Alexandra Wastewater Management Facility Desludging
Stage 2 of desludging works commenced
Goulburn Valley Water has been undertaking desludging works at the Alexandra Wastewater Management Facility (WMF) over the last six weeks.
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. The sludge builds up and reduces the capacity of the treatment facility to effectively treat the wastewater and can cause odour. After 5 - 20 years of operation (depending on the location) GVW remove the sludge to reduce these odours and reinstate the capacity of the lagoon.
The desludging of the lagoons has finished and we are now moving into the drying phase, which will take place over the next 4-6 weeks. The sludge, having been removed from the treatment lagoons, has been 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.
During the desludging process GVW has been monitoring air quality and regularly auditing the site to ensure the project is completed in a safe, timely and environmentally acceptable manner. During the works an odour supressing spray system was installed to mask the odour from the sludge. Tutti-fruity odour supression units were strategically placed around sludge drying area to mask the odour.
About the project
GVW provides water and wastewater services to Alexandra. The Alexandra WMF is located on the Maroondah Highway, east of the township. The present WMF conisits of five lagoons that biologically treat wastewater. After it is treated the recycled water is reused to irrigate neighbouring property during the summer months and returned to stream during winter.
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 Alexandra WMF, 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 Alexandra 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 Alexandra project 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.
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.
Project timeframes and costs
GVW has awarded a tender and it is expected that the Contractor will commence work on-site at the WMF in January 2018. Desludging will be carried out during February and the project is expected to be completed in March when the facility will return to normal operation.
Air quality at the Alexandra WMF will be monitored continuously throughout the project and reported to the EPA on a regular basis. Alexandra 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 Alexandra Wastewater Management Facility 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 township of Alexandra.