Two identical fibreglass
tanks each with a capacity of 200 litres were set
up. Each tank was fitted with an Onga MD10 (40W) pump,
a Waterco Filter King-5 micron cartridge filter and
an Email type 4503 (1500W) immersion heater.
The plumbing for the tanks allowed for cross mixing
so that the water in both tanks could be made chemically
identical. During the period of the Aquabrite treatment
however, cross mixing was prevented by operating a
system of valves and each tank became a separate system
with its own pump and filter.
Sydney tap water is low in dissolved mineral salts,
it was therefore necessary to add minerals in order
to increase the electrical conductivity and stabilise
the pH of the water by the resultant buffering effect.
The following mineral salts were added to the tank
water. The tanks were prepared on 6th November 1995.
Urea was added to simulate
real swimming water and provide some nutrients for
bacteria. The original (400 L) tap water was dechlorinated
by using a solution of 10% sodium thiosulphate solution
dropwise until no colour was produced in the samples
tested with a Palin's test kit. (DPD No. 1 tablet
followed by a DPD No. 3 tablet .) A chemical analysis
of the test water and control water appear in appendix
4.
-
Choice of Challenge Organisms -
Challenge organisms were chosen to coincide
with the NSW Health Department's "Guidelines for Disinfecting
Public Swimming Pools and Spa Pools", NSW Health Department,
1991 vis: E.Coli, Ps.Aeruginosa, Standard Plate Count
Organisms..
-
Analytical Methods -
Chemical
Analyses of both the control and test water was conducted
by Analchem-Bioassay according to accepted A.P.H.A.
Standard Methods. Low copper and silver concentrations
were analysed by C.R.A. (see appendix 1)
-
Quality Assurance and Quality Control -
· pH was measured
by a two buffer calibrated meter using a combined glass
electrode.
· Temperature was measured by
a calibrated total immersion mercury in glass thermometer
0-50C in 0.1C divisions.
· Copper ion in the original preparation
of the test water was measured using a Taylor colorimetric
test kit.
· Chlorine was measured by using
the Palin's DPD method.
*Laboratory quality assurance and
control procedures in accordance with NATA requirements
included the following:
(i)
Media check for:
· Sterility ·
pH ·
Positive control recovery ·
Typical colony morphology
(ii) Calibration of Equipment/Instructions
on the following:
· Incubators
· Water baths
· pH meters
· Thermometers
· Autoclaves
