efficiency. Besides that, waterborne
pathogenic bacteria transmit diseases that cause gastrointestinal disorder (Drinan, Spellman
2013).
Viruses
Viruses are parasitic microorganisms that are much smaller than bacteria. They are not easily
trapped by standard filtration methods, as the varieties of viruses are extremely minute (Drinan,
Spellman 2013).
Generally, waterborne viral infections cause nervous system disorder. Viruses rely on a host to
live and reproduce. As it remains dormant until an appropriate host ingests them, viruses that
reenter the water supply from wastewater effluent can cause problems for downstream water
use (Drinan, Spellman 2013).
Algae
Algae are aquatic plants that live in water. They only grow near the water surface in order to get
sunlight for photosynthesis. Aquatic algae are found in freshwater, wastewater, marine waters
as well as polluted water.
In aerobic and facultative ponds, algae usually supply oxygen for microbial breakdown of
wastes. During days, algae rely on sunlight to produce oxygen and use up carbon dioxide
whereas on dark days or nights, they use up oxygen to produce carbon dioxide. However,
heavy algae growths will raise the level of suspended solids concentration in the wastewater
effluent (Drinan, Spellman 2013).
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Protozoa
Protozoa are the simplest animal species that are widely distributed and highly adaptable
(Drinan, Spellman 2013). Some protozoa are parasitic, while others are free living.
Protozoan populations are an essential part of activated sludge treatment processes and they
are removed by sedimentation after the process (Drinan, Spellman 2013).
Effluent must not contain too much protozoan levels. In order to remove them from wastewater,
filtration method is usually used.
Worms (helminthes)
Worms are organisms with aerobic requirements that inhabit mud and slime (Drinan, Spellman
2013).
Worms can metabolize solid organic matters that other microbes cannot degrade, and feed on
sludge deposits. This helps to break down the organic matters in the water stream (Drinan,
Spellman 2013).
Indicator organisms
Testing and identification of pathogens presents inherent problems. Some organisms are tough
and persistent, and others from protective spores that allow them to resist treatment processes
designed to kill off pathogens. The indicator organisms alert us to the possible presence of
sewage contamination. For example, coliforms that present in the wastewater indicate sewage
contamination, it as well mean that the water source could contain pathogenic microorganisms
(Drinan, Spellman 2013).
Coliforms
Wastewater contains more coliform groups than polluted water. For example, fecal coliforms are
present in the intestinal tracts of all mammals. Coliform group testing involves estimating the
number of fecal coliform bacteria present in a measured water sample. This will provides a ratio
of contamination to define the quantity of water (Drinan, Spellman 2013).
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2. Conventional Wastewater Treatment
2.1 Introduction
Conventional here carries the meaning of generally practiced or used in most places. A
conventional wastewater treatment has a combination of physical, chemical and biological
processes and functions to dispose solids and organic or inorganic matter in the wastewater.
There are a few stages involved called preliminary, primary, secondary and tertiary wastewater
treatment. Different treatment plants utilized different types of treatment and thus some may
skip one of the treatment stages. Regardless of that, the main aim of all treatment plants to
achieve a high quality effluent that is safe to the humans and environment.
Figure 2.1 summary of a conventional wastewater treatment process
Source: (Ohioline, n.d.)
2.2 Preliminary sewage system
2.2.1 Introduction
Preliminary sewage system is mainly the removal of sewage constituents that ensures the
treatment operations to go on smoothly as well as gain a satisfactory quality of final effluent
( Indah Water Konsortium, 2013). Moreover, a treated sludge could be produce that is suitable
for recovering it for specified disposal objectives such as disposal for the purpose of agriculture
(Epa Environmenta Protection Agency, 1995).
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2.2.2 Types of Treatment Process
The major processes in preliminary sewage system are screening and comminution (grinding),
grit removal, pre-aeration, flow measurement and flow balancing ( Indah Water Konsortium,
2013).
Figure 2.2 Screening
Source: (Cooke, 2014)
Screening
Screening is the first operational process for the wastewater treatment process. It involves the
removal of non-biodegradable and floating solid such as rags, plastics, tin, containers, papers,
and wood that may cause blockage of the accumulation of unwanted material as well as protect
the downstream plant from damage ( GAH Global, 2010). There are fine screening and coarse
screening. Coarse screen is to remove and eliminate the large solid rags and debris from
wastewater with the opening of 0.25 inch while fine screen with the opening of 0.1 inch to 0.6
inch is to reduce the amount of suspended solids before entering to the primary treatment
process (United State Environment Protection Agency, 2003).
The cleaning methods of the screen involve manually cleaning screen and mechanically
cleaning the screen. Manually cleaning is important to avoid the accumulation of the solid inside
the screen (R.Spellman, n.d.). The solids are removed manually and frequently by the operators
as it may cause the emanation of the odors, insects and rodent problem (R.Spellman, n.d.).
While mechanically cleaned screen uses the mechanized rake to discharge them out and keep
in a storage hopper with maintenance work such as lubricating the equipment (R.Spellman,
n.d.).
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Moreover, the disposal ways of solids are by burial in an approved landfill or grinding the solids
into small particle and later placed back to the wastewater flow for further processing in both
manually and mechanically cleaned screen (R.Spellman, n.d.).
Figure 2.3 Comminutor
Source: (Cooke, 2014)
Comminution
Comminution is under the process called shredding which is an alternative to screening to
reduce the sizes of the solids and able to pass through the plant without causing clogging to the
machine (R.Spellman, n.d.). The solid that pass through are chopped between the cutters
however floating or large objects are not able to be discharged. Aligning, sharpening and
replacing the cutters are needed to maintain the good condition of the comminutors (R.Spellman,
n.d.).
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Figure 2.4 Grit Chamber
Source: (Cooke, 2014)
Grit removal
Grit removal is physical unit operation through grit chamber or centrifugal separation of the
sludge (about civil.org, 2014). The main function of the grit removal is to remove heavy
inorganic solids which include sand, gravel, clay, egg shell, coffee grounds, metal filing and
seeds to prevent the excessive mechanical wears (R.Spellman, n.d.).
Pre-aeration
Pre-aeration is a process of forcing and compressing the air into the wastewater by mechanical
agitation to promote the absorption of the atmosphere air hence increases the reduction of
Biochemical Oxygen Demand (BOD) in grit chamber (Cooke, 2014) .
Flow measurement
Flow measurement is used to ensure the efficiency of wastewater treatment process, collect
information for hydraulic and organic loading, and preparation of the compliance report. Flow
rates are gained from the quantity of liquid that passes through the specific point at a given time.
(Darine, 2000)
Flow balancing
Flow balancing or flow equalization is to enhance the performance of the treatment plant by
providing stable organic loading (Darine, 2000). The excessive flow is directed to the storage
basin and hence maintains an adequate mixing and aeration during low flow period for the
safety
purpose
(Darine,
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2000).
2.3 Primary sewage system
2.3.1 Introduction
In primary sewage system, the processes involved are sedimentation and floatation to separate
the suspended sludge and high amount of organic matter from wastewater using primary
clarifier ( Indah Water Konsortium, 2013). Total suspended solid and the Biochemical Oxygen
Demand level could also be reduced in this stage (Evoqua Water Technologies, 2014).
2.3.2 Treatment Process
Primary Clarifier
Primary clarifier is the process when wastewater flows slowly into the large tank from the
screening and grit removal process (Alberta Capital Region Wastewater Commision, 2014).
Organic sludge will settle and later pumped to the gravity thickener according to the solid‟s
weight. The surface of the wastewater will float with the grease and scum will appear on the
surface of the wastewater (The City of Watertown, New York, n.d.). The scum is then skimmed
off the tank by decanting and sent to the digesters for biological treatment. The remaining
clarified liquid with dissolved material will flow to the secondary stage (Alberta Capital Region
Wastewater Commision, 2014).
Figure 2.5 Sedimentation and Floatation
Source: (Alberta Capital Region Wastewater Commision, 2014)
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2.4 Secondary Sewage Treatment
2.4.1 Introduction
Secondary sewage treatment involves the process of activated sludge, bio- infiltration and
sedimentation ( Indah Water Konsortium, 2013). The objective for the secondary treatment or
biological treatment is to provide biochemical oxygen demand (BOD) by converting dissolved,
suspended, and colloidal organic wastes to more stable solids so that it can be removed
through settling and released to the environment without causing harm (R.Spellman, n.d.).
