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Western Treatment Plant inputs and discharges

Raw sewage monitoring

(All data in mg/L unless otherwise indicated)
Waste Indicator 2007/2008 2006/2007
Median		 2005/2006
Median		 % Change
06/07 - 07/08
Median 90th %ile Maximum
Flow (ML/d) 412 442 693 431 448 -4%
BOD5 460 600 820 430 400 7%
Total Suspended Solids 420 560 1100 360 380 17%
Ammonia as N 46 52 70 43 33 7%
Total Nitrogen 70 79 96 65 60 8%
Total Phosporus as P 12 14 16 12 11 0%
pH units 7.4 7.8 8.4 7.4 7.3 1%
Colour Pt/Co units 80 120 120 100 85 -20%
Anionic Surfactants as MBAS 3.2 5.1 5.9 4.2 4.6 -25%
Silicate 13 15 19 13 13 0%
Electrical Conductivity (μS/cm) 2100 2300 3500 2000 1800 5%
Total Dissolved Solids 1000 1200 1500 970 950 3%
 
Cadmium 0.00030 0.00050 0.0010 0.00030 0.00065 0%
Chromium 0.022 0.049 0.13 0.028 0.033 -22%
Copper 0.13 0.16 0.18 0.11 0.12 18%
Lead 0.010 0.014 0.016 0.0080 0.0090 19%
Mercury 0.000050 0.00020 0.00040 0.00010 0.00020 -50%
Nickel 0.020 0.028 0.040 0.021 0.023 -5%
Zinc 0.20 0.30 0.39 0.17 0.17 15%
 
Benzene 0.00050 0.00050 0.0030 0.00050 0.00050 0%
Toluene 0.0010 0.0020 0.010 0.0015 0.0025 -33%
Phenols (total) 0.81 1.6 1.9 0.68 0.44 18%
Total PAHs 0.0035 0.013 0.028 0.0048 0.0045 -27%

Licence compliance

The following tables show the plant's compliance performance. Plant wide limits for all discharge parameters in the licence are based on a flow weighted average calculated using the formula:

discharge parameters in the licence are based on a flow weighted average calculated using the formula

Conditions of the EPA Victoria discharge licence outline the performance limits for effluent discharged to Port Phillip Bay via the four discharge points at the Western Treatment Plant.
The licence states that compliance with all licence parameter limits are to be calculated on a flow-weighted basis.

There is a plant wide limit of 700 million litres a day averaged over the year. The Western Treatment Plant complied with licence waste discharge limits for all parameters.

Annual average daily discharges for 2007/08

 

Outlet
Average Daily Volume (ML)
15 East Outlet
131
145 West Outlet
53
Lake Borrie Outlet
36
Murtcaim Outlet
1.16
Total
221

 

Annual discharge to Port Phillip Bay

The treatment plant's performance against the EPA licence limits for 2007/08 shown below shows that the Western Treatment Plant complied with the effluent discharge limits for all parameters. The results for 2007/08 are shown below:

(All data in mg/L unless otherwise indicated)

Waste indicators that must comply with medians, 90th percentiles or maximum limits

Waste indicator Median 90th %ile Maximum
Limit Result Limit Result Limit Result
CBOD5 10 2.2 20 3.7
Total Suspended Solids 30 22 60 50
Total Phosporus as P 15 11
Colour Pt/Co units 200 46 400 54
Ammonia as N 10 2.0 30 12
Anionic Surfactants as MBAS 0.8 0.21 1 0.52

Waste indicators that must comply with 75th percentiles or maximum limits

Waste indicator 75th %ile Maximum
Limit Result Limit Result
Cadmium 0.0011 0.00040 0.005 0.00055
Chromium 0.04 0.0086 0.1 0.018
Copper 0.028 0.011 0.1 0.019
Lead 0.015 0.0041 0.06 0.011
Mercury 0.0004 0.00010 0.001 0.00013
Nickel 0.0229 0.021 0.06 0.026
Zinc 0.06 0.034 0.2 0.053
 
Benzene 0.005 0.00050 0.01 0.00050
Toluene 0.005 0.00050 0.01 0.0038
Phenols (total) 0.04 0.0028 0.08 0.010
Total PAHs 0.0004 0.000010 0.0008 0.00030

Annual nitrogen load to Port Phillip Bay

The nitrogen output from the Western Treatment Plant was 1,239 tonnes per annum for 2007/08. The annual loads for the last three years are shown in the following table, which demonstrates that Melbourne Water has complied with the maximum target of 3100 tonnes per annum.

