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Wastewater Treatment Technology: A Green Application in Aquaculture
© 2014 All rights reserved. No part of this publication may be reproduced or transmitted in any form or by any means, electronic or mechanical including photocopy, recording or any information storage and retrieval system, without permission in writing from the Director, Penerbit UMT, Universiti Malaysia Terengganu, 21030 Kuala Terengganu, Terengganu, Malaysia.
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Published in Malaysia by / Diterbitkan oleh Penerbit UMT, Universiti Malaysia Terengganu, 21030 Kuala Terengganu, Terengganu, Malaysia.
http://www.umt.edu.my/penerbitumt E-maill: [email protected]
Perpustakaan Negara Malaysia Cataloguing-in-Publication Data
Ahmad Jusoh, 1955- WASTEWATER TRAETMENT TECHNOLOGY: A GREEN APPLICATION
IN AQUACULTURE : INAUGURAL LECTURE UNIVERSITI MALAYSIA TERENGGANU / Ahmad Jusoh.
Bibliografi: ms. 39 ISBN 978-967-0524-52-8 1. Sewage--Purification. 2. Water--Purification. I. Title. 628.3
Set in Arial
Reka bentuk: Penerbit UMTReka letak: Penerbit UMT
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Contents
WASTEWATER TREATMENT TECHNOLOGY: A GREEN APPLICATION IN AQUACULTURE 1Abstract 1Introduction of Water 2Properties of Water 3Hydrologic Cycle 6Source of Water 7 Surface Water 7 Groundwater 9
A GREEN TECHNOLOGY OF WASTEWATER TREATMENT IN AQUACULTURE 11Physico-chemical Treatment 11 Filtration 12 Adsorption 16 Membrane Filtration 18 Ion Exchange 20 Ultra-violet and Ozonation 22 Solar Distillation 24Biological Treatment 25 Trickling Filter and Bio-tower 26 Rotating Biological Contactor 28 Fluidized Bed Filters 29 Reed Bed and Constructed Wetland 30 Microalgae Phytoremediation 33 Bio-floc Technology 37Electrochemical Technology 39 Electrochemical Reduction of Nitrate 40 Electrochemical Oxidation of Organic Compound 41Bio-electrochemical Technology 42 Bio-electrochemical Reduction of Nitrate 43 Bio-electrochemical Oxidation of Organic Compound 44
WATER MONITORING AND CONTROL SYSTEM 47
CONCLUSION 51
References 53
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List of Tables
Table 1: Typical types of contaminants found in water (McKinney et al., 2012) 7
Table 2: BET surface area analysis of CSAC and PSAC (Jusoh et al., 2011) 18
Table 3: Specifications and properties of UF and MF membranes (Lee et al., 2004) 19
Table 4: Uptake data for ammonium ion onto clinoptilolite in the presence of magnesium, calcium and potassium ions (Weatherley & Miladinovic, 2004) 21Table 5: Second-order rate constants of pharmaceuticals
oxidation and pathogen inactivation at pH 8 and T = 20°C (Huber et al., 2005; von Gunten, 2003) 23
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List of Figures
Figure 1: Distribution of Earth Water (Gleick, 1993) 3Figure 2: Triple point of water 4Figure 3: Flow diagram of hydrologic cycle (Sylvan
Source, 2013) 6Figure 4: Confined and unconfined aquifers (NGWA, 2007) 9Figure 5: Saltwater intrusion due to overpumping
of ground water at coastal area 10Figure 6: Transport mechanism in filtration
(Jusoh et al., 2011) 12Figure 7: Production of BOPS from oil palm
(Jusoh et al., 2009) 13Figure 8: A schematic diagram of deep-bed filtration
system (Jusoh et al., 2007a) 14Figure 9: Progress of specific deposit and head loss
in a dual-media BOPS-sand filter with effective size of 0.6:0.5 mm. 15
Figure 10: Pore structure of activated carbon particle consist of macropore, mesopore and micropore 17
Figure 11: Ammonium ion uptake equilibria onto clinoptilolite 22
Figure 12: Schematic diagram of typical complete trickling filter system 27
Figure 13: Isometric view of RAS prototype (Endut et al., 2011; Endut et al., 2010) 31
Figure 14: Theoretical scheme of ammonia in RAS 31Figure 15: Nitrogen mass balance for production system
based on the mass fraction of nitrogen composition relative to the culture feed input 32
Figure 16: Upscale procedure for microalgae cultivation. 33Figure 17: Aquaculture wastewater treatment using immobilized microalgae (de-Bashan
& Bashan, 2010) 34
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Figure 18: Eight different species of microalgae isolated from the South China Sea 35
Figure 19: Microalgae technology transfer with Kerapu Online Hatchery, Besut, Terengganu 36Figure 20: Cultivation of Chlorella sp. for outdoor mass
cultivation at Kerapu Online Hatchery, Besut, Terengganu 37
Figure 21: Symbiotic relationship of microorganism in biofloc technology 38
Figure 22: Induction of bio-flocs formation at Freshwater Hatchery, Faculty of Science and Technology UMT 39
Figure 23: Mechanism of nitrate electro-reduction using zinc and copper electrodes 41
Figure 24: Mechanism of bio-electrochemical reduction of nitrate 44
Figure 25: Mechanism of bio-electrochemical oxidation of organic matter 45
Figure 26: A real-time control system for recirculation aquaculture (Ali, 2010) 48
Figure 27: Remote monitoring system based on 3G networks and ARM-Android embedded
system (Wang et al., 2012) 49
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WASTEWATER TREATMENT TECHNOLOGY: A GREEN APPLICATION
IN AQUACULTURE
Abstract
Nowadays, it is well understood that we must make every possible
effort to protect the environment. The most viable and effective
approach for that purpose is the utilization of green technology. The
main challenge that green technology had to face is the operational
quest for sustainability. Sustainability of the green technology
means the way of running aquaculture industry that can continue
indefinitely into the future without damaging or depleting natural
resources. In addition, green technology could reduce the waste
and pollution by optimizing patterns of aquaculture production
and consumption of the resources. For instance, by facilitating
direct water reuse that reduce the use of hazardous chemicals
require less non-renewable energy source as well as to remove
contaminant. Aquaculture technology could be developed based
on alternatives which is based on renewable energy and materials
which caused insignificant damage to the health and environment.
Among them the most important are physic-chemical, biological,
electrochemical and bio-electrochemical technologies. Normally,
the aquaculture wastewater is physically treated as it runs
through channels or columns of charcoal (activated carbon) and
sand filters. The water ends in final sedimentation tank prior to
fish tank or discharging to water body. Biological treatment using
microorganisms would produce biomass and excess biological
sludge simultaneously with the treatment of the wastewater.
Thus, the sludge handling and disposal process would also have
strong influence on the overall environmental impact. Proper
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management of the produced biomass is vital for the sustainability
of green technology. By proper management, the produced
biomass would contribute greatly to the production of biodiesel,
pharmaceutical precursors and bio-fertilizers whereas poor
management leads to contamination of the environment. Thus,
the use of organic coagulant such as Moringa oleifera, biofloc and
auto-flocculating microalgae Ankistrodesmus sp. were utilized in
the flocculation and biomass harvesting process which is highly
potential and energy efficient approach which could spearhead
the development of renewable energy in this third world country.