2.4.2 Types of Treatment Process
Activated Sludge
In activated sludge process, the aeration tank or the basin acts as the dispersed- growth reactor
that mixes the suspended solid in the wastewater and microorganism for the purpose of
supplying oxygen to the biological suspension by aeration devices. Next, the microorganisms
are separated from the liquid through sedimentation and clarified liquid is produced as
secondary effluent. Part of the biological sludge is recycled to the aeration basin to maintain the
level of suspended solids. The remaining sludge are removed and sent for further sludge
processes (Natural Resources Management and Environment Department, 2014).
Bio-Filter
A bio-filter consists of a basin support media such as stones, plastic shapes or wooden slats. A
layer of biological and fixed film is formed when the microorganism is in contact with the media.
Oxygen by natural flow and forced air by blowers are supplied to the film (Natural Resources
Management and Environment Department, 2014). As the result, the thicknesses of bio-film
increase as the new organisms grow (Natural Resources Management and Environment
Department, 2014). A portion of the film is removed or sloughed off from the media by
separating the liquid in a secondary clarifier and the clarifier liquid is a secondary effluent
(Natural Resources Management and Environment Department, 2014). To enhance the
performance of the hydraulic distribution filter, part of the film is being recycled to the bio-filter
(Natural Resources Management and Environment Department, 2014).
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Rotating Biological Contactors (RBCs)
Rotating biological contactors (RBCs) carries the same function with bio-filter (Natural
Resources Management and Environment Department, 2014). However, the media in RBCs is
a rotating dics that sinks partially into the flowing wastewater in the reactor (Natural Resources
Management and Environment Department, 2014). The attachment of the bio-film from the air
could supply oxygen when the film is exposed on the air or submerged in the liquid (Natural
Resources Management and Environment Department, 2014). The transfer of the oxygen to the
wastewater by surface turbulence can create the dics rotation (Natural Resources Management
and Environment Department, 2014).
Fixed Film System
In fixed film system, biological growth such as biomass or slime is used to adjoin to the media
which may be stone, redwood, and other durable substances that could withstand against
weather (R.Spellman, n.d.). When the wastewater in contact with the slime and the media, the
organisms will remove and oxidize the organic solids (R.Spellman, n.d.). The media is used to
provide large open space ventilation for slime growth. Trickling filters and rotating biological
contractors are under the process of fixed film devices (R.Spellman, n.d.).
Suspended Growth System
Suspended growth system uses a biological growth mixed with wastewater. To improve water
quality, wastewater reacts with the microorganism in the surface of the water to allow the
breakdown of the organisms (IHS Global Spec, 2014).
2.5 Tertiary sewage system
2.5.1 Introduction
Tertiary sewage system is a chemical and biological process treatment to discharge the
nutrients, toxic substances including heavy metals, suspended solids and pathogen ( Indah
Water Konsortium, 2013). The processes include filtration, disinfection and tertiary ponds.
However, not all countries go through tertiary treatment system, some countries stop at
secondary treatment. For example, in Malaysia, the wastewater treatment systems mainly focus
on the basic standard of preliminary, primary and secondary treatment ( Indah Water
Konsortium, 2013).
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2.5.2 Treatment Process
Disinfection
The method of disinfection involves injecting chlorine solution at the head end of the chlorine
contact basin. Moreover, ozone and ultra violet irradiation can be used for disinfection but is not
common. Chlorine contact basins are designed in rectangular shape channels with baffles to
prevent short circuiting as well as to provide a contact time of 30 minutes. PH, contact time,
organic content and effluent temperature are the other factors when disinfection takes place
(Natural Resources Management and Environment Department, 2014).
Figure 2.6 maturation ponds in Korba, Tunisia
2.6 Benefits of Conventional Wastewater Treatment System
In general, all wastewater treatment plants play a major role to the entire population in the world.
There are a few benefits of conventional wastewater treatment system such as solving the
problem of insufficient water supply and protecting the environment and living beings
Insufficient Water Supply
Although the Earth surface is covered over 70% of water, but the real issue that is concerning
the human population is the quantity of clean and fresh water available. Referring to T. Dooley
(2014), out of 70% of water on Earth surface, 97.5% of it is salt water, thus leaving 2.5% as
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fresh water. In 2.5% of fresh water, approximately 70% of that fresh water is frozen in the
icecaps of Greenland and Antarctica; thus leaving the remaining present as soil moisture, or
present in deep the underground aquifers as groundwater which is not accessible for human to
use. Hence, there is only less than 1% of the world's fresh water (approximately 0.007% of all
water on earth) is accessible for direct human consumption. This is the water found in lakes,
rivers, reservoirs and those underground sources that are shallow enough to be recovered at a
reasonable cost. Hence it can be said that only this amount is frequently renewed by rain and
snowfall, and is therefore available on a sustainable basis. According to Soli J Arceivala and
Shyam R Asolekar (2006), there are two types of reusable wastewater after treatment, reuse of
urban wastewater in agriculture and horticulture from sewered areas, and reuse in industrial and
commercial establishments to meet chronic water shortages in public water supplies.
The reuse of urban wastewater in agriculture and horticulture are collected from sewered areas
and later treated to be clean and reused for a good cause. If the water is not treated, it may
improve or deteriorate the soil condition, which affects the farming activity. Besides that, the
reuse of urban wastewater in industry and commerce is able to meet water shortage with a
simple step of water conservation and obeying the code which mentions that the greater the
extent of reuse one wants, the higher the degree of treatment will be. Hence, by conserving, the
recycle process of wastewater is reduced and maintaining sufficient of water supply.
Protect Environment and All Living Beings
Wastewater that is not treated or treated partially would affect the aquaculture or even leading
to pollution and hazard disease. Microorganisms present in the wastewater will contaminate the
water source, hence resulting in killing millions of aqua creatures, and producing a strong odor
which may cause the livings near the area to suffer, or human suffering from water borne
diseases that may be fatal. Thus, the wastewater produced must be treated with suitable
treatment methods before discharging into any water course to avoid unwanted problems to
occur.
2.7 Problems with Conventional Wastewater Treatments Systems
All machines, systems or methods will always have its benefits and problems. Thus, the
problems associated with conventional wastewater treatment system is cost involved throughout
the whole operation
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High cost
Generally, all conventional wastewater treatment systems need a high cost for construction,
operating and maintenance. The initial capital costs, land purchase, engineering design and
supervision charges, civil construction, interest charged on loan during, if any, during
construction period. After the start-up of plant which include direct operating costs and fixed
costs, such as, staff salary, fuel and electricity, transport, maintenance and repairs, and
insurance.
Based on Soli J Arceivala and Shyam R Asolekar (2006), it mentioned that municipal and
industrial effluent treatment plants operate at a high cost. Treatment costs essentially depend
on the type of wastewater to be treated, its quantity and on the treatment process used to
achieve the desired quality of effluent. Studies also indicate that industrial wastewater treatment
is generally more expensive than municipal wastewater due to its high chemical content that
requires advance treatment processes.
2.8 Application of bio-solids and bio-effluents in Malaysia
2.8.1 Introduction
In Malaysia, the average annual rainfall is 2800mm and has an estimated total surface area of
566 cubic meters which is more than enough water to supply for agriculture, domestic and
industry and power sectors (Rifici, n.d.). As sludge could be easily treated with suitable methods,
it should reuse in an organized way to minimize the greenhouse effect that is currently harming
the environment.
2.8.2 Application Methods
On 24th April 2012, Port Dickson Local Council (PLDA) agreed to use the bio-solid and bioeffluent generated from the Indah Water‟s treatment plant for landscaping purpose. These may
in return help in saving cost by replacing the usage of commercial fertilizers to the bio-solid and
bio- effluent in landscaping (Engku Azman Tuan Mat, n.d.).
A research conducted by Agriculture University of Malaysia (UPM) shown that rubber tree with
the application bio-solid has a better growth rate compared to those rubber trees which used the
conventional fertilizers
(Indah Water Konsortium, 2012). From the interview of “The Most
Prospect Group”, mentions that plants that uses sludge fertilizers grew very quickly as sludge is
rich in various nutrients (Kadir, 2013).
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The chairman of Indah Water Konsortium, Datuk Ir Abdul Kadir Mohd Din said, “The sludge is
reusable and recyclable in the form of solid, liquid and waste. The effluent can be reused in
cooling system in industrial area. In domestic area, the effluent can flush toilets as well as
gardening and landscaping based on the concept of sustainability through zero waste
management” (Rifici, n.d.).
Moreover, Indah Water Company had proposed to produce bricks using bio-solid through latest
advance technology – Nanotechnology (Rifici, n.d.). As the brick quality is indicated by the
sludge proportional and the firing temperature, results shows that sludge contents can decrease
the brick shrinkage when firing. Through compressive tests, the strength of the brick added with
10% of sludge is similar to the normal clay bricks (Chih-Huang Weng, 2002).
