Similar words often loosely used interchangeably. Adsorption is a surface effect in which the adsorbate (the substance being removed by the process of adsorption) is adsorbed onto the surface of the adsorbent. The process is normally reversible, allowing the adsorbent to be removed and regenerated. Specific surface area and porosity are critically important in the performance of many adsorption processes. Adsorption is a process where the substance being removed is taken within the absorbent; it is not a surface effect.

A term used loosely to denote how acidic water is. Water with a pH value of less than 7 is termed acidic, meaning that it has a higher concentration of hydrogen ions than neutral water, which has a pH value of 7. Acidity may be due to natural causes such as the presence of free CO ₂ or humic or other naturally occurring acids, but it can also result from industrial pollution. Any water with a pH value below 7 is termed acidic. Waters with low pH values are normally corrosive.

A coagulant aid which is prepared from sodium silicate activated by various chemicals which include chlorine, sodium bicarbonate, sulfuric and hydrochloric acid, and CO ₂. These act as neutralizing agents on the sodium silicate to form a silica sol which may improve the performance of the primary coagulant. It is little used in potable water nowadays.

A material consisting mainly of carbon. It is very porous with a very high...