Page 400 - Industrial Wastewater Treatment, Recycling and Reuse

372 Industrial Wastewater Treatment, Recycling, and Reuse

Organic contaminants

Water
Oxygen
Aerobic
bacteria
Nutrients
Carbon dioxide

New cells
Aerobic principle

Figure 9.2 Aerobic principle.

aerobes) that use molecular/free oxygen to assimilate organic impurities, that
is, convert them into carbon dioxide, water, biomass, and inorganic nitrogen
products at ambient temperature without significant onerous by-product
formation. The anaerobic treatment processes, on other hand, take place in
the absence of air (and thus molecular/free oxygen), and exploit those micro-
organisms (also called anaerobes) that do not require air (molecular/free
oxygen) to assimilate organic impurities. The final products of organic
assimilation in anaerobic treatment are methane and carbon dioxide gas
and biomass. The illustrations in Figures 9.2 and 9.3 depict simplified princi-
ples of the two processes. Biotreatment processes are generally robust to var-
iable organic loads, create little odor (if aerobic), and generate a waste product
(sludge).

9.3 AEROBIC TREATMENT PRINCIPLE

As explained earlier, the aerobic treatment process is classified depending on
the working principles and also according to the process configuration, feed
condition, and oxidation state. Process configuration defines the way in
which water is in contact with the biomass, which can form a layer on some