Goulburn Valley Water will be undertaking desludging works at the Eildon and Nathalia Wastewater Management Facilities (WMF).

Desludging is necessary to remove the sludge that builds up slowly at a WMF. Sludge is solid waste that bacteria produce when breaking down the wastewater.

These solids settle to the bottom of the lagoon and form a sludge deposit. As the sludge builds up it reduces the capacity of the facility to effectively treat wastewater and can cause odour. After 5 - 20 years of operation (depending on the location) GVW removes the sludge to reduce these odours and reinstate the capacity of the lagoon.

Desludging can produce odours as the lagoon is disturbed. These odours are short term and only present during the actual desludging works. During the works an odour supressing spray system will be installed to mask the odour from the sludge. These odour suppression units will be strategically placed around the sludge drying area to mask the odour.

Once the desludging of the lagoons has finished the sludge will enter the drying phase, which will take place over 4-6 weeks. The sludge, having been removed from the treatment lagoons, will be spread out over six of the WMF irrigation bays to dry. The air drying process is expected to take 4 to 6 weeks to complete depending on the weather conditions. Once dried, the sludge becomes biosolids which will be stockpiled in a dedicated area for up to 3 years before been reused as a soil conditioner to improve soil fertility. It is estimated that 400/800 tonnes of biosolids will be stored on site as a result of the works.

During the desludging process GVW will monitor air quality and regularly audit the site to ensure the project is completed in a safe, timely and environmentally acceptable manner.

About the project

Wastewater By-products
Wastewater treatment processes produce by-products including biogas and biosolids. Biosolids are the solid waste that bacteria produce when they break down wastewater. These solids settle to the bottom of the lagoons and form a sludge deposit. The sludge slowly builds up over time, around 25 years, and can casue unpleasant odours (biogas). These odours can be mitigated by removing the accumulated sludge (cleaning out the lagoons). Given the age of the lagoons at the Eildon and Nathalia WMF's, desludging will be completed to remove the biosolids which will improve the capability of the treatment facility as well as reduce odours at the site.

Odour Reduction Program
The desludging project at Eildon and Nathalia WMF is part of GVW's extensive Odour Management Program. Over the past five years, the Corporation has spend over $1.8m on odour reduction projects across the region. This has included trialling odour reduction solutions, both short term and long term, which has managed to provide residents with some welcome relief. Various options were looked at for the projects and desludging was the most cost effective proposal to deliver the project in a safe and timely manner with an environmentally acceptable solution.

Desludging is undertaken by siphoning the sludge (biosolids) from the lagoon floor without emptying it, enabling the wastewater treatment process to continue. A side effect of desludging is that when sludge is disturbed, it can produce unpleasant smells. GVW is working with the Environment Protection Authority (EPA) to ensure there are no health risks associated with the works. It is expected however, that there will be a disruption to aesthetics due to an increase in odours. Smells will vary throughout the project depending on weather and environmental conditions.

Biosolids Reuse
Once the organic material is removed from the lagoons it is left to dry for a period of time. The dried biosolids are then reused as fertiliser or soil conditioner.

Reporting Odours
Air quality at the Eildon and Nathalia WMFs will be monitored continuously throughout the project and reported to the EPA on a regular basis. Residents can report odours to GVW’s 24 hour Customer Service Centre on phone 1800 454 500.

Various options were looked at to improve the Wastewater Management Facilities and desludging was the most cost effective proposal to deliver the project in a safe and timely manner, with an environmentally acceptable solution. Although there will be short term aesthetic issues due to desludging, overall the works are expected to ultimately reduce odours at the facility, a long term improvement solution for the townships.