Water treatment

Lilly Corradi

Process

1. Pre-treatment: controls algae and arrests any biological growth

2. Aeration: along with pre-chlorination, removes dissolved iron and manganese

3. Coagulation: prepares for flocculation

4. Sedimentation: for solids separation, that is, removal of suspended solids trapped in the floc

5. Filtration: removing particles from water

6. Disinfection: for killing bacteria

Pre-treatment1. Pumping and containment: water must be pumped from its source or directed into

pipes or holding tanks. 

2. Screening: remove large debris such as sticks, leaves, rubbish and other large particles

3. Storage: water from rivers may also be stored in bankside reservoirs for periods between a few days and many months to allow natural biological purification to take place.

4. Pre-conditioning: water rich in hardness salts is treated with sodium carbonate to precipitate calcium carbonate out

5. Pre-chlorination: water is chlorinated to minimize the growth of fouling organisms on the pipe-work and tanks

AerationIn the process of aeration, water first goes to aeration tanks where large

quantities of air are injected into and bubble through the water. Aeration can reduce tastes and odors and can oxidize soluble iron.

Aeration Tank

Coagulation

Coagulation tanks

 Alum and other chemicals are added to the water, which cause small particles to clump together (coagulate), forming floc. These floc attract dirt particles, making

them eventually heavy enough to sink to the bottom of the water storage tank. Some of the floc begins to settle during this stage.

SedimentationGravity and time are all that is needed to remove the floc from the water. The water and floc flow into a sedimentation basin. These settling basins are typically twelve to eighteen feet deep and hold the water for two to four hours at a forward velocity of 0.5 to 3 feet per minute.As the water sits there, the heavy floc settle to the bottom,

where they remain until removal.

Bollman Water Treatment Plant Sedimentation Basins at Concord, CA

FiltrationWater passes through layers of gravel, sand and perhaps charcoal, which serve to

filter out any remaining particles. Suspended materials (such as floc, microorganisms, algae, silt, iron, and manganese) are filtered out when water passes through beds of granular material, usually composed of layers of sand, gravel, coal,

garnet, or related substances.

Fluoridation & Disinfection

In most places, Fluoride (F-) is added to water to reduce tooth decay. During disinfection, disease-causing organisms are destroyed or disabled. Chlorine (Cl2) is

the most common disinfectant used in the United States because it is practical, effective and economical. Ozone is used in some places as well. A small amount of chlorine is added to kill any bacteria or microorganisms that may be in the water.

StorageFinished water (the term water treatment professionals use) is stored in holding

tanks, in order to serve homes and businesses in the community.

Storage Tanks - Norfolk, VA

South Cross BayouWater Reclamation Facility

- Serves South Pinellas County from Ulmerton Road to Tyrone Boulevard- Owned and operated by Pinellas County Utilities

Bibliography

http://water.epa.gov/learn/kids/drinkingwater/watertreatmentplant_index.cfm

http://en.wikipedia.org/wiki/Water_treatment

http://www.bcwater.org/waterfacts/waterpurification.asp

http://www.zistab.ir/publication.htm

http://www.h2ou.com/h2trtmntstages.htm

http://www.pinellascounty.org/utilities/reclaim-facilities.html#southcross

http://greeleygov.com/Water/watertreatment.aspx

http://www.norfolk.gov/utilities/produce/process.asp