MANAGEMENT OF DRINKING WATER QUALITY FROM SEAWATER ... · Perception that seawater desalination...

Wor World Congress/Perth Convention and Exhibition Centre (PCEC), Perth, Western Australia September 4-9, 2011 REF: IDAWC/PER11-294

MANAGEMENT OF DRINKING WATER QUALITY FROM SEAWATER DESALINATION: CASE STUDIES FROM WESTERN AUSTRALIA Authors: Andrew Bath, Steve Christie, Kathy Blakeway, Rachael Miller & Richard Walker Presenter: Andrew Bath Water Quality Operations Manager – Water Corporation, Leederville – Australia Abstract In Western Australia (WA), seawater desalination is now a key component of the water supply infrastructure and the Water Corporation currently owns three plants: Perth Seawater Desalination Plant (PSDP) at Kwinana, a seawater desalination plant providing industrial grade water on the Burrup Peninsula, and the new Southern Seawater Desalination Plant (SSDP) at Binningup. Provision of safe drinking water to customers is one of our highest corporate priorities, with legal requirements placed on the organisation by the Department of Health and Economic Regulation Authority. In WA, as a result of the drying climate, seawater desalination is now a key strategic source of drinking water. The case studies presented in this paper show a number of potential impediments exist in providing adequate protection of our marine intakes from the influence of natural or anthropogenic contamination. Source protection is constrained by: No direct guidance for the management of marine intakes and desalination in the current (2004)

Australian Drinking Water Guidelines (ADWG), Limitations with the application of current source protection legislation for marine intakes, Inability to prevent inappropriate land use development in coastal areas adjacent to marine intakes,

and Perception that seawater desalination provides the ultimate barrier to contamination and source

protection is not essential. As seawater desalination is a relative new technology in Western Australia, tools, processes and procedures were developed by the Water Corporation to ensure supply of safe drinking water. This paper describes the development, use and role of Source Protection Strategies (SPS), Water Safety Plans (WSP) and water quality management plans in providing safe drinking water. It is shown the protection of marine intakes is largely a “reactive” response to an incident or change in seawater quality. There is now an urgent need to amend current legislation to support proactive management of all activity and development around seawater intakes.

IDA World Congress – Perth Convention and Exhibition Centre (PCEC), Perth, Western Australia September 4-9, 2011

REF: IDAWC/PER11-294 -2-

I. INTRODUCTION Water Corporation is the main supplier of drinking water in Western Australia. We serve a population of over 2 million people with 245 drinking water supply schemes deriving water from surface, groundwater and seawater (via desalination). Our Memorandum of Understanding with the Department of Health requires the Corporation to provide safe drinking water. As such, Corporation is committed to implement the Australian Drinking Water Quality Guidelines (ADWG) with the development of Water Safety Plans (WSP), Catchment Management Strategies (CMS) for surface and groundwater sources, and Water Source Protection Strategies (SPS) for seawater desalination. CMS, SPS and WSPs use a proactive approach to prevent contamination of the drinking water source. SPSs focus on the raw water source, systems and stakeholders whilst the WSPs are used to manage the whole system from water source through to the customer’s tap. As seawater desalination is a key source of drinking water in WA, these plans are being developed for our new seawater sources and desalination plants. This paper describes the development of WSPs and SPS for each desalination plant, how these provide clear benefits in the provision of safe drinking water, and highlight the challenges in management of seawater sources. 1.1 Drinking Water Quality Management in WA: focus on public health Waterborne disease is one of the major health concerns in the world (Hrudey & Hrudey 2004). The supply of safe drinking water to customers is the Water Corporation’s highest priority (WC 2006a). There are many factors that affect the quality of our raw water sources. These include contaminated runoff from urban, agricultural and industrial areas causing microbial, chemical and radiological contamination of surface and ground waters. Management tools have been developed to ensure the provision of safe drinking water. The World Health Organization developed guidelines and documentation to support the provision of safe drinking water (WHO 2004 & WHO 2005). In Australia, National Health and Medical Research Council (NHMRC) developed the Australia Drinking Water Guidelines (NHMRC 2004). ADWG promotes best management principles to ensure the safety of water supplies. These principles are packaged within twelve elements of the NHMRC’s Framework for the management of drinking water (referred to as the Framework). The principles include: management from source to the customer’s tap, use of multiple barriers, protection of water sources, risk-based assessment, preventative management (not relying on downstream treatment) and use of critical control points. The risk based approach incorporates the Hazard Analysis and Critical Control Point (HACCP) methodology. The Corporation has committed to implement the Framework and included ADWG principles into our drinking water quality policy, standards and procedures. Elements 2 to 5 of the Framework provide guidance in the design, development and implementation of our SPS and WSP for each source. 1.2 Catchment Management & Water Source Protection Strategies In line with the ADWG Framework, the Corporation developed a Source Protection Operations Manual requiring all sources to have a CMS. These strategies underpin the Department of Water’s (publically consulted) Drinking Water Source Protection Plan, that outlines protection areas under the Country Areas Water Supply Act (1947) and Metropolitan Water Supply, Sewerage and Drainage Act (1909) and applies land-use planning as required under the Statement of Planning Policy 2.7. CMSs provide an operational plan describing the Corporation’s roles, activities and responsibilities in the management of a source.