This means looking for strategies where water management is
combine with energy and nutrient recovery. As a conclusion,
engineers could provide the insights for better understanding of the
green technology treatment system development which leading
towards a sustainable standards of living to protect environment,
animal and human health especially in Malaysia.
Introduction of water
Water is known as a chemical substance with the formula of
H2O which is also known as dihydrogen monoxide. Water is the
only common substance found naturally in three common states
as solid, liquid and gaseous. Water exist as liquid at ambient
conditions, however, it often co-exists with its solid and gaseous
state as water vapor. A dynamic equilibrium where solid, liquid
and gaseous state of water coexist at specified standard
temperature and pressure is known as the triple point.
Water is the most abundant compound, covering about
two-third (71%) of the Earth’s surface. The waters of the earth
are found on land, in the ocean, and in the atmosphere. The
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distribution of water resources of the earth is shown in Figure 1.
The vast majority of the earth’s water of about 96.5% is available
in the ocean as saltwater, 1.7% in ground water (0.93% saline
and 0.75% freshwater) and 0.001% of the atmospheric water as
vapor, cloud and precipitation (mainly rainfall, only about 2.5%
of the Earth’s water is freshwater). Most of the freshwater is
available as polar ice and ground water.
Figure 1: Distribution of Earth Water (Gleick, 1993).
Properties of Water
Water is a tasteless and odorless liquid and appears colorless in
small quantities even though it has very slight blue hue. Water
vapor is invisible as a gas. Water is relatively transparent in the
visible light, near ultraviolet light and far-red light electromagnetic
spectrum. However, water absorbs most ultraviolet light, infrared
light and microwaves. The aquatic plant can live in water due to
sunlight can penetrate in a transparent water. Pure water has
a neutral pH of 7.0 which is neither basic nor acidic. Initially
rainwater is neutral. However, rainwater falling on earth is
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potentially acidic due to the dissolved carbon dioxide and sulfur
dioxide in the atmosphere.
In addition, other unique physical properties of water are the
triple point. As shown in Figure 2, the temperature and pressure
at which solid, liquid and gaseous water coexist in equilibrium is
called the triple point of water. Thus, the triple point of water is
rather a prescribed value than a measured quantity.
Figure 2: Triple point of water.
Water has relatively high melting and boiling points.
Water also has a very high specific heat capacity and heat of
vaporization. Therefore, it can absorb a huge amount of heat or
energy before it becomes hot. On the contrary, water releases
heat slowly during cooling process. The special conditions
of a high specific heat of water help organisms to regulate or
acclimatized effectively their body temperature with respect to
the surrounding. On top of that, these two unique properties of
water contribute to moderate the Earth’s temperature.
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Water is an excellent solvent which is also known as the
universal solvent. It can dissolve numerous substances or
chemical compounds such as sugars, salts, alkalis, acids and
some gases. A large water bodies such as river and ocean can
dilute specific amount of pollutants. However, there are still many
compounds that are partially or totally insoluble in water. The
soluble properties enable water to carry substances together
during surface runoff, infiltration, ground water flow as well as
water transportation in living organisms.
Water is miscible with some liquids producing the homogenous
liquid. On the other hand, water is also immiscible with some
liquids such as oil and grease, which forming distinctive layers
between liquids and water. Some substances that dissolve in
water are referred as hydrophilic or water loving substances, on
the other hand substances that do not dissolve are known as
hydrophobic or water fear substances.
Pure water functions as an excellent insulator because it
contains no ions. Since water is such a good solvent, it easily
undergoes auto-ionization especially when some solute is
dissolved. A small amount of impurities such as salt readily
separate into various ions in aqueous solution that generate
an electric current. Generally, pure water has a relatively low
electrical conductivity and it increases significantly with the
increasing of dissolved ionic material. Due to water easily
conducts heat than any other liquid (except mercury), large
water bodies such as oceans and lakes have a relatively uniform
vertical temperature profile.
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Hydrologic Cycle
Hydrology is the science of water, which involved with the
occurrence, circulation, and distribution of water on the surface
of the earth and underground as well as in the atmosphere. The
hydrologic cycle is defined as a series of processes of water
as it moves in various phases through the atmosphere, over
and through the land, such as to the river, lake and ocean, and
back to the atmosphere. In this cycle, water is conserved where
there is no water gained or lost, however the water quantity may
fluctuate due to the variations in the source and the changes
encountered during delivery.
Figure 3: Flow diagram of hydrologic cycle (Sylvan Source, 2013).
The major hydrologic processes and their flow path are
illustrated in Figure 3. Assume that the hydrologic cycle may
begin with the evaporation of water from water bodies driven by
energy from the sun. Transpiration is the biological which water
is transferred from the plant to the atmosphere as water vapor
through the leaves opening. The combinations of the evaporation
and transpiration are also known as evapo-transpiration (ET).
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The evaporated vapor, rises by convection to form clouds;
condenses at the dew point in the atmosphere and precipitates
as rain or snow onto the land and ocean surfaces. The quality of
water varies considerably as it moves through the hydrological
phases. Types of contaminants commonly found in water, follow
with some examples are illustrated in Table 1.
Table 1: Typical types of contaminants found in water (McKinney et al., 2012).
Source of Water
Surface Water
Surface water is water collecting on the ground or in a stream,
river, lake, wetland, or the ocean; it is related to water collecting
as ground water or atmospheric water. Surface water is naturally
replenished by precipitation and naturally lost through discharge
to evaporation and sub-surface seepage into the ground.
Contaminant class Types of contaminantsOxygen-demanding waste Plant and animal material
Infective agents Bacteria and viruses
Plant nutrients Fertilizer such as nitrates and phosphates
Organic chemicals Pesticides, such as DDT, detergent molecules
Inorganic chemicals Acids from coal mine drainage, inorganic chemicals such as iron from steel plant
Sediment from land erosion
Clay silt from the stream bed
Radioactive substances Waste product from mining and processing of radioactive material, radioactive isotopes after use
Heat from industry Cooling water used in steam generation of electricity
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Lakes are natural depressions of the land which are filled up
with water. The water in lakes is supplied by a direct rainfall on
the surface of the lake, by surface run-off from the catchment, or
by ground water that seeps through the soil. Fresh water lakes
have a natural outlet through which the excess water discharg-
es. On the other hand, lakes lose water through surface evapo-
ration, via the lake’s natural outlet, or through percolation from
the bottom or side of the lake to the ground water.
Rivers served its purpose around the world as a source
of irrigation and drinking water. The most typical characteristic
defining a river is a flow and not like a reservoir that contains
a fixed amount of water. A new quantity of water is passing at
any given time and location along the river. However, the flow of
river fluctuates over time, which depend on the precipitation. The
flows of some rivers fluctuate greatly especially small rivers in a
small catchment. The water quality of rivers directly influenced
by surface erosion which depend on the land use or activities in
the catchment area. Therefore, the surface water may contain
higher suspended solids as compared to ground water. Even
rainwater has traces of substances dissolved in it that were
picked up during passage through the atmosphere. Much of this
material that washes out of the atmosphere today is pollution,
but there are also natural substances present.
