Conventional Surface Water Treatment for Drinking Water.ppt

Conventional Surface Water Treatment for Drinking Water
Coagulation / ulation
Physical and chemical processes to induce collisions and growth of particles, and to remove some soluble contaminants
Coagulation: Formally, means making particles “sticky”(rapid mix step); colloquially, also refers to forming new particles that collect dissolved contaminants
ulation: Causing collisions among sticky particles (slow mix step), to form fewer, larger ones
Suspensions in which most particles remain in the water are “stable,” so coagulation is sometimes referred to as “particle destabilization.”
Particle Removal Regulations
EPA’s surface water treatment rules require systems using surface water or groundwater under the direct influence of surface water to (1) disinfect their water, and (2) filter their water or meet criteria for avoiding filtration so that the following contaminants are controlled at the following levels:
Cryptosporidium 99 percent removal.
Giardia lamblia: percent removal/inactivation
Viruses: percent removal/inactivation
Turbidity: Turbidity can never exceed 1 nephelometric turbidity unit (NTU), and must not exceed NTU in 95 percent of daily samples in any month
Some Properties of anic Matter (NOM)
One Person’s Idea of an NOM Molecule
Some H+ ions, especially from COOH groups, “jump” to water molecules, leaving the remaining molecule with a negative charge
+H2O
+H3O+
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Some Properties of anic Matter (NOM)
NOM molecules have a strong affinity for surfaces of natural particles and for polyvalent dissolved ions (Fe3+, Al3+). In most natural waters, the ratio of NOM to particles is large, so particles are substantially coated, and most NOM is dissolved
If a little Fe3+ or Al3+ is added, it bines with NOM (both dissolved and on solids).
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