Sewage System

Introduction

Sewage is the mixture of water and whatever wastes that contains some ions, solid wastes or harmful bacteria from the domestic and industry wastes. Sewage system are built in order to collect and transport wastewater from residential and commercial areas , which typically has a relatively high concentration of biodegradable organic and inorganic compounds that can be easily utilized by microorganisms for cells growth and life maintenance . All the sewage or wastewater from the buildings must be treated before released back to the waterways such as the lake, sea or river. There are no holidays for wastewater treatment, and most plants operate 24 hours per day every day along the year. Wastewater treatment plants operate at a critical point of the water cycle, helping nature to prevent water from excessive pollution.

Figure 1 Sewage from the building flows through the underground sewer pipelines into the public sewage treatment plant for treatment before released back into the waterways.

Installation Process

1. Population Estimation (PE)

First is to estimate the population and capacity flow of the people’s wastewater of the stated area. It is counted in m3/day at 24 hours operation. As this is to prevent underestimation where the size of the treatment plant is not able to support the wastewater discharge.

2. Design the size of the treatment tanks and electrical functions

To design and provide the necessary drawing for the proposed treatment system. This is done by the civil and structure engineers. Whereas mechanical and electrical engineer will be in charge for electronic connection.

(Example)

3. Design Basis

The treatment plant design must design based on the following raw sewage influent and is able to comply with the required standards mentioned below:

(Example)

* Influent - current wastewater treated result

* Effluent Discharge - Malaysia industrial regulation standard (must be followed)

4. Test-run of the whole treatment plant

To undertake the testing and commissioning works. This is to ensure the performance of the treatment is guaranteed to comply with discharge specification.

(Example-Biomass Monitoring)

Most treatment plants have Primary Treatment, Secondary Treatment and Tertiary Treatment.

Primary treatment is to remove solid and some organic materials. It consists of:

1. Screening: to remove large material such as stone or rubbish, that could block the tank inlets.2. Grit Chamber: to remove the grit 3. Sedimentation: sludge settles down and will be pump away, while oil floats on top and are skim

off

Secondary treatment uses biological process to remove the dissolved organic matter that could not be screen in the primary treatment. These biological options include:

1. * Activated Sludge2. * Trickling Filters3. * Lagoons

After passing through primary and secondary treatment, wastewater is disinfected using chlorine ,UV light or other disinfecting compounds. Tertiary treatment includes the process of removing nutrients such as nitrogen, phosphates, and carbon absorption to remove chemicals. These process consist of physical, chemical or biological method.

After completing the primary and secondary treatment, the end product will be called as s ludge. It will go through further treatment which is sludge treatment to reduce the water content in it. As this may save lots of space during storage and easy transportation.

*Activated Sludge: Use microorganisms to break down organic matter with aeration and then allows solids to settle out. Bacteria that contained “activated sludge” are continually recirculated back to the aeration basin to increase the rate of organic decomposition.

*Trickling Filters: A biological process that uses coarse media contained in a tank that serves as a surface on which microbiological growth occurs. Wastewater trickles over the media and microorganisms remove the pollutants. Trickling filters are followed by settling tanks to remove microorganisms that wash off or pass through the trickling filter media.

*Lagoon: A wastewater treatment that uses ponds to treat water. They rely on the interaction of sunlight, algae, microorganisms, and oxygen to break down the organic matter.

Sewage Treatment Process

Sewage treatment process is divided into three phases: Primary treatment, Secondary treatment and Tertiary treatment.

A – Taking the wastewater away.

B - Screening - To remove floating objects, large solids (those with a diameter more than 2cm ) and grit (heavy solids ) that may damage the equipments.

C – Primary Treatment

- Wastewater will than transfer into a large settlement tank called clarifier.- In this circular tank, a large arm will slowly move around the tank and bubbles will be released and rise to the surface of water carrying the suspended solids. The sludge will be floated on the top surface of water and will be collected by sludge spiral scoop for removal from the unit.We called it “Sludge Treatment”.- The sludge will then transferred to the sludge holding tank and further dewatering.-The clarified wastewater will overflow to the next tank for biological treatment for next stage of the treatment process.

