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

activated sludge separation. This enables treatment plants to reuse the treated waste
water as supply water for recultivation, etc. A disadvantage of this technology is the
gradual clogging of the membranes, which causes constant maintenance and a reduced
service life of 7 to 10 years.
Inclusion of the membrane filters is especially advantageous when increasing WWTP
capacity or modernising existing facilities. Where there is a lack of building space, in
cases where it is necessary to eliminate seasonal deviations of waste water quality and
quantity, in case of required high quality discharge from the treatment plant and when
it is necessary to recirculate treated water back into operation recirculation back to the
operation, this technology may be also used for all WWTP size categories.
In Graph 2, the discharge parameters are illustrative for a WWTP with a membrane
placed in the activation with a size corresponding to the home WWTP category. Very low
discharge concentrations are obvious from the Graph, mainly in the IS 16 (2 mg.l -1 ) and
BOD 5
17
(3 mg.l -1 ) parameters. At the same time in this WWTP size category, the values of
IS and BOD 5 about 10 mg.l -1 and COD Cr
18
about 70 mg.l -1 are considered good results.
GRAPH 2 | Discharge concentrations of a WWTP with a membrane in activation [mg.l -1 ]
12
WWTP with a membrane in activation
120
10
100
8
80
IS, BSK5 (mg/l)
6
4
60
40
CODCr (mg/l)
BOD5
IS
CODCr
2
20
0
0 10 20 30 40 50 60 70 80
number of days
0
SOURCE | Schönbauerová, Kučera, Jun (2009)
16 IS – insoluble substances in water
17 BOD 5 – biochemical oxygen demand for 5 days
18 COD Cr – chemical oxygen demand determined by the ‘dichromate method’
84 | 85