CSIRO (2009) estimated high, median and low future water demand of 14 demand groups (potable, residential irrigation, industrial, horticulture etc) and compared them with groundwater supply options under wet, median and dry future climate scenarios. The results for the Cockburn Groundwater
Management Area showed that demand would exceed supply in 2015 under a high demand scenario, by 2022 under a median demand scenario and be able to meet 2030 requirements if there was a low demand scenario (Figure 4.3). There was little discrimination in this area between climate scenarios, possibly because of the high transmissivity of the Tamala Limestone aquifer (resulting in only small changes in groundwater levels) and the fact that the planning horizon was short (22 years).
Figure 4.3 Supply and demand scenarios for the Cockburn Groundwater Management Area (CSIRO 2009)
4.4
References
Burns and Roe Worley (BRW) (2006) Kwinana Industrial Area water planning study 2006, Report for Kwinana Industries Council. Burns and Roe Worley, Australia.
CSIRO (2009) Water yields and demands in south-west Western Australia. A report to the Australian Government form the CSIRO South-West Western Australia Sustainable Yields Project
EDAW (2009) Rockingham industry zone water management strategy: preliminary scoping report, Prepared for LandCorp. EDAW, Australia.
Department of Water (2013) Western Trade Coast water supply and Peel wastewater reuse, Phase 1: Water demand-supply situation paper. Department of Water, Australia.
Department of Sustainability, Environment, Water, Population and Communities (DEWPaC) (2010) Approval: Rockingham Industrial Zone, WA (EPBC 2010/5337). DWEWPC, Australia. Resource Economics Unit (2008) Water futures for Western Australia 2008-2030. Prepared for the
Department of Water. Resource Economics Unit, Australia.
GHD (2015) Kwinana managed aquifer recharge study: Industrial water supply options assessment, Report to CSIRO. GHD, Australia.
Landcorp (2010) Latitude 32 district structure plan. Landcorp, Australia.
Water Corporation (2014) Use of Cape Peron outlet pipeline to dispose of industrial wastewater to sepia depression, Kwinana: Ministerial Statement 665 2013-14 Performance and compliance report. Water Corporation , Australia.
Western Australian Planning Commission (2014) 2014/14 Urban land development outlook: Perth metropolitan region and Peel sub-region. Western Australian Planning Commission, Australia.
0.0 10.0 20.0 30.0 40.0 50.0 60.0 70.0 80.0 2005 2010 2015 2020 2025 2030 2035 T o tal D em an d v T o tal A vai lab le Y iel d (G L /y r) 2030 Low 2030 Medium
2030 High 2030 Scenario A : Historical Climate (1975-07) 2030 Scenario B : Recent Climate (1997-07) 2030 Scenario C : Cwet Future Climate 2030 Scenario C : Cmid Future Climate 2030 Scenario C : Cdry Future Climate
5
Wastewater availability and quality
Authors: Mike Donn and Don McFarlane
Key findings
• The Sepia Depression Ocean Outfall Line provides an abundant source of treated wastewater for
Managed Aquifer Recharge. The smaller Kwinana WWTP is projected only to have modest increases in treated wastewater.
• Salinity and pH of treated wastewater is similar to the ambient groundwater and is within wetland
ecosystem trigger values
• Treated wastewater nutrient concentrations generally exceed ambient groundwater and wetland
ecosystem protection trigger values, however high ambient nitrogen concentrations exist as the result of anthropogenic and natural processes
• Treated wastewater is generally of higher quality from the Kwinana WWTP (and the soon to be
commissioned East Rockingham WWTP) than Woodman Point WWTP and hence the Sepia Depression Ocean Outfall Line
5.1
Introduction
Water Corporation currently operates three wastewater treatment plants (WWTPs) in the Cockburn Catchment; Woodman Point, Kwinana and Point Peron (Figure 5.1). A fourth plant is currently being constructed in East Rockingham and is expected to commence operation in early 2016. Woodman Point and Kwinana WWTPs are of primary interest due to their location and current operation. All treatment plants use similar processes for the primary treatment of wastewater. Treated wastewater from the Point Peron plant is only primary treated (Water Corporation, 2014a) with the remaining plants utilising activated sludge technology for secondary treatment. Currently secondary treatment at the Woodman Point plant is based on a sequencing batch reactor (Water Corporation, 2009) with an upgrade to a continuous process, based on the Modified Ludzack-Ettinger process, proposed to occur in 2019 (source: Water Corporation). Treated wastewater quality data from the Beenyup WWTP was used to indicate the potential changes to future water quality as a result of future treatment process changes at the Woodman Point WWTP. The Beenyup WWTP services the northern suburbs of Perth (Figure 6.1). Both the Kwinana and new East
Rockingham treatment plants utilise oxidation ditch technology for secondary treatment, thus water quality at East Rockingham WWTP is likely to be similar to Kwinana.
The majority of the treated wastewater (TWW) is disposed of via the Sepia Depression Ocean Outlet Landline (SDOOL) which transfers the TWW to an ocean outlet located in the Sepia Depression, approximately 4 km south-west of Point Peron (Figure 5.1). In 2013-2014, approximately 151 ML/d
(55 GL/yr) of TWW was disposed of through the Sepia Depression ocean outlet (Water Corporation, 2014b). With respect to the TWW disposed through the SDOOL, a relatively small amount of TWW (~3%) is
disposed of to land through infiltration basins. Based on the licence requirements, the Kwinana WWTP can dispose of up to 4.7 ML/d (~1.7 GL/yr) to land, with excess TWW disposed of through the SDOOL (DER, 2014).
Inputs to and off-takes from the SDOOL for 2013-14 are shown schematically in Figure 5.2; these have potential implications from quantity and quality of TWW available for managed aquifer recharge (MAR). While Figure 5.2 indicates the 2013-14 quantities there is the potential for greater recycling through the Kwinana Water Reclamation Plant (KWRP) and industry return and these are outlined below. Off-take of
TWW for KWRP of up to 24 ML/d in the current configuration (Department of Health, 2009) is used to produce high quality recycled water for industry by reverse osmosis (Water Corporation, 2014c). The disposal of industrial wastewater to the SDOOL of up to 30 ML/d (~11 GL/yr) is approved by Western Australian government (Ministerial statement 665, 2004). Industrial wastewater disposal is currently approved for KWRP concentrate (up to 7 ML/d, Department of Health, 2009) and wastewater from CSBP, BP and the Kwinana Cogeneration Plant (Water Corporation, 2014a).
Figure 5.1 Location of wastewater treatment plants (WWTPs) and the Sepia Depression Ocean Outlet Landline (SDOOL) and associated treated wastewater pipeline connections
Figure 5.2 Schematic of the inputs to and off-takes from the Sepia Depression Ocean Outlet Landline (SDOOL) for the 2013/14 financial year. These include the three wastewater treatment plants (WWTPs), the Kwinana Water Reclamation Plant (KWRP) and selected industries. Data sourced from Water Corporation (2014b)
The disposal of TWW to the Sepia Depression has a nitrogen load limit of 1778 t/yr (equivalent to N load in 1994, Environmental Protection Authority, 2004), with appropriate licenced load limits set for industrial discharges to the SDOOL to ensure the total nitrogen loads do not exceed this value (e.g. 200 kg/d for CSBP (DER, 2013)). Relative to the inputs of total nitrogen from the Woodman Point WWTP (2072 kg/d in 2013) the input from industry is low. As a result the change in SDOOL water quality resulting from industry and KWRP wastewater additions are not considered in the analysis of MAR source water.