D – Secondary Treatment

- In this treatment it uses biological unit process to remove dissolved organic matter.- The wastewater is transferred into rectangular tanks called ‘aeration lanes’.- Oxygen is introduce into the system to encourage the bacteria to digest the organic matter.

E – Final Treatment / Tertiary Treatment

- After the sludge settles to the bottom of the tank, the treated wastewater will be transferred to the final settlement tank. - Later on, chemicals are also added to remove nutrients and toxic substances that contains heavy metals. This also includes balancing the pH level to the required state.- Effluent discharge from the tertiary treatment are of high standard and are suitable for reuse.

F – Sludge Treatment - The sludge that has been collected from the beginning of the process will then go through thickening process, dewatering process and lastly drying process.- The final product of the sludge is called as sludge cake.- Most of it is recycled for agricultural fertilizer usage or it can also be used to generate energy.- Other than that it is mostly used as a landfill material.

G – Treated clean water are sent back to the river.

Sewage Treatment Methods

A) Physical Unit Operation To remove inorganic and organic solid from the wastewater. It implies solid-liquid separation process and also called as sedimentation. They uses the concept of gravity to aid sedimentation for the solid-liquid separation

process. So they uses the physics’ law for designing a system to remove solids from liquids. For

example, sedimentation tank. Gas transfer is also an important physical unit operation for the removal of iron,

manganese, sense of taste and odor by using the aeration way. Example: Sedimentation, screening, aeration, filtration, flotation, skimming, de-

gasification, equalization and so on.

B) Chemical Unit Process It consists of using chemical reaction to improve the quality and purification of water. Including chemical coagulation, chemical precipitation, chemical oxidation, chemical

adsorption, disinfection so on and so forth. Examples of type of chemical used:

Name of chemical Usage

Poly Aluminum Chloride (PAC) Act as a coagulant

Sodium Hydroxide (NaOH) To control the pH level

Urea Act as a food for the bacteria

Physical & Chemical Biological

-Screens & grit removal-Sedimentation-Sludge Thickeners-Sludge dewatering devices-Ion-exchange-Multimedia filtration-Adsorption-Reverse osmosis-Ultrafiltration-Membrane bioreactors

Aerobic Anaerobic

-Contact Beds-UASBs-Sludge digesters-Anaerobic Ponds

Suspended Growth Attached Growth

-Activated sludge-Extended aeration-Aerated lagoons-Waste stabilization-Ponds

-Trickling filters-Rotating bio discs-Land treatment-Constructed wetlands -Vermiculture

Sodium Chloride (NaCI) Chlorine, kills harmful bacteria

Polymer Act as flocculant

C) Biological Unit Process Mostly used at the secondary treatment. It is because most of the solid are organic. So

biological unit process is the most cost effective and efficient to be used. BOD and COD are organic matters that are excreted from the human body which

normally comes from the food that they have consumed or food waste. The organic matter that is present in the sewage water is highly degradable. Where BOD

and COD ratio is very high. Hence by using biological process it is more efficient to dissolve them.

Microorganisms, mostly bacteria assists biochemical decomposition of wastewaters to remove pollutants and produces stable end products.

Biological unit process can be divided into two, which are aerobic and anaerobic, they reacts based on the availability of dissolved oxygen.

Oxygen is introduced into the wastewater where it supplies oxygen to the microorganisms and the microorganism feeds on the organic matter and then produces carbon dioxide.

During this period aeration continues until complete biodegradation of BOD and at this stage some microorganisms will die because lack of food and will help reduce the volume of settling sludge.

After the sludge concentration is reached, the aerators are shut off and the settling period begins.

Later on solid separation takes place, leaving clear treated effluent above the sludge blanket.

Example:- Aerobic : Activated sludge treatment, trickling filtration, oxidation pond, lagoons,

aerobic digestion.- Anaerobic : Anaerobic digestion, septic tank, lagoon.

Flow Chart between Sewage Treatment Process and the Sewage Treatment Methods

Preliminary Treatment

dd

Primary Treatment

dd

Secondary Treatment

dd

Tertiary Treatment

dd

Physical Unit Operation

Physical Unit Operation

*Biological / Physical Unit Process

*Chemical / Biological Unit Process

Removal of solid rubbish, grease, oil and also removal of settleable solids and floatable matters.