As rainwater passes through soil and percolates through
rocks, it dissolves some of the minerals. This process is known
as weathering. Eventually, this water with its small load of
dissolved minerals or salts reaches a stream and finally flows
into the ocean. The annual addition of dissolved salts by rivers
is only a tiny fraction of the total salt in the ocean. The dissolved
salts carried by all the world’s rivers in the ocean had happened
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for millions of years. The evaporation process only transfers
pure water to the atmosphere and left the minerals or salt in the
ocean. Another example of this phenomenon is the Great Salt
Lake and the Dead Sea. Unlike other freshwater lakes that has
an outlet, these lakes have no outlet and water escapes only by
evaporation. In addition, the hydrothermal vents also contributed
to the salinity of the where water has seeped into the rocks of the
oceanic crust and dissolved some of the minerals from the crust.
Groundwater
Ground water is defined as the water below the land surface in
soil pore spaces and in the fracture of rock formation. An aquifer
is a layer of porous media which contains and transmits water.
The upper layer of an aquifer is considered unconfined when the
water can flow directly between the surface and the saturated
zone. As shown in Figure 4, The upper level of the saturated
zone of an unconfined aquifer is known as the water table. An
aquifer that is overlain by an impermeable layer or clay is called
confined aquifer.
Figure 4: Confined and unconfined aquifers (NGWA, 2007).
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Groundwater is eventually flow to and recharged from, the
surface naturally; natural discharge often occurs at springs
and seeps, and can form oases or wetland or as the beginning
point of a stream and river. Ground water is a major source of
freshwater and serve as a natural reservoir of the water cycle.
It is protected and relatively free of pollution. The hardness in
ground water may be higher as it passes through a limestone
area.
Saltwater intrusion is the movement of saline water into
freshwater aquifers, which can lead to contamination of drinking
water sources (Figure 5). Saltwater intrusion occurs naturally
in most coastal aquifers. Since saltwater has a higher mineral
content than freshwater, it is denser and has a higher water
pressure. Water extraction or ground water pumping from
coastal freshwater wells contribute to the increase of saltwater
intrusion in coastal areas. This activity reduces the level of fresh
ground water and its pressure, thus allowing saltwater to flow
further inland. Furthermore, saltwater intrusion may also include
agricultural and drainage channels, which provide conduits for
saltwater to move inland. The phenomenon of saltwater intrusion
can be mitigated by providing recharge wells or conduit.
Figure 5: Saltwater intrusion due to overpumping of ground water at coastal area.
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A GREEN TECHNOLOGY OF WASTEWATER TREATMENT
IN AQUACULTURE
Water and wastewater treatment is very important in the
aquaculture industries. The level of water treatment depends on
the quality of the source of water. Water treatment is defined as
the processing of the source of water to achieve a water quality
standard that suitable for the specific purpose of aquaculture
requirement. The recent challenges in water treatments are the
elimination of water borne diseases. The main focus shifted from
the acute illnesses to the chronic health effects of trace quantities
of organic, inorganic and microbiological contaminants.
In the aquaculture system, the effluent wastewater must
be treated in accordance to the Department of Environment
(DOE) before discharging to the water bodies. In the case of
recirculation aquaculture system, the wastewater must be
treated up to the influent water quality before entering the
rearing tank. The water and wastewater commonly shared a
similar technology of treatment which include physico-chemical,
biological, electrochemical and bio-electrochemical treatments.
Physico-chemical Treatment
Physico-chemical treatment may include filtration, activated
carbon adsorption, ion exchange, membrane filtration and electro-
dialysis. In certain industrial wastewater treatment processes
strong or undesirable wastes are sometimes produced over
short periods of time (MECC, 2010). Since the periodic inputs
of such wastes would damage a biological treatment process,
these wastes are sometimes held, mixed with other wastewaters,
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and gradually released, thus eliminating shocks to the treatment
plant. This type of process is call equalization. Another type of
equalization can be used to even out wide variations in flow rates.
In addition, physico-chemical treatment is employed to reduce
the fluctuation of waste concentration such as organic loading
and toxic to the following biological and chemical treatments.
Filtration
Filtration is a physical process that commonly used for the
removing particulate matter in water and wastewater treatment.
Granular filter media has been found effective for removing
particulate of a wide range of sizes up to 50 µm that readily exist
in water (Osmak et al., 1997). Most surface waters may contain
high suspended solid contributed by sediment, clay, colloidal
humic compound, other organic and inorganic particulate
matter and microorganism such as algae, viruses, pathogens.
Even though much progress has been made in the aspect of
filtration modelling, there are still no reliable and comprehensive
applicable models of the filtration process (Jusoh et al., 2009).
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Figure 6: Transport mechanism in filtration (Jusoh et al., 2011).
As shown in Figure 6, suspended particles deposited within
a filter increases with time and alters the structure of the filter
media and the nature of the surface interactions between
particles and the filter media (Jusoh et al., 2011). Moreover, the
attachment process is dependent upon the interaction forces
condition, contributed by the charge of the particles, filter grains
and ionic chemicals being used in the influent. Therefore, the
filtration efficiency and the permeability of the media changes
with the operation time. The usage dual-media filter of burned
oil palm shell granule and sand will enhanced the operation
time up to five times compared to a conventional single media
sand (Jusoh et al., 2011). The production of BOPS, filtration
configuration and the results of dual-media are shown in Figure
7, Figure 8 and Figure 9.
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Figure 7: Production of BOPS from oil palm (Jusoh et al., 2009).
Figure 8: A schematic diagram of deep-bed filtration system (Jusoh et al., 2007a).
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Figure 9: Progress of specific deposit and head loss in a dual-media BOPS-sand filter with effective size of 0.6:0.5 mm. (a) filtration velocity, V = 3.62 m/hr and (b) V = 5.81 m/hr; and effective size of 0.8:0.5 mm (c) V = 3.62 m/hr and (d) V = 5.81 m/hr (Jusoh et al., 2009).
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Adsorption
Adsorption is the adhesion of atoms, ions, or molecules from
a dissolved solid that form a film on the adsorbent surface.
Activated carbon adsorption has been extensively used in
potable water and wastewater treatment. The most important
criteria of the activated carbon are the high porosity and surface
area. Activated carbon, also known as porous, has been widely
used as an adsorbent in the separation and purification of liquid.
As shown in Figure 10, activated carbon particle consist of
various structures of pores. Adsorption process has been also
adopted in aquaculture wastewater treatment to remove organic
chemicals and dissolved organic carbon (DOC) (Wang, 1993).
Aitcheson et al. (2001) studied on aquaculture therapeutants
and dissolved organic carbon onto the coal-based granular
activated carbon. They found that the therapeutants Malachite
Green, Chloramine-T and Oxytetracycline were generally
more strongly adsorbed than the dissolved organic carbon.
This therapeutants compounds were utilized in controlling fish
parasites and diseases.
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Figure 10: Pore structure of activated carbon particle consist of macropore (width greater than 50nm), mesopore (between 2 - 50nm) and micropore (less than 2nm).
According to Mostofa et al. (2005) the main components of
dissolved organic carbon in aquaculture wastewater are fulvic
acids, humic acids, carbohydrates, protein-like substance,
phenols, organic peroxides and low molecular weight aldehydes.
The author also had compared the characteristics between
coconut shell activated carbon (CSAC) and palm shell activated
carbon (PSAC) in term of surface area analysis (Jusoh et
al., 2011; Jusoh et al., 2009). As shown in Table 2, Brunauer,
Emmett and Teller (BET) was performed for the activated carbon
prior to the absorption experiments on various contaminants and
toxic compounds. In addition, Jusoh et al. (2011) and Jusoh et al.
