3.2   Assessing the risk of cyanotoxin intake and breakthrough in drinking-water abstraction and treatment
 
 

 


So far, you have dealt with assessing the risk of cyanobacterial proliferation in the water-body. As a result, you have either identified a risk of occurrence that you wish to address with appropriate control measures, or you found that you could not exclude such a risk. Therefore, to protect public health from cyanotoxins in drinking-water, it is important to assess the efficacy of further barriers potentially in place through your offtake strategy or drinking-water treatment system.

 

If bank filtration / soil passage is in place, please assess its characteristics:  example for filling in this table

 

For this assessment, including hydrogeological expertise in the team is recommended. For further information click here.

 

 

Y

P

N

?

Your assessment of the situation

Uncertainty of your assessment

Substrate oxidised ?

 

 

 

 

 

 

Travel time > 4 weeks

 

 

 

 

Substrate fine-grained

 

 

 

 

Temperatures > 10 °C

 

 

 

 

Accumulation of lysing cyanobacterial cells on the sediment likely to be low

 

 

 

 

…..

 

 

 

 

Y = yes
P = partially

N = no

?= insufficient information

 

 

 

If the raw water source is a reservoir, where is the offtake located ?  example for filling in this table

For this assessment, including expertise in reservoir management is recommended.

 

Y

P

N

?

Your assessment of the situation

Uncertainty of this assessment

Is offtake depth and/or site variable ?

 

 

 

 

 

 

Are water layers used for offtake continuously monitored for indication of cyanobacterial cells (e.g. by on-line turbidity- or fluorescence recording)?

 

 

 

 

Is variability of offtake sufficient to avoid layers with cyanobacteria?

 

 

 

 

…..

 

 

 

 

Y = yes
P = partially

N = no

?= insufficient information

 

 

 

Which treatment steps are implemented at the treatment plant ?  example for filling in this table

For this assessment, including expertise in drinking-water treatment is recommended.

 

Y

P

N

?

Your assessment of the situation

Uncertainty of this assessment

No[c1]  pre-oxidation, or under control for lysis and liberation of dissolved toxin  

 

 

 

 

 

 

Flocculation

 

 

 

 

Filtration

 

 

 

 

Post-oxidation

 

 

 

 

Dosing powdered activated carbon (PAC)

 

 

 

 

Granular carbon filtration (GAC)

 

 

 

 

…..

 

 

 

 

Y = yes
P = partially

N = no

?= insufficient information

 

On to   è  Evaluation of your assessment of the risk of cyanotoxin intake and breakthrough

 

Back to    è   START

 

 

 [c1]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.