Environmental Engineering Reference
In-Depth Information
Table 10.3 Standard number of sampling locations (Government of Ontario 2010 )
Column
1
Column 2
Column 3
Column 4
Column 5
Item
Population
served by
drinking water
system
Number of
sampling points
in plumbing that
serves private
residences
Number of sampling
points in plumbing that
does not serve private
residences
Number of
sampling
points in
distribution
system
1.
1
99
5
1
1
-
2.
100 - 499
10
1
2
3.
500
3,299
20
2
4
-
4.
3,300
9,999
40
4
8
-
5.
10,000
- 49,999
60
6
12
6.
50,000
99,999
80
8
16
-
7.
100,000 or
more
100
10
20
(2) Fully Flushed (FF): A sample taken after a period of
flushing at the drinking
water tap.
(3) 30 Minute Stagnation (30MS): After a period of
flushing at the tap, water is
allowed to remain in the system for 30 min before a sample is taken.
These sampling protocols were evaluated against the composite proportional
sampling (COMP) method. The COMP sampler is a sampling device, which is
attached to the consumer
s kitchen tap in order to determine the average lead
concentration over a period of 1 week. It is a consumer-operated device which,
when turned on properly, captures 5 percent of volume of water drawn. Consumers
are required to turn on the device only when they are consuming water for dietetic
purposes. According to the EU Report, the COMP sample is the only method that
captures all the factors in
'
uencing average weekly lead intake by consumers (EU
Report, p. 32).
The EU Report recommended that either the RDT or the 30MS be used as
protocols for statutory monitoring purposes and zone assessment while the effect of
treating water, e.g. orthophosphate dosing at a treatment plant, can be assessed
using RDT and lead pipe test (which involves setting up a lead pipe rig at treatment
facilities and having samples taken after a 24 h stagnation period). For an
accurate,
and repeatable, value for average weekly lead concentration
(EU Report, 9. iv), the
Report recommends the 30MS sampling protocol. The stagnation time of 30 min
was based on
findings from Bailey et al. ( 1986b ), Baron ( 1996 ) and Van den Hoven
( 1986 ), which showed strong correlation between COMP and 30MS times. Note
that this is a statistical correlation, without any basis in metal chemistry. The
following section provides a critique of the EU
'
s assessment of the various
Search WWH ::




Custom Search