Costs, Practicality and Consumer Acceptance

Example of monitoring costs Under the following assumptions, we can calculate costs for the different monitoring protocols  

Proeedure Time needed by sampler Praetieality Consumer aeceptance 

Using the times given in Table 3.4, this results in the following costs  

This example shows that the differences in monitoring costs are considerable. The composite flow proportional sample, as expected, is the most expensive. For the costs of one COMP sample, three properties can be sampled using RDT Obviously the 30-minute stagnation time makes 30MS protocols expensive. 

Practicality covers several aspects of the procedure, such as is the procedure easily applicable, are skilled samplers needed, does the procedure need specific tools, etc. A practical method is easily applied (score good), an impractical method needs more attention (score poor). 

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Random daytime sampling (RDT) is defined as a sample taken at the consumers tap at a random, unannoimced, time during office hours. At a composite COMP lead level of 10 ug/l, the 90% prediction range of RDT is 9 8 ug/l. Nevertheless, in the European study, RDT enables detection of 83 % of properties where the lead concentration of the proportional sample exceeds 10 ug/l (problem properties under the Drinking Water Directive). The number of falsely detected properties amounts to 10%. The reproducibility of RDT sampling is poor (the median relative range is 0.6 at lead levels around 10 ug/l). In terms of costs, practicality and consumer acceptance, RDT is the most favourable protocol. 

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