CMS contain considerable information on a water source, including: catchment characteristics including water body form, public access, landform and hydrology, governance of the water source in terms of roles and responsibilities, water quality review of the source, strategic importance of the source, and land-use within the catchment, including compatible and incompatible activities, as well as future

development options. These information form input to the CMS risk assessment identifying hazards that may influence source water quality. Water Corporation has developed a source risk assessment tool to ensure consistency in assessment across the State. This includes development of risk matrices for various land uses and activities in surface water and groundwater catchments. Each potential hazard to source quality is assessed in terms of maximum risk; where existing control measures are not considered, and residual risk; where control measures are considered in determining the risk rating. Assessing maximum risk is useful to identify high priority hazards and determine where management attention should be focussed. Output from the risk assessment is a four-tier scale of risk increasing from ‘low risk’ whereby the risk is acceptable and managed by normal operation, through to ‘extreme risk’ whereby the risk is unacceptable and a risk management plan is required. The risk assessment forms input to: A source water sampling program An operational plan including inspection and surveillance requirements as well as source water

quality targets to trigger operational response if they are exceeded. An action plan incorporating capital, operational and maintenance improvements. Information gathered as part of the CMS implementation goes into the in-house Governance Report and also to our regulators: Department of Water (DoW) and Department of Health (DoH). Where seawater is used for desalination, the CMS has been modified to form a Water Source Protection Strategy (SPS) and provides the main content described above but with some amendments. These are: Instead of a proclaimed area under the relevant Act, the recognition of a sampling zone, based on the

hydrodynamic area of influence around the marine intake whereby floating sampling instrumentation and grab samples can supply proactive information on intake water quality;

Educating users of the risks to seawater desalination water quality, as opposed to restricting their activities; and

Instead of land use planning to restrict incompatible land uses, key land uses critical in the marine coastal area around the intake, provide timely notification of spills or contamination issues.

It was intended that whilst this was a more reactionary approach to source protection of desalination intakes, insight and learning’s generated would feed continuous improvement. 1.3 Water Safety Plans As part of the regulatory requirements placed on the Corporation by Department of Health (DoH) and Economic Regulatory Authority (ERA), the Corporation has consistently achieved 100 percent microbiological performance (WC 2010). However, these compliance samples are drawn from a



relatively small proportion of the total water supplied to our customers, only a limited number of constituents are tested, and the analytical results may be received weeks after the water was consumed. Thus, compliance monitoring provides a narrow picture on the health performance of a water supply. As advocated by ADWG, operational monitoring provides a near continuous level of assurance our barriers are effective and we deliver safe drinking water. Furthermore, analysis of our chemical, microbiological and radiological data set (running from the 1980’s) shows microbiological contamination presents one of our greatest risks. Furthermore, microbial constituents of drinking-water can cause adverse health effects from a single exposure. Water Safety Plans are used by the Corporation as they go beyond regulatory requirements and provide a systematic risk management approach through the whole supply system from source to the customer’s tap. Risks assessed in each water supply ensure appropriate preventative measures are in place with operational control necessary to ensure the safety of the drinking water. Thus, there is a considerable focus in WSPs on microbiological risks. WSP design ensures clearly defined operational monitoring requirements and practical management actions. Components of WSPs include (Bath et al., 2007): Detailed review of the scheme to delineate the treatment, storage and distribution of the supply with

attention to monitoring of process and critical control points. Data analysis reviews the microbiological and chemical data of the raw source and treated water. Disinfection is a critical control point in our water supplies and is reviewed in light of our surface

water treatment matrix to assess the microbial health-risk associated with the provision of safe drinking water (WC 2010).

