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Municipal sewage treatment

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Lora Hines

on 22 January 2013

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Transcript of Municipal sewage treatment

Municipal Sewage Treatment - Primary, Secondary, Tertiary Primary Treatment Secondary Treatment Tertiary Treatment Types of Tertiary Treatments - Most of the larger coarse solids are removed by the preliminary treatment which takes place long before any primary or secondary stages occur.
- Large obstacles are removed to avoid any blockage and damaging the structure.

- The stage where loose and separate organic and inorganic elements and suspended solids are present.
- Sedimentation tanks: where solids will eventually sink to the bottom by gravity
- Creating Primary Sludge. The purpose of tertiary treatment is to further improve the quality of the water before it is discharged into rivers and lakes.

This is done by processes such as Filtration, Lagooning, and Nutrient removal. These processes remove nutrients such as nitrogen, phosphorus and any other fine suspended particless that may have been left behind. as well as removing nutrients the tertiary stage also aims to kill off any disease causing organisms or viruses. Filtration
- sand filtration: flowing water through a sand bed to remove any suspended particles.
- filtration of activated carbon: removes specific particles such as non-biodegradable organic compounds, toxins, pesticides and many others.
Nutrient Removal
-nitrogen removal: nitrification and Biological oxidation.
-phosphorus removal:Enhanced Biological removal.
Coagulation Sedimentation
-chemicals are added allowing the smaller particles clump or 'floc' together
-which then settle in the sedimentation tank
-this helps to reduce phosphorus - removes up to 90% of organic matter
- uses biological treatment processes
- two most used processes are:
- Attached Growth
- Suspended Growth Attached Growth Process - microbial growth occurs on surface of a media (rock)
- oxygen added to wastewater encourages growth of microorganisms
- water filters through trickling filter
- bacteria attach while filtering, slime layer formed
- microorganisms break down organic matter Suspended Growth Process - microbial growth suspended in aerated wastewater
- water pumped into tank with microbial culture: bacteria, fungi & algae
- oxygen promotes growth of microorganisms, breakdown of organic matter
- settling, sludge recycled, continue cycle with new water
- wastewater discharged or further treatment Biologically Chemically - bacteria in water consume organic matter when oxygen is present
- new bacteria and other by-products form
- added oxygen speeds process, microorganisms grow & metabolize organic pollutants
- physical removal of remaining matter - chemicals: alum, lime or iron salts added
- causing flocculation
- larger masses easier removed
- phosphate concentration reduced by >95% - treated waste water is lighter and more buoyant than salt water
- ocean current moves the lighter water diluting it.
- very cost efficient and sustainably efficient
- treated waste water being dumped into salt water has minimal known impacts.
- main threat is the excess nutrients that may smother seaweed and sea grass as well as create algae bloom.
- lakes and reservoirs (freshwater) are more vulnerable than streams and salt water resources
- caused by excess nutrients and toxins due to low flow and less difference in water density.
- bacteria levels become unstable in smaller more condensed fresh water resources. Salt Water vs Fresh water Waste Disposal Sources Cited Miller, G.T. & D. Hackett (2011). "Living in the Environment" (Canadian Edition). Nelson Education. Excerpt from Chapter 22: pp: 522-547.

EPA (2004). "Premier for Municipal Wastewater Treatment Systems". http://www.epa.gov/npdes/pubs/primer.pdf. Document No. EPA 832-R-04-001.

FWR (2010). "Sewage Treatment". Retrieved from WEBSITE on January 15, 2013.

Water Corporation (n.d.). "Ocean Disposal of Treated Wastewater". Retrieved from http://www.watercorporation.com.au/O/ocean_disposal.cfm on January 20, 2013.

Siemens (2011). "Tertiary Wastewater Treatment". Retrieved from http://www.water.siemens.com/en/applications/wastewater_treatment/tertiary_treatment/Pages/default.aspx on January 21, 2013.

CRD (2013). "How Wastewater Treatment Works". Retrieved from http://www.wastewatermadeclear.ca/what/howitworks.htm on January 21, 2013. Accumulated Water Pollution resulting in:
human health and environmental issues
- diarrhea
- E. Coli - certain species indicate the level of pollution in water such as trout and mayflies require high oxygen content to thrive. What happens? Why do we need a primary treatment? http://resources.ccc.govt.nz//images/homeliving/wastewater/treatmentplant/chchwastewatertreatmentplant/WastewaterTreatmentPlant-770px.jpg Tertiary Treatment -further improve the quality of the water before it is discharged into rivers and lakes.
-in order to create a higher quality of water we must remove excess nitrogen, phosphorus, and any other fine suspended particles.
-tertiary treatment also aims to kill off any disease-causing organisms and viruses.
- tertiary treatment has three main types that it used to further clean waste water.
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