Continuous Cultivation - Bioprocess Engineering: Kinetics, Biosystems, Sustainability and Reactor Design - page 635

1

d ln( P - P 1 )
dt

= D = 0.15 h -1

0.1

0 2 4 6 8 10 12 14 16 18 20

Time, h

FIGURE E12-4.2 A semilog plot of the concentration difference of a secondary metabolite (to the feed
concentration) in a batch culture. Chemostat culture can be determined by the tangent with its slope equal to the
dilution rate.

carbohydrates, alcohols, lipids, and aromatic organics. Industrial wastes are rich in
carbon compounds and usually deficient in nitrogen (high C/N ratio); therefore, the
biological treatment of industrial wastes usually requires supplemental addition of
nitrogen compounds and other nutrients. The presence of potentially toxic compounds
must be carefully considered in devising a treatment strategy.
(2) Domestic wastes are treated by municipalities and derived from humans and their daily
activities. They include ground garbage, laundry water, excrement, and often some
industrial wastes that have been sewered into the municipal system. Domestic waste
varies significantly with time in terms of flow and composition due to the periodic nature
of human activity (e.g. flow decreases at night when most people sleep).
(3) Agricultural wastes are produced by farm animals (e.g. manure) and include waste
plants, such as straws. Agricultural wastes are usually carbon rich because of high-
cellulosic material content, although some wastes, such as poultry manure, are high in
nitrogen.

Each of these waste materials has its own characteristics and treatment methods vary
depending on these characteristics.
Three major waste treatment methods are:
(1) Physical treatment includes screening, flocculation, sedimentation, filtration, and flotation,
which are usually used for the removal of insoluble materials.
(2) Chemical treatment includes chemical oxidations (chlorination, ozonation) and chemical
precipitation using CaCl 2 , FeCl 3 , Ca(OH) 2 ,orAl 2 (SO 4 ) 3 .