Hazard analyses are used to identify parts of the supply where the provision of safe drinking water could be compromised. The hazard analysis process although qualitative is used to identify the need for new barriers (such as a new tank roof) or where barriers must be added (such as treatment). Recommendations for improvement of a scheme are captured in the WSP Action Plan.

A key component of each WSP is the process control plan that allows operators to manage the system to ensure water safety is maintained 100 percent of the time. They include what operational parameters should be sampled, frequency of sampling, the acceptable range within which the operational results should fall and corrective action that should be taken. Particular importance is placed on the critical control point(s). These are so important that a failure means the water may not be safe to drink. In which case, DoH is notified and consideration must be given to a public advisory. Accordingly, critical control points require continuous monitoring and alarms.

II CASE STUDIES FROM SEAWATER DESALINATION IN WA

2.1 Perth Seawater Desalination Plant (PSDP): First Metropolitan SW Desalination Plant

2.1.1 Background to the PSDP Project - Planning for Perth’s first large scale desalination plant started in 2003 with an initial capacity of 30 GL/year plant that was quickly increased up to 45 GL/year after a worse than expected rainfall in 2004. Government approval was gained in 2005 to proceed and the contract was awarded in May 2005 with commissioning starting 18 months later in November 2006.

Figure 1 shows the location of PSDP on the coast adjacent to Cockburn Sound some 20 km south of Perth. Garden Island extends along the western side of the Sound, providing shelter from ocean swells and making the Sound an ideal place for recreation and fishing. The sheltered, deep waters of the Sound make it equally ideal as an outer harbour for the Perth/Fremantle area, a site for industries requiring port



facilities and a strategic naval base (DAL, 2002). Two industries located near the PSDP are Kwinana Power Station (KPS) and Alcoa of Australia Ltd, an alumina refinery (IDB 2004). 2.1.2 Challenges in the management of DW - During the planning of PSDP, it was apparent that methods used to manage surface and groundwater sources were not applicable for reasons outlined below. Limited drinking water-based State policy and legislation The Australian Drinking Water

Guidelines (ADWG) are largely silent on the management of seawater desalination as a source of safe drinking water. ADWG provides very clear guidance in the management of terrestrial sources (surface and groundwater sources) but there is no guidance in the methods to manage, protect and treat seawater. Furthermore, the ANZECC marine guidelines provide no guidance on the water quality requirements for desalination. Review of the relevant legislation shows that unlike surface and groundwater Public Drinking Water Source Areas (PDWSA) proclaimed under the Metropolitan Water Supply Sewerage and Drainage Act (1909), seawater abstracted from coastal areas is not covered under this legislation. This Act provides powers necessary to legally define the boundary of the drinking water source and provides by-laws that allow the State to protect the quality of these sources. For near-shore coastal areas, no legislation is available in WA to protect the quality of the seawater and provide powers of enforcement to prohibit activities near or adjacent to the seawater intake. The Western Australian Planning Commission (WAPC) developed the Statement of Planning Policy Number 2.7 June 2003 Public Drinking Water Sources to protect drinking water sources from potential contamination from

Figure 1 Location of PSDP in Cockburn Sound, WA



development. The policy however has no powers in coastal areas. In WA, coastal land is at a premium with considerable demand for residential and industrial zoning and thus a risk exists of incompatible land use zoning adjacent to marine intakes. In coastal areas, there is greater focus on the conservation of coastal areas in terms of their ecological values rather than protecting seawater as a source of public drinking water.

Lack of Corporate Standards In 2006, PSDP was the first seawater desalination plant and as such

our corporate business management processes and procedures did not address water quality management of seawater intakes.

Perception of DWQ risk Desalination has, for some time been seen as the ‘ultimate treatment

barrier” as the reverse osmosis membranes act as a barrier to dissolved salts and certain organic molecules. As such, RO membranes are thought to not require proactive or even reactive source protection. However, there is also a public perception that our coastal areas receive considerable quantities of treated wastewater and thus seawater is unsuitable as drinking water source. However, with the construction of SWRO plants around Australia there is an acceptance that SW desalination is not just a “supplementary source” but also a key strategic source of drinking water.

