Slurry erosion is critical to the alumina industry.

Ragging and obstruction of wastewater pumps and pump impellors is a significant performance issue across Water Corporation’s wastewater pump stations, incurring a substantial corrective maintenance cost to the organisation, and driving a recognised overflow risk. Root cause investigations thus far have focussed on Make and Model of sewer pumps and impellors, and is yet to be completed. Other potential root causes are not well-understood and it is believed that there is a body of work that can be done to better understand all major factors associated with the ragging and obstruction of sewer pumps and impellors. A more robust understanding of these root causes would then drive improvements to maintenance and operation strategies for sewer pumps and pump stations, driving down corrective maintenance costs and overflow risks.

The Water Corporation currently has 4 pressure managed district metered areas (DMA) in the Perth metropolitan area and effectively operates many towns as such. A basic DMA is a discrete hydraulic zone containing approximately 1500 to 3000 customer connections and is supplied through a single bulk flow meter connected to SCADA.

The DMA’s flow data is monitored daily for changes in leakage and leakage trends over time. Leakage can be calculated using international methods such as bottom-up methods involving minimum night flows (MNF) and by top-down water balances using total flow and by subtracting customer consumption.

The Corporation is interested in developing its leakage calculations using the MNF method whereby a customer night use allowance is subtracted from the minimum night flow to best estimate the unreported leakage.

An issue faced by Water Corporation is that winter is currently the only time that a best estimate of leakage can be assessed using the MNF. This is mostly because during winter a ban is placed on the use of garden sprinklers and evaporative air conditioners are not in use.

This project aims to create a customer summer night use model that can be used to best estimate leakage during summer, or at any other time of the year and to also detect sudden or trending changes in leakage.

Natural seawater is known to have a number of commercially important elements that are of increasing value to society such as Na, K, Ca, Mg and even Li.

The Perth Seawater Desalination Plant (PSDP) harvests natural seawater, removes approximately 45% of the available water and then disposes the remaining concentrated seawater back into the ocean.

Magnesium is believed to be the most economically attractive element to recover from seawater and there are a number of commercially viable operations around the world where magnesium recovery is performed. Magnesium is commercially available as either MgO or Mg(OH)2. It is proposed that the Magnesium is to be recovered as Mg(OH)2 as either a 55% w/w slurry or as a dried product. MgO production is considered to be out of scope at this stage.

This project aims to provide the necessary background information to enable the Water Corporation to make an investment decision as to whether Magnesium recovery from desalination brine is attractive.