Drainage, Sewerage Disposal and Treatment

Sewerage

Drainage system

• Is a system of piping within private or public premises that conveys sewage, rainwater or any other liquid waste to an approved point of disposal.

Sanitary appliance

• It is a fixture connected to the sewer pipe. It allows a person to put in sewage or liquids into the sewage system.

Sewerage

Sanitary appliances

Waste / Soil pipes

Main Sewer Pipe

Sewer Treatment

River

Design Consideration

• In compliance to building by law, for the protection of public health and safety, not only must it sufficient but:-

• Located in rooms separated from places where food is stored or prepared.

Design Consideration

Designed and installed with safe, sanitary disposal of waste water from the sanitary appliances in a building to ensure the following does not occur:

• leak out foul gas or waste water itself.

• Solids depositing in the pipes.

• The waste water flowing back to the sanitary appliances.

Design Consideration

• Should not be difficult in maintenance, cleaning and inspection.

• 10% natural ventilation by means of window, skylight which open directly to external air.

TRAPS

Traps

• A feature needed by all sanitary appliances.

• It prevents bad smells, gasses and pest, which are harmful to health.

Water Seal Traps

• To prevent the entry of waste water gases and pest into the building, water seals traps are fitted just after the sanitary appliances.

• Traps some flushing water to create a water seal in the waste water pipe.

• Made of steel, cast iron, plastic or brass etc

• For toilet bowl and urinal, traps are cast together with the sanitary appliance.

S Trap and P Trap

• A trap is a curved section of drain pipe that fills up with water, providing a seal.

• Drains that penetrate a wall have a P trap and those that go through the floor have a S trap.

• The water held by the trap is replaced each time the fixture is used.

S Trap and P Trap

Bottle Trap • Bottle trap

• This trap is popular because it can be used if the space between the appliances and the sewer is restricted and if the P trap cannot be used.

SEWAGE SYSTEM

• Any liquid waste which contains animal, vegetable or chemical waste in solution

• Domestic waste water which not only contain excreta or urine but bathing laundering and kitchen activities

What is sewage?

What is sewage?

• Sewage is the mix of water and whatever wastes from domestic and industrial life are flushed into the sewer.

• To retrieve the precious water, the sewage is then “treated,” that is, “cleaned,” in what are called “treatment plants.”

What is sewage sludge?

• Sewage sludge is the solid wastes that are separated from the liquid wastes through wastewater treatment. It includes solid wastes that is flushed into the sewer system.

• Sludge is thus inevitably a noxious brew of vastly various and incompatible materials unpredictable in themselves and in the toxicity of their amalgamation, incalculably but certainly wildly dangerous to life

Definition of sewage pollution • “Pollution is defined as ‘Loadings’ to the environment

which exceeds the prescribed upper (absolute) limits as specified via regulatory standards”

• Key sewage pollution measures are: Biochemical Oxygen Demand (BOD)

– BOD is the amount of oxygen required for microbial decomposition in organic matter in sample .

– Oxygen is removed from water when organic matter is consumed by bacteria.

– Low oxygen conditions may kill fish and other organism.

Sewage Pollution and How It Affect Water Quality

• Sewage pollution occur from sources such as domestic sewage, septic tank leakage, and fertilizer runoff, urban runoff carries pet wastes from streets and sidewalks, which contain the organic matters that increase biological oxygen demand.

• Oxygen consumed in the decomposition process by the bacteria robs other aquatic organisms of the oxygen they need to live.

• If dissolved oxygen concentrations drop, fish will be unable to live.

Why should sewage be treated before disposal?

• Sewage treatment involves breakdown of complex organic compounds in it into simpler compounds that are stable and nuisance-free, either physico-chemically and/or by using micro-organisms (biological treatment).

• The adverse environmental impact of allowing untreated wastewater to be discharged in groundwater or surface water bodies and/ or land are as follows:

Impact of untreated wastewater

1. The decomposition of the organic materials contained in wastewater can lead to the production of large quantities of malodorous gases.