To remove organic matters.

To remove nutrients

and pathogens.

*Mainly used.

Sludge Treatment System (In Details)

Figure 2 Sludge Treatment Process

Sludge is the solid waste that are separated from the liquid waste through wastewater treatment.Through sewage treatment process, whether from the start of the process until the end of the process, can produce significant amounts of sludge that require further treatment and put to good use. Untreated sludge is a significant environmental and public health hazard. So, sludge must be treated before being disposed off in an environmentally safe manner.

A Thickening Process -Gravity thickener uses gravity to thickened the primary sludge from the primary clarifier and then the thickened sludge is stabilized in the anaerobic digester.-Mechanical thickener uses a polymer to thicken the secondary sludge before being stabilized in the digester.

B Digesting Process -Treats the sludge using a process called “Anaerobic Digester”.-This is where the sludge is heated to encourage the bacteria to eat it and creates biogas that we then burn to create heat, which in turn creates electricity. -The gas produces from this process is collected and flared.-The anaerobic digester further stabilizes the thickened sludge.

C Dewatering Process (Thermal Destruction)

-The stabilized sludge is dewatered in a screw press or belt press.- A polymer is added to dry the sludge cake.

D Sludge Storage Area -Treated sludge is temporarily stored in the sludge hopper or yard before disposal.

E Treated Sludge is transported for disposal

-Treated sludge maybe used for land reclamation, in agricultural or reforestation.- It may also use as the top soil cover at landfill sites.

SLUDGE TREATMENT

1. Sludge Pre Thickener

2. Sludge Feeding Onto The Thickener Thickener Dewatering In Progress

3. Sludge Treatment - Screw Press & Belt Press 4. The Thickener Partial Dry Sludge Continue Into The Belt Press Or Screw Press

5. Belt Press - Biological Sludge 6. Final Product

Sewage Treatment Plant

1. Screening.

2. Settling Tank.

3. Aeration Sedimentation

4.Treatment Lagoon / Pond

4. Aeration System

5. Oxidation Ditch

6. Oxidation Pond

Case Study 1

Name of Company Fuji Clean Co. Ltd

Origin Japan

Main Business Manufacturing, sales and maintenance of on-site wastewater treatment systems; 1-360m3/day and air pump; 30L-200L/min

Fuji Clean Co. Ltd provides domestic and commercial wastewater treatment system using modern Japanese technology replacing old style septic tanks and sewage treatment systems. Reliable, transportable sewerage systems producing high quality recyclable wastewater which can be easily customized for various commercial application.

Process

1. Sedimentation Chamber

Separation of solid waste and removal of greese and oil.

2. Anaerobic Filtration Chamber

Organisms are introduced to digest waste

3. Aerobic Filtration Chamber

Stimulates aerobic bacteria to consume BOD into sludge

4. Storage chamber

Act as a room for the bacteria to break down the BOD and with the help of the air-lift pump to produce oxygen for the bacteria to stay alive.

4. Disinfection chamber

This is used to sterilize the wastewater , to kill harmful bacteria.

Feature

1. Reliable High Performance

Although it is small and compact, it's performance is extremely efficient and reliable and it produces a very high quality effluent.

Peak-cut System which can effectively cope with shock loadings. The water level in the system varies according to the presence of any inflow or not.

2. Lower Operational Cost

As Fuji Clean Co. Ltd also uses their own manufactured air blower, which is most energy efficient. It uses just 52watts compared to 80watts of other blowers. This results in much lower ongoing operational costs and makes the unit more environmentally friendly.

3. Compact And Easy To Install

This small, compact unit has been specifically designed using advanced Japanese engineering tools and technology to achieve maximum operational efficiency without leaving a large footprint on the environment.Due to its light weight and compact design it is extremely easy to freight and install.