Annual nitrogen load from Western Treatment Plant

Financial Year
2007 / 2008
2006 / 2007
2005 / 2006
3 year rolling average
EIP Target
Total N Load (tonnes/annum) 1,239 1.560 1.969 1,589 3,100

 

Dioxins and furans

Melbourne Water monitors polychlorinated dibenzo dioxins and furans (PCDD/F), as toxic equivalents of 2,3,7,8 tetrochloro-dibenzo-p-dioxin. Sampling of PCDD/F is carried out at the 15 East Outlet in the month of January, 145 West outlet in April, Lake Borrie outlet in July and Murtcaim Outlet in October each year. The raw sewage is sampled for PCDD/F each time an outlet is sampled (i.e. 4 times a year).

The toxic equivalent (TEQ) is calculated for each sample using the World Health Organisation’s toxic equivalency factors (WHO98-TEQ) method and is represented in the following table. Results for preceding years are also presented for comparison.

PCDD/F as World Health Organisation Total Toxic Equivalents of 2,3,7,8 TCDD for 2004/05
(All results in pg/L)

Melbourne Water monitors polychlorinated dibenzo dioxins and furans (PCDD/F), as toxic equivalents of 2,3,7,8 tetrachloro-dibenzo-p-dioxin. Sampling of PCDD/F is carried out at the 15 East Outlet in the month of January, 145 West outlet in April, Lake Borrie outlet in July and Murtcaim Outlet in October each year. The outlet results are reported as a flow weighted average. The raw sewage results are reported as an average of four samples taken each time an outlet is sampled (i.e. 4 times a year).

The toxic equivalent (TEQ) are calculated for each sample using the World Health Organisation’s toxic equivalency factors (WHO05-TEQ) method where results below the limit of detection are summed as ½ the limit of detection. The results were 6.2 and 2.8 pg/l respectively for raw sewage and the outlets.

Bacteriological monitoring

Melbourne Water conducts bacteriological monitoring by collecting a sample of seawater in 60 centimetre depth of water off-shore from Beach Road and 160 South Road every seven days and analysed to determine the concentration of E. coli in the sample. These two points are public access points to Port Phillip Bay within the Western Treatment Plant and outside the designated mixing zones for E.coli.

The State Environment Protection Policy (Waters of Victoria) schedule F6 for the Werribee segment requires the 42 day geometric mean E.coli values to be less than 1000 orgs/100ml. Melbourne Water has calculated the 42 day Geometric mean and 42 day 80th percentile for the E.coli at the two sites.

E.coli- 42-Day Geometric Means and 80th Percentiles

(All results orgs/100 ml)

 
Geometric Mean
80th Percentile
42 Day
Period Ends
160 South Rd
Beach Rd
160 South Rd
Beach Rd
03-Jul-07
 2 2 2 2
14-Aug-07
 12 2.7 48 10
25-Sep-07
 11 2 30 10
06-Nov-07
 3.4 4.6 10 10
18-Dec-07
 6.7 4 17 6
29-Jan-08
 1.6 0.49 4 0
11-Mar-08
 3 1.1 8 4
22-Apr-08
 1.3 0.66 6 2
03-Jun-08
 0.84 0.49 2 0

 

The above results indicate that the two sites within the Werribee segment achieve the State Environment Protection Policy (Waters of Victoria), Schedule F6, Werribee Segment, bacteriological organisms quality objective of <1000 E-coli organisms / 100ml.