Researched by Emily R.
2000-01
 

• PURPOSE 
• HYPOTHESIS 
• EXPERIMENT DESIGN 
• MATERIALS 
• PROCEDURES 
• RESULTS 
• CONCLUSION 

• RESEARCH REPORT 
• BIBLIOGRAPHY
• ACKNOWLEDGEMENTS

• ABOUT THE RESEARCHER

INTRODUCTION
 

Human health is very important. To live people need shelter, food, and clean water. Without clean water deadly diseases can occur such as cholera, dysentery, and typhoid.

FILTRATION

Filtration is the process of a liquid passing through materials to purify the water. If water gets too polluted and is consumed deadly diseases can occur. 

Parts of Filters

One of the largest filters is a city filter. There are many steps and parts of a city filter. As the water flows in it flows through screens to keep the large things out like fish and plants. Coagulation is next; it is when the water is mixed with chemicals that cause impurities to clump together. Settling is where the extra particles settle on the bottom. Coagulation and settling both clean out the majority of the water. Next the water passes through a filter which contains sand and charcoal. This is so all the remaining particles can be trapped in the filter. Then chlorine is added to the water. The chlorine can be added before or after the filter but most likely is added after. There are several more steps at the end to reduce the bad smell and taste. Aeration reduces the bad smell and taste of the water. Activated carbon also reduces the smell and taste, but it also removes toxic chemicals. Not every city filter adds lime or soda ash but it prevent the pipes from rusting. The water then flows into a reservoir. From there it flows to houses, buildings, and factories, or where it is needed.
Sand, rapid, and slow filters all are very simple to work and run. They all have a layer of gravel along with a layer of sand. 
Sedimentary filters have several natural layers like bark, sand, and rocks. These have more layers than sand, rapid, and slow filters because they are supposed to act like wells. 

How Filters Work

Almost every filter works the same. Filters basically all have layers to run a liquid through and a collector at the end. Filters are made for cleaning a liquid or gas by running the liquid through layers.
City filters add chemicals, coagulation, aeration, and sometimes lime or soda ash. They also have a larger water supply for the whole city. 
Sand, rapid, and slow filters all work the same. These filters all are smaller filters that have two layers one of sand and the other gravel. 
Sedimentary filters work just like wells except smaller.

Types of Filters

Sand filters are layers of sand. Since sand is so small, it only allows smaller particles still to get through. 
   Sedimentary filters are layers of natural materials. One type of a sedimentary filter is a well. Well water is collected when it rains or when snow melts. It travels though the ground, through porous rocks and layers, which clean the water. Water can be polluted when sewers leak. 
  A slow filter is the process of a layer of sand and gravel. It was invented in the era when they were trying to reduce the spread of cholera, dysentery, and typhoid. These types of filters are not as popular as the rapid filters because they are more expensive and time consuming. The reason they are expensive and time consuming is, that dirt gathers and sticks together that is called a slime-mat, which causes a clog. To remove the slime mat is very expensive and time consuming. 
Rapid filters are most popular because of how fast, inexpensive, and is easier compared to the slow filter. It is easier and faster because the sand is much coarser. Which allows water to flow through the filter faster. The rapid filter uses chemicals, settling, and coagulation.
City filters are just a large version of other types of filters except these add chemicals, settlmentation, and are much larger water supply kept in reservoirs.

WATER QUALITY

Water quality is very important to the world. In the United States alone, half of the rivers, lakes, and streams are considered polluted. Clean water is very important to the world. Without clean water everything can die or get diseases. 

Water Pollution

Pollution is one of our largest problems. The water is getting more and more polluted every day. The three major water pollution sources and the causes happen daily. Everyday water is being polluted because of laziness and carelessness. 

Types and Causes

Industrial toxins, sewage, and agriculture waste cause water pollution problems. Laziness and carelessness allow these water pollution problems to continue. 
Industrial pollution is caused by chemical waste, hot water, or smoke and fumes.
The chemical wastes and hot water that are dumped into water by industrial buildings cause many things to die. 
Another type of pollution that is not realized by many people is sewage leaks. When water is used it goes underground and sometimes leaks into water pipes, lakes or rivers. 
The last major water pollution is agriculture. That happens when it rains or snow melts, the rain collects fertilizers, pesticides, and animal wastes above and below the ground. 

Turbidity

Turbidity is sediment particles mixed into water. After a while these particles that settle at the bottom make layers which is called floc. 

SUMMARY

Filtration is one way to purify water. Sand filters work well to remove sediments.

Crawford, Maria. "Sedimentary Rocks," World Book Encyclopedia, 1998 Pp. 280

Likens, Gene. "Water Pollution," World Book Encyclopedia, 1998 Pp. 136-139

Keinath, Thomas. "Water," World Book Encyclopedia, 1998 Pp. 116-132 

Powell, Evan. "Filter," World Book Encyclopedia, 1998 Pp. 102

Foster, William. New Book of Popular Science, Philippines and China, Grolier International Inc., 1998 

Torok, Melissa. "Filtration," [Online] http://www.osmonics.com/products/Page710.htm November 21, 2000

"Sand," [Online] http://www.bartleby.com/65/sa/sand.html November 19, 2000