2.1.3 Development of the Source Water Protection Strategy for PSDP - The SPS for the Perth Seawater Desalination Plant was the first to be developed for a Water Corporation seawater desalination plant. Due to the unique nature of the source and absence of regulation in terms of source protection, the Water Corporation developed a source protection policy specific to the source. The policy recognises (1) the multiple barriers present in the treatment process and known reliability and (2) challenges in protecting the source from contamination. As a consequence, it was determined source protection will be reactive, focussing on stakeholder education, communication, incident planning, and an early warning monitoring program to detect critical changes in seawater quality. In accordance with the Framework and the Water Corporations Source Protection Operations Manual, a risk assessment was undertaken as part of the SPS. The risk assessment focussed on hazards that have the potential to influence the RO membranes and subsequently compromise treatment, including: accidental hydrocarbon release by boats and ships, runoff from adjacent land, recreation activity and boating in proximity with the submerged marine intake, and algal growth arising from favourable nutrient and temperature conditions. Management strategies were identified to mitigate risks: Education of users in Cockburn Sound regarding the desalination process, Engagement with local management and industry committees, Water quality monitoring, including continuous on-line monitoring at the inflow to the plant, Involvement as a key stakeholder in incident notification relating to water contamination, and Knowledge of shipping movements and activities in Cockburn Sound.

2.1.4 Development of the Water Safety Plan for PSDP - During planning of PSDP, a Water Safety Plan was developed (the first for a seawater desalination plant WC 2005, Bath 2006) and included: description of the system (from seawater source through to the customers tap), develop a schematic (showing the flow path, treatment, processes and critical control points),



review of the barriers to contamination, review of seawater quality data, assess the health related risks, define the health related criteria for the water supply, define critical control points and define operational monitoring and control measures (WHO 2003), define the operation strategy including the operational monitoring process control table, and develop an Action Plan outlining immediate and long term operational, and maintenance needs. Water quality review: Assessment of water quality of the source is fundamental to the efficient design and operation of a reverse osmosis plant and even dictates the level of pre-treatment and choice of membrane. The WSP provides a detailed review of the available data for Cockburn Sound. Overall, the concentration of major-ions in Cockburn Sound is comparable with those measured in the oceanic seawater. Most trace metals are below their analytical detection limits. Other anions are present at typical seawater concentrations. Total suspended solids (TSS) ranges from <1 to 9 mg/L. Changes in TSS are caused by boat movements, extended rainfall and re-suspension of sediment by wind action and storm events. Nutrient levels near the Kwinana Power Station site are higher than those in Perth’s open coastal waters because of input from groundwater and some industrial discharges (DAL 2002). In the PSDP Desalination Feasibility Study (WC 2002), it was stated the quality of Cockburn Sound is high and does not present a challenge for conventional desalination treatment.

Figure 2 PSDP Water Safety Plan Schematic



Physical Barrier Review: This includes review of all the barriers to contamination.

Source protection – Cockburn Sound is a multi-use confined coastal water body. Submerged intake reduces the risk of abstracting floating oils, algae or scums. Pre-chlorination – Intermittent booster chlorination reduces biofouling of the intake and pipeline. Screening – Screening of large particulate material that is entrained into the intake structure. Dual media and cartridge filtration – Removal of fine particulate material. Reverse osmosis membranes – Main barrier for the separation of dissolved salts and micro-

organisms from seawater (critical barrier 1). Permeate tank roof – Prevents ingress of contaminants into the tank (e.g. rainwater, dust and birds). Chlorine dosing and disinfection – Disinfection of product drinking water (critical barrier 2). Clear water tank and tank roof – Provides contact time (in the storage) and the roof prevents

contamination of product water from contaminated ingress into the tank. WSP: Hazard analysis identified potential water quality issues with the source waters: Groundwater Inflow: There are concerted efforts by industry to reduce nitrogen inputs to Cockburn Sound, particularly from groundwater. Over the past few years, the nitrogen content of the Sound has reduced as a result of these controls. Stormwater: Surface runoff from Rockingham, Shoalwater, Kwinana and Safety Bay drains into Cockburn Sound. Available data show that stormwater drainage is unlikely to be an issue for the seawater quality at KPS site (IDB 2004, DAL 2002). Industrial impacts: Two large industries close to PSDP are: Alcoa of Australia Ltd, an alumina refinery and jetty, and Western Power Kwinana Power Station. The KPS2 site is approximately 1 km south of the Alcoa jetty, and 250 m from the Kwinana Power Station cooling water outfalls. The water quality at this site is unaffected by the alumina refining activities, or discharge from Kwinana Power Station. Oil spill risk: Overall, the risk of oil spills or incidents affecting the intake water of the desalination plant is low, although the risk increases with the proposed port developments (discussed below). Feedwater quality is monitored on-line at the seawater intake. If oil spill and hydrocarbons (HC) are detected, the plant may be shut down depending on the severity of the contamination. Future Port Developments: Two future port developments are planned for the area immediately adjacent to the PSDP site. Figure 1 shows these are: James Point Port Development and Fremantle Port Authority (IDB 2004). The hazard analysis process includes these development scenarios in the assessment of the risks on the multiple barriers in the PSDP plant. Process Control Plan: The process control plan shows the key monitoring points, critical limits and corrective actions (see Figure 3). The Water Safety Plan focuses on performance of the desalination process with critical control points identified at the reverse osmosis membranes and at the chlorine disinfection point. As such, the WSP process control table provides clear and concise operational monitoring to ensure the provision of safe drinking water. As Cockburn Sound is a multi-use waterbody, operational monitoring plays a key role to trigger corrective action if the process becomes challenged.