Comparison Between Malaysia and Japanese Sewage Treatment System

Japanese Malaysia

Name of The Company Fuji Clean Co. Ltd Techkem Water Sdn Bhd

Volume 2.063 - 15.568 m3 (depends on different model)

Depends on needs

Installation Easy (manufactured in the factory) Built on site

Space Required Small Large

Operational Cost Low High

Specialty Small and compatible Can treat a huge amount of wastewater

Conclusion

Japan’s sewage treatment system is more compact, as all the people knows that Japan’s topography is consider as packed and space is limited to built a sewage treatment plant that is similar as Malaysia’s. They have chosen to produce a small yet efficient sewage treatment system that suits the needs of the people and assort to their country’s terrain. Although it is small it can work effectively to purify the water and reuse the treated water in many ways. We can also see that the steps of process used by Fuji Clean Company is also similar to ours. In conclusion, our country may learn from them and try to transform and develop with the aim of space savey concept of sewage treatment system.

Case Study 2

Septage management initiatives

Manila, Philippines

a) About Metropolitan Waterworks and Sewerage System (MWSS) The Metropolitan Waterworks and Sewage System (MWSS) is a government corporation mandated to provide water supply, sewage, and sanitation services within Metro Manila and some cities within the province.  MWSS is one of the oldest and most formidable government organizations in the Philippines. The main aim of this company is to provide a better water services to the citizens.

b) Brief introduction about Manila Water Company, Inc. (MWCI) East Zone

Manila Water Company, Inc. is a Philippine company that holds the exclusive right to provide water and wastewater services to the eastern side (“East Zone”) of Metro Manila, under a Agreement between the company and Metropolitan Waterworks and Sewerage System ("MWSS").

Manila Water has achieved the following in terms of wastewater or “used water” management. They had initiated the sanitation or septic tank desludging program in the country with 50 desludging trucks and two septage treatment plants in operation, which both are the largest septage treatment facility in Asia treatment plant and Asia Leading sewerage operator. Also with 39 sewage treatment plants that consistently comply with the effluent standards and regulatory requirements of the Department of Environment .

i) Water treatment applied by Manila Water Company, Inc. Water Treatment in consists of four processes, which include coagulation/flocculation, sedimentation, filtration and disinfection.

In the first process which is coagulation, flocculation, coagulants and coagulant aids are mixed uniformly with water to be treated allowing bridging or adhesion of individual particles into flocs that settle more easily. This is accomplished by a slow, extended mixing process that converts minute particles into discrete, suspended particles. Balara Treatment Plant No. 1 has 12 vertical-type, motor-driven flocculators per basin while Balara Treatment Plant No. 2 has nine flocculators per basin. Detention time is 20 minutes. Balara Treatment Plant No. 2 has 12 basins, each of which has a capacity of 120 MLD. Balara Treatment Plant No. 1, meanwhile, has two basins with a capacity of 140 MLD per basin. Determination of coagulant/coagulant aid dosage to be adopted for plant use is obtained by conducting a jar test.

The flocs are then made to settle down in the sedimentation basin which is the second process. This is accomplished by enlarging the area of the basin to reduce the velocity of the water and adopting a chemical dosage which has a greater settling rate than the designed overflow rate of the basin.

Detention time is about two hours. After the sedimentation process, third process, which is filtration will be carried out where water to be treated is passed through a media consisting of several layers of graded sand and anthracite to screen out all foreign particles which did not settle down in the sedimentation basin. Detention time is around 20 minutes.

The last process is disinfection where the Balara Treatment Plant uses the chlorination method of disinfecting water. Chlorine is applied at three points: pre, intermediate and post-chlorination. Pre-chlorination is applied for taste and odor removal and is usually 0.3 mgl. Intermediate chlorination is for filter aid while post-chlorination is for disinfection purposes, having dosages of 0.3 and 1.2 mgl, respectively. Finally, water is then sent to distribution by gravity and by pumping.

The rest of Manila Water's concession area that is not connected to a sewerage system disposes its wastewater into septic tanks. Because septic tanks provide only primary treatment, they eventually leak out pollution into the groundwater or into municipal drainage systems, eventually finding its way into our rivers.

Hauled septage from septic tanks are then brought to a Septage Treatment Plant. The byproducts of septage treatment are treated wastewater (effluent) which are recycled or discharged safely, and biosolids (organic sludge). The residue is then shipped to Central Luzon for use as fertilizer, ensuring a natural means of disposal.

c) Brief introduction about Maynilad Water Services Inc. (MWSI) West Zone

Maynilad provides services covering the area of potable water with piped-in water supply that is safe to be consumed and used for daily life activities. Maynilad will

provide the whole West Zone with 24-hour supply at a minimum pressure of 7 psi (pounds per square inch) as well as sewerage services for covered areas.

