PREPARED BY : HADI ZAH BI NTI MOHD KAS
Understand Septic Tank and Oxidation Pond.
.1 Recognize methods of public sewage treatment
•aerated lagoons (AL)
•extended aeration systems
•rotating biological contractors (RBC)
•high rate trickling filter (HRTF)
.2 Recognize methods of individual septic tank (IST
age is wastewater that consist of waste and wastewater from
es, indusrial Premises and agricultural areas. Sewage is
gorised into three types, which are :
mestic sewage :
sewage originates from residential house, public building a
ricultural sewage :
sewage produced by agricultural and farming activities.
ndustrial sewage :
ewage produced by industrial activities.
Septic tank – Private tank
Structure constructed underground
according to some specifications for
Its normally used in individual houses,
schools, hotels and office buildings.
The size if septic tank depends on the
sewage generated by these premises.
For building or premises with many
occupants, such as school, the size of
septic tank should be large enough to
contain and treat the generated sewage.
The minimum volume of septic tank is
-this layer contains waste such as
-consists of suspended solid and bacteria.
-sludge layer at the tank base consists of
both decomposable and non-decomposable
Oxidation pond – Public tank
Oxidation Ponds (or Stabilization Ponds) are
a popular sewage treatment method for small
communities because of their low construction
and operating costs.
Oxygen is supplied from natural surface.
The first pond reduces the organic material
using aerobic digestion while the second pond
polishes the effluent and reduces the
pathogens present in sewage.
After retention for several days, the flow is
often passed into a second pond for further
treatment before it is discharged into a drain.
+ aerated (diudarakan)
+ decomposition process of organic pollutants form (water
and carbon dioxide) by bacteria with the aid of oxygen.
+ non-aerated (Bukan Diudara)
+ decomposition process of organic pollutants by bacteria
without the aid of oxygen.
+ this process produces methane (flammable gas-gas yang
mudah terbakar) and other gas as well as water and
There are a few types :
•aerated lagoons (AL)
•extended aeration systems
•high rate trickling filter (HRTF)
Treat sewage by using a Larges surface
pond area as compare to Oxidation
Ponds or waste stabilizer pond.
The pond is also deeper(lebih dalam),
having a depth of 3m to 5m.
These operation aid the aeration
process by dissolving and decomposing
organic matter. (proses pengudaraan dengan
melarutkan dan penguraian bahan organik.)
Aerated Lagoons are relatively simple plants to operate and maintain. However, they
require large land areas and are therefore rarely found in densely populated urban
The AL process normally comprises two or three lagoons in a sequence.
The first lagoon has surface aerators, which are like large "paddle mixers". The
aerators float on the surface of the pond and continuously stir the incoming sewage,
serving to maintain oxygen content in the sewage and preventing any solids from
Sewage has an average retention in the first pond of five days. During this time,
bacteria consumed the oxygen to breaking down the organic material in the sewage.
Effluent is passed into the second pond where the degraded organic matter and
sediments are settle out to form sludge. The effluent may then pass to a third pond
for polishing or be discharged to a receiving waterway. The average retention time in
the second pond is one day.
Care must be taken in managing the settling pond in warm climates. These ponds can
suffer from algal growth and/or odour generated by anaerobic digestion of the sludge
at the bottom of the pond. Depending upon their design these ponds must be
desludged approximately every 10 years.
There are approximately 40 AL sewage treatment plants in Malaysia.
Aerated Lagoons (AL)
Treat high volume of sewage
Require high maintenance cost
Require large land area
Require short detention time
Require skills work force
Extended aeration systems activated
Method of aerobic sewage treatment
Bacteria in the form of solids is suspended in
sewage and decompose the organic matters
with the aid oxygen
The activated sludge system consists of
activated sludge treatment tank, clarification
pond and disposal site
Activated sludge treatment tank is normally
rectangular, but there is cylindrical tank too.
Air or oxygen is supplied into:+ Using agitator(pembiak/penghasut) at the tank
+ Using air diffuser(penyebar diudara) at the
Fine Bubble Diffused Air Extended Aeration Systems (FBDAEA) are mechanical
secondary treatment systems. FBDAEA systems are robust and can withstand surges in
hydraulic or organic load.
To breakdown the organic material in sewage, bacteria require oxygen. This may be
introduced by agitation (using surface aerators) or by submerged "diffusers".