Reporting on WSP performance: Information on the performance of critical control points (chlorine disinfection and membrane integrity) and process control points is transferred to on-line to the PSDP control room for immediate corrective action. Summary information on plant performance is compiled into monthly reports for management review.

2.1.5 Development of the Water Quality Management Plan for PSDP - Prior to commissioning of PSDP, it was determined that treated water from PSDP will introduce water into the Perth metropolitan distribution system with lower TDS, lower hardness, low DOC and higher chlorine residuals. As a result, aesthetic changes in quality may increase customer complaints. A water quality management plan was developed to (1) allow a phased introduction of treated water from PSDP into the metro distribution system, (2) extensive monitoring of chlorine residual, turbidity, colour and customer complaints (3) air scouring of certain supply zones, and (4) corrective action if the water went outside define operating limits. Implementation of the plan was a success in that there were no increases in customer complains. Furthermore, after commissioning there was a decrease in complaints in zones fed by PSDP.

Community and Stakeholder Engagement: Meetings were held with key community groups to assess their views on seawater desalination as a source of drinking water. Key issues were raised and discussed. The most common concerns were in regard to site location, plant noise, site aesthetics, brine discharge impacts and potential recreational and industrial limitations around the intake. Engagement with local industry used existing networks. The intent was to identify current and future operational and development issues that may impact on the site security, regulation requirements and operating needs.

Learning’s from the operation of PSDP Stakeholder engagement with FPA, KIC and CSMC and other key stakeholders was effective in

ensuring cooperative management and good communication on water quality issues. Extensive water quality data collected from Cockburn Sound provided a good understanding of the

changes in the source quality and supported operation of PSDP.

Figure 3: PSDP Process Control Plan (forming part of the WSP)



PSDP integrated the requirements of the WSP, SPS into their monitoring, operation and reporting and SCADA systems. PSDP meets the requirements of the WSP.

Extensive monitoring was undertaken of the IWSS prior to PSDP coming on-line as part of the WQMP. Introduction of PSDP into the metro supply zones of Thompson’s Lake and Hamilton Hill has had direct benefits with stabilisation of chlorine residuals, reduction in THMs, and also reductions in the concentration of iron, manganese, aluminium and turbidity.

2.2 Planning for the West Pilbara Seawater Desalination Plant on the Burrup Peninsula 2.2.1 Background to project - In the West Pilbara, towns of Karratha, Dampier, Roebourne, Wickham and Point Samson as well as the Dampier and Cape Lambert ports are currently supplied with drinking water from the West Pilbara Water Supply Scheme (WPWSS) sourced from Harding River Dam and Millstream borefield. These sources operate concurrently and are restricted to an annual abstraction of 15 GL/year. Water Corporation estimates indicate an annual abstraction of 10 GL/year is a more realistic long term yield. Demand for water from the WPWSS has greatly increased in recent years with considerable expansion by industry and the residential population. As a result, demand on the WPWSS system is predicted to exceed the long term yield of the scheme. To overcome shortfalls in supply, Water Corporation is looking at an option to build another seawater desalination plant on the Burrup peninsula East of King Bay. The future, West Pilbara Seawater Desalination Plant (WPSDP), once built, would then be the third major seawater reverse osmosis (SWRO) desalination plant owned Figure 4 Location of the current marine intake and desal plant in King Bay



