Water Journal : Water Journal September 2012-1
refereed paper water recycling water SEPTEMBER 2012 89 • Monitoring in response to incidents and emergencies may include increased and strategic monitoring of recycled water and the receiving environment at short notice with minimum turnaround times. Existing Recycled Water Schemes Hunter Water has a long track record of using recycled water in industry, agriculture and on municipal facilities such as golf courses. During 2011--12, approximately 4,660ML of recycled water was supplied to customers by 16 recycled water schemes (Table 1), of which 40% directly substituted the use of potable water. These schemes consisted of a number of agricultural and municipal irrigation applications as well as two significant industrial reuse schemes. Indirect recycled water use accounted for treated effluent discharged to receiving waters and then extracted by downstream farmers. The recycled water was supplied from 10 out of 18 WWTPs owned by Hunter Water. Figure 2 shows the locations of these recycled water schemes. Recycled water is also used at a number of WWTPs for chemical mixing, wash- down and general process water. • Karuah Effluent Reuse Enterprise (ERE) Background Karuah WWTP and the ERE were established as part of the Hunter Sewerage Project (HSP) in 2002. The objectives of the HSP were to protect water quality in Karuah River and the adjacent marine environment, safeguard public health, reduce local pollution and minimise impacts to local oyster industry, and optimise resource use. Karuah WWTP and the ERE are fully owned by Hunter Water and managed by Hunter Water Australia (HWA), a subsidiary company of Hunter Water. The Karuah ERE is situated adjacent to Karuah WWTP off Scotts Road, approximately 3km north-west of the township of Karuah. It is located on a 100-hectare (ha) property owned by Hunter Water. Much of the site had been cleared by the previous owner. An area of 70ha has been developed for irrigation of recycled water and site access. Significant areas of native trees have been maintained. A native tree buffer zone (20m) has been established along the northern and north-western boundaries. The Karuah ERE has a capacity to irrigate up to 290kL per day (1,450 EP) of recycled water from Karuah WWTP. A site plan of the Karuah ERE is shown in Figure 3 and the historical recycled water usage data are presented in Table 2. Irrigation System The final recycled water from Karuah WWTP is stored in a 100ML-capacity dam located to the west of the central ridge on the ERE land, before being pumped to the reuse area via a centrifugal pump. The reuse area consists of 34ha of pastoral land irrigated by one full-circle (Pivot 2) and one part-circle centre pivot irrigator (Pivot 1). Pivot irrigation was selected as the preferred irrigation method because it allows variable application rates, optimised spraying to avoid run-off, irrigation of part circles, simplicity of operation with low labour and energy requirements, and low potential for spray drift. Crops Harvested Currently a mixture of lucerne, rye grass and clover is being grown on the irrigation area. Due to the slightly different elevation, topography and groundwater levels at each pivot area, the success of the different crops vary. A combination of rye grass and lucerne grows well on Pivot 2, with clover being the predominant crop on Pivot 1. Site Management Plan The Site Management Plan (SMP) has been developed for the identification of potential environmental impacts due to operation of the scheme and measures to mitigate these risks. One of the key risk areas of any agricultural effluent reuse enterprise is appropriate irrigation scheduling. Consequently, an Irrigation Management Plan, based on the NSW Department of Primary Industries guidelines on Irrigation and Drainage Management Plan (IDMP), has been developed as part of the SMP. Performance Management of Existing Schemes The performance of existing recycled water schemes is regularly monitored by Hunter Water's Recycled Water Quality Committee (RWQC) as well as other key Hunter Water personnel and senior management. Health and environmental risk assessments were Table 2. Historical recycled water usage data for the Karuah Effluent Reuse Enterprise (ERE). Financial Year Recycled Water Usage (ML) Annual Rainfall (mm)* 2002--03^ 48.24 741.5 2003--04 119.20 842.0 2004--05 88.29 979.0 2005--06 78.11 756.0 2006--07 90.55 1372.5 2007--08 112.26 1273.5 2008--09 159.54 1376.0 2009--10 128.10 773.0 2010--11 188.61 1168.8 2011--12 135.51 1354.0 * Indicative rainfall data from Raymond Terrace WWTP, ^ Data from September 2002 to June 2003. Figure 2. Locations of current recycled water schemes and future opportunities.
Water Journal November 2012-1
Water Journal August 2012