Whatever the system, it is important that each employee be trained to effectively
use the system and that well-intentioned housekeeping efforts do not result in
excessive waste volumes.
The primary treatments for aqueous waste are
liquid-solid separation such as flocculation and filtration
purification by reverse osmosis
The primary treatments for organic solvents are:
-- Solvent extraction
Virtually all of these processes (except pH adjustment) are likely to result in
secondary waste that requires treatment and/or disposal. In all cases, recycling of
the primary solution is desirable because it reduces monitoring cost and waste-
disposal liability and cost. A brief description of the use of each of these treatment
methods is given below. Extensive design and engineering should be done before
any method is selected in order to ensure meeting design objectives.
22.214.171.124 pH Adjustment
This treatment is used on aqueous systems to meet discharge limitations or
to make the solution amenable to other treatment. A mineral acid, such as
sulfuric, hydrochloric, or nitric, is normally used to lower the pH. A base,
such as sodium, potassium hydroxide, or occasionally ammonia, is used to
raise the pH. The solubility of some contaminants will be affected by the
pH of the solution. For example, an acidic solution containing iron may
show a copious precipitate of ferric hydroxide upon the addition of a base.