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NEUTRA-MILL
WATER TEATMENT SYSTEM - CASE STUDY
DRINKING
WATER - RURAL WATER AUTHORITY - AUSTRALIA
• pH CORRECTED
• IMPROVED DISINFECTION
• COLOUR IMPROVED
• MULTIPLE SITES TREATED WITH ONE NEUTRA-MILL
• TURBIDITY LOWERED
• REQUIRES MINIMALEXISTING INFRASTRUCTURE AT SITE
LOCATION
North-central Victoria, Australia. 150 kilometres north of Melbourne
(Latitude: 36° 30' S, Longitude: 145° 00' E).
SETTING
AND CLIMATE
The Goulburn Valley is recognised as one of the "food bowl" areas of
Australia. Despite an annual rainfall of only 500mm, the region hosts
a multi-billion dollar food industry based on dairy and horticultural
produce. Much of this activity is dependent on irrigation derived from
the Goulburn River through an extensive network of irrigation channels.
CLIENT
Goulburn Valley Water (GVW).
BACKGROUND
For most towns in the region, raw water for drinking purposes is sourced
from clay-lined open irrigation channels, and is often of poor quality.
Treatment facilities are not always present, especially in the smaller
towns where it is generally uneconomic.
ISSUES
Raw water from the irrigation channels requires treatment to lower turbidity,
improve colour, pH correction and disinfection to satisfy drinking water
guidelines (5 NTU, 15 HU, pH 6.5-8.5). While most small towns have in-line
chlorine gas disinfection systems, only a limited number have any additional
beneficiation equipment, and very few could justify the expense of a
conventional treatment plant. As a consequence residents tended to rely
on rain water as their primary source of drinking water.
TREATMENT
PROGRAM
Following successful trials, a purpose-built mobile Neutra-Mill system,
the Turbidity Mill, was developed and is now used as the primary method
of coagulation/flocculation for five separate towns for the authority.
The unit is transported to a site requiring treatment, treatment is
conducted and then the unit is transported to the next site - often
on the same day.
Once onsite the unit is deployed to the waterbody, charged with reagent
(aluminium sulphate - alum, and/or hydrated lime) and then slowly propelled
across the surface of the water body whilst it dispenses reagent. Further
reagent is added continuously as required until the entire waterbody
is treated.
Chemical dispensing can take as little as 2-3 hours, and clarification
occurs in 2-7 days. The water storage capacity at many small towns means
that treatment need only be conducted periodically (eg. 1-4 times per
annum) rather than continuously.
RESULTS
Since routine water treatment started with the Neutra-Mill all water
quality analyses for these five towns have stated "This water complies
with the recommended guidelines [WHO] for drinking water quality".
Typical water quality analyses are presented in the table below showing
conformance with WHO Water Quality Guidelines.
COST
BENEFITS
Significant cost benefits have been achieved by using one Turbidity
Mill unit to treat the drinking water at the five towns:
• Capital costs - one Turbidity Mill unit cost $45,000 compared
with planned conventional plant costs of $250,000-$400,000
• Operating costs - between 3-6 cents per thousand litres of WHO
quality drinking water.
Raw water treatment with the Turbidity Mill had the additional benefits
of lowering chlorine dosing requirements, raising residual chlorine
levels in reticulation systems, and reducing consumer complaints.
| Site |
pH |
Colour
(Pt/Co units) |
Turbidity
(NTU) |
Aluminium
(mg/L) |
| Untreated
channel water |
7.4 |
40 |
28 |
0.15 |
 |
| Treated
water |
|
| Township
1 |
7.5
|
3 |
1.0 |
0.11 |
| Township
2 |
7.9 |
8 |
1.6 |
<0.05 |
| Township
3 |
7.3 |
8 |
1.6 |
0.06 |
| Township
4 |
7.7 |
5 |
2.1 |
0.08 |
| Township
5 |
7.4 |
6 |
1.0 |
0.14 |
|
| WHO
guidelines |
6.5-8.5 |
15 |
5 |
0.2 |
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Typical
water quality data; October 1999.
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From
near to far; irrigation channel, pond under treatment and treated
pond, at Stanhope Central Victoria.
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Launching
a Turbidity Mill from its custom built trailer
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