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(2005) also reported that GAC could be used to effectively adsorb
pesticide (malathion) from agricultural surface water runoff. This
would reduce the risk of water contamination in the aquaculture
ponds. In the case of heavy metal treatment from water source,
Jusoh et al. (2007b) had predicted the breakthrough curve and
obtain the adsorption capacity of cadmium and lead on GAC.
Table 2: BET surface area analysis of CSAC and PSAC (Jusoh et al., 2011).
Membrane Filtration
Membrane filtration such as reverse osmosis (RO) has potential
to remove proteins, organic chemical and ions in brackish water
and sea water (Afonso et al., 2004; Hilal et al., 2004; Kim et
al., 2009). RO has high efficiency performance in permeability
of selective ion, unchanged molecular structure at room
temperature, no product accumulation in the membrane and
environmental friendly. However, the capital and operation cost
of RO are more expensive. Lee et al. (2004) had reported the
comparison of the physical properties of Ultrafiltration (UF)
and Microfiltration (MF) membranes (Table 3). Moreover, the
UF and nanofiltration (NF) membrane technology are potential
in removing ammonia–nitrogen from the aquaculture system
(Noráaini et al., 2009).
Type of Granular Activated Carbon
Surface Area(m2/g)
Pore Volume(cc/g)
Median Pore Radius
(A)CSAC 850 281 21.78PSAC 788 261 17.27
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Table 3: Specifications and properties of UF and MF membranes (Lee et al., 2004).
* At pH 7.0 and 5mM KCl.
The detail studies aimed to investigate the effect of polymer
concentration on the morphology and perfor mance of an
asymmetric UF membrane for bovine serum albumin (BSA)
separation was reported by Ali et al. (2011). BSA representative
the excreted fish proteins, ammonia and faeces. This research
also proved that polymer concentration would greatly affect the
membrane performance and structural properties, consecutively
enhancing the membranes ability for BSA separation (Ali et al.,
2005). Further investigation has been conducted on the potential
of nano-filtration membrane technology in removing ammonia–
nitrogen from the aquaculture system (Ali et al., 2010). Membrane
productivity and separation performance were assessed via pure
water, salt and ammonia–nitrogen permeation experiments. The
Membrane type
Ultrafiltration (UF) Microfiltration (MF)
Hydrophobic Hydrophilic Hydrophobic Hydrophilic
Membrane code PES, Orelis
YM100, Millipore
GVHP, Millipore
GSWP, Millipore
Pore size 100 kDa 100 kDa 0.22 µm 0.22 µm
Materials PES Regenerated cellulose PVDFMixed
cellulose ester
Pure water permeability
5.15 (gal/ft2 day
psi)
5.15 (gal/ft2 day
psi)
5.15 (gal/ft2 day
psi)
5.15 (gal/ft2 day
psi)
122(L/m2 h bar)
122(L/m2 h bar)
122(L/m2 h bar)
122(L/m2 h bar)
Contact angle 58° 18° 83° 19°
Zeta potential
(mV)*-32 -3 -7 +20
Roughness 6.4 22.9 94.1 96.7
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study managed to remove about 68% of ammonia–nitrogen
and proved nano-membrane technology as a potential in the
treatment of aquaculture wastewater.
Ion Exchange
Ion exchange is the process where ions in solution are transferred
to a solid matrix which, in turn releases ions of a different type
with the same polarity. In other words the ions in solutions
are substituted by different ions originally exist in the solid. Ion
exchange is used in the purification and decontamination of
aqueous solutions solid polymeric or mineral as ion exchangers.
Typical ion exchangers are resins, zeolites, montmorillonite and
soil humus (GATCO, 2012). In fact, ion exchangers are widely
used for water softening by exchanging calcium and magnesium
cations with sodium or hydrogen cations. In aquaculture
wastewater, ammonium ions are normally accompanied with
organic pollutant. Heterotrophic bacteria, which utilize the organic
species, inhibit the growth of nitrifying bacteria to consume
ammonia. Thus, ion exchangers offer an alternative method to
remove ammonia in aquaculture wastewater. Weatherley and
Miladinovic (2004) had carried out experiment to compare the
ion exchange uptake of ammonium ion onto naturally available
minerals, clinoptolite and mordenite. Clinoptilolite is a zeolite
occurring in abundance, especially in volcanic areas and it is
known to have high affinity for ammonium ions. Table 4 shows
the ammonia, magnesium, calcium and potassium ions uptake
on the clinoptilotile via ion exchange mechanism.
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Table 4: Uptake data for ammonium ion onto clinoptilolite in the presence of magnesium, calcium and potassium ions (Weatherley & Miladinovic, 2004).
Jorgensen and Weatherley (2003) investigated on ammonia
removal from wastewater by ion exchange clinoptilolite in
the presence of organic contaminants. In the experiment,
the ammonium ion uptake equilibria onto clinoptilolite was
successfully determined (Figure 11). It was also found that in
most of the cases studied, the presence of organic compounds
enhances the uptake of ammonium ion onto the ion exchangers.
On top of that, ion exchange offer more flexible system, which
can responds rapidly to changes in feed water concentration or
organic loading that associated with flow rate. It can operate
on-line as it immediate responds and offer significantly greater
turndown flexibility compared with bio-filtration. Another
advantage of ion exchange is that the water treatment can
be maintained over a wider range of concentrations and
temperatures. Therefore, ion exchange technique is more
appropriate to be applied to aquaculture systems for water
treatment during fish transportation and as a backup system to
biological filtration system.
Initial ammonia
concentration (N-mg/L)
Percentage of removed ammonia (%)
NH4+ Mg Ca K
10 98.82 94.73 93.66 95.95
40 92.37 86.68 84.78 89.25
70 83.61 79.45 75.65 80.18
90 75.97 71.76 68.50 71.30
150 57.45 54.43 50.40 52.17
200 46.28 42.69 40.09 41.99
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Figure 11: Ammonium ion uptake equilibria onto clinoptilolite (Jorgensen & Weatherley, 2003).
Ultra-violet and Ozonation
Higher stocking density would result in greater stress and related
health implication on fish stock. Common disinfection methods
used in treating water and wastewater are chlorination, ozonation
and ultra-violet (UV) light facilities. However, chlorination is not
suitable for recirculation aquaculture system since this method
produces residual chlorine in the treated water which is harmful
to the aquatic lives. Therefore, RAS commonly utilized UV light
or ozone to destroy any pathogens, parasites and diseases
that may exist in water. Ozone is also helping in oxidizing nitrite
to nitrate, organic matter and total ammonia nitrogen (Aloui et
al., 2009; Bullock et al., 1997). UV light is used together with
ozone treatment because it will destroy excess ozone residuals
(Summerfelt, 2003). UV consists of electromagnetic radiation
of wavelengths ranging from 10 to 400 nanometer (nm). For
instance, UV light at wavelength of 254 nm penetrates the cell
wall of the microorganism. The UV energy permanently alters
the DNA structure of the microorganism. Thus, this inactivates
the microorganism and renders it unable to reproduce or infect.
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The main advantage is that the UV light triggers inactivation
process in a very short time.
