Wastewater Treatment

Topics: Sewage treatment, Water pollution, Activated sludge Pages: 5 (1311 words) Published: June 11, 2013

Activated sludge is a term that refers to suspended aerobic consisting of flocs of active bacteria, which are mixed with wastewater. The bacteria consume and remove aerobically biodegradable organic substances from screened; or screened and presettled wastewater in an aerated tank. The organic pollutants in the wastewater are used by the bacteria to grow and transform it to energy, water, CO2 and new cell material. Activated sludge systems are suspended-growth type and are used in conventional high-tech wastewater treatment plants to treat almost every wastewater influent such as , brownwater, greywater, faecal sludge and industrial wastewater as long as it is biodegradable.

1.PRELIMINERY TREATMENT (Primary & Secondary Filtration)
Pump station:
Water from public channel network and storm water basin enters the inlet chamber. Bar Screen:
Screening - removing particles such as plastics paper, cloths, and other large debris that may damage mechanical equipments. Screened solids are landfilled or incenerated.
Grit Chamber:
Aeration – removing sand and other heavy particles from other suspended solids within a short period of time. Aerated sand are landfilled or incenerated.

2.PRIMARY TREATMENT (Primary Clarifier)
Primary Sedimentation Tank:
Settling - Waste water spends a number of hours to allow the finer solids to settle or float and the sludge produced is scraped along the base of the tank for desludging. The primary-treated waste water is passed to an aeration tank.

3.SECONDARY TREATMENT (Aeration & Sceondary Clarifier)
Aeration Tank:
Aeration provides oxygen to the activated sludge and at the same time thoroughly mixes the sludge and the wastewater. Aeration is by either bubbling air through diffusers at the bottom of the aeration tank, or by mechanically agitating the surface of the water. After the aeration stage the waste water enters a second sedimentation tank. Secondary Sedimentation Tank:

Settling - where the flocculated microorganisms settle and are removed from the effluent stream. The settled microorganisms (the activated sludge) are then recycled to the head end of the aeration tank to be mixed again with wastewater and continue to grow and form new sludge and to degrade organics.

4.LAST TREATMENT (Tertiary Filtration & Disinfection)
Filter Tank:
Filtering – To remove suspended particles from water by passing the water through a medium such as sand. Chlorination Tank:
Disinfecting – To remove or inactivate all disease-causing organisms in water.

1.The purpose of the sludge process is
* To reduce the liquid content of the sludge and volume to minimize downstream costs and stabilize the sludge to allow safe beneficial use for land conditioning or alternate disposal methods. * The stabilization process minimizes the potential for odor generation and also destroys the pathogens. 2.The parts consist of:

* anaerobic digestion
* thickening
* incineration (not yet implemented in Malaysia due to high in cost) * Safe disposal in a landfill
3. More sustainable way would be to compost the sludge in order to reuse the nutrients in agriculture.


Sequencing Batch Reactor (SBR) – the activated sludge process designed to operate under non-steady state conditions. SBR System - wastewater is added to the system and undergoes all processes including aeration and sludge settlement both in the same tank. WASTEWATER TREATMENT

1.Anoxic Fill
* Wastewater enters the reactor through the influent distribution manifold * Wastewater is distributed throughout the settled sludge to provide good contact between the microorganisms and the substrate. * Aeration begins at this period.

2.Aerated Fill
* This is when the microorganisms are in contact with the substrate and a large amount of oxygen is provided to...

References: United Nations Environment Programme. Activated Sludge Treatment. (International Source Book on Environmentally Sound Technologies for Wastewater and Stormwater Management). 4.2.1 (online). Retrieved from http://www.unep.or.jp/ietc/publications/techpublications/techpub-15/2-4/4-2-1.asp
Sustainable Sanitation and Water Management. Activated Sludge (online). Retrieved from http://www.sswm.info/category/implementation-tools/wastewater-treatment/hardware/semi-centralised-wastewater-treatments-7
The Scottish Government. Wastewater Treatment Process Overview. (Code of Practice on Assessment of Odour Nuisance from Waste Water Treatment Works). Part 1 (online). Retrieved from http://www.scotland.gov.uk/Publications/2005/04/2994932/49358
Luis H. Abreu & E. Saribel. Sequencing Batch Reactors: An Efficient Alternative to Wastewater Treatment (online). Retrieved from http://www.rpi.edu/dept/chem-eng/Biotech-Environ/Environmental/Steps/EnvSysSBR.html#anoxic
Wastewater Engineering Group. SBR – Sequencing Batch Reactor Systems from Wastewater Treatment (online). Retrieved from http://wastewaterengineering.com/sbr_sequencing_batch_reactors.htm
R. Hamzah & P. M. Victor. (2008). Design and Performance of Waste Stabilization Ponds (online). Retrieved from http://stabilizationponds.sdsu.edu/
The Wastewater Treatments. Waste Stabilization Ponds (online). Retrieved from http://www.thewatertreatments.com/wastewater-sewage-treatment/waste-stabilization-ponds-waste-water-treatment
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