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pollutants in waste water
heavy metals (mining and industrial processes), pesticides (farming), dioxins (waste incineration w/Cl), polychlorinated bipheryls (PCBs) (capacitors, transformers), organic matter (farming), nitrates (intensive animal farming, fertilizers), phosphates (detergents)
primary treatment: flocculation
removes suspended solids during precipiation (Al2(SO4)3 + 3Ca(OH)2 --> 2Al(O)3 (s) + 3CaSO4
activated sludge process (removes most of O2-demanding wastes): 1. sewage treated w/O2 in sedimentation tank; 2.sludge containing bacteria, microbes settles out; 3. discharged water is disinfected w/chlorine or ozone
removal of heavy metals, removal of phosphates, removal of remaining organic matter, removal of nitrates
removal of remaining organic matter
activated carbon beds, oxidize absorbed organic matter when heated to CO2 and H2O
removal of nitrates
ion exchange: passed through resins with silicates/zealites, Na(+) replaced by H(+), Cl(-) by OH(-) (H(+) + OH(-) -->H2O), requires no heating or fuel, but resins need to be replaced/regenerated
1. seawater heated; 2. in another container, pressure is lowered and seawater boils rapidly; 3. remaining seawater sent through additional stages, each w/ lower pressure
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