by the Water Corporation, following Perth Seawater Desalination Plant (PSDP) and Southern Seawater Desalination Plant (SSDP). The Project could supply 6 GL/year of potable water with provisions for expansion to 12 GL/year. At present, the Burrup seawater desalination plant supplies industrial grade process water to Burrup Fertilisers Pty Ltd, one of the largest producers of liquid ammonia. The plant uses mechanical vapour compression (MVC) and comprises: supply and discharge pipelines, seawater intake and brine discharge outfall (see Figure 4). The plant has three parallel MVC units. This plant is expected to be used to augment the current drinking water supply in late 2011, once potabilised. Figure 4 shows the location of the existing seawater intake adjacent to the Mermaid Marine Supply Base facility. Seawater is pumped up to Three Sisters service tank at a high point approximately 2.5 km from the jetty pump station. In the future, augmentation of the West Pilbara Scheme may also include the construction of a WPSDP. Seawater would also be abstracted from the existing offshore inlet in King Bay and the SWRO desalination process including: coagulation with flocculation, dissolved air flotation (DAF), membrane filtration, reverse osmosis, potabilisation, chlorine disinfection and fluoridation. 2.2.2 DWQ Challenges for the WPSDP - Figure 4 shows the existing infrastructure and also the site for a future West Pilbara Desalination Plant (WPSDP). All other available land is owned by Woodside, or located on a floodplain which would require major civil works to improve the site location. Multi-use site: Management of King Bay is facilitated by Dampier Port Authority (DPA) together with its stakeholders, including Mermaid Marine Australia, Woodside Energy Limited and Burrup Fertilizers. Management of King Bay currently focuses on preserving the environmental health of the bay and not specifically on preserving seawater quality for treatment and supply to the public. The DPA site is zoned “Strategic Industry” under the Shire of Roebourne Town Planning Scheme No. 8, where industrial uses, and uses associated with port operations, are promoted. DPA is required to apply to the relevant Building Codes and undertake appropriate consultation with the Shire of Roebourne for any new developments (DPA Port Development Plan 2010). It is expected that all industries currently operating on the Burrup Peninsula will expand their operations over the next 10 years. Water Quality of King Bay: Seawater in King Bay is naturally turbid throughout the year due to the nature of the seabed, the wind and the high tide variation (Bath et al. 2004). In North West coastal waters, the dominant cause of high turbidity is inorganic suspended sediment. Elevated turbidity is further increased during extreme weather events (e.g. cyclones). Mermaid Sound and King Bay are not pristine areas. Woodside Energy has conducted chemical and ecological monitoring of Mermaid Sound including sampling sites close to King Bay. Analysis of metals in rock oysters during 1993 found elevated levels of copper at most sites from the southern part of Dampier Port and north to the Woodside LNG Plant. Levels of zinc were also elevated on one side of King Bay. 2.2.3 Source Water Protection Strategy for the Burrup seawater desal and future WPSDP - A Source Protection Strategy has been developed that outlines strategies for minimising and mitigating risk associated with sourcing water from King Bay to potabilise the existing Thermal Desalination Plant and for the proposed WPSDP, based on hazard identification and risk assessment.



Although seawater monitoring shows there are some challenges with the quality of King Bay, the bay contains potential sources of chemical and microbiological contamination. Similar to PSDP and SSDP, the source is unique in that it is not a gazetted PDWSA. As a result, Acts, Regulations, Policies and Guidelines to protect the source don’t exist. As desalination treatment process provides robust multiple barriers and is a well proven technology, it was determined reliance be placed on these multiple barriers to ensure safe water. As such, source protection for the existing thermal desalination plant and the proposed WPSDP focus on:

1. A reactive approach to source protection involving the determination of potential hazards to the integrity of the treatment process,

2. Use of a risk-based early warning system to identify contamination. 3. Minimise the risk of seawater contamination through education of stakeholders in King Bay, and 4. Water Corporation plays a key role in the notification of seawater incidents in the bay.

Both the SPS and WSP are closely linked for the thermal desalination plant, defining the critical control points, process control points and operational monitoring.

Learning’s: The existing location in King Bay was the only one available for the seawater intake. As such, high turbidity of the seawater has a direct influence on the operation and maintenance of the current seawater supplies scheme. This will need consideration in the design of a future SWRO plant.

2.3 Seawater Desalination No. 3: Planning for SSDP

2.3.1 Background to project - The selected site for the SSDP is situated on the coast along the southern side of Taranto Road, between Binningup and Myalup beaches. Although the plant is 130 km south of Perth, bulk water infrastructure is already in place to bring the drinking water up to Perth. Most of the 84 ha site was owned by the Corporation where it operates a pond-system Wastewater Treatment Plant. The other part of the land purchased specifically for the SSDP was formerly a quarry. Two variations on the plant layout were considered for this site: the first directly adjacent to Taranto Road and set approximately 250 m from the shoreline; and the second situated in a slightly more southerly location to take advantage of the relatively flat topography. The final layout however was restricted by the environmental impact assessment, and the best location to eliminate visibility of the plant from Binningup town, and from the beach. SSDP is designed for an initial annual production of 50 GL/year, with flexibility for expansion to 100 GL/year. First water is expected in August 2011.