Chairman of Indah water had proposed to invest in renewable energy resources with bio-solid
during the interview of “The Most Prospect Group” (Kadir, 2013). Methane gas is the by product
from the wastewater treatment can be used as renewable energy source while reducing
greenhouse effect (Rifici, n.d.). In Indah Water‟s Research and Development, they are looking
forward to change sludge into coal (Kadir, 2013).
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3. Sustainable Wastewater Treatment
3.1 Introduction
Statistics have shown that there are approximately two million tons of sewage waste coming
from industries and agriculture sectors being discharged into waterways and there is a minimum
of 1.8 million children at the age below five that suffers from water related disease and dies
(United Nations Environment Programme, 2010).
Throughout the years, the word „sustainable‟ has been defined in various ways by different
individuals. According to the World Commission on Environment and Development,
sustainability is the ability to meet the needs of the present without affecting the ability of the
future generations to meet their own needs (Evans, 2014). On the other hand, World Wide Fund
for Nature defined sustainable as” improving the quality of human life while living within the
carrying capacity of the Earth‟s supporting ecosystem” (Evans, 2014).
Thus, sustainable wastewater treatments is needed to produce a higher quality effluent that will
cause a minimum amount of damage Mother Nature without the usage of additional chemicals
that may pollute the environment neither a higher usage of energy as the earth‟s resources are
depleting.
3.2 Factors Affecting the Design of the Wastewater Treatment System
Health and Hygiene
The concerns of the public on the risk of being expose to harmful pathogens and dangerous
substances that could affect their health through the sanitation system such as toilets (Women
in Europe for a Common Future, 2010).
Environment and Natural Resources
The energy, water and other resources that are needed for the construction, maintenance and
operation of the treatment system and also the potential release of gases that could harm the
environment is involved in this category. Other than that, it also includes the recycling and reuse of the wastewater, biogas and bio solids (Women in Europe for a Common Future, 2010).
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Technology and Operation
The entire system must be able to function in an easy manner which includes collection,
transport, treatment and re-use of final products, as well as the operation of the systems by the
local authority or technicians. Besides that, whether or not the area has a vulnerability of power
failures, floods, and inadequate water source (Women in Europe for a Common Future, 2010).
Financial and Economic
This factor relates to the issue of the capacity of households and the communities to pay for the
sanitation provided which includes, construction, operations, maintenance and other required
areas (Women in Europe for a Common Future, 2010).
3.3 Types of sustainable wastewater treatments
The types of sustainable wastewater treatments that will be discussed in this section are
Microbial Fuel Cell (MFC), Constructed Wetland Treatment and Up-Flow Anaerobic Sludge
Blanket (UASB)
3.3.1 Microbial Fuel Cell
3.3.1.1 Introduction
Microbial Fuel Cell (MFC) is a new approach towards the production of electricity from
wastewater treatment. There is a similarity to the Chemical Fuel Cell (CFC) which is both cells
convert chemical energy into electricity. The main difference between these two cells is that
CFC uses elemental catalyst to speed up the process whereas MFC uses bacteria to catalyze
the fuel oxidation (Satira Hambali et al., 2014). Bacteria are microorganisms that are able to
convert a variety of organic compounds into useful resources (Microbial Fuel Cell, 2008).
MFC is also called a bioreactor that uses catalytic reactions of various microorganisms which is
put in anaerobic conditions to convert chemical energy into electricity. Microbes or
microorganisms have a natural presence in the waste and will generate electrons as the digest
the organic material in the sludge (Saiful Bahri Kamaruddin, 2013). It is a sustainable
wastewater treatment as it addresses to the issue of bioenergy and has a minimum amount of
sludge production. The reason for the reduced amount of sludge produced is because only a
small fraction of energy is used up by the microorganism for growth (sludge) while a large
portion is being utilized for the conversion of bioenergy (Satira Hambali et al., 2014).
22
3.3.1.2 Working Principle
MFC has an anode (anaerobic chamber) and cathode (aerobic chamber) compartment
separated by a Proton Exchange Membrane (PEM).
At the anode compartment,
microorganisms oxidize the fuel and hence producing carbon dioxide (CO2), electrons and
protons. Through an external circuit, electrons are transferred to the cathode while protons are
being transferred through the PEM. At the cathode compartment, electrons and protons are
used up combining with oxygen to produce water (Saiful Bahri Kamaruddin, 2013). The related
equations are shown below:
(CH2O)n + nH2O
4e- + 4H+ + O2
nnCO2 + 4ne- + 4nH+ (Oxidation reaction at the anode)
2H2O (Reduction reaction at the cathode)
The overall reaction is the degradation of the organic matter and the generation of electricity
(Satira Hambali et al., 2014).
Figure 3.1 The sequence of the process in the Microbial Fuel Cell
Source : (Mercer, 2012)
Although this waste treatment is sustainable, however there are still a few challenges to
overcome. Firstly, the electricity generated is still small and hence may still be unable to supply
sufficient power to the waste water treatment plant. Besides that, materials used for the MFC is
costly such as Platinum which is used at the cathode and PEM (Saiful Bahri Kamaruddin, 2013).
However, further researches are being conducted to increase the production of electrical power
23
such as reduced anode-cathode spacing and new separator materials (Westenhaus, 2012). A
possible substitution material for platinum that is being looked into is the biocathodes that uses
bacteria as a catalyst (Satira Hambali et al., 2014).
3.3.2 Constructed Wetlands
3.3.2.1 Introduction
Constructed wetlands are “wastewater treatment systems that are composed of one or more
treatment cells in a built and partially controlled environment designed and constructed to
provide wastewater treatment” (United States Environmental Protection Agency, 2000). Wetland
is considered to be one of the most biologically diverse and productive natural ecosystems.
Wetlands are being constructed to treat wastewater in less dense areas as it aids in the
improvement of the water quality and help save wildlife habitat. Furthermore, constructed
wetlands also have a lower operating and maintaining and are able to support fluctuating water
levels. In addition, constructed wetlands is a favorable choice of treating wastewater because it
gives aesthetical value to the land and eliminate odors coming from the wastewater (United
States Environmental Protection Agency, 2004).
3.3.2.2 Guidelines for Construction of Wetlands Treatment
Certain guidelines are needed in order to construct a successful wetland. Firstly, to avoid
damage to the natural wetlands and aquatic life, construction can only be carried out on uplands
and outside floodplains. Secondly, the role of the wetlands must also be looked into. For
example impact on water quality or adjacent land uses. Other than that, soil suitability,
vegetation and existence of endangered species must also be considered before deciding the
location of construction. There must also be suitable control of water that will be easy to adapt if
changes in quality, depth or flow is required. Lastly, a good management plan is needed to
ensure its sustainability in a long-term (United States Environmental Protection Agency, 2004).
Generally, constructed wetlands provide a pretreatment for the wastewater by filtration, settling
and decomposition of bacteria. The treated effluent produced should have less than 30mg/ liter
of Biochemical Oxygen Demand (BOD), less than 25mg/liter Total Suspended Solids (TSS) and
less than 10000cfu/100mL fecal coliform bacteria in it (Gustafon et al., 2002).
24
3.3.2.3 Types of Constructed Wetlands
There are two types of constructed wetlands, named Surface Flow (SF) and Subsurface Flow
(SSF).
Surface Flow Wetland
SF wetlands is more similar to natural wetlands from appearance as they have aquatic plants
that are planted in the soil on the bottom of the wetland where the water will flow through the
leaves and stems of plants (United Environmental Protection Agency, 2000). A common SF
system consists of a basin or channel that is surrounded by a barrier of ponded wastewater and
soil to support the roots of the vegetation‟s. This type of constructed wetland is more suitable for
large community systems in mild climates (Gustafson et al., 2002).
Figure 3.2 A schematic diagram of the Surface Flow Wetland
Source: (Water Online, 1999)
Subsurface Flow Wetland
SSF wetlands has a different appearance from natural wetlands as this system does not have
standing water, instead it contains a bed of crushed rocks sand or soil that has aquatic plant on
top. Wastewater flows beneath the soil or crushed rocks through the roots and rhizomes of the
plant; hence the wastewater is not visible to others (United Environment Protection Agency,
2000). SSF wetland is normally used for small flows of wastewater such as individual homes or
small cluster of resorts (Gustafson et al., 2002).
25
Figure 3.3 The Process of a Conventional Subsurface Wastewater Infiltration System
Source : (Feeney, n.d.)
