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Michigan Environmental Education Curriculum
Drinking Water Treatment

Activated Carbon

Carbon-containing materials such as coconut shells or wood are heated in the absence of oxygen, exposed to steam. and then ground into grains.  Activated carbon grains or granules have a great capacity to attract (absorb) organic chemicals and remove them from air or water.

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Adsorption

The process where chemicals in a gas or liquid are attracted to a solid, such as activated carbon, and held in a thin layer at the surface of the solid.

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Alum

A chemical, aluminum sulfate, added to drinking water to neutralize negative charges on particles so that they will clump together and settle more rapidly; also added to wastewater to remove phosphorus by precipitation.

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Backwash

When drinking water is treated by filtration, the filter eventually becomes clogged with particles.  The water is then pumped back through the filter (backwash) to flush out the particles.  The washwater is then sent to a wastewater treatment plant. 

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Bacteria

A group of microscopic organisms, shaped like commas, rods, spheres or spirals found almost everywhere in air, water, soil and plants and animals.  Some bacteria cause disease, but most do not.

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Chlorinated

A finished drinking water or wastewater which has had chlorine added to kill disease-causing organisms.

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Chlorine

A chemical added to drinking water and wastewater to kill disease-causing organisms.

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Clarified

Having made water clear by reducing the number of particles.  In water treatment, this is the sedimentation step.  In wastewater treatment, this occurs in the primary clarifier and the secondary clarifier.

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Coagulation

The process in which the negative charge on particles is neutralized, usually by addition of positive charges such as those provided by alum.  The neutralization of particles allows them to clump together forming larger particles which are easier to settle.

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Consumption

As applied here, consumption refers to the use of water for drinking.

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Contamination

The addition of something that makes water, for example, impure or unsuitable for a particular use.

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Disinfectant

Something, usually a chemical, that kills disease-causing microorganisms.

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Disinfection

The process of killing disease-causing microorganisms.

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Distribution

As used here, moving water from the storage that follows drinking water treatment to the customers who will use the water.

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Distribution System

The collection of pipes, pumps and storage tanks used for drinking water distribution.

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Fecal

Waste matter discharged from the intestines.

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Filtration

The process of passing water through a filter to remove particles.  In water treatment, the filter material is typically sand, sometimes with a layer of anthracite (coal) above.

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Flocculation

In water treatment, the slow mixing process in which particles that have had their charge neutralized (coagulation) are encouraged to clump together with other particles, creating larger masses that will settle more rapidly.

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Floc

A tuft-like mass of particles formed in water treatment.

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Groundwater

Water present below the ground in the pores between soil particles and cracks of rocks.

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Hardness

The tendency of a water to form scale or soap scum due to the presence of dissolved minerals, primarily calcium and magnesium.

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Herbicide

A substance that kills plants or limits their growth.

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Inorganic

Not organic; not coming from living things; mineral.

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Ion Exchange

A process in water treatment used to remove chemicals, especially those causing hardness.  The ion exchange resin is composed of small plastic beads which have sodium ions on the surface.  When untreated water is passed through the resion, the hardness ions (calcium and magnesium) exchange with the sodium ions on the resin, reducing the hardness of the water.

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Limestone

A rock consisting of calcium carbonate and calcium-magnesium carbonate.

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Maximum Contaminant Level

(MCL), a limit on the concentration of a chemical in drinking water which will protect the public health.

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Municipal

Having to do with a town or city.

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Organic

Substances containing carbon; coming from living things.

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Palatable

Good tasting.

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Pathogens

Disease-causing organisms.

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Potable

Safe to drink.

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Precipitate

As a noun, a solid substance; as a verb, to form a solid substance.

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Protozoa

One-celled, animal-like organisms, many of which are capable of movement.

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Recharge

As used here, refreshing an ion exchange resin once it becomes filled up with calcium and magnesium ions (hardness); done in home water softeners by addition of sodium ions (salt).

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Reservoirs

Artificial lakes, usually formed by building a dam on a stream or river.

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Resin Bed

A column or tube containing small (~0.5 mm diameter) plastic spheres (the resin) used to soften water.

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Scale

A crusty coating formed by precipitation of minerals from water.

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Sedimentation

Settling.

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Softening

The process of removing hardness (calcium and magnesium) from drinking water; done by chemical addition in municipal supplied and by ion exchange in homes.

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Surface Water

Water in direct contact with the atmosphere, e.g. rivers and lakes.

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Synthetic

Produced by humans; as opposed to materials of natural origin.

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Trihalomethanes (THMs)

Organic chemicals containing chlorine which are formed when chlorine is added to drinking water or wastewater for disinfection; some of these are known to be hazardous to human health.

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Toxic

Poisonous.

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Turbid

Cloudy; as used here, due to the presence of small particles such as algae and clays in a drinking wtaer source.

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Underdrain

In drinking water treatment, a set of pipes placed below the sand and gravel in a filter to collect the treated water.

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Viruses

Disease-causing agents, smaller than bacteria, that depend on other organisms for reproduction and growth.

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