2007 Annual Report - Central Queensland University

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2007 Centre for Plant & Water Science Annual ReportSOUTH AUSTRALIAN WASTEWATER AND RECYCLING TRAINING DAY SERIESSUMMARYCPWS of CQUniversity has been working in conjunction with Tom Woods (Onkaparinga CityCouncil) and the South Australian Institute of Environmental Health to provide practicaltraining days on on-site wastewater and water recycling for South Australian governmentemployees.Due to the outstanding success of the first South Australian Training Day held in the AdelaideHills in June 2006 (on the coldest day on record); a second training day was held north ofAdelaide in February 2007 (maximum temperature for the day 44 C). The training days are thebrainchild of Tim Woods of the Onkaparinga City Council. The aim is to educateenvironmental and public health officials about on-site wastewater treatment and waterrecycling through practical demonstrations.The 2007 training day involved installing a 4000 L septic tank, a holding tank, and a purple podrecycled water irrigation system. The purple pod system was the first to be installed in SouthAustralia, and comprises a 77 mm diameter chamber within a grilled exit that is resistant toclogging. Over the course of the day 51 people attended the training from 11 different localgovernments and three different State government departments. Ben Kele spoke on the issues ofsoil type on recycled water schemes and Barry Hood on the importance of maintenance for onsitesystems.The third training day in the series is scheduled to occur at South Australia’s Maslin’s Beach inApril 2008.Figure 1. Views of the training dayPROJECT STAFF Principal Investigator: Ben KeleCo-Principal Investigator: David MidmoreOthers: Tim Woods (Onkaparinga City Council)Barry Hood, GBG Project Management Pty LtdSouth Australian Branch of the Australian Institute ofEnvironmental HealthFUNDINGCentral Queensland University37

2007 Centre for Plant & Water Science Annual ReportPHYTOCAPPING: AN EFFECTIVE TECHNIQUE FOR LANDFILLREMEDIATIONLandfills have been the major repositories of urban wastes, and they will continue to be built; solong as the humans live in communities. The costs of construction of landfills have beenescalating due to introduction of stringent environmental laws. Research is therefore required toidentify alternative techniques that will not only minimise the costs, but also demonstrateincreased environmental performance. An alternative landfill capping technique known as‘Phytocapping’ (establishment of plants on a layer of soil placed over the waste) was trialled atRockhampton, Australia. Twenty one tree species were grown for 3 years on two types ofphytocaps (thick cap; 1400 mm and thin cap; 700 mm; Fig. 1) and their growth, transpirationloss, canopy rainfall interception and methane oxidation were studied. The results show that thecanopy of the trees grown on the phytocaps intercepted, on an average, 30% of the rainfall thuspreventing a significant proportion of the rain water from entering the soil. The long-term sapflow monitoring data showed that the 2 to 3 year-old trees could remove 0.9 to 2.1 mm day -1 .The phytocaps were also found very effective in oxidising methane. The methane concentrationswere 4 to 5 times lower in phytocaps than in the adjacent non-vegetated landfill sites. TheHYDRUS 1D computer simulation model using 15 years of weather data and the plant and soilparameters collected from this trial revealed a percolation rate of 16.7 mm yr -1 in thick phytocapand 23.8 mm yr -1 in thin phytocap. These values are significantly lower than those expectedfrom compacted clay (78 mm yr -1 ; i.e., 10% of the rainfall). Overall, results of this studydemonstrate that the phytocaps are effective in limiting percolation of water into the waste atRockhampton which has a semi-arid climate. The trial also demonstrates the potential ofphytocaps to reduce landfill remediation costs while offering additional environmental benefits.Further research is currently being conducted to extend this novel method of landfillremediation to other agro-climatic regions of Australia(http://www.wmaa.com.au/aacap/aacap.html), with the view to providing scientific data toregulatory authorities to seek their approval to use phytocapping as an alternative technique forlandfill remediation.Figure 1. A closer view of the thick (left) and thin phytocaps (right) two years of plantingPROJECT STAFF Principal Investigators: Assoc. Prof. Nanjappa AshwathCo-investigators: K. Venkatraman and Dr N. SuFUNDING Central Queensland University post graduate scholarship38

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