Environmental Technologies and Eco-innovation in the Czech ...

Biological waste water treatment may be divided into processes stimulating the
natural conditions (earth filters, root treatment plants) or controlled processes
taking place in reactors. The treatment methods in reactors may be further divided
into processes with microorganisms in suspension (activation) and into processes
with sessile microorganisms (sprinkling biological columns, rotary disc reactors). We
can still divide waste water biological treatment into reactors according to whether
the microorganisms ensuring the treatment process require the presence of oxygen
(aerobic conditions) or whether they can work without the presence of oxygen
(anaerobic conditions). Anaerobic waste water treatment methods are mainly used
for industrial waste water with high organic substance concentrations, while aerobic
treatment methods with the microorganisms in suspension are used in the majority of
cases for municipal waste water treatment.
The basic principle of treatment is the formation of activated sludge 10 aerated in
activation tanks. The microorganisms in activated sludge make use of the individual
components of the waste water for their life and growth, and thus they remove the
polluting components from the waste water – they clean it. A biological treatment
plant consists of an aeration tank in which the process of waste water treatment with
simultaneous activated sludge production takes place and a final settling tank where
the treated waste water and the activated sludge are separated from each other by
sedimentation. The treated waste water flows from the biological treatment plant into
a recipient or it may be reused. The activated sludge thickened through sedimentation
is returned back into the activation tank (returnable activated sludge). Because over
course of treatment the activated sludge concentration in the tank increases (based on
nutrients being constantly brought in with the waste water, the microorganisms grow
and reproduce), it is necessary to regularly draw off a part of the activated sludge (the
excessive activated sludge) from the system.
The issue of removing specific substances in the water has been gaining greater
significance, such as detergents, synthetic dyes, heavy metals and, last but not
least, the remnants of pharmaceuticals, steroids and hormones. These substances
are not removed to a sufficient extent in common municipal waste water treatment
plants. For this reason, biodegradation properties of other organisms are being
searched for that would remove these special substances from waste water. Today,
experiments with some cultures of ligninolytic fungi 11 , which have the capacity to
10 activated sludge – a mixed bacterial culture possibly also containing other organisms such as fungi, moulds, yeast and
protozoa, but also suspended and colloidal substances absorbed from water
11 ligninolytic fungi – known also as white rot fungi; the wood-destroying fungi decompose mainly the lignine components
of wood; the white rot fungi prefer the dark lignine of the wood, and a light fibrous surface remains that consists mainly of
cellulose fibres