Sydney Water's New Biosolids Management Strategy Builds on Strategic Process Modeling Capacity

Sydney Water Corporation (SWC) provides water and wastewater services for the metropolitan Sydney area of New South Wales (NSW), Australia, operating a total of 29 sewage treatment plants (STPs). Almost all of the captured solids across all plants are used beneficially in agriculture, composting or land rehabilitation. Sydney's population is projected to increase by almost 20% between 2010 and 2031 to around 5.3 million. Over this period, the total biosolids production is expected to increase due to growth by about 38% from 39,000 dry tonnes per year (dT/yr, or 42,900 dry tons per year or DTPY) to 54,000 dT/yr (59,400 DTPY).Presently SWC predominantly produces a digested and dewatered cake that has a high water content and a moderate to high odor potential. Anaerobic digestion is deployed at the larger treatment works, and aerobic digestion otherwise.SWC has just completed (2011) the development of a biosolids management strategy for the 20 year period to 2032. The strategy is focused on the likely capacities of marketplaces for high and low value biosolids products, and the risks associated with the present practices. A technology assessment was done as an integral part of the strategy to provide performance and cost estimates, and is the subject of this paper.