2. Untreated wastewater (sewage) containing a large amount of organic matter, if discharged into a river / stream, will consume the dissolved oxygen for satisfying the Biochemical Oxygen Demand (BOD) of wastewater and thus deplete the dissolved oxygen of the stream, thereby causing fish kills and other undesirable effects.

Impact of untreated wastewater

3. Wastewater may also contain nutrients, which can be stimulate the growth of aquatic plants and algal blooms, thus leading to eutrophication of the lakes and streams.

4. Untreated wastewater usually contains numerous pathogenic, or disease causing microorganisms and toxic compounds, that dwell in the human intestinal tract or may be present in certain industrial waste. These may contaminate the land or the water body, where such sewage is disposed.

Main causes of deterioration of river water quality

• Discharges of sewage and domestic wastewater

• Urban Surface runoff (such as pet wastes)

• Discharges from restaurants, wet markets & foodcourt

• Animal farming

• Land clearing & earthworks

• Sand mining

• Agricultural and manufacturing activities

Sources of pollution

SEWAGE TREATMENT

Aim of sewage treatment

• We must note that, though the aim of sewage treatment is to produce clean water, it is never to produce “clean” sludge.

• From the early 1900s there has been a steady evolution of sewage treatment into today's modern sewage treatment plants producing high quality effluent, which can be safely discharged to the environment or reused.

Sewage Treatment Plant

• The ideal of the treatment plant is to remove the solid wastes as all the wastes and water are mixed.

• The water is “cleaned” in the degree to which the pollutants in the sewage, are removed by treatment process-primary, secondary, and tertiary.

Sewage treatment methods

Sewage treatment methods classified into

• physical unit operations.

• chemical unit processes.

• biological unit processes.

Physical unit operations

• Physical unit operations are treatment methods, which use the application of physical forces to treat sewage.

• These include screening, mixing, flocculation, sedimentation, filtration and flotation.

Chemical unit processes

• Treatment methods in which the removal or conversion of pollutants by the addition of chemicals or by chemical reactions are known as Chemical Unit Processes.

• These include precipitation, adsorption and disinfection.

Biological unit processes

• Biological unit processes describe methods, which remove pollutants by biological activity.

• Biodegradable organic substances are converted into gases that escape to the atmosphere and cell tissue is removed by settling.

OXIDATION POND

Sewage treatment Process

• Primary Sewage Treatment

• Secondary Sewage Treatment

• Tertiary Sewage Treatment

Primary sewage treatment

• Removing solids and some organic materials.

• (These are then dumped or landfilled somewhere).

Secondary sewage treatment

• Uses biological process to catch the dissolved organic matter missed in primary treatment.

• The main purpose of Secondary treatment is to reduce BOD (Biochemical Oxygen Demand)

• Many plants use the activated sludge to more effectively reduce BOD

• This form of treatment is standard now.

• Sludge dominantly made up of bacteria is a by-product.

Tertiary sewage treatment

• Major purpose is to reduce nitrogen and phosphates.

• Nitrogen and phosphates act as fertilizers, and can cause serious problems when they get into our streams, ponds, lakes, oceans and sounds by enhancing the growth of algae blooms which results in eutrophication.

• This form of treatment is still somewhat rare, but this is changing.

• Tertiary treatment uses bacteria to denitrify nitrates in the water producing nitrogen gas which is then released into the atmosphere(NH3 --> NO3 --> N2).

Sewage treatment methods

Sludge Treatment

Sludge treatment : Sludge cycle

Sewage Treatment Plant

Aerated lagoon

• An aerated lagoon or aerated basin is a holding and/or treatment pond provided with artificial aeration to promote the biological oxidation of wastewaters.

• There are many other biological processes for treatment of wastewaters, for example activated sludge, trickling filters, rotating biological contactors and biofilters.

• They all have in common the use of oxygen (or air) and microbial action to biotreat the pollutants in wastewaters.

Sewage treatment plant Extended aeration systems

Sewage treatment plant Oxidation ditch

Sewage Treatment Plant Rotating biological contactor

Sewage treatment plant High rate trickling filter

Sewage treatment plant Oxidation pond (OP)

Types of Sewerage Systems in Malaysia

• There are mainly two types of sewerage systems/services in Malaysia.