2.3.2 Management of DWQ at SSDP - Site selection for SSDP raw water intakes: Historically, unlike water source development of freshwater systems, raw water risks have not been considered in the siting of seawater desalination plants. This is largely due to an assumption that the desalination treatment process and membranes provide a complete barrier and remove most contaminants from seawater. However, as seawater is a source of drinking water, it is essential the Corporation is consistent with the Precautionary Principle and ADWG Framework's requirements. These can be translated into the following management guidance for seawater desalination:

1. Select seawater with the lowest risk of contamination 2. Protect the source to maintain acceptable feed quality 3. Monitor the source to react-to and pre-empt changes in quality 4. Select an appropriate intake site to minimise the risk of a water quality incident caused by natural

events such as storms increasing turbidity, summer algal blooms and even red-tides. Or, man-made factors attributed to harbour runoff and activities, industrial discharges, recreational boating, or mariculture.



Some raw water risks have the capacity to influence the integrity of the membranes and thus affect plant operation. Specifically, these seawater risks include algae, algal extracellular products, microbial growth, hydrocarbons and certain organics as they can foul the reverse osmosis membranes and even transfer contaminants to the permeate. As such, it is appropriate that the conditions under which these risks are generated are considered in the location of future seawater desalination plant intake structures.

As part of the site selection for SSDP, a decision tool was developed to guide the assessment, ranking and selection of ocean intake sites along the WA coast for seawater desalination. Based on guidance from ADWG where the goal is to use the source with the lowest risk, criteria were identified to guide the assessment of marine intake sites. The tool deals with the initial screening of a series of intake sites and then more detailed assessment of a particular site. Input to the risk assessment includes: (1) description of high risk activities near the intake sites, (2) water quality and oceanographic mixing characteristics of each site, and (3) possible mitigation measures. Higher risk activities include shipping, harbour facilities, land drainage, wastewater outlets, recreation and mariculture. Water quality challenges include: algae, red tides, fuel spills, high turbidity events, local runoff and local mixing. These activities are assessed in terms of mitigation and management measures to derive a residual risk for each site.

Figure 5 Location of SSDP at Binningup



Community concerns and consultation: SSDP site is less than 1 km from the Binningup Township, a small coastal community of 700 residents. Community concerns were included as a major input to the site selection and planning process after extensive community consultation. Fortnightly community reference meetings were undertaken during the construction phase. Community concerns were environmental, noise and visual impact. Design of the plant was undertaken to minimise any adverse visual effect from the town, a commitment of 30dB noise limit at the site boundary, and implement an environmental management plan. Development of the water quality management plan includes elements of the WSP and CMS:

- Water supply system description and analysis, - Assessment of water quality data and its ability to meet health-related targets, - Identification of hazards, risk assessment, multiple barriers and critical control points, and - Recommend operational procedures and improvements.

Raw seawater is sourced from the Indian Ocean, from a submerged intake immediately to the west of the plant site, approximately 500 m offshore at a mean sea level depth of 9.5 m. The centre of the openings in the intake structure is located 4.5 m above the seabed so high turbidity seawater is not entrained. Extensive baseline seawater quality monitoring was conducted prior to construction and did not identify any concerns with the proximity of industry in terms of effect on seawater quality. Industrial activities near the plant include the Collie Power Station (with outfall 7 km south of the intake site), Millennium Chemicals (with outfall 7 km south of the intake site), Bunbury Port, Kemerton Industrial Area and Bunbury Wastewater Treatment Plant (>25km south of the intake). The intake site is not within any major shipping lanes. Figure 5 shows the location of Harvey Diversion Drain, 2 km north of the intake. The drain is the main freshwater outlet in the local area and can thus influence the TDS, salinity and nutrient levels of the near-shore areas adjacent to the intake (typically during winter). Harvey Diversion Drain was constructed to reduce flooding and water-logging in the Harvey irrigation area and carries runoff and agricultural drainage. Even though the intake is not within any major shipping channels, waters around the intake are used by boats, particularly recreational pleasure craft. On-site continuous monitoring includes measurement of hydro carbons. If hydrocarbons are detected, the plant may be shut down depending on the severity of the contamination. In the unlikely event of an oil spill, it is expected that most of the oil will float and should not be drawn into the submerged intake. III CONCLUSION ADWG provides clear and concise guidance regarding the provision of safe drinking water from conventional water supplies, using surface and groundwater sources. However, ADWG is silent on the management of drinking water sourced from seawater desalination. As such this paper describes management processes developed by the Corporation to assist with the delivery of safe drinking water from seawater desalination. Furthermore, unlike conventional surface and groundwater sources,



