Eurobodalla Integrated Water Cycle Management Strategy

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134 Eurobodalla Integrated Water Cycle Management Strategy Initiating regular and systematic monitoring of operational parameters such as daily water use, sewage flows, water quality etc., and more strategic environmental and social parameters. Establishing a water supply reticulation network model to confirm pressure and firefighting service standards. Updating the asset registers to ensure the asset information is complete and up-todate. Reviewing and updating the Batemans Bay stormwater management plan with information and suggestions contained in this report. Medium to Long term Water Cycle Management Opportunities The medium to long term opportunities are related to enhancing the sustainability of the water cycle, protecting public health and the environment and improving the service standards. Analysis suggests that even after the implementation of immediate measures, the sewage management at Batemans Bay needs to be enhanced in the medium to long term due to inadequate sewage treatment plant hydraulic capacity, and the close proximity of the main sewer pipeline to the beaches. Table 9-10 presents the water cycle management opportunities, their relative capital and present value costs over a 30-year period at an annual discount rate of 7%. For details of costs see appendix Q. Whilst the costs are indicative only, the relative cost difference between the opportunities should be similar. Table 9-10 Medium to Long term Water Cycle Management Opportunities for Batemans Bay Opportunity Costs $m Capital NPV@7% Provision of a new local reservoir 1.25 0.8 Enhance capability of existing sewage treatment plant 1 New sewage treatment plant in North Batemans Bay 1 10 12.1 13.4 15.9 Transfer of southern catchment sewage load to Tomakin 1 11.8 13.8 STP Stormwater quantity and quality control measures for high priority sub-catchments Stormwater quantity and quality control measures for low priority sub-catchments 5.4 5.75 1.0 1.1 Local urban open space stormwater reuse 2.4 3 Note 1 : This cost indicates artificial UV treatment of the effluent. The quality could be further enhanced with sand or membrane filtration and/or with wetland treatment. Enhance the Biological and Hydraulic Capability of the Existing Sewage Treatment Plant Preliminary investigations suggest that the existing hydraulic capacity of the reactor and clarifier at the STP is about 6.6 ML/d (27 500 EP) and this capacity could be enhanced by the addition of chemicals to 9.2 ML/d (38 000 EP) provided the pipelines linking the various treatment process units are adequate. However, at these high flows, the process safety
Eurobodalla Integrated Water Cycle Management Strategy margins are compromised and during wet weather flows plant by-pass will continue to occur, albeit the frequency may be lower with the proposed inflow reduction management. The by-pass of raw diluted sewage could be avoided by installing additional clarifiers to settle the solids and provide some treatment. To reduce public health risk an artificial UV irradiation plant could be installed at the outlet of the maturation pond, which could be used to disinfect the effluent prior to discharge through the ocean outfall, and the reclaimed water used at the golf club. The other works necessary for plant capacity augmentation include: New inlet works Minor process modifications Additional aeration capacity and/or an aerated balancing storage at the inlet, and Overall OH&S improvement for the plant. An alternative to this process optimisation strategy is to build a parallel process train with similar capacity to the current plant. To overcome the incidence of sewage overflows from the coastal area, a dedicated pipeline along Spine Road alignment could also be installed to convey sewage from the northern catchment to the treatment plant. A New Sewage Treatment Plant to Serve the North Batemans Bay Catchment In this strategy, a new STP with an initial biological capacity of 5 000 EP would be built north of Clyde River to treat all the sewage generated from the northern catchment. The plant would be located on Council owned land. The reclaimed water from the plant would be conveyed via the proposed Spine Road sewage main to the existing outfall. The advantage of this strategy is the conveyance of reclaimed water across the Clyde River and up to the existing plant as opposed to the conveyance of raw sewage. Another benefit may be the reduction and/or elimination in the wet weather storage capacities within the existing sewer network. In this strategy the existing STP would still need new inlet works and other minor rehabilitation works to meet OH&S requirements. The reclaimed water discharged from both STPs would be artificially disinfected using a common UV facility at the existing STP. Transfer of Southern Catchment Sewage Load to Tomakin Sewage Treatment Plant In this strategy, the sewage from the southern catchment would be transferred to the existing Tomakin STP. Reversing the flow from the main southern pump station and constructing a rising/gravity main to the Tomakin plant could achieve this. The benefit of this strategy option is that the new rising/gravity main could be integrated with the proposed rising/gravity main to serve the Rosedale and Guerilla Bay areas. Further, this opportunity also maximises the utilisation of the currently under loaded Tomakin plant and discharges the reclaimed water through a relatively better performing ocean outfall (verbal advice from NSW EPA). In this opportunity the existing Batemans Bay plant would still require new inlet works and other minor rehabilitation work to meet OH&S requirements. The reclaimed water discharged from both STPs would be artificially disinfected using UV facilities located at the respective STPs. The Tomakin plant would need minor upgrades to meet the increased loads. Preliminary analysis shows that the performance of the plant could be enhanced by optimising the treatment process and by dosing chemicals during periods of peak holiday loads. Assessment of Medium to Long term Water Cycle Management Opportunity The TBL assessment in Table 9-11 provides the comparative environmental and social benefits of the sewerage management component of the water cycle management opportunities for Batemans Bay. 135
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FACT SHEET 3 Rainwater Tanks 18 Eur
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FACT SHEET 9 Loss Reduction 24 Euro
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38 Number of Persons 2,500 2,000 1,
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42 % Occupancy 80% 70% 60% 50% 40%
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46 Annual Volume (ML/Yr) 2,500 2,00
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48 Demand ML/a Eurobodalla Integrat
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6.5.3 Stormwater Issues 58 Euroboda
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9.14.2 What are the Issues? 202 Eur
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9.15.2 What Are the Issues? 208 Eur
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214 ML/a 8000 7000 6000 5000 4000 3
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228 SCENARIO 1 Regional Water Suppl
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