Imaginary
example of the drinking-water treatment plant at Reservoir W
Which treatment steps are
implemented at the treatment plant ?
|
|
Y |
P |
N |
? |
Your assessment of the
situation |
Uncertainty of this
assessment |
|
|
|
X |
|
Pre-oxidation is performed and may risk lysis and toxin release. Filtration will
retain intact cells quite effectively; however, more frequent back-washing of
filters during mass developments is important in order to avoid accumulation
of a substantial biomass of lysing cyanobacterial cells which may release
toxin; PAC is available
for dosing in an emergency. |
Investigations of
toxin release through pre-oxidation have not been performed on site, but
literature indicates this to be a risk . Effective
retention of cells is validated, and an adequate backwashing regime is in
place. The efficacy of
PAC-dosing has not been validated on site, and so far has been used only twice,
without investigating cyanotoxin levels in finished water.. |
|
|
Flocculation |
X |
|
|
|
||
|
Filtration |
X |
|
|
|
||
|
Post-oxidation |
|
|
X |
|
||
|
Dosing
powdered activated carbon (PAC) |
|
|
|
X |
||
|
Granular
carbon filtration (GAC) |
|
|
X |
|
||
|
….. |
|
|
|
|
Y = yes
P = partially
[N1] Pre-oxidation risks damaging cells, i.e. inducing
lysis and toxin release without providing sufficient oxidation potential for
toxin degradation. This may constitute a risk, which is why “no“ should be
entered here if pre-oxidation is being practiced.