legislation is not applicable in WA to protect seawater intakes to exclude undesirable activities, enforce control measures and prevent inappropriate land use development. 3.1 Perth Seawater Desalination Plant At PSDP, the variation in seawater quality is attributed to natural events such as seasonal nutrient shifts, storms, and stratification as well as anthropogenic factors such as runoff from adjacent properties, and algal blooms responding to elevated nutrients. As Cockburn Sound is a multi-use waterbody with considerable shoreline industrial development, recreation and mariculture there is an increased risk of contaminants reaching the marine intakes. However, over the past four years, water quality has not had a direct influence on operation of PSDP. Occasional winter storms increase the turbidity of the intake, necessitating changes to the operation of the pre-treatment filtration. As there appears to be minimal legal force to protect the source, provision of safe drinking water from seawater desalination is dependent on the effectiveness of multiple barriers. This runs counter to the advice given in ADWG that promotes use of the highest quality source, protection of the source and decreased dependence on downstream treatment. Water quality management of the marine intakes feeding PSDP includes the development of a range of tools, processes and procedures to ensure the provision of safe drinking water. These include a water source protection strategy, water safety plan and a water quality management plan. The Water Source Protection Strategy evolved from the catchment management strategies developed for surface and groundwater sources. A seawater desalination SP policy was developed to provide overall guidance in the strategic management of marine intakes. These tools play a valuable part in the daily operation of PSDP. One of the greatest potential risks to the quality of the marine intakes is development on the shoreline adjacent to the intake. Proposed developments include a port facility and also a live animal handling facility. Risks include the potential, if inadequately designed, to contribute a considerable microbiological load to the seawater around the intake. 3.2 Southern Seawater Desalination Plant As part of the planning for PSDP, a management tool was developed to compare locations for the seawater desalination intakes. As part of the preliminary design studies for SSDP, the tool was used to provide a comparison of various sites and identify high risk issues that may require further investigation. A water quality management plan is being developed for SSDP including a water safety plan, water source protection plan and management plan addressing all 12 Elements of the ADWG Framework. 3.3 West Pilbara Water Supply Seawater Desalination Plant Seawater intakes are located in King Bay that supply seawater to an MVC desalination plant supplying industrial grade water. This plant will shortly be upgraded to include potabilisation, chlorination and fluoridation with the water augmenting the West Pilbara water supply. Quality of the feedwater is turbid caused by the large tidal movement and activities within the harbour facilities. Existing problems are experienced with biofouling and sedimentation within the seawater pipelines. A water source protection strategy has been developed for the near-shore area around the intake in King Bay. As the quality of the seawater is largely governed by natural influences, there are limited opportunities to manage the source. However, the SPS promotes engagement with local industry partners to raise awareness in the



importance of protecting water quality, education of stakeholders and emergency incident response. Unlike PSDP, provision of safe drinking water is dependent on the ability to operate the plant within specification. A water safety plan is being developed for the system. 3.4 Way forward With ever increasing development taking place along our coastlines there is a need for new legislation (or revisions to existing Acts) to provide greater protection of marine intakes and minimise all risks of seawater contamination. Legislation should include: Definition and location of exclusion zones around marine intakes,

Definition of incompatible activities for exclusion zones,

Prohibition of incompatible activities in, or near, the exclusion zone,

Development of by-laws to enable enforcement and penalties, and

Management of the planning process for approval of coastal development near marine intakes.

The Corporation is currently investigating whether existing source protection legislation may be applied to define a protection zone around its desalination seawater intakes. This would subsequently provide a mechanism for planning controls on incompatible activities.

IV REFERENCES Bath A., Shackleton B. and Botica C. (2004) Development of Temperature Criteria for Marine

Discharge from a large Industrial Seawater Supplies Project in Western Australia, Water SA Volume 30 No. 5 p.100-106.

Bath A J Capewell S & Walker R (2006) Water Safety Plans and Drinking Water Quality Management in Western Australia, case study: Perth Seawater Desalination Plant, Proceedings of the IWA Biennial conference Beijing, China September 2006.

Bath, AJ, Walker, R and Bowman, M (2007) Development of Water Safety Plans in the provision of safe drinking water in Western Australia, proceedings of the Ozwater Conference, Sydney 2007. Paper o7073.

Dampier Port Authority website www.dpa.wa.