1. Basic principles of purification

1.1 Defining biological phenomena

The decomposition of all organic matter (protein, lipid or carbohydrate), formed from a range of increasingly complex products, is the result of the life of autotrophic and heterotrophic micro-organisms, which develop spontaneously in wastewater in anaerobic or aerobic environments.

These bacteria use biodegradable carbonaceous organic matter as their preferred substrate, which is measured by BOD ₅ . [J 3 940].

The driving force behind any degradation of organic substances is, in fact, the enzymes secreted by bacteria, which are organic catalysts that transform and regenerate in the course of...