Figure 3.4 A schematic diagram of a subsurface wetland system
Source: (Gustafon et al., 2002)
SSF wetlands is normally more favourable than SF wetlands as the issue on mosquito‟s are
negligible, have less ordor issues, have better thermal protection as wastewater flows beneath
the soil and the soil or rock gives a bigger surface area that supports the development of
microorganisms (State of Ohio Environmental Protection Agency, 2007).
3.3.2.4 Treatment Process by Constructed Wetlands
After going through the septic tanks, the wastewater enters into the constructed wetlands
through the distribution box. As the wastewater flow through the plants, solids are being
removed by filtration and settling within the root hair of the plants. Some organic matter will also
be removed but eventually it will be removed through biodegradation where bacteria consume
the waste materials and hence converting them into other forms for example methane or carbon
dioxide. These products produced are then used up the plants or bacteria. The biological
treatment involved here may be anaerobic (septic tanks) or aerobic as wetlands are exposed to
26
the atmosphere or by “leaking” of the oxygen coming from the roots of the various aquatic plants.
Some septic tanks also have active aeration component in cooperated in it for aerobic process
to take place and thus fully breaking down the BOD and nitrifying the ammonium (Gustafon et
al., 2002).
Constructed Wetlands consists of four components, which are liner, distribution box, plants and
underdrain system.
Liner functions as the separator to prevent groundwater from entering the system from below
(Gustafon et al., 2002).
Distribution box serves as the purpose to distribute the wastewater across the wetland, either by
gravity or pressure (Gustafon et al., 2002).
Plants in the system are used to filter and break down organic matter. The flower must grow and
flourish in the system so that the system can operate at a maximum efficiency (Gustafon et al.,
2002).
The underdrain system which is located the end of the wetland carries the treated effluent out of
the wetland and maintains the level of the effluent below the surface of the gravel or rocks to
prevent the breeding of mosquitoes (Gustafon et al., 2002).
However, there are also drawbacks of using a constructed wetland system to treat wastewater.
Firstly, wastewater with a high concentration of certain pollutant may not be suitable as it may
not be able to filter out the pollutant. Each wetland is required to be built differently depending
on the usage and climate of the community (State of Ohio Environmental Protection Agency
2007). Moreover, this system requires a large area of land for construction and hence is not
appropriate for high density areas (Feeney, n.d.).
3.3.3 Up-Flow Anaerobic Sludge Blanket (UASB)
3.3.3.1 Introduction
UASB reactor is an anaerobic treatment system that functions based on the break-down of
organic materials through anaerobic digestion (Spuhler, 2014). Through anaerobic digestion,
the UASB reactor produces methane as a biogas and forms a blanket of granular sludge that is
processed by the anaerobic microorganisms (Miller, 2013). Conversion rate in UASB is higher
compared to the conventional anaerobic processes because of its high biomass concentration
27
(Uemura, Harada, 2010). UASB utilizes minimum amount of energy because it neither requires
mechanical mixing within the reactor nor recirculation of sludge and effluent is needed (Uemura,
Harada 2010). Other than that, the biogas (methane) produced can be recovered and used as a
source of energy in the treatment plant (Uemura, Harada, 2010).
3.3.3.2 Treatment Process
UASB treat waste starting from the bottom of the reactor. The substrate slows rise up through
the sludge bed first and later passes through the sludge blanket that is made from a biologically
form of granules and particles (Karthikeyan, Kandasamy, n.a.). The microorganisms that are
present in the sludge blanket will digest the organic pollutants in the wastewater. Granular
sludge is formed from the maturation of suspended sludge and is vital as the bacteria present in
the granules have a better efficiency rate in producing biogas (Spuhler, n.d.).
Figure 3.5 The cross section of a UASB
Source: (Spuhler, n.d.)
28
Figure 3.6 A Up-Flow Anaerobic Sludge Blanket used in China
Source: (Tian Yue, 2010)
The UASB reactor also has a 3 phase (Gas-Liquid-Solid or also known as GLS) separator
situated on top of the sludge blanket to separate solid particles (sludge) apart from the gas,
liquid and solid formed (Miller, 2013). Biogas that is formed is prevented from going in the
settling compartment but is instead being collected in the gas collector for later usage,
suspended solids settles down in the compartment while the effluent is being released for
further treatment (Lier, Anand Vashi, Lubbe, Heffernan, 2010) .
One of the major disadvantages of using this type of treatment to treat wastewater is the posttreatment is required before the water can be discharged as the effluent may still contain
bacteria or viruses. Furthermore, a constant temperature of 15 degrees Celsius to 35 degrees
Celsius is needed for the anaerobic process hence it is not suitable for cold weather countries.
Highly skilled people are needed for the operation and monitoring of this system (Beddow,
2010).
29
4. Sustainable Wastewater Management
4.1 Introduction
Water pollution and water scarcity have been one of the major issues discussed in today‟s world
(Dr. Seetharam Chittoor Jhansi, etc., 2013). As discussed in the previous sections, water
scarcity has and always been an issue in today‟s world. With the fast pace of human population
growth, the source of potable water will be threaten.
A sustainable wastewater treatment management is a treatment system that is energy saving,
easy to operate, low in investment, operation and maintenance cost, and environmental friendly
(Dr. Seetharam Chittoor Jhansi, etc, 2013).
Table 4.1 The Three Main Urban-Water and Resource-Management Sustainability Goals
Economy

Able to achieve a financially stable state with sufficient
resources to sustain infrastructures
Environment

Able to have a locally sustainable water supply

Energy-neutral system with a minimum amount of
chemical consumption

An efficient nutrients management that reduces the
disposal and thus protecting the aquatic environment
Society

Able to have easy access to clean water and suitable
sanitation for all
Source : (Daigger, 2008)
In order to face future environmental issues in a sustainable method, wastewater must be
acknowledged as an alternative source of water, energy, nutrients and other materials (The
International Water Association, 2014).
4.2 Reasons of Why Countries have Unsustainable WWM
One of the reasons why certain countries have unsustainable WWM is because of the
commonly used centralized treatment systems. Based on Centre for Science and Environment
(2013), these systems have been said to be costly, difficult to operate and failed to cater the
massive amount of wastewater produced. Partially treated of untreated effluent then flows to the
water body can thus causes harm to the environment.
30
Other than that, the other reason is that some developing countries utilize technologies that are
the same from Western treatment systems without considering the inappropriateness no matter
in culture, land and climate. In addition, different countries produces different amount of sewage.
For instance, domestic wastewater in arid areas such as the Middle East has a higher
concentration of oxygen demand per volume sewage compared to countries such as US and
Europe (Dr. Seetharam Chittoor Jhansi, etc., 2013).
4.3 Methods to have a Sustainable Wastewater Management
There are various methods to produce a sustainable wastewater management system as such
using a decentralized treatment system and having proper energy management
4.3.1 Utilizing a Decentralized Treatment System
Up to now, there are still many countries that use centralized wastewater treatment system.
Centralized treatment systems or known as “public sewer systems”, commonly provide service
for established towns and large cities. It carries the wastewater to a central location for
treatment. On the other hand, decentralized treatment systems are systems that are not linked
to a public treatment system. The wastewater collected from houses can either be treated onsite or to a private treatment plant (Idaho Department of Environmental Quality, 2014).
Table 4.2. Comparison of centralized and decentralized wastewater treatment system
Centralized Treatment System
Old
and
taught
in
Differences
engineering Knowledge
schools
High in capital cost
Decentralized Treatment System
New and not taught in engineering
schools
Capital Cost
Transfers water away from source Effluent
Low in capital cost
Keeps water close
basin
Highly trained operators
Skills
Basic operation skills
Long, disruptive construction
Construction
Short, less-disruptive construction
Source : (Kreissl, 2009)
4.3.1.1 Benefits of Decentralized Treatment System
There are many benefits of using decentralized wastewater treatment system instead of
centralized treatment system. The benefits are as below:
31
Increasing Water Quality and Availability
Decentralized wastewater treatment system is able to treat domestic sewage effectively and
efficiently thus protecting and supporting local water supplies. Besides that, wastewater from
this system maintains in the local watershed. As the wastewater returns to the drain field, it
disperses into the underlying soil and later recharges the groundwater or flow back to the local
watershed. The treatment level for advanced decentralized treatment systems are comparable
to the centralized wastewater treatment system and at the same time keeping the amount of
phosphate and nitrogen that enter into the groundwater to a minimum. In addition, more
contaminants can be removed when the wastewater is discharged to the soil (United States
Environmental Protection Agency 2014). Furthermore, this system can also be design to suit the
community needs. For example different communities have different soil conditions, water
tables, locations of stream or rivers from the community and different ecosystem (Ministry for
the Environment, 2014).