• The premises' sewerage systems are either connected to a public sewage treatment plant or have an individual septic tank.

• IWK is mainly responsible for operating and maintaining the public sewage treatment plants and network of underground sewerage pipelines.

Individual Septic Tank (IST)

• Large rural areas utilize Individual Septic Tank (IST)

• Malaysia's most common form of sewerage system is the individual septic tank (IST).

• Premises with a proper individual septic tank (Malaysian Standards - MS 1228 ) has 3 to 4 rectangular metal covers and is usually located outside the premises compound either at the side, rear or front.

• The septic tank only provides partial treatment of the sewage that flows into it and needs to be desludged on a regular basis, approximately once in two years, to ensure that it functions efficiently.

• IWK provides this important and mandatory scheduled desludging service to the premises with the septic tank.

• Septic tanks usually comprise two chambers and do not fully treat sewage.

• They are settlement tanks that require regular desludging.

• The maximum amount of sludge that a septic tank can store is approximately a third of its total volume.

• Raw sewage flows into septic tanks, and solid matter or sludge settles to the bottom.

• Oil and grease from the sewage floats to the top, forming a layer of scum.

• Scum prevents oxygen from dissolving in the sewage and results in anaerobic digestion taking place.

• Raw sewage has to be retained for at least twenty-four hours for anaerobic digestion to breakdown the solid matter.

Individual septic tank De-sludging service

• If desludging is not carried out, the sludge level may exceed maximum level.

• When this happens, sewage retention time decreases.

• This will result in an incomplete breakdown of sewage and thus, untreated sewage and sludge solids will be released from the septic tank into the drain.

• Where septic tanks have a filter bed after the settlement chamber, the filter beds will become choked.

• This too will result in untreated sewage and sludge solids being discharged into drains.

Connected Sewage System to Sewage Treatment Plant

Connected sewage system

• Connected sewerage service customers have sewage outlets that are directly linked to a sewage treatment plant via an underground network of sewer pipes.

• IWK is responsible for the operations and maintenance of all public sewage treatment plants.

• Public sewage treatment plants are plants which have been handed over to the Government (National Water Services Commission, Ministry of Energy, Green Technology & Water) by the Developer.

Connected services > Sewage system

• Connected sewerage systems comprise a network of underground sewer pipes, pump stations, sewage treatment plants and sludge treatment facilities.

• They generally operate by gravity.

• As a result, sewage treatment plants are usually located at drainage catchment outlets so that they can capture all the sewage easily without the high cost required for pumping.

• A network of public sewer pipes is being constructed in areas currently being served by individual septic tanks to link homes to sewage treatment plants.

• The responsibility for laying the public sewer pipes rests with Indah Water while house owners are required to lay the private connection pipe that will connect their sewage outlet to the public sewer pipe.

• In order to do this, house owners need to first disconnect their septic tanks and connect the sewage outlet to these networks.

• The unused septic tanks will need to be desludged, disinfected and filled in as part of the process.

• Private connection pipes and inspection chambers are then installed.

• Connection to the public sewerage system is made only when all systems are operational so that any likely disruptions to the household are minimised.

• This is an ongoing process to upgrade existing individual septic tanks to connected sewerage services in line with the objectives of the privatisation move.

• House connections are not easily made and thus, may be temporarily disruptive to households.

• The new private sewer pipes may have to pass under existing utility services such as monsoon drains.

• Private contractors are usually hired by property owners to facilitate the process.

Connected services > Blockages

• Underground sewer pipes can be classified into two categories: – private connection pipes

– public sewer pipes.

• A private connection pipe links a homeowner's sewage outlet to the public sewer pipe.

• The public sewer pipe, which is much larger in size, is the main underground pipeline that links a homeowner's private connection pipe to a sewage treatment plant.

• Blockages in sewer pipes are caused by the indiscriminate disposal of objects such as rags, solid waste, refuse or other materials into the toilet.

• Such blockages cause toilets and manholes to overflow, resulting in undue inconvenience to all concerned as well as polluting the environment.

• As such, the public is requested to refrain from such actions.

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