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Defining these includes basic investment
decisions on treatment systems to use (e.g. whether to use pre-oxidation to
enhance flocculation and precipitation of algae and cyanobacteria, to install
ozonation and granular activated carbon filtration), adequate planning and
design of the elements in the treatment chain, and operational controls to
ensure that treatment is functioning as it should at all times – e.g.
even when challenged by a massive cyanobacterial bloom.
The monitoring and surveillance of such control measures is crucial to
ensure that they are in place and effective. This does not primarily imply
cyanotoxin monitoring, but rather checking whether controls are operating as
intended, i.e. operational monitoring
as well as surveillance over plans,
design and maintenance of structures.
When developing your Water Safety Plan
(WSP) your WSP-team will WSP-team will assess the control measures already in place. If they are
found to be insufficient, it will suggest upgrading or select new ones. The
list of examples suggested below is not comprehensive, but merely intended for
demonstrating the nature of control measures and their monitoring, and to
trigger your own development of control measures adequate for your setting.
This requires expertise in drinking-water treatment, particularly including an
understanding of the treatment challenges for removal of algae and
cyanobacteria.
For each control measure chosen, your Water Safety Plan should document the reasons for its
choice and the targets it should achieve as well as how you validate that it is adequate for achieving the
targets you set. Furthermore a management plan
should be developed which defines how their performance is monitored and which
corrective action should be taken if monitoring indicates poor performance or
if incidents occur.
Note: this is not a comprehensive catalogue of examples,
but merely intends to trigger your own setting-specific concept of control
measures !
|
Process
Step |
Examples of
control measures for catchment management |
Operational
monitoring, surveillance and verification |
|
Planning |
Plan treatment steps in relation to
cyanobacterial bloom occurrence, e.g. to optimise removal of cells and
dissolved toxins – see bottom of system assessment for
treatment steps relevant to cyanotoxin removal |
Review plans and applications for permits in
relation to available information on cyanotoxin occurrence in the source
water |
|
Plan situation-specific periodic dosing of
powdered activated carbon (PAC) in relation to requirements of your specific
setting |
Review choice of carbon, amounts stored for use
during bloom situations, conditions that trigger application |
|
|
… ? |
… ? |
|
|
Design, construction and maintenance |
Design, construct and maintain filters so that backwashing
effectively removes cells and cellular debris |
Review plans, inspect structures and documented
records of maintenance works |
|
Design, construct and maintain dosing for
oxidants so that dose and contact time can be maintained as targeted |
||
|
|
|
|
|
… ? |
… ? |
|
|
Operation |
If pre-oxidation is performed, ascertain
sufficient dosing of oxidant to ensure oxidation of released toxin, or ensure
subsequent treatment steps will remove it (see below) |
Monitor oxidant dosing in relation to pre-determined
minimal amount (see validation) required for
toxin oxidation, or monitor the subsequent treatment steps that should remove
dissolved toxin (see below) |
|
Operate filters to ensure they retain cyanobacterial
cells |
Monitor on-line parameter that would indicate
break-through, e.g. turbidity or pigment fluorescence |
|
|
Operate filters to avoid cell lysis and release
of dissolved cyanotoxins by adapting backwashing frequency to the amount of
cellular material accumulated on the filter |
Monitor filter resistance in relation to
pre-determined threshold that would indicate elevated risk of break-through
(see validation) |
|
|
If post-oxidation is performed to remove dissolved
toxin, operate it as specified to meet this target |
Monitor dosing of oxidant in relation to
pre-determined dose and contact time needed to ascertain sufficient oxidation
(see validation) |
|
|
If granular activated carbon filtration (GAC)
or PAC dosing is performed to remove dissolved toxin, operate it as specified
to meet this target |
Monitor filtration or dosing of PAC in relation
to pre-determined dose and contact time needed to ascertain sufficient
binding of dissolved toxin (see validation) |
|
|
… ? |
… ? |
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