Sewage entering a plant in passed through primary treatment where coarse material
and grit is removed. The sewage then passes to secondary treatment in the form of
any aeration tank where it is injected with fine bubbles of air from submerged
Solids in the sewage are held in suspension by the bubbles and bacteria in the sewage
break down organic materials. Sewage is held in the aeration tank between 18-24
The effluent with suspended material is then passed into a "clarifier" (sedimentation
tank) where the material settles as a sludge. The sludge is drawn off with some being
returned to the aeration tank to ensure enough bacteria are present in the tank to
continue the process of breaking down newly introduced sewage.
The effluent is then polished and/or discharged to the receiving environment.
These plants only require moderate areas of land.
There are currently approximately 60 extended aeration systems in Malaysia and this is expected
to significantly increase to some 200 plants as older systems are phased out.
Activated sludge is an efficient
treatment method because the sludge
produces is recycle to facilitate further
High maintenance cost due to the
utilization of electrical agitator or
diffuser to supply diffused air
It does not required large area
Require technical skills maintain and
operate the system
Is a single or multiple shallow ponds designed to treat
The depth of the pond from the surface is 0.5m to
1.0m for aerobic process, 1m to 2m for facultive
process and 2m to 4m for anaerobic process.
Oxygen dissolve readily in the water through natural
wind induction process.
Oxygen is the main component in the degration of
pollutants using aerated bacteria.
The Oxidation Ditch (OD) is a modified form of the activated sludge system. Oxidation
ditches are mechanical secondary treatment systems which are tolerant of variations in
hydraulic and organic loads.
The OD consists of a "ring or oval shaped channel" equipped with mechanical aeration
devices. Screened wastewater, which enters the ditch is aerated and circulated. ODs typically
have long detention times and are capable of removing between 75% and 95% of the
Biological Oxygen Demand (BOD).
The proprietary "Orbal System" uses three channels or ditches concentrically placed. Each
channel is independently aerated and can be configured to act in parallel or series with the
other channels, depending upon the degree of treatment required.
After screening and grit removal, sewage enters the outer channel where most of the
biological reaction takes place. The second channel is held at a slightly higher dissolved oxygen
content for further BOD and nutrient reduction. The innermost channel is used for
polishing the effluent before it passes to a clarifier.
ODs require more land than other processes but can be cheaper to construct and
operate. There are currently approximately 30 ODs in Malaysia. The new modified ODs
in Malaysia are located in Sg. Besi - Kuala Lumpur, Bayan Baru - Penang and
Easy to maintain and does not require high Do not have the capacity to treat high
concentration industrial sewage.
Effiency of the treatment can reach up to
Not suitable for urban area due to high
Require large land area
Using aerobic and facultative bacteria.
Bacteria growth on the rotating discs in contact with the
sewage and decompose the organic matter in it.
The rotating biological contactor consists of these parts:+ circular discs made of plastic or other non-corrosive and
+ Shaft rod assembled to the circular discs for rotation.
+ Durable motor is required to rotate the shaft at a low speed,
which is 2 to 4 rotation per minute.
+ Tank to retain sewage.
Suitable for treatment of domestic Easily clogged due to rapid
Require small construction areas
Suitable in urban areas
Require technical skills maintain
Rotating Biological Contactors (RBCs) are mechanical secondary treatment systems, which are
robust and capable of withstanding surges in organic load.
Sewage entering a plant is passed through primary treatment where coarse material and grit is
removed. The sewage then passes through one or more RBC units, which have historically been
built in a variety of configurations.
An RBC unit comprises a series of closely spaced "circular disks" normally made from a plastic
material. The disks are partially submerged in the sewage and are slowly rotated through it.
The rotating disks support the growth of bacteria and micro-organisms present in the sewage,
which breakdown and stabilise organic pollutants. To be successful, micro-organisms need both
oxygen to live and food grow. Oxygen is obtained from the atmosphere as the disks rotate.
Effluent from the RBC is then passed through final clarifiers where the micro-organisms in
suspension settle as a sludge. The sludge is withdrawn from the clarifier for further treatment.
The Submerged Biological Contactor (SBC) is the modified version of the conventional RBC
where the disks are 80% -100% submerged and forced air is introduced.
RBC units are suitable where land is restricted. They are quite and consistently produce a high
quality effluent. Because they are modular they are also suitable for a staged development.
Operations and maintenance costs are lower than for other forms of mechanical treatment.
There are currently approximately 40 RBC plants in Malaysia
Aerobic sewage treatment method. The sewage is sprinkled
onto the filtering layer and trickles through the filtering media.
The bacteria grows and cover the filtering media, trap and
decompose the organic matter in the sewage when its passes
through the trickling filter.
trickling filter consist of a circular tank which contains filtering
media such as gravel or plastic synthetic medium, with a
dimension of 50mm to 100mm. This recommended size keeps
filtering media from clogging.