Using the Natural Treatment Properties of the Soil
Decentralized treatment system enables wastewater to be treated by using the natural
environment.
Pollutants and the money spent on solving pollution can be reduced by
preventing them from entering the lakes and rivers. Soil plays a role in filtering and providing the
natural treatment by filtering out those harmful bacteria, viruses and nutrients (United States
Environmental Protection Agency, 2014).
4.3.2 Proper Energy Management
In the past, the cost of fossil fuels and electricity was relatively low and stable and thus not
much attention was paid on the design and operation of the wastewater treatment system.
However, with the increasing cost of energy, depleting source of fossil fuels suppliers and
impacts of greenhouse gas emissions, efficient energy management is needed (Metcalf, Eddy
2014). Proper energy management is vital to take the opportunity to recover and utilize energy
from sources within the treatment facilities (Metcalf, Eddy, 2014).
4.3.2.1 Factors for Energy Management
The factors of achieving a more efficient energy management are to save the cost of energy
and to improve energy supply reliability
32
Energy Cost Savings
To operate a wastewater treatment facility, a massive amount of energy resources is required to
bring about various reactions. The cost spent on operating the system comes second after
labour cost. Thus energy cost can be saved by using energy efficient equipment, controlling the
process for optimized energy use and selecting the suitable energy sources (Metcalf, Eddy,
2014).
Reliable Supply of Energy
A reliable supply of energy for treatment systems are vital as unforeseeable events for instance
a major blackout of power supply. Although most of the treatment plants have emergency
generators, but the power from the generators are not sufficient to operate in full scale. In reality,
wastewater actually contains more energy than that needed for treatment, hence it can also be
said that if all the energy in the wastewater are recovered, the treatment plants could become
the net exporters of energy (Metcalf, Eddy, 2014).
4.3.2.2 Types of Energy in Wastewater
Wastewater contains chemical energy and thermal energy. Energy that is contained in organic
molecules is chemical energy that can be released through chemical reactions. Thermal energy
is the heat retained in the wastewater (Metcalf, Eddy, 2014).
Chemical Energy
Wastewater contains inorganic and organic molecules which will release the chemical energy
retained in the molecules when it undergoes exothermic reactions. A certain portion of the
chemical energy is taken from the liquid stream in the form of sludge in preliminary and primary
stage of treatment. Besides that, another part of the chemical energy is transformed into
biomass and reaction products such as carbon dioxide and methane during the biology
treatment. During sludge processing, methane gas can be recovered and used at a source of
energy (Metcalf, Eddy, 2014).
33
Figure 4.1 shows the distribution of chemical energy in conventional wastewater treatment plant
through anaerobic treatment and activated sludge treatment
Source: (Metcalf, Eddy, 2014)
Chemical energy that has been recovered can be utilized after transforming the wastewater
constituents that contains the chemical energy into fuel. The recovering of chemical energy has
been used at treatment plants by generating biogas from sludge with anaerobic sludge digestion.
These biogases have been used for boilers and other combustion systems to provide energy for
others. Other than that, dried biosolids can also be used a source of energy. The principal
technologies used to produce electricity from the burning of gaseous fuels taken from
wastewater are reciprocating engines, gas turbines and microturbines (Metcalf, Eddy, 2014).
Figure 4.2 Typical processes for recovering and utilizing biogas produced by anaerobic
digestion of sludge
Source: (Metcalf, Eddy, 2014)
34
Figure 4.3 Typical processes for recovering of chemical energy by the combustion of sludges
and biosolids
Source: (Metcalf, Eddy, 2014)
In addition, boilers can also be used to recover gaseous fuels. Boilers are commonly used at
treatment facilities to produce hot water or steam for steam turbines, space heating and hot
water supply. Heat is required at treatment plants to heat up anaerobic digester and building,
and sludge pretreatment and drying. The difference between using engines or turbines and
boilers to recover gaseous fuels is that gas pretreatment is not need when biogas is used for
boilers (Metcalf, Eddy, 2014).
Thermal Energy
In wastewater, thermal energy exists in the form of temperature. Wastewater effluents, heated
air or exhaust from unit processes that involves combustion of fuels are sources where thermal
energy can be recovered. These excess heats can be used for heating the digester, drying up
the solids, supplying hot water and warming up the space. Restoring and usage of thermal
energy involves the transferring of heat energy from a heat source to a heat demand (Metcalf,
Eddy, 2014).
Heat can be recovered from two sources, which are combustion systems and wastewater.
Exhaust heat from engine generators generates a high temperature of waste heat to produce
hot water or steam. Wastewater typically has a higher temperature compared to the ambient
temperature and thus can act as a reliable source of thermal energy. During warmer seasons, it
35
can be utilized as a heat sink. Due to the low availability of heat in the wastewater, a heat pump
is used to recover the heat from the wastewater (Metcalf, Eddy, 2014).
4.3.3 Methods of Proper Energy Management
Method of proper energy management includes minimizing the usage of energy at treatments
plants and increasing the energy production at the treatment plant itself.
Minimizing Usage of Energy
Energy usage at treatment plants can be reduced to a minimum by making some modification
and optimization to the treatment processes. For example controlling dissolved oxygen in
activated sludge. This method will not only reduce power consumption but at the same time
increase process performance reliability
(Metcalf, Eddy, 2014).
Increasing Energy Production Onsite
Energy production can be increased by having a more efficient method to remove organic
materials from wastewater before introducing it to the biological secondary treatment for
anaerobic digestion. Research has shown that it is possible to remove a total of 70% of the total
suspended solids in the primary effluent. Other than that, improving the volatile solid destruction
in the anaerobic digesters is also another method to increase energy production (Metcalf, Eddy,
2014).
36
5. Case Study
5.1 Introduction
Each countries produces different amount of waste, which may contain different kinds of organic
or inorganic materials, and thus have different treatment facilities to treat the waste. There are
certain countries that have their wastewater to undergo primary process but some do not.
Hence, case study is conducted to have a better understanding on different wastewater
treatment plants that are operating in different countries. In this report, there will be two case
studies discussed, the first one is an Up-flow Anaerobic Sludge Blanket Reactor-Ceramic
Membrane Bioreactor Plant (UASB-Ceramic MBR Plant) situated in Jurong, Singapore and the
other is Eco Machine at the heart of Omega Center for Sustainable Living, Rhinebeck, New
York.
5.2 UASB-Ceramic MBR Plant, Jurong, Singapore
5.2.1 Introduction
“With one of the most advanced water management systems in the world, Singapore is fast
becoming a global hub for water management knowledge, technology and services”
(International Enterprise Singapore 2014). Singapore has been recognized for its excellent field
in health, economic and education system, however one of the major issues faced is that
Singapore do not have sufficient water source to meet its needs. In the past years, Singapore
has been importing millions of liters of potable water from neighboring country, Malaysia through
pipelines (Duerr 2013). Although there is rain all year round in Singapore, however due to
limited space, additional reservoirs can‟t be built (Duerr, 2013).
Hence, PUB, Singapore‟s national water agency and MEIDEN Singapore collaborated to build
Singapore‟s first UASB-Ceramic MBR Plant to not only treat wastewater but also to recycle
industrial used water (Water World, 2014).This treatment plant has a treatment capacity of
4550m3 approximately 1 million gallons per day (Science Direct, 2014).
5.2.2 Treatment Process
UASB-Ceramic MBR Plant is the first of its kind in Singapore that merges two types of
technology, named the up-flow anaerobic sludge blanket (UASB) and the ceramic membrane
bioreactor (MBR) (Woo, 2014).
37
5.2.2.1 Up-Flow Anaerobic Sludge Blanket (UASB)
Up-Flow Anaerobic Sludge Blanket is an anaerobic treatment process that breaks down organic
matter through digestion. Further information has been discussed in section 3 of sustainable
wastewater treatment. Singapore decided to use UASB in this treatment system as it is able to
remove organic contaminants more efficiently compare to other conventional pretreatment
systems (Science Direct, 2014).
5.2.2.2 Ceramic Membrane Bioreactor (MBR)
Figure 5.1 A Flat-Sheet Ceramic MBR by MEIDEN
Source: (Meidensha Corporation, 2013)
UASB reactor discussed above is a pretreatment for wastewater and thus post treatment is
required. Membrane bioreactor (MBR) is a combination of a filtration process such as
microfiltration or ultrafiltration along with an activated sludge treatment to produce a high quality
effluent (Lesjean, Judd, 2006). There are many types of MBR available in the market, however
in this case study, the flat-sheet ceramic membrane is used. The flat-sheet ceramic membrane
from Meiden has a precise removal of suspended solids of 0.1 μm or larger and has a good
resistance towards chemicals, oil and heat. Other than that, it also has a low deterioration rate
on a long-term usage and saves more energy compared to other membrane. The efficiency of
the membrane filtration can be recovered by cleaning the membrane with high pressure water
or suitable chemical accordingly (Meiden Water Treatment Solutions, 2009).