Magallanes Village in Makati and parts of Muntinlupa. Septage treatment system is provided for the areas not covered under the sewerage services where the wastewater is disposed through their own septic tanks or sewerage treatment facilities for big commercial and industrial customers. While, Residential and semi-business customers who are located outside sewered areas and maintain their own septic tanks may avail of Maynilad’s septic tank cleaning (desludging).

i) Water treatment plants operated by Maynilad

Maynilad maintains and operates three world-class water treatment plants which are La Mesa Treatment Plant 1, La Mesa Treatment Plant 2 and Putatan Treatment Plant which meet the Philippine National Standards for Drinking Water (PNSDW) of the Department of Health (DOH).

La Mesa Treatment Plant 1 is a conventional-type plant with a maximum design capacity of 1500 million liters per day (MLD). It was designed by American company Camp, Dresser and Mckee.

La Mesa Treatment Plant 2 is a pulsator-type plant that has a design capacity of 900 MLD. It was designed by Degrémont, a French company recognized as a world specialist in water treatment plants.

Putatan Treatment Plant is the largest membrane-based water treatment plant in the Philippines, and is also the first type used in Philippines to use large-scale microfiltration and reverse osmosis.

ii) Wastewater management of Maynilad Water Services Inc.

Maynilad maintains and operates 20 wastewater treatment plants that process wastewater and sludge collected from customers. This is to prevent the pollution of waterways and bodies of water.

Septage management process for Manila Water Company, Inc. & Maynilad Water Services Inc.

Process Manila Water Company, Inc. Maynilad Water Services Inc.

Collection and transport

91 various sizes of vacuum tanks

25 vacuum tankers and seven mobile dewatering units (MDUs)

Treatment and reuse.

Operates two septage treatment plants (in Taguig & San Mateo, Rizal)

The treatment processes include: (i) Primary treatment:

screening, grit & scum removal

(ii) secondary treatment: Coagulant-assisted mechanical

dewatering: add polymers & screw presses the sludge

Mechanical compaction: stabilization & reduction of volume

The filtrate (liquid component) is treated further in a conventional sewage treatment facility.

The biosolids are processed to

Operates two septage treatment plants

(I) In North western part of metropolis, Dagat-Dagatan septage treatment plant is a semi-mechanized treatment system. Wastewater is treated in waste stabilization lagoons and wetlands.

(II) In Project 7, Quezon City, the septage dewatering is done using screw press with chemical coagulation to achieve dried solids with up to 20% moisture content other than using sequential batch reactor.

Another private company collects and hauls the biosolids to a fertilizer production facility in Alaminos, Laguna (Southern Luzon).

yield higher value soil conditioners and then brought to lahar-affected areas in Tarlac and Pampanga provinces (Central Luzon) for composting and inoculation.

Treated biosolids are given or sold to corn, sugarcane and mango producers in these areas.

Currently constructing its third septage treatment plant in the southern part of Metro Manila.

Conclusion for Manila Water Company, Inc. & Maynilad Water Services Inc.

Although both companies in charge of different zones, but still the main source are linked together which come from the 3 dams, Ipo Dam, Angat reservoir and Umiray river. After all the water sources are gathered, it will be send to the big settling basin where then only separate and delivered to 2 zones which are West and East zone.

Both of the companies have the same mission and vision which are to provide better services of potable water, sewerage and sanitation, hoping the citizens can use the best quality, safe and clean water for drinking and daily usage while at the same time, to maintain the balance of the environment life cycle and also always relate to the concept of sustainable development.

Possible Problem Faced By The System

1. Size of Domestic Individual Septic Tank

This septic tank is usually located outside the premises compound and comprise of two chambers.

De-sludging will be carried out every year to make sure that it is able to function well. The amount of sludge in septic tank should not exceed the maximum sludge level, it usually ables to store only third of its total volume.

If the sludge in the storage is surpass the maximum level, sewage retention time will decrease result in the solid matter is not breakdown completely and released into the drain when this happen water pollution will occur. Not only that it may also threaten human health due to the untreated sewage contains virus that will cause diseases.

