Decentralised systems - definition and drivers in the current context.

This paper explores the current context for decentralised approaches in the provision of urban water services. It examines the recent history of decentralised systems' implementation in Australia and identifies its drivers. The drivers included addressing capacity constraints of centralised systems, mitigating the environmental impact of urban development, and increasing the resilience of urban water systems to episodic droughts and the projected impacts of climate change. The concepts of integrated urban water management and water sensitive urban design were prevalent in many of the innovative approaches used for the provision of decentralised urban water services. However, there remains a degree of confusion among water professionals in the terminology adopted for on-site and decentralised systems. Based on a literature review, consultation with water industry professionals and examination of decentralised urban developments in Australia, this paper has developed a generalised definition of decentralised systems for adoption across the water sector. The definition encompasses the various development scales in which decentralised systems are implemented, and reflects the new functions and characteristics inherent to those systems.

Performance characterisation of a constructed wetland.

Performance of a constructed wetland is commonly reported as being variable due to the site specific nature of influential factors. This paper discusses the outcomes from an in-depth study which characterised the treatment performance of a wetland based on the variation in the runoff regime. The study included a comprehensive field monitoring of a well-established constructed wetland in Gold Coast, Australia. Samples collected at the inlet and outlet were tested for Total Suspended Solids (TSS), Total Nitrogen (TN) and Total Phosphorus (TP). Pollutant concentrations in the outflow were found to be consistent irrespective of the variation in inflow water quality. The analysis revealed two different treatment characteristics for events with different rainfall depths. TSS and TN load reduction was found to be strongly influenced by the hydraulic retention time where performance was relatively superior for rainfall events below the design event. For small events, treatment performance was higher at the beginning of the event and gradually decreased during the course of the event. For large events, the treatment performance was comparatively poor at the beginning and improved during the course of the event. The analysis also confirmed the variable treatment trends for different pollutant types.

Quantitative PCR assay of sewage-associated Bacteroides markers to assess sewage pollution in an urban lake in Dhaka, Bangladesh.

This paper aimed to assess the magnitude of sewage pollution in an urban lake in Dhaka, Bangladesh, by using quantitative PCR of sewage-associated Bacteroides HF183 markers. PCR was also used for the quantitative detection of ruminant wastewater-associated CF128 markers along with the enumeration of traditional fecal indicator bacteria, namely enterococci. The number of enterococci in lake water samples ranged from 1.1 × 104 to 1.9 × 105 colony-forming units/100 mL water. From the 20 water samples tested, 14 (70%) and 7 (35%) were PCR positive for HF183 and CF128 markers, respectively. The numbers of HF183 and CF128 markers in lake water samples were 3.9 × 104 to 6.3 × 107 and 9.3 × 10³ to 6.3 × 105 genomic units/100 mL water, respectively. The high numbers of enterococci and HF183 markers are indicative of sewage pollution and potential health risks to those who use the lake water for nonpotable purposes such as bathing and washing clothes. This is the first study that investigated the presence of microbial source tracking markers in Dhaka, Bangladesh, where diarrhoeal disease is one of the major causes of childhood mortality. The molecular assay used in this study can provide valuable information on the extent of sewage pollution, thus facilitating the development of robust strategies to minimize potential health risks.