38
Figure 5.2 Types and sizes of suspended solid removed by the flat type ceramic MBR
Source: (Meiden Water Treatment Solution, 2009)
Figure 5.3 Ceramic MBR units used at the Jurong, Singapore treatment plant
Source: (Woo, 2014)
39
Figure 5.4 Equalization Tanks (EQ Tanks) at the Jurong reclamation plant
Source: (Woo, 2014)
Figure 5.5 Aeration tank for Ceramic MBR at Jurong
Source: (Woo, 2014)
40
5.2.3 Recycled Potable Water (NEWater)
5.2.3.1 Introduction
UASB-Ceramic MBR Plant situated at Jurong, Singapore is able to treat and recycle wastewater
up to 1 million gallons per day for industrial usage only. However, in order to produce potable
water, further advance treatment is needed. NEWater is of high quality recycled water produced
from treated effluents that undergoes further treatment in order to enable the water to be safe to
drink. It has passed approximately one hundred thousand tests and fulfilled the World Health
Organization requirements (Singapore Public Utilities Board, 2013). NEWater now meets up to
30% of Singapore‟s water requirements (Singapore Economic Development Board, 2014).
5.2.3.2 Process Involved in NEWater
Microfiltration (MF)
The first stage of treating the treated wastewater is through MF. Treated effluents passes
across the membrane to remove or filter out suspended solids, bacteria or viruses thus only
remaining dissolved solids and organic molecules (Singapore Public Utilities Board, 2013).
Reverse Osmosis (RO)
In this stage of treatment, a semi permeable membrane is used to only permit very small
molecules for example water molecules to pass through. Hence, it further filtrate unwanted
contaminants. At this stage, the water produced is considered of high quality (Singapore Public
Utilities Board, 2013).
Ultraviolet or UV Disinfection
UV disinfection is the last stage of treatment to ensure that all harmful organisms are inactivated
and thus the purity of the produced water is guaranteed (Singapore Public Utilities Board, 2013).
41
5.3 Eco Machine, Omega Center for Sustainable Living, Rhinebeck, New York
5.3.1 Introduction
Eco Machine, situated at the core of the Omega Center for Sustainable Living is water filtration
system that does not have an appearance of a wastewater treatment plant. The naturalinfluenced technology used by the Eco Machine is designed by Dr. John Todd, who is a pioneer
in ecological design (OMEGA, 2014). Eco Machine is a water reclamation system that uses
plants, bacteria, algae and fungi to recycle the wastewater. In other words, Eco Machine is a
constructed wetland. It is able to treat up till 5 million gallons of wastewater per year (BNIM,
2010). Treated water will be returned to the large aquifer deep below the campus (OMEGA,
2014). The whole building operates based on solar and geothermal power only and hence no
additional energy is needed for operation. Other than that, Omega Center for Sustainable Living
also serves as a learning place to educate people on the power of nature (Tackett, 2013).
Figure 5.6 The Outside appearance of the Eco Machine.
Source: (Tackett, 2013)
42
Figure 5.7 People visiting Omega Center for Sustainable Living
Source: (Tackett, 2013)
5.3.2 Treatment Process
Wastewater from the campus is collected and conveyed into two equalization tanks (EQ tanks)
so that the system is able to consistently know the range of the water flow as it depends on the
people in the campus. The wastewater from the EQ tanks is then put through the treatment
processes (John Todd Ecological Design, 2012). There are a few stages involved which are
septic tanks, equalization and anoxic tanks, constructed wetlands, treatment lagoons and recirculating sand filter.
Stage one (Septic Tanks)
Initially, all the wastewater from the EQ tanks is distributed into two huge septic tanks. Organic
matters are being break down in the septic tanks through anaerobic process. The suspended
solids in the tanks are digested and settle to the bottom of the tanks (John Todd Ecological
Design, 2012).
Stage two (Equalization and Anoxic Tanks)
Effluent from the septic tanks flows into two equalization tanks where additional separation of
water and solid takes place. Since the inflow wastewater is not balanced due to the number of
occupants, the EQ tanks will evenly distribute the wastewater to the anoxic tanks over a 24-hour
43
cycle. In the anoxic tanks, nitrates and phosphate is removed and the partially treated
wastewater flow to the splitter where it is further distributed to four constructed wetlands (John
Todd Ecological Design, 2012).
Stage three (Constructed Wetlands)
A total of four wetlands are constructed by Omega. “Native loving plants” which are recognized
for their ability to aid in treating wastewater are used at the wetlands. Oxygen is contributed by
the roots of the plants to the water. The roots of the plants also serve a purpose of supplying a
surface area for the bacterial processes to metabolize the nutrients present in the wastewater.
Through this process, ammonia is converted into nitrates. These nitrates are then converted into
nitrogen gas which is not harmful to the environment (John Todd Ecological Design, 2012).
Stage 4 (Treatment Lagoons)
Treatment lagoons contain plants, fungi, algae, snails, and bacteria to further clean the water.
On the other hand, these living organisms use the nutrient coming from the water to grow and
thrive (Solaripedia, 2009).
Stage 5 (Sand Filtration)
The water is then further cleaned though sand filtration. Microorganisms that are living or
attached to the sand grain traps the solids or consumes the organic compound. At this stage,
the water has achieved a high quality state that is able to be reused for non-potable usage
(John Todd Ecological Design, 2012).
Stage 6 (Dispersal Field)
The treated effluent is then returned to the underground aquifer through the soil. The purified
water is able to be used for usage such as toilet flushing in the campus (John Todd Ecological
Design, 2012).
44
Septic tanks
Subsurface Dispersal
Constructed
Wetlands
Aerated Lagoons
Sand Filter
Figure 5.8 The plan view of the Omega Center for Sustainable Living and the location of the
treatment processes
Source: (The Omega Center for Sustainable Living, 2007)
45
6. Recommendations for Future Improvement of Wastewater Treatment Processes
6.1 Introduction
In the recent years, many scientist and researchers have been developing innovative ways to
provide the world with various alternatives to treat wastewater efficiently without harming the
environment. The main objective is to recover excess energy that is stored in other sources and
to minimize the energy usage by undergoing different biological processes (Metcalf, Eddy,
2014).
6.2 Methods of Improvements
Recovering Excess Energy Contained in Various Sources
Normal conventional primary clarification obtains approximately 50% of total suspended solids
(TTS) and 30%-40% of chemical oxygen demand (COD). TTS and COD that have not been
removed in the primary treatment process will undergo the secondary process for further
treatment. If there is a method to remove all of the particulate COD before the biological
treatment, more energy could be recovered. One of the methods that could be used is the
Primary Effluent filtration (PEF). Thus, with a combination of PEF and primary sedimentation,
approximately 90% of TTS and 60 % of COD could be removed (Metcalf, Eddy, 2014).
Minimizing the Usage of Energy by Using Different Biological Processes
Currently, there are various upcoming biological processes that are being looked further into for
their potential in saving energy and chemical consumption, for example the removal of nitrogen.
A new process called partial nitritation and deammonification can be utilized to reduce 60% of
oxygen demand as well and reduces 90% of its demand for external carbon sources compared
to the conventional nitrification and denitrification (Metcalf, Eddy, 2014).
Anaerobic Baffled Reactor can be used to improve the treatment for wastewater. It is capable to
remove heavy sediment solids; consequently carryover wastewater will have lower chemical
oxygen demand level before going to next step of processes. A common construction of
Anaerobic Baffled Reactor includes different compartments with various outlet levels and series
of baffles plates so that heavy solids have no chance of escaping. Basically, it is an enhanced
septic tank which aims to boost up the removal efficiency and dissolved solids. Furthermore, it
uses a series of baffles to force the wastewater to flow under and over the baffles as it passes
from the inlet to the outlet. In addition, anaerobic treatment processes consume less energy and
46
produce less sludge, consequently lead to lower operational costs compared to aerobic
processes. Although Anaerobic Baffled Reactor treatment is beneficial, but both remaining
sludge and effluents still need further treatment in order to be reused or discharged properly.
