Intern

APPENDIX A. LIST OF DEFINITIONS

A.1 List of Definitions

accuracy. How closely an instrument measures the true or actual value of the process

variable being measured or sensed.

acidic. The condition of water or soil which contains a sufficient amount of acid

substances to lower the pH below 7.0.

activated carbon. Adsorptive particles or granules of carbon usually obtained by heating

carbon (such as wood). These particles or granules have a high capacity to selectively

remove certain trace and soluble organic materials from water.

air binding. A situation where air enters the filter media. Air is harmful to both the

filtration and backwash processes. Air can prevent the passage of water during the

filtration process and can cause the loss of filter media during the backwash process.

alarm contact. A switch that operates when some pre-set low, high or abnormal

condition exists.

algae. Microscopic plants which contain chlorophyll and live floating or suspended in

water. They also may be attached to structures, rocks or other submerged surfaces. They

are food for fish and small aquatic animals. Excess algal growths can impart tastes and

odors to potable water. Algae produce oxygen during sunlight hours and use oxygen

during the night hours. Their biological activities appreciably affect the pH and dissolved

oxygen of the water.

alkaline. The condition of water or soil which contains a sufficient amount of alkali

substances to raise the pH above 7.0.

alkalinity. The capacity of water to neutralize acids. This capacity is caused by the

water's content of carbonate, bicarbonate, hydroxide and occasionally borate, silicate, and

phosphate. Alkalinity is expressed in milligrams per liter of equivalent calcium carbonate.

Alkalinity is not the same as pH because water does not have to be strongly basic (high

pH) to have a high alkalinity. Alkalinity is a measure of how much acid can be added to a

liquid without causing a great change in pH.

analog....