The filtering media is 2m to 3m thick
Rotating speed can be changed to
suit the required treatment level
Requires minimum detention time,
that is between 3 to 6 hours
Can eliminate up to 95%
contaminant in the sewage
Do not require frequent maintenance
because the slow rotating speed will
only causes minimum damage
Efficiency drops when temperature
of the sewage decreases
The modern trickling filter comprises a bed of highly permeable medium to which microorganisms are attached. Sewage is percolated or trickled through this media which is
made from rocks (2cm to 10cm in size) or specially designed plastic.
Rock beds are typically 2 meters deep and are circular. A revolving arm is used to
distribute the sewage over the media. Plastic media varies in design with depths ranging
from 4 to 12 meters depending upon the organic load.
Filters under the media drain the effluent and biological solids, which have become
detached from the media. Air is circulated back through the drainage system to the
media. The effluent from the drain is settled before discharge to the receiving
Some effluent from the drain is recycled to dilute the strength of the incoming sewage
and to ensure the media remain moist.
As the effluent passes through the media organic material is absorbed onto the
biological film or slime layer covering the media. Here is it degraded by aerobic microorganisms. As the slime layer grows an anaerobic environment is created near the
Filters are classified by hydraulic or organic loading rates. Classifications are low rate,
intermediate rate, high rate, super high rate and roughing. Re-circulation of filter effluent
permits higher organic loadings in high rate filters.
High rate trickling filters remove between 65% to 85% of the organic load. They are
used where there is sufficient land available and where a quiet operation is required.
They can sustain some variation is hydraulic or organic load.
Recognize methods of individual septic tank
Sistem pembentungan yang banyak terdapat di
Malaysia ialah tangki septik individu.
Dianggarkan lebih kurang 1.2 juta premis
mempunyai tangki septik individu.
Tangki septik individu yang sempurna iaitu
mengikut piawaian Malaysia-MS 1228.
3 hingga 4 penutup segi empat tepat dan pada
lazimnya berada di luar kawasan premis.
Kumbahan najis yang mengalir kedalam tangki
septik tidak menjalani rawatan sepenuhnya dan
tangki septik tersebut perlu dikosongkan secara
berjadual lebih kurang setiap 2 tahun sekali
agar ia berfungsi dengan lebih efisyen.
Kenapa Pengosongan Tangki Septik
• Tanpa pengosongan tangki septik secara
berjadual, air kumbahan yang tidak dirawat
serta pepejal enap cemar najis akan mengalir
ke saliran longkang seterusnya ke dalam
• Ini akan menyebabkan kandungan oksigen
yang terlarut di dalam sungai berkurangan dan
mengakibatkan kematian hidupan akuatik
Air kumbahan yang tidak dirawat juga
mengancam kesihatan awam kerana ia
mengandungi bakteria dan virus patogenik
yang boleh menyebabkan penyakit bawaan air
Individual Septic Tanks is one of the simplest forms of sewage treatment
and dates back to the sewerage system development in France in 1860.
An IST comprises two chambers connected in a series. In the first
chamber, solids from the incoming sewage settle forming a "sludge",
while greases and oils float to the surface forming a "scum" layer.
Effluent from between the scum and sludge layers then passes into the
second chamber where further sedimentation occurs. Finally, the
effluent leaves the second chamber and is discharged into a drain or
allowed to percolate into the soil.
The sludge in the tank undergoes anaerobic digestion and is converted into
more stable organic compounds and gases such as carbon dioxide (CO2),
methane (CH4) and hydrogen sulfide (H2S). ISTs are usually designed for a
24-hour retention time. Enough storage capacity is
provided so that scum and sludge can be deposited in the tank for up two years
after which it must be desludged to keep the tank operating satisfactory.
ISTs are suitable for single dwellings or individual buildings with a population
equivalent (PE) up to 150 and installed where there is no central sewerage
systems and where effluent discharges will not adversely effect the
environment. It is a cheap solution to disposing of sewage. However, ISTs only
partially treat sewage and concentrated groups oftanks can overload the
capacity of the receiving environment creating health and odour problems.
There are currently over one million ISTs in Malaysia, making it by far the most
Typical figures for ISTs are as follows: -
Biochemical Oxygen Demand
50 } not
100 } ISTs.
The final disposal process being carried
Large surface water bodies
Smaller, closed surface water bodies
Wetlands and lagoons
A particular slide catching your eye?
Clipping is a handy way to collect important slides you want to go back to later.