Ozone has been successfully improved water quality
in recirculation aquaculture system by reducing parameter
such as carbonaceous oxygen demand, nitrogenous waste,
total suspended solid and color (Summerfelt et al., 1997;
Summerfelt et al., 2004). As shown in Table 5, Buffle et al. 2006)
reported the effectiveness of ozone for the oxidation of harmful
pharmaceutical effluent and pathogen inactivation. In fact, the
main function of ozone in the recirculation aquaculture system
is to eliminate bacteria levels and any fish pathogen (Sharrer
& Summerfelt, 2007; Summerfelt et al., 2009), (Buffle et al.,
2006). Furthermore, Park et al. (2011) evaluated the effects of
two different ozone doses on seawater recirculating systems for
black sea bream Acanthopagrus schlegeli (Bleeker): They found
that ozonation improved the removal efficiency of heterotrophic
bacteria, even at the lowest concentration.
Table 5: Second-order rate constants of pharmaceuticals oxidation and pathogens inactivation at pH 8 and T = 20°C (Huber et al., 2005; von Gunten, 2003).
Pharmaceuticals oxidation
K’’Ozone(M-1 s-1)
K’’Hydroxide(M-1 s-1)
Pathogens inactivation
K’’Ozone(M-1 s-1)
17α-ethinylestradiol 3.16 x 107 9.8 x 109 Escherichia coli 1.04 x 105
Sulfamethoxazol 2.4 x 106 5.5 x 109 Escherichia coli 6 x 104
Diclofenac 105 7.5 x 109 Escherichia coli 2.3 x 104
Carbamazepine 3 x 105 8.8 x 109 Escherichia coli 1.2 x 104
Bezafibrate 5.9 x 102 7.4 x 109 Escherichia coli 6.7 x 102
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Solar Distillation
Solar water distillation is a natural phenomenon on earth that
heats water from water bodies such as rivers, lakes and seas,
evaporates it to water vapor, and condenses it as cloud to
fall back on earth as precipitation. Thus, solar still distillation
represent this natural phenomenon on a small scale. Distillation
is one of many processes that commonly used in laboratory as
well as in community to obtain such pure water. It functions by
evaporating the water from a mixture (or saline) solution and
subsequent condensation of the mineral-free vapor.
Aybar et al. (2005) have investigated on an inclined solar
water distillation system. The results found that the wicks plate
increased the water generation about three times as compared
to bare plate. Therefore, solar distillation process succeed to
remove impurities such as salts, heavy metals and eliminate
microbiological organisms. The end result is a relatively pure
water and in fact cleaner than the purest rainwater. Various
active distillation systems have been developed to overcome
such a lower distillate output in passive solar stills. The solar
distillation proves to be an economical and eco-friendly
technique particularly in suburban areas (Sampathkumar et al.,
2010). In the recent report, Mokhtar et al. (2012) have studied on
the techno-economic assessment for a case study in New South
Wales, Australia using actual weather and wholesale electricity
price data. It is shown that the proposed technology can be
economically viable for solar collector at current retail electricity
prices This is one of the promising technologies for reducing
carbon dioxide from existing fossil fuel power plant.
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Biological Treatment
There are commonly five types of biological treatment used in
aquaculture system including trickling filter, fluidized bed reactor,
rotating biological contactor (RBC) and reedbed (constructed
wetland). These bio-filters have the ability to remove ammonia,
nitrites and dissolved organic solids. Fish produce ammonia,
nitrites and uneaten food as toxic metabolic waste products.
These waste materials need to be treated or converted to less
harmful compound such as nitrate. Normally, three types of
aerobic microorganism colonized bio-filters for aquaculture that
are heteretrophic bacteria, Nitrosomonas sp. and Nitrospira
sp.. Heterotrophic bacteria utilized the dissolved carbonaceous
material as their food source. Nitrosomonas sp. bacteria convert
ammonia to nitrite whereas Nitrospira sp. utilize nitrite to produce
nitrates as a waste product. In order to have a more effective
treatment in removing ammonia, the carbonaceous BOD have
to be removed prior to the bio-filter system.
Bio-filter bacteria (such as Pseudomonas sp. and Nitrobacter
sp.) convert ammonia to nitrite and then nitrate in the nitrification
process as illustrated in Eqn. 2.1 and 2.2.
Ammonia, NH3 + O2 → Nitrite, NO2 (2.1)
Nitrite, NO2 + O2 → Nitrate, NO3 (2.2)
The appropriate materials used in the bio-filter should be
inert material, non-corrodible, UV-resistant, resistant to decay
and impervious to chemical attack. The bio-filter should be
inexpensive to build and easy in operation and maintenance.
Moreover, the bio-filter should be tough enough to withstand the
wear and tear of the aquacultural environment. The energy cost
to operate the bio-filter should be minimal, especially in terms
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of running operation cost. The bio-filter should normally be self
cleaning and does not have any inherent dangers to the aquatic
species and operator.
Trickling Filter and Bio-tower
Trickling filters are one of the most conventional fixed film
biological filters. As shown in Figure 12, rickling filters commonly
filled with packed media of rock, coal or porous media for effluent
wastewater treatment. The high surface area of media provides
the substrate enhancing the growth of a bio-film. In some cases,
air is forced into the filter media to increase the amount of
oxygen for the effective oxidation. Since trickling filters are an
aerobic process, additional oxygen supply is required. Trickling
filters also act as effective strippers to remove carbon dioxide,
hydrogen sulfide, nitrogen or other undesirable volatile gases.
The major drawback of this filter is the energy cost especially in
terms of pumps, aerators and compressors. Thus, trickling filters
is rather rugged, easy to operate and low maintenance cost. A
trickling filter can be upgraded to a bio-tower by supplying extra
capacity (surface area) in the bio-filter to allow a huge number of
bacteria to grow. On top of that, this method helps in making a
longer plug flow path through the bio-filter.
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Figure 12: Schematic diagram of typical complete trickling filter system (Chowdhury et al., 2010).
Asaduzzaman (2006) have been studied on design and
development of a steady state close-cycle aquaculture system
that equipped with trickling filter for intensive culture of
freshwater fish species at Universiti Malaysia Terengganu. Their
findings showed that the density of Oreochromis niloticus (red
tilapia) of about 76 kg/m3 produced a better performance in
terms specific growth rate (SGR), feed conversion ratio (FCR)
and protein efficiency rato (PER) with the ratio of volume of the
rearing unit and the volume of the biological filter of 5:1 compared
to other ratio of 45:1, 23:1 and 10:1. The biomass yield was 5.36,
24.36 and 42.05 kg/m3 for the ratio of the 45:1, 23:1 and 10:1,
respectively. The efficiency of the trickling filter was 37, 54, 70
and 70%, for the ratio of 45:1, 23:1, 10:1 and 5:1, respectively.
On top of that, this system was producing TAN at the rate of
255.90, 454.35, 308.12 and 548.35 g/day, respectively, and at
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the same time the removing of TAN was at the rate of 226.87,
400.78, 284.80 and 527.62 g/day, respectively.
Rotating Biological Contactor
Rotating Biological Contactors (RBC) were commonly used
in domestic wastewater treatment and later being used in
aquaculture wastewater. The RBC reactor is utilizing a unique
attached-growth of bio-film, similar to the trickling filter. A typical
design consist of a bundle of plastic packing that are installed
to a horizontal rotating shaft. Several modules are normally
arranged in parallel and/or in series to accommodate with the
flow and treatment requirements. The disks are about 40 to 50
percent submerged in the wastewater with a very slow speed of
1 to 5 rpm (Brazil, 2006). Alternating exposure to nutrient in the
wastewater and oxygen during rotation is similar concept to the
trickling filter with rotating distributor. Microorganisms growing on
the disks surface treat the nutrient from wastewater and absorb
oxygen from the air to sustain their aerobic metabolic processes.
