How to control de pH
The pH is the measure of free hydrogen activity in water or in more
practical terms the measure of free acidity or free alkalinity of water, is
expressed like as:
pH= -log[H+]
The pH is
measured in a scale of 0-14, solutions with a pH lower than 7 are acids (orange
juice and acid rain), and higher are bases (blood and soap). Bases are used to
neutralize acids and acids are used to neutralize alkalis. Byproducts are
normally salt (they could be soluble or not) and water.
The task of any pH adjustment
is to regulate the pH of the process stream into the acceptable discharge
range. In the case of an acid neutralization, caustic (NaOH) is added to the pH
in order to neutralize the solution.
There are two primary system
designs for pH adjustment systems: continuous and batch.
Continuous system are very
suitable for relatively high flows of slightly acidic or alkaline wastewaters
(example: 2.0 < pH < 12.0).
For more demanding
applications, such as those with changing flows those who are characterized by
highly acidic or highly alkaline wastewater then a batch system is a more appropriate choice.