Until 1995, the Dandenong South Treatment Complex accepted a range of waste streams which were treated via biofiltration and land filtration prior to discharge to Dandenong Creek. Two distinct sewage streams entered the facility and were treated separately. One was known as the "Trade Waste Stream", the other the "Domestic Waste Stream". Three industrial inputs alone made up the "Trade Waste stream" some of the domestic waste stream was mixed with the trade waste to improve nitrogen and phosphorus content for biological activity in the biofiltration process (McCormick 1993). The so called trade waste stream had dioxin levels around 25 times lower than the domestic waste stream. The reason for this is that in reality the domestic waste plant also accepted large amounts of industrial waste from within the catchment (Letter, Newman 1993).

The "Trade Waste Stream" took waste from three large industrial sites; HJ Heinz, Marplex and General Motors. The General Motors plant at the time had two tenants Toyota Motor Corporation and Isuzu-General Motors.

The two waste streams were mixed after treatment and apart from some pasture irrigation in summer/autumn the two waste streams were directed through sequential ponds discharging to a drain which until 1995 entered directly into Dandenong Creek.

A 1993 study of toxic contaminants at the plant found high levels of dioxins entering the trade waste treatment lagoon. The most significant features of the data were:

That 2,3,7,8-tetrachlorodibenzo- p-dioxin was detected in all samples except the upstream sample;

The total toxic equivalent values of five samples exceed 1.0 part per billion, with the highest levels being around 30 part per billion; and

That the ration of dioxins to furans is uncharacteristically high;

The study concluded that "industrial inputs are delivering substantial amounts of dioxins to the plant and have been doing so for some time". (Mc Cormick 1993).

According to a 1993 Environmental Audit by consultants Camp Scott Furphy Pty Ltd, there are elevated levels of dioxins in the sludge lagoons and areas which have been irrigated with sludge from the treatment works. The land area contaminated by irrigation has dioxin levels up to 43.7 ng/g I-TEQ. Furthermore, there are over 2 million cubic meters of wet sludge and 83,000 tonnes of dry sludge with levels above 1 ng/g I-TEQ from the trade waste sludge lagoon and effluent lagoons. In addition there is 64,000 m3 of wet sludge from lagoon 1 and 19,000 tonnes of dry sludge from lagoon 1, with high levels of dioxin contamination (between 6-22.7 ng/g I-TEQ of dioxin)

The Camp Scott Furphy 1993 Audit estimated that historically the sewage plant released around 1.95g of dioxin per year into Dandenong Creek. This treatment works was decommissioned in 1994 and the sewer has been linked to the trunk sewer which is discharging into Bass Strait through the ocean outfall at Boags Rock after treatment at the South Eastern Purification Plant (SEPP).

Victoria estimated that the Eastern Treatment Plant releases 16 grams of 2,3,7,8,-TCDD and 45 grams of 2,3,7,8-TCDF (furan) per year as effluent (raw not ITEQ) via ocean outfall into Bass Strait. (Murfitt et al. 1994).

The now abandoned Dandenong South Treatment Complex, remains a contaminated site. The Victorian Environment Protection Authority revoked the licence to operate the plant in 1994 and issued a Pollution Abatement Notice in September 1996. The abatement notice required Melbourne Water to undertake further investigation of the site and ultimately a risk assessment and clean up. A series of groundwater studies (March and September 1998) have been undertaken on the site to determine if dioxin is moving off-site. The results of these studies are of great concern. The March 1998 ground water study found levels of dioxin between 9-69 pg/l I-TEQ, the highest values from holes adjacent to Dandenong Creek. (Camp Scott Furphy Pty Ltd.,1998a). The second study in October 1998 confirmed the levels of dioxin recording between 0.382-30.1 pg/l I-TEQ in ground water. The highest value again coming from the bore hole adjacent to Dandenong Creek. (Camp Scott Furphy Pty Ltd.,1998b).

Considering the low solubility of dioxin, the occurrence of relatively high levels of dioxin in the ground water are of great concern, and indicates that dioxin from the contaminated site is migrating into the surrounding environment. The two highest results are between 2-4 times higher than Aquatic Life Protection guidelines set by the USEPA and Canadian drinking water guidelines (15pg/l ITEQ). The potential for dioxin to move off-site reaffirms the urgent need for clean up of this area and for further investigation of the contamination surrounding the plant including sampling of transient wildlife i.e. birds etc, and Dandenong Creek.

South East Water, who now has responsibility for trade waste services in the Dandenong South Treatment Complex catchment, have required trade waste 'customers' not to discharge dioxin between 5 pg/g - 40 pg/g ITEQ. Some of the major industrial inputs to the 'trade waste' stream have since closed down, it is unclear how the inputs from the broader catchment have changed.


Melbourne Water Corporation immediately begin work to remediate the Dandenong South Treatment Works using non-incineration technologies.

Melbourne Water Corporation and the Victoria Environment Protection Authority ensure inputs of dioxin to other sewage plants particularly the Werribee Treatment Complex are eliminated.

The Victorian Government supports the development of national measures to eliminate dioxin.


Mc Cormick., M., (1993). A Study of Toxicants at the Dandenong South Treatment Complex., A report prepared for Melbourne Water., Department of Applied Chemistry., RMIT.,

Letter., Newman, I to Manager Technical Services, Melbourne Water to Dr Peter Nadebaum., 30 April 1993

Murfitt, P., Giobbi, T., LeCouteur, J., (1994). Melbourne's Toxic Sewers., Environment Victoria., September

Camp Scott Furphy Pty Ltd.,(1998a) Groundwater Sampling Dandenong South Treatment Plant., prepared for Melbourne Water., March

Camp Scott Furphy Pty Ltd.,(1998b) Groundwater Sampling Dandenong South Treatment Plant., prepared for Melbourne Water., October