Bài giảng Environmental Sciences - Chapter 17 Water Pollution

Chapter 17Water PollutionIn the U.S.Sewage treatment is a common practiceIn the 1970’s many cities were still dumping raw sewage into waterwaysIn 1972, the Clean water act provided funding for upgrading sewage treatment plantsCurrently water ways are the much better1°, 2° use preliminary but no moreTest for sewage contamination in drinking H2O  Fecal Coliform testSewage TreatmentSewage TreatmentSewage TreatmentSewage TreatmentRaw sewage (99% H2O)Preliminary Treatment- allow grit to settle1° separating Raw Sludge from H2O2° AKA Biological Treatment- bacteria feeds on the organic materialTrickling filters contain bacteria  remove raw sludge from the H2OSewage Treatment cont’dCategories of sewage treatment:Debris, particulate organics, colloidal + dissolved organics, dissolved inorganicsRaw Sludge May contain heavy metalsIf it does it needs 3° treatment, to remove the toxic chemicalsSewage Treatment cont’dIf raw sludge does not contain toxic chemicals, it may beAnaerobically (without O2) decomposedCompostedApplied to farms after treatmentWaste water in the US is treated by adding Chlorine gas to the H2O This can lead to the formation of hazardous chlorinated hydrocarbon componentsHome Septic systemsHome Septic Systems:do not use Chlorine Do use settling tank to settle organic solidsLets waste water percolate into the soil bacterial decompositionSeptic TankProblemsPoint Source PollutantsEnter from a specific sourceEasiest to monitor and testLocations evidentPermits are required for pollutantsEutrophicationExcess Nitrogen and Phosphorous