Figure 6.1 The Cross Section of an ABR
According to MOREL & DIENER (2006), anaerobic baffled reactors are based on a physical
treatment and a biological treatment. One of the advantages of using this system is that it
generally requires low level of maintenance because basically there are no mechanical moving
parts and the baffles position is already fixed without needing further renovation. However,
when the sludge accumulation starts to increase and eventually build up to spill over to another
section. Therefore, it needs auto desludging system to prevent waste from carryover to the
corresponding compartment.
Another major advantage of using anaerobic baffled reactor is that energy usage and
consumption will be at minimal level. The only requirement is to drive the pump to transfer
wastewater to a higher level elevated tank which then feeds by gravitational force going to the
reactor. Some of the anaerobic baffled reactor had hybrid systems which increase the treatment
efficiency. The figure below show had a reactor contains two baffled up-flow and two anaerobic
filter chambers after an initial settling tank. Anaerobic treatment in the pond enhances the
47
microbial
quality
of
the
effluent
(SASSE,
1998)
Figure 6.2 Cross section of a hybrid baffled septic tank with clarifier
Other methods to reduce the energy usage are anaerobic treatment at ambient temperature and
membrane-absorption process. Anaerobic processes utilized less energy compared to aerobic
processes as they do not need aeration for the removal of biodegradable chemical oxygen
demand and also produce biogas that can be used for energy production. On the other hand,
membrane-absorption process is a process that will not need biological treatment to treat
wastewater. Wastewater that has been filtered will further undergo a series of different
membranes and residual organic matter that passes through the membrane will be absorbed
(Metcalf, Eddy, 2014).
48
7. Conclusion
In conclusion, the process of acquiring recycled and reusable water has to be well-developed
and planned. In order to obtain the recycled water efficiently, a R&D (research and development)
department is an essential. Wastewater treatment plants are changing and also different from a
country to another as different countries have different needs as discussed in the previous
section. Thus, the researchers must keep on developing new techniques or a better way to
obtain a higher quality effluent that is able to be reused. In such ways, new processes may save
more energy, time and resources, and prevent pollution, which then is available for others to
use it immediately.
49
8. References
About Civil 2014, Preliminary Treatment of Water by Screening, Grit Removal and Sedimentation, About
Civil, Available at: http://www.aboutcivil.org/preliminary-treatment-process-of-waste-water.html
[Accessed 26 May 2014]
Alberta Capital Region Wastewater Commission 2014, Primary Clarifiers, Alberta Capital Region
Wastewater Commission, Available at:
http://www.acrwc.ab.ca/index.php?option=com_content&view=article&id=61&Itemid=200112,
[Accessed 27 May 2014]
Beddow, V 2010, Up-Flow- Anaerobic Sludge Blanket Reactor (UASB), Available at:
http://www.iwawaterwiki.org/xwiki/bin/view/Articles/UpflowAnaerobicSludgeBlanketReactor#HAbout
Upflow%2DAnaerobicSludgeBlanketReactor28UASB29, [Accessed 15 May 2014]
BNIM 2010, Omega Center for Sustainable Living First Green Building in America to Achieve Both
LEED© Platinum and Living Building Challenge™ Certification, BNIM, Available at:
http://www.bnim.com/news/omega-center-sustainable-living-first-green-building-americaachieve-both-leed%C2%A9-platinum-and-li, [Accessed 26 May 2014]
BNIM 2013, Omega Center for Sustainable Living, BNIM, Available at:
http://www.bnim.com/work/omega-center-sustainable-living, [Accessed 24 May 2014]
Centre for Science and Environment 2013, Decentralized/ Sustainable Wastewater Treatment,
Centre for Science and Environment, Available at: http://www.cseindia.org/node/3798,
[Accessed 21 May 2014]
Chih-Huang Weng, D.-F. L. ,. P.-C. C., 2002. Utilization of sludge as brick material. Advance on
enviromental research, p. 1.
Cooke, R.L. 2014, Wastewater distance learning, Available at: http://water.me.vccs.edu/,
[Accessed 24 May 2014]
Daigger, GT 2008, New Approaches and Technologies for Wastewater Management, The Bridge, 38(3),
p.p. 40-47, Available at: https://www.nae.edu/File.aspx?id=7423, [Accessed 20 May 2014]
Darine, J., 2000, Flow Measurement, Available at:
http://books.google.com.my/books?id=2z24NRadPMkC&printsec=frontcover#v=onepage&q&f=
false, [Accessed 26 May 2014]
Drinan, J.E, Spellman, F.R., 2013, Water and Wastewater Treatment 2nd edi, Taylor & Francis Group, LLC
Duerr/ss, R.I., 2013, Water Scarcity in Singapore Pushes ‘Toilet To Tap’ Concept, Available at:
http://www.dw.de/water-scarcity-in-singapore-pushes-toilet-to-tap-concept/a- 16904636,
[Accessed 18 May 2014]
50
Engku Azman Tuan Mat, J. S. V. K. H., n.d. Wastewater Production, Treatment and use in Malaysia,
Malaysia: s.n.
Environmental Protection Agency 1995, Preliminary water treatment, Environmental Protection
Agency, Environmental Protection Agency, Available at:
https://www.epa.ie/pubs/advice/water/wastewater/EPA_water_treatment_manual_preliminar
y.pdf, [Accessed 25 May 2014]
Evans, M 2014, What is Sustainability?, Available at:
http://sustainability.about.com/od/Sustainability/a/What-Is-Sustainability.htm, [Accessed 20 May 2014]
Evoqua Water Technologies 2014, Primary Wastewater Treatment, Evoqua Water Technologies,
Available at:
http://www.water.siemens.com/en/applications/wastewater_treatment/primary_treatment/Pa
ges/default.aspx, [Accessed 27 May 2014]
Feeney, K, n.d., Guidance for Using Decentralized Wastewater Treatment Systems in Santa Barbara
County, Available at:
http://www2.bren.ucsb.edu/~keller/courses/GP_reports/Wastewater%20Guidance%20Book_Final.pdf,
[Accessed 5 June 2014]
GAH Global, 2010, Screening, Gah Global, Available at: http://www.gahglobal.com/index.php?option=com_content&view=article&id=100&Itemid=90, [Accessed 5 June
2014]
Gustafson, D.M., Anderson, J.L., Christopherson, S.H., Axler, R., 2002, Constructed Wetlands, Available
at: http://www.extension.umn.edu/environment/water/onsite-sewage-treatment/innovative-sewagetreatment-systems-series/constructed-wetlands/index.html, [Accessed 26 May 2014]
Improware Project, n.d., Swim Program, Available at:
http://athene.geo.univie.ac.at/pucher/gallery/view_photo.php?set_albumName=album57&id=
Photo1, [Accessed 10 June 2014]
Indah Water Konsortium, 2012, Indah Water supports green technology, helps reduce the usage of
precious potable water, s.l.: Indah Water Konsortium.
Indah Water Konsortium 2013, Sewage Treatment Methods, Indah Water Konsortium, Available
at: http://www.iwk.com.my/v/knowledge-arena/sewage-treatment-methods, [Accessed 21 May
2014]
International Enterprise Singapore 2014, Water and Wastewater Management, International Enterprise
Singapore, Available at:
http://www.iesingapore.gov.sg/~/media/IE%20Singapore/Files/Publications/Brochures%20Foreign%20C
ompanies/Water%20Wastewater%20Management/IE_Water%20and%20Wastewater%20Management
_EN.pdf, [Accessed 28 May 2014]
51
Kadir, I. A., 2013, Wastewater management and sustainability in Malaysia [Interview] (3 March
2013).
Kalman, M., 2011, A Less Wasteful Way to Deal with Wastewater, Available at:
http://www.technologyreview.com/news/424582/a-less-wasteful-way-to-deal- with-wastewater/,
[Accessed 5 June 2014]
Kreissl, J 2009, Centralized vs Decentralized Wastewater Management For CAPE COD, Available
at:
http://www.chathamct.org/images/2009/12/CAPE%20COD%20JK%2012.05.09%20MASHPEE.pd
f, [Accessed 22 May 2014]
Metcalf, Eddy, 2014, Wastewater Engineering: Treatment and Resource Recovery 5th edn, McGraw Hill,
New York, U.S.
