■ FILTRATION—removes clays, natural organic matter, precipitants, and silts
from the treatment process. Filtration clarifies water and enhances the
effectiveness of disinfection.
■ FLOCULATION SEDIMENTATION—a process that combines small particles
into larger particles that then settle out of the water as sediment. Alum,
iron salts, or synthetic organic polymers are used to promote coagulation.
■ ION EXCHANGE—removes inorganic constituents and can be used to
remove arsenic, chromium, excess fluoride, nitrates, radium, and uranium.SEPTIC SYSTEMS/SEWAGE TREATMENT
Sewage treatment incorporates physical, chemical, and biological processes to
remove contaminates from wastewater.
Septic Systems
A septic system consists of an underground tank and a drain field. Wastewater
from the home enters the tank to allow solids to settle while anaerobic bacteria
digest the settled solids to reduce their volume. The excess liquid leaves the tank
and moves through a pipe with a hole in it to a leach field where the water then
percolates into the soil. Some pollutants, especially nitrogen, do not decompose
in a septic system and may contaminate the groundwater. Periodic preventive
maintenance (pumping out the solids from the tank) is required. Approximately
25% of the population in North America relies on septic tanks.