Drinking Water Qualityand Water Treatment

Water Quality Issues

Is the water we’re drinking safe?

How is it treated to ensure safety?

Can we swim and fish in our rivers?

Safe Drinking Water Act, 1974

Clean Water Act, 1972Both have been amended several times since!visit www.epa.gov/ogwdw

Drinking Water Standards5.10

Sometimes the goal isn’t practical

International Water Supplies

WHO/UNICEF Joint Monitoring Programme for Water Supply and Sanitation

http://www.wssinfo.org/en/22_wat_global_en.html#

Water Supplies in Southcentral Asia

Turkmenistan

Afghanistan

Source: http://www.wssinfo.org/en/335_san_asiaSC_en.html

Sanitation in Southcentral Asia

How is Drinking Water Treated to Make It Safe?

Disinfection technologies:

• chlorination (Cl2, NaOCl, or Ca(OCl)2)

• ozonation (O3)

• UV radiation

Fluoridation – to prevent tooth decay

Instrumentation and Measurement of Water Pollutants

• Atomic absorption spectroscopy is commonly used to measure metals (e.g. lead)

• Gas chromatography is commonly used to measure organic compounds (e.g. benzene)

Gas Chromatograph

Hard Water

• contains dissolved minerals such as CaCO3

• Is hard water good or bad?

– calcium is good for your bones, right?– causes deposits on pipes, industrial equipment– interferes with soaps

Water Treatment Technologies

• Water softening (by ion exchange)

Na2Z (s) + Ca2+ (aq) CaZ (s) + 2 Na+ (aq)

sodium zeolite calcium zeolite

• Distillation

• Reverse Osmosis

• Carbon Adsorption

Distillation

Reverse Osmosis Systems

Carbon Adsorption

Wastewater Treatment

• Primary Treatment• Secondary Treatment• Tertiary Treatment

Primary Treatment

• Removes large objects from the water– Sticks– Tires– Trash

• Screening• Primary Settling (physical)

Secondary Treatment

• Uses biologically activated organisms to consume nutrients and other organic constituents

• Aerobic digestion– Uses organisms that thrive with oxygen– Produce CO2

• Anaerobic digestion– Uses organisms that thrive without oxygen– Produce CH4

• Final settling (physical)

Tertiary Treatment

• Whatever chemical treatment of remaining water is required

• Usually includes disinfection (e.g. with chlorine)• Can include other chemical treatments depending

on the sources of the wastewater