2. Underestimate Size of Sewage Treatment System

Most of the time developers may want to save cost in sewage treatment system hence they may require the engineers to built according the estimated population of the area stated. In the end it may cause sewage treatment disorder and even the wastewater is not screen properly and thoroughly. Normally professionals may suggest to built bigger and estimate more that the estimated population to prevent future problems.

2. Broken Connected Services

Underground sewer pipes comprise two types of pipe which is private connection pipe and public sewer pipe. Underground pipeline enables every household’s private connection pipe links to the public sewer pipe.

Blockages in sewer pipe occurs when disposal of object into the toilet or any inlets . When this happen it will cause blockage in the toilet, between pipes and even manholes hence overflow will occur.

Other than that broken pipes is also a common problem. This usually occurs when the quality of the pipe has worn-off over the years and it may also caused by the surrounding environment.

Recommendation For Future Improvement

1. Encourage 3R

3R consist of reduce, recycle and reuse. For future improvement to sustainable wastewater treatment is to carry out the concept of 3R. By reducing the use of clean water we can reuse the treated water for irrigation, agriculture, toilet flushing and also public parks, by doing this will help to conserve water.

The gas that has been discharged during the sewage treatment process can be used efficiently. As it contains about 70% methane that can be converted into electricity. Biogas is produced during anaerobic digestion. One of the benefit is that it can replace fossil based electricity.

Sludge can be converted into organic fertilizer, there are many advantages of using organic fertilizer such as greater resistance to disease and insect attack, reduce the amount of chemical fertilizer used and also increase water holding capacity. Moreover sludge can be manufactured into bricks and coal, by doing this it saves cost and encourage environment friendly.

2. Compact Sewage Treatment System

While nowadays land are very limited, space savey sewage treatment systems are required to cope with this issue. A compatible yet efficient sewage treatment is needed, simultaneously this type of science and technology has been going on in the overseas quite sometime. Hence we hope that we get to learn from it and transformed our common sewage treatment system in Malaysia.

Learning Outcome

From this project, we have learned how much importance is sewage treatment system is to us. It is a total miracle to see how sewage is transformed slowly into clean water. They not only uses the genius physics theories and also magical chemistry equations to help the process of sewage treatment faster and efficient. Moreover, bacteria are used to break down the BOD into sludge effectively before sending it to be sterilize. The process starting from sedimentation, flocculation, chemical treatment, biological treatment, aeration and settlement are wisely used to give full support during the sewage treatment process. All the process are so on point where it also reduces unnecessary energy usage and eliminates the waste of time.

All in all, have you ever thought that what if this type of sewage treatment system has never exist, it may be human’s worst nightmare. As sewage that are created are not able to be solved and more and more is produce endlessly. Hence we must be grateful to what have been invented for us and we must not waste natural resources unnecessarily. From this we can realise that water has been such a wonderful helper if we have it with us and without it we will be so in trouble. On top of that our country are encourage to learn more from overseas countries of how amazing they can treat sewage with different ways effectively. While upgrading our style of wastewater treatment is also not a bad thing to do.

Let us be grateful and live a better tomorrow.

Thank you.

Reference

http://mwss.gov.ph/?page_id=232

http://www.mayniladwater.com.oh/

http://www.manilawater.com/Pages/Home.aspx

http://watsanexp.ning.com/profiles/blogs/the-separate-/management-system-of-the

baliwagwater-district

http://www.mayniladwater.com.ph/facilities-wastewater.php

http://www.mayniladwater.com.ph/facilities-wastewater.php

http://www.iwk.com.my/do-you-know/sewage-treatment-objectives

http://www.iwk.com.my/do-you-know/sewage-treatment-methods

http://www.fujiclean.co.jp/fujiclean/english/index.html

http://www.fujiclean.com.au/Default.aspx

http://arkitrek.com/http:/arkitrek.com/in-the-shit-a-septic-tank-guide/

http://www.bem.org.my/publication/march-may2005/ENVIRO(IWK3).pdf

http://www.theprospectgroup.com/indah-water-ceo-ir-abdul-kadir-on-wastewater

management-and-sustainability-in-malaysia-81314/