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Sunday, 17 February 2008 |
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When you ask people what makes a healthy community, the answer is almost always much broader than "medical care," "hospitals," "doctors," or "access to good health insurance." The people in a healthy community are safe and feel safe, are well informed, feel that they have the power to make choices, have lasting bonds with one another, have strong families, and a sense of meaning in their lives. Linda Bergthold, a principal of the human resource and benefits consulting firm William M. Mercer, says that "health is only in a very minor way about medical care." The evidence is there in any hospital: half the cases that come in the door are rooted in behavior, another 30 percent in the safety of the environment. Though the diseases and traumas happen to individual bodies, their roots are soci |
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Last Updated ( Monday, 30 June 2008 )
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Saturday, 16 February 2008 |
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Sewage is the wastewater released by residences, businesses and industries in a community. It is 99.94 percent water, with only 0.06 percent of the wastewater dissolved and suspended solid material. The cloudiness of sewage is caused by suspended particles which in untreated sewage ranges from 100 to 350 mg/l. A measure of the strength of the wastewater is biochemical oxygen demand, or BOD5. The BOD5 measures the amount of oxygen microorganisms require in five days to break down sewage. Untreated sewage has a BOD5 ranging from 100 mg/l to 300 mg/l. Pathogens or disease-causing organisms are present in sewage. Coliform bacteria are used as an indicator of disease-causing organisms. Sewage also contains nutrients (such as ammonia and phosphorus), minerals, and metals. Ammonia can range from 12 to 50 mg/l and phosphorus can range from 6 to 20 mg/l in untreated sewage. Primary TreatmentPrimary treatment is the second step in treatment and separates suspended solids and greases from wastewater. Waste-water is held in a quiet tank for several hours allowing the particles to settle to the bottom and the greases to float to the top. The solids drawn off the bottom and skimmed off the top receive further treatment as sludge. The clarified wastewater flows on to the next stage of wastewater treatment. Clarifiers and septic tanks are usually used to provide primary treatment. Secondary TreatmentSecondary treatment is a biological treatment process to remove dissolved organic matter from wastewater. Sewage microorganisms are cultivated and added to the wastewater. The microorganisms absorb organic matter from sewage as their food supply. Three approaches are used to accomplish secondary treatment; fixed film, suspended film and lagoon systems. |
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Last Updated ( Thursday, 03 July 2008 )
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