MBR-Network 2006, Facts on MBR-Technology, Available at: http://mbr-network.eu/mbrprojects/index.php, [Accessed 19 May 2014]
Ministry for the Environment 2014, Wastewater Management Systems, Ministry for the Environment,
Available at: http://www.mfe.govt.nz/publications/waste/wastewater-mgmt-jun03/html/part1section3.html, [Accessed 25 May 2014]
MEIDENSG 2007, Water Technology, MEIDENSG, Available at:
http://www.meidensg.com.sg/ceramicmembrane.htm, [Accessed 16 May 2014]
MEIDENSHA 2009, Ceramic Membrane Unit, MEIDENSHA, Available at: http://watersolution.meidensha.co.jp/filter_e/#section-01, [Accessed 15 May 2014]
Mercer, J 2012, Microbial Fuel Cells: Generating Power from Waste, Available at:
http://illumin.usc.edu/printer/134/microbial-fuel-cells-generating-power-from-waste/,
[Accessed 19 May 2014]
Microbial Fuel Cells 2008, General Principles of MFCs, Microbial Fuel Cells, Available at:
http://www.microbialfuelcell.org/www/index.php/General/General-priniciples-of-MFCs.html, [Accessed
15 May 2014]
Morel, A., Diener, S., 2006, Greywater Management in Low and Middle-Income Countries,
Available at:
http://www.sswm.info/sites/default/files/reference_attachments/MOREL%20and%20DIENER%
202006%20Greywater%20Management.pdf, [Accessed 3 June 2014]
Murphy, S., 2007, General Information on Solids, Available at:
http://bcn.boulder.co.us/basin/data/NEW/info/TDS.html, [Accessed 15 May 2014]
Natural Resources Management and Environment Department, 2014. Wastewater characteristic
and effluent quality parameter, s.l.: s.n.
52
Ohio Environmental Protection Agency 2007, Small Subsurface Flow Constructed Wetlands with Soil
Dispersal System, Ohio Environmental Protection Agency, Available at:
http://www.epa.ohio.gov/portals/35/guidance/pti3.pdf, [Accessed 2 June 2014]
Ohioline, n.d., Wastewater Treatment Principles and Regulations, Ohioline, Available at:
http://ohioline.osu.edu/aex-fact/0768.html, [Accessed 3 June 2014]
OMEGA 2014, Eco Machine, OMEGA, Available at: http://www.eomega.org/omega-in-action/keyinitiatives/omega-center-for-sustainable-living/eco-machine%E2%84%A2, [Accessed 2 June 2014]
R.Spellman, F., n.d, Spellman's Standard Handbook In: Wastewater Operators, Taylor& Francis
Group, United State ,pp. 233,234.
Rifici, v., n.d., IWK adds values to waste, Available at: http://www.worldfolio.co.uk/print.php?id=542,
[Accessed 30 May 2014]
Saiful Bahri Kamaruddin 2013, Power Generation through Waste Water Treatment Using
Microbial Fuel Cell, Available at: http://www.ukm.my/news/index.php/research-news/1355power-generation-through-waste-water-treatment-using-microbial-fuel-cell.html, [Accessed 18
May 2014]
Sassel, L., 1998, Decentralized Wastewater Treatment in Developing Countries, Available at:
http://www.sswm.info/sites/default/files/reference_attachments/SASSE%201998%20DEWATS%20Dece
ntralised%20Wastewater%20Treatment%20in%20Developing%20Countries_0.pdf, [Accessed 28 May
2014]
Satira Hambali, Suhaimi abdul Talib, 2011, Microbial Fuel Cell: Transformation of Wastewater to
Green Energy, Jurutera, pp 18-20
Seetharam Chittoor Jhansi, Santosh Kumar Mishra, 2013, Wastewater Treatment and Reuse:
Sustainability Options, Consilience: The Journal of Sustainable Development, 10(1), p.p 1-15, Available at:
http://www.consiliencejournal.org/index.php/consilience/article/viewFile/308/159, [Accessed 20 May
2014]
Singapore Economy Development Board 2014, Singapore’s four solutions for water scarcity,
Singapore Economy Development Board, Available at:
http://www.edb.gov.sg/content/edb/en/news-and-events/news/singapore-businessnews/Feature/Singapores-four-solutions-for-water-scarcity.html, [Accessed 12 May 2014]
Singapore Public Utilities Board 2013, NEWater Technology, Singapore Public Utilities Board, Available
at: http://www.pub.gov.sg/water/newater/newatertech/Pages/default.aspx, [Accessed 14 May 2014]
Solaripedia 2007, The Omega Center for Sustainable Living, Solaripedia, Available at:
http://www.solaripedia.com/files/383.pdf, [Accessed 6 June 2014]
53
Solaripedia 2009, Project: Omega Center for Sustainable Living (New York, USA), Solaripedia, Available
at: http://www.solaripedia.com/13/101/914/omega_center_floor_plan_(new_york).html, [Accessed 29
May 2014]
Spec, I.G., 2014, Suspended Growth Treatment Systems Information, Available at:
http://www.globalspec.com/learnmore/manufacturing_process_equipment/environmental_ins
truments_equipment/suspended_growth_treatment_systems, [Accessed 10 June 2014}
Spuhler, D 2014, UASB Reactor, Available at: http://www.sswm.info/category/implementationtools/wastewater- treatment/hardware/semi-centralised-wastewater-treatments/u, [Accessed 18 May
2014]
Tackett, C 2013, The World’s Most Beautiful Wastewater Treatment Plant, Available at:
http://www.treehugger.com/green-architecture/omega-center-sustainable-living-eco-machineliving-building-water-treatment.html, [Accessed 5 June 2014]
The City of Watertown,N.Y, n.d., Sewage Treatment Plant, Avaialble at: https://www.watertownny.gov/index.asp?NID=684, [Accessed 26 May 2014]
Tian Yue 2010, New UASB Reactor, Tian Yue, Available at: http://www.tianyueep.com/tianyue/files/product236.htm, [Accessed 4 June 2014]
The International Water Association 2014, IWA Specialist Conference on Global Challenges for
Sustainable Wastewater Treatment and Resource Recovery, The International Water Association,
Available at: http://www.iwahq.org/271/events/iwa-events/2014/global-challenges.html, [Accessed 25
June 2014]
Uemura, S., Harada, H., 2010, Application of UASB Technology for Sewage Treatment with a
Novel Post-Treatment Process, Environmental Anaerobic Technology: Applications and New
Developments, Imperial College Press, pp91-109
United States Environmental Protection Agency 2000, Manual: Constructed Wetlands Treatment of
Municipal Wastewaters, United States Environmental Protection Agency, Available at: http://my.ewbusa.org/theme/library/myewb-usa/projectresources/technical/EPA%20625r99010%20Const%20Wetland%20Manual.pdf, [Accessed 25 May 2014]
United State Environment Protection Agency 2003, Wastewater Technology Fact Sheet, United
State Environment Protection Agency, Available at:
http://water.epa.gov/aboutow/owm/upload/2004_07_07_septics_final_sgrit_removal.pdf,
[Accessed 21 May 2014]
United States Environmental Protection Agency 2004, Constructed Treatment Wetlands, United States
Environmental Protection Agency, Available at:
http://www.epa.gov/owow/wetlands/pdf/ConstructedW.pdf, [Accessed 23 May 2014]
54
United States Environmental Protection Agency 2012, What is turbidity and why is it important?,
United States Environmental Protection Agency, Available at:
http://water.epa.gov/type/rsl/monitoring/vms55.cfm, [Accessed 25 May 2014]
United States Environmental Protection Agency 2014, How can Decentralized Wastewater Treatment be
Green, United States Environmental Protection Agency, Available at:
http://water.epa.gov/infrastructure/septic/upload/MOU-Green-Paper-081712-V2.pdf, [Accessed 25
May 2014]
Water Online 1999, Surface Flow Systems Work Like Natural Wetlands, Water Online, Available
at: http://www.wateronline.com/doc/surface-flow-systems-work-like-natural-wetlan-0001,
[Accessed 29 May 2014]
Water World 2014, Industrial water in Singapore Treated with Ceramic MBR and UASB Process, Water
World, Available at: http://www.waterworld.com/articles/2014/03/industrial-water-in-singaporetreated-with-ceramic-mbr-and-uasb-process.html, [Accessed 18 May 2014]
Westenhaus, B 2012, New Microbial Fuel Cell can Produce Electricity from Waste Water,
Available at: http://oilprice.com/Alternative-Energy/Fuel-Cells/New-Microbial-Fuel-Cell-canProduce-Electricity-from-Waste-Water.html, [Accessed 13 May 2014]
Women in Europe for a Common Future 2010, Sustainable and cost effective wastewater systems,
Women in Europe for a Common Future, Available at:
http://www.wecf.eu/download/2010/03/guidancepaperengl.pdf, [Accessed 21 May 2014]
Woo, SB 2014, PUB, Japanese firm open new water recycling and treatment plant in Jurong,
Today Online, Available at: http://www.todayonline.com/singapore/pub-japanese-firm-opennew-water-recycling-and-treatment-plant-jurong, [Accessed 19 May 2014]
55