A treatment system begins with primary sedimentation
preceding the RBC reactor and finally followed by secondary
sedimentation. Waste sludge is mainly withdrawn from the
primary and secondary clarifiers for disposal. RBC units are
preferably protected either under separate plastic covers lined
with insulation or in a building with adequate ventilation. The
main advantages of RBC are high specific surface area, low
energy requirement, less chances of clogging, relatively short
hydraulic retention time and higher tolerance to toxic substrate
(Chowdhury et al., 2010).
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Fluidized Bed Filters
Regular sand filter used for potable water filters are inappropriate
to be used as a biofilter for aquaculture. This is due to the rapid
bio-film buildup in the void spaces between the grains and
produce higher head losses or pressure drop across the filter.
Therefore, more frequent back washing is required and the
beneficial active bio-film is removed each time. On the other
hand, fluidized bed filter can overcome these problems and have
been successfully adapted for aquaculture wastewater filtrations
(Crab et al., 2007; Summerfelt, 2006). A sand filter becomes
fluidized when the sufficient water upflow velocity raise the
grains up. This means that the drag on each particle is sufficient
to overcome the weight of the grain particle and the particle is
suspended in the stream of water.
Fluidized bed filters have several advantages over any other
types of biofilter because they packed higher biologically active
surface area in such a tall column. Thus, it has a small footprint
and alse develop self cleaning as well as higher tolerance with
different nutrient loadings. In contrast, fluidized bed filters have
several disadvantages since they required relatively high energy
requirement to overcome high pressure drop. Furthermore, they
required an additional aeration system to enhance the treatment
performance (Summerfelt, 2006). (Guerdat et al., 2011) have
evaluated the effect of organic carbon on biological filtration
performance in a large scale RAS. The system contained three
types of filters: fluidized sand, floating bead, and moving bed.
The study was based on a 60m3 tilapia with average daily feed
rates of 45 kg using a 40% protein feed and an average biomass
of 6750 kg. The effect of elevated organic carbon concentrations
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on total ammoniacal nitrogen (TAN) removal rates was
evaluated and determined based on biofilter media volume. The
performance of fluidized bed filter is comparable to floating bead
and moving bed.
Reed Bed and Constructed Wetland
The combination of aquaculture and hydroponics are known
as Aquaponics aquaculture systems. In addition to commercial
terrestrial plant grown in a hydroponics system, aquatic plants
such as water hyacinths and duckweed can be used to absorb
nitrates and phosphorus from the aquaculture wastewater.
Emergent plants required water for their root support while their
stems and leaves shoot up above the water surface. The most
common emergent plants locally available with high economic
value are water spinach (Ipomea aquatica) and Watercress
(Nasturtium officinale). Substrates that are normally used are
sand and gravel. The main advantage of the water spinach and
watercress are rapidly growing and can be regularly harvested.
Submerged plants grow completely under water with their
root system attach into substrates such as sand. For example,
submerged aquarium plants like eel grass (Vallisneria sp.) can
be grown in RAS (Figure 13). Furthermore, they also useful
in mitigating the growth of phytoplankton and enhancing the
production of dissolved oxygen in water. The major nutrients
which are required in relatively large quantities to support
the plant growth may include nitrate, phosphate, potassium,
calcium, sulfur oxide and magnesium. Hydroponic plants may
require 10 to 20 percent of total nitrogen as ammonium to
stimulate vegetative growth. Theoretical scheme of ammonia in
recirculation aquaculture system is shown in Figure 14. However,
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a sufficient nitrogen requirement can be produced by the fish in
aquaponic systems and thus no additional nitrogen required.
Figure 13: Isometric view of RAS prototype (Endut et al., 2011; Endut et al., 2010).
Figure 14: Theoretical scheme of ammonia in RAS.
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Nutrient removal is essential for aquaculture wastewater
treatment to protect receiving water from eutrophication and for
potential reuse of the treated water. Figure 15 shows the nitrogen
composition from nitrogen mass balance of the production
system of aquaculture pond. The integration of aquaculture
with agri culture appears to be an excellent way of saving water,
disposing aquaculture wastewater and pro viding fertilizer to the
agricultural crop.
Endut et al. (2011) evaluated aquaponic recirculation
system (ARS) performance in removing inorganic nitrogen and
phosphate from aquaculture wastewater using water spinach
(Ipomoea aquatica) and mustard green (Brassica juncea) in
Universiti Malaysia Terengganu. Overall results suggest that
water spinach is better than mustard green in nutrient removal in
the aquaponics system used due to its root structures provided
more microbial attachment sites, sufficient wastewater residence
time, trapping and settlement of sus pended particles, surface
area for pollutant adsorption, uptake, and assimilation in plant
tissues (Endut et al., 2011).
Figure 15: Nitrogen mass balance for production system based on the mass fraction of nitrogen composition relative to the culture feed input.
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Microalgae Phytoremediation
Microalgae provide a very promising alternative for wastewater
treatment. Its population will be co-propagated as a result of
organic matter bioconversion and incorporation of inorganic
carbon such from carbon dioxide into the cell biomass (Jeong
et al., 2003). Consequently, microalgae phytoremediation also
act in producing microalgae biomass to fulfil the demand for
biofuel productions (Brennan & Owende, 2010; Sharif Hossain
et al., 2008). In addition, microalgae technology also reported to
significantly contribute to the environmental conservation. With
moderate technology and expertise, maintenance and cultivation
of pure culture microalgae could be carried out without any
difficulties. As shown in Figure 16, the upscale of Chlorella sp.
from primary stock culture to 30L mass culture was performed
at the Institute of Tropical Aquaculture by the author’s research
team which focused on the removal of ammonia and phosphate
from aquaculture wastewater.
Figure 16: Upscale procedure for microalgae cultivation. (a) Colony isolation on agar plate, (b) Subculture in 250 mL sterile medium, (c) and (d) Cultivation in 5000 mL and 30 L acrylic tank.
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Nowadays, phytoremediation using microalgae mainly
focused on the use of immobilized culture. Efforts on the
application of suspended microalgae phytoremediation became
less apparent due to the difficulties in biomass separation and
culture maintenance. In immobilized culture, the microalgae
is embedded within the thin film of permeable membrane or
within porous alginate beads. Thus, the microalgae biomass
are immobilized or trapped within the fibrous structure of the
agar preventing free microalgae cell from being suspended in
the water column. Figure 17 shows the utilization of immobilized
microalgae culture in phytoremediating aquaculture wastewater.
Once the treatment had been completed, alginate beads or
membrane is discarded using nets leaving clear treated water.
Its advantage is the easiness of separating microalgae biomass
from the treated with the expense of valuable alginates and
agarose membrane.
Figure 17: Aquaculture wastewater treatment using immobilized microalgae. (a) Nannochloropsis sp. is immobilized in alginate beads, (b) Alginate beads turns into darker green due to microalgae growth (de-Bashan & Bashan, 2010).
In the other hand, the author focused on the utilization of
suspended microalgae in the believe of unlimited absorption
capability and growth performance promised by the
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characteristics of large surface area per volume as compared
to the immobilized culture. Prior to the further researches
on the potential of microalgae as aquaculture wastewater
phytoremediator, the author had screened the best microalgae
species from those isolated from the South China Sea as shown
in Figure 18 with highest ammonia and phosphate removal
efficiency, tolerance to wide range of salinity, temperature
fluctuations and illumination irregularity (Ahmad et al., 2013;
Fathurrahman et al., 2013).
Figure 18: Eight different species of microalgae isolated from the South China Sea.
In addition, field study involving the use of marine microalgae,
Chlorella sp. and Chaetoceros sp. was also performed by the
author and the research team. The biological treatment of
aquaculture wastewater incorporating microalgae is reported
to be successfully adopted in the open pond and enclosed
photobioreactor system (Acién Fernández et al., 2003; Arbib
et al., 2012; Christenson & Sims, 2011). A knowledge transfer
program involving the technique in maintaining and upscaling
microalgae culture was done between the research team with
Kerapu Online Hatchery, Besut on January 2013. Maintenance
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of indoor culture and upscaling of outdoor with very economical
cost was pioneered for the adoption of the technology for the
industry (Figure 19).
Figure 19: Microalgae technology transfer with Kerapu Online Hatchery, Besut, Terengganu. (a) Maintenance of stock culture in control room condition, (b) Cultivation of Chlorella sp. under direct sunlight, (c) Outdoor low-cost cultivation of microalgae.
Marine microalgae were cultivated at community-based
hatchery located at Kampung Air Tawar, Besut, Terengganu
for the purpose of wastewater treatment and live feeds to
fish hatchlings and zooplanktons. In this project, the hatchery
manage to maintain the microalgae production with regular
advice from the university. Figure 20 shows the potential of
marine microalgae mass cultivation to be adopted and practiced
by the community.
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Figure 20: Cultivation of Chlorella sp. for outdoor mass cultivation at Kerapu Online Hatchery, Besut, Terengganu. (a) Inoculation of microalgae on Day 1, (b and c) Growth and increase of biomass density on Day 3 - 5, (d) Microalgae ready for feeding.
Bio-floc Technology
Bio-floc encourages the development a microbial community
in the pond or raceway. Once bio-floc community established,
microbial-dominated areas are more stable than algae-
dominated areas. The microbial accumulate in flocs and
consume the nitrogenous waste more effectively than algae.
Microbial community continuously convert nitrogenous waste
into high protein feed source for the aquatic organism (Crab
et al., 2009). This conversion processes enhanced in a well
balanced of carbon and nitrogen composition as shown in Figure
21. As shown in Figure 22, bio-flocs consist of variety of bacteria,
microalgae (phytoplankton), fungi, aggregates of living and dead
particulate organic matter suspend in water. These bio-flocs
capable of absorbing dissolved and organic particulate waste
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and convert it into microbial biomass. Thus, bio-flocs assist in
reducing feed and disposal waste cost. In order to measure
the amount of bioflocs, Imhoff cones is use as a simple tool as
shown in Figure 22. The following procedure is recommended:
transfer a water sample from the pond to the Imhoff cone and
let it stand for 15-20 minutes and then measure the volume of
settled bioflocs.
Figure 21: Symbiotic relationship of microorganism in biofloc technology (Peavy et al., 1985).
In the case of shrimp farming in pond with intensive aeration,
the recycling of waste is commonly carried out in the following
tank that equipped with bio-flocs reactor. Microorganisms are kept
in suspension in the bio-reactor where flocs is provided. Organic
material and nitrogenous waste are absorbed and assimilated
by the bio-flocs. The uptake of inorganic nitrogen by bacteria
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is reported to be effective when the C/N ratio is greater than 10
(Burford et al., 2003). According to Zhu and Chen (2001), further
addition of organic carbon contributed to heterotrophic bacteria
growth and resulting in limitation of the denitrification process.
Figure 22: Induction of bio-flocs formation at Freshwater Hatchery, Faculty of Science and Technology UMT. (a) Formation of bio-flocs in catfish tank, (b) Measurement of bio-flocs in imhoff cones, (c) Microorganism composition in bio-flocs complex.
Electrochemical Technology
Electrochemical is applying electro-chemical processes in
any types of industrial application such as nanotechnologies,
synthesis of pharmaceutical products, wastewater treatment and
heavy metal recovery. One of the most relevant applications of
(a)
(b) (c)
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the electrochemical technology in aquaculture is the treatment
of wastewater with high organic compounds. Electro-chemical
technologies have several advantages over biological treatments
such as the ability in treating high toxic waste, operation at
ambient temperature and environmental friendly. Electrochemical
concept can be used in water and wastewater treatment in terms
of deposition for heavy metal recovery, coagulation of suspended
solid, floatation in generating gas bubbles attaching to flocs,
oxidation of chlorine and ozone and microbial disinfection.
Electrochemical Reduction of Nitrate
Electrochemical technology can be adopted to induce the
reduction of nitrate and nitrite ions to nitrogen on the cathode
(Figure 23). Li et al. (2009) studied on the simultaneous reduction
of nitrate and oxidation using electro chemical technology. They
achieved nitrate removal of about 90% a current density of 40
mA/cm2. A further improvement made by Li et al. (2010) on the
nitrate removal by adopting iron and titanium as cathode and
anode, respectively. They found out the nitrate removals are about
93 and 87% with the absence and presence of 500 mg/L NaCl,
respectively. Yunqing and Jianwei (2011) investigated regarding
the electrochemical process found that ammonia and nitrite
were indirectly oxidized by electro generating hyperchlorous
acid, whereas organic compounds were directly oxidized at the
anode surface. They found out in order to achieve simultaneous
removal of total ammonia nitrogen, nitrite and chemical oxygen
demand, the current had to be controlled over 23.4 A/m2.
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Figure 23: Mechanism of nitrate electro-reduction using zinc and copper electrodes.
Electrochemical Oxidation of Organic Compound
Electrochemical oxidation of organic method is highly efficient
and economical for wastewater that contains toxic or non-
biodegradable organic pollutants. The wastewater may oxidize
with ozone, which is a powerful oxidant however the total organic
carbon removal was quite low (less than 30%). The oxidation by
using hydrogen peroxide in the presence of iron as a catalyst is
also given the same result of the lower total organic removal.
Therefore, research on the electrochemical oxidation of organic
compounds from wastewater has been carried out. Diaz et al.
(2011) have investigated the kinetics of electro-oxidation of
ammonia, nitrites and COD from a marine RAS using boron doped
diamond (BDD) anodes. They used current density in the range
of 5 to 50 A m-2 and kinetic constants for the anodic oxidation.
Furthermore, the formation of free chlorine and trihalomethanes
by-products (THMs) was monitored during the electro-oxidation
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process. However, a hybrid process that combines an adsorption
step onto activated carbon to the electro oxidation cell in order to
remove the generated THMS and residual chlorine is currently
being studied.
Bio-electrochemical Technology
The utilization of microorganisms in catalyzing an oxidation and/
or reduction reaction at an anode and cathode is known as bio-
electrochemical system (BES). The anode and the cathode are
installed and connected through an electrical circuit. BES can
be divided into two major groups which are microbial fuel cell
(MFC), where the electrical power is generated from the circuit
and microbial electrolysis cell (MEC). This BES is also known as
bio-energy and bio-fuel cell (Mook et al., 2012; Rabaey, 2010).
Bio-electrochemical systems applied biological capacities of
microbes, enzymes and plants for the catalysis of electrochemical
reactions. Emerging systems biology approaches to the study
of microorganisms interacting with electrodes are expected to
contribute to improved microbial fuel cells (Clauwaert et al., 2008).
Only recently, electron transfer in both anodes and cathodes has
been described without the external addition of artificial electron
mediators (Bond & Lovley, 2003; Clauwaert et al., 2007; Rabaey
et al., 2005). Among typical application of BES are Plant-
Microbial Fuel Cell, Enzymatic Fuel Cells, Microbial Fuel Cells,
Microbial Electrolysis Cells, Microbial Electrosynthesis Cells and
Microbial Desalination Cells (Rozendal et al., 2008).
BES have recently emerged as a promising technology for
an alternative or renewable energy as well as for providing many
valuable products such as ethanol, hydrogen and other organic
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compounds. On top of that BES appear as an alternative for
treating various types wastewaters and simultaneously fit within
the biorefinery purposes. BES have been effectively removed of
organic materials as anodic oxidation with a lower sludge yield
compared to a common aerobic activated sludge processes.
Bio-electrochemical Reduction of Nitrate
Biological denitrification is capable of reducing inorganic nitrate
compounds to harmless nitrogen gas (Figure 24). Based
on numerous studies in biological denitrification of nitrate in
aquaculture wastewater, it was confirmed that potential of BES
towards the remediation of different concentrations of nitrate
is highly potential. BES can be utilized to eliminate nitrate
through a cathodic reduction process. Denitrifying bacteria are
accommodated to enhance nitrate removing efficiency. Review
of heterotrophic and autotrophic denitrifications with different
food and energy sources concluded that autotrophic denitrifiers
are more efficient in denitrification (Ghafari et al., 2008). For
instance, autotrophic denitrifying microorganisms use hydrogen
gas as the electron donor that is produced on the cathode
surface by electrolysis of water (Zhang et al., 2006). Hydrogen
gas is used to reduce nitrate to nitrite which further reacts with
hydrogen to form nitric oxide. Then, this compound continues to
be reduced to nitrous oxide and finally forms nitrogen gas.
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Wastewater Treatment Technology: A Green Application in Aquaculture
44
Figure 24: Mechanism of bio-electrochemical reduction of nitrate. (a) Interaction between biofilm and cathode, (b) Nitrate bio-electroduction reaction steps.
Bio-electrochemical Oxidation of Organic Compound
Microbial production of electricity may become a newly potential
form of bio-energy since it offers the possibility of extracting
electrical current from a wide range of complex organic wastes
and renewable biomass. However, the limitation of microbial fuel
cells as an alternative energy source is that the power densities
are still low for most regular applications. It is important to
understand the range of microorganisms that known to function
either as electrode-reducing at the anode or as electrode-
oxidizing microorganisms at the cathode. Microorganisms that
can completely oxidize organic compounds with an electrode
serving as the sole electron acceptor are expected to be the
primary contributors to power production (Figure 25).
Current practical applications are sediment microbial fuel cells
that extract electrons from organic matter in marine sediments
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A Green Technology of Wastewater Treatment in Aquaculture
45
to power electronic monitoring devices and possibly sediment
fuel cells which can serve as a light source or battery charger
in off-grid areas (Lovley, 2008). Substantial improvements will
be required before other commonly projected uses of microbial
fuel cells, such as large-scale conversion of organic wastes and
biomass to electricity, or powering vehicles, mobile electronic
devices, or households with suitably scaled microbial fuel cells
will be possible.
Figure 25: Mechanism of bio-electrochemical oxidation of organic matter.
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47
WATER MONITORING AND CONTROL SYSTEM
The implementation of process control system technique into
the monitoring and control will assist in the efficient execution
and management of the water quality for the aquaculture system
and finally contribute to the increase in aquaculture production.
Control system can be applied in various aquaculture facilities
such as water quality monitoring, water flow, aerators, pumps,
alarms and communication devices. In addition, these systems
can be customized to serve from the simplest to the most
complex aquaculture system.
Ali (2010) had developed the remote monitoring and
control system for aquaculture system in Universiti Malaysia
Terengganu. The developed system is connected to the sensors
(temperature, pH and dissolved oxygen), data acquisition
module, monitoring software and water quality database system.
The system was developed by connecting water quality sensors
with Remote Terminal Unit (RTU) which acts as an interfacing
device between these sensors and a host computer. Within the
system development as shown in Figure 26, it is intended that
database system provides the platform to record water quality
data so that operators will be able to study and analyses the
water quality related data for optimizing the aquaculture system.
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Wastewater Treatment Technology: A Green Application in Aquaculture
48
Figure 26: A real-time control system for recirculation aquaculture (Ali, 2010).
Another new technology of monitoring and control system
was developed by Qi et al. (2011) based on wireless sensor
network for RAS. With the advance of communication technology,
the recent progress of remote monitoring system for aquaculture
system was developed based on 3G networks and ARM-Android
embedded system (Wang et al., 2012). Structure of the remote
monitoring system is as shown on Figure 27. Automatic control
module and detecting module of aquaculture detecting terminal
can get real time water quality parameters and video information,
which is saved to storage module, compressed by the CPU of the
control module, and later sent to the portable monitor terminal
through the wireless network of 3G module.
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Water Monitoring and Control System
49
Figure 27: Remote monitoring system based on 3G networks and ARM-Android embedded system (Wang et al., 2012).
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51
CONCLUSION
Aquaculture industry could be dependent on the surface and
ground water as its water source. The selection of water source
is typically based on the quality and quantity of water that can be
provided. Aquaculture industry should possess water source with
a very minimal treatment and the most cost effective. Selection
of aquaculture technology commonly based on the availability
of water source, economic affordability and the technological
know-how of the industry. Various types of aquaculture system
range from a high water requirement system as a flow through
raceway to a very low water usage as in high-tech recirculating
aquaculture systems.
Thus, various types of aquaculture wastewater treatment
available that focused on specific aquaculture system. There is a
variety of water and wastewater treatment technologies could be
accommodated in providing such a high quality of water source
and to render the wastewater reusable or safely discharged into
the environment. However, the most important consideration
for the aquaculture wastewater treatment system should be
based on green technology of physico-chemical and biological
treatments.
Phytoremediation is a biological or green technology
in removing nutrient and organic pollutant in aquaculture.
Aquaponics is a kind of green technology used in the same
principle of constructed wetlands that can be used as
recirculation aquaculture system. Subsurface flow constructed
wetland is the effective green technology in removing
Escherichia coli and total coliforms. Current trends of research
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Wastewater Treatment Technology: A Green Application in Aquaculture
52
focused on the electrochemical and bio-electrochemical which
is a green technology for water and wastewater treatment.
Several alternative wastewater treatment is the use of plant
and microorganism such as Moringa oleifera, biofloc and auto-
flocculating microalgae Ankistrodesmus sp. to absorb the
pollutant from the generated wastewater.
Activated sludge has been the most frequently used
biological process in wastewater treatment. Biological treatment
using microorganisms would produce biomass simultaneously
with the treatment of the wastewater. Thus, proper management
of the biomass is crucial for the sustainability of green technology.
The biomass would contribute greatly to the production of
biodiesel, pharmaceutical precursors and bio-fertilizers however
mismanagement of it would leads to the contamination of the
environment. Therefore, the use of organic coagulant and
innovative biomass harvesting process would be highly potential
and energy efficient approach which could spearhead the
development of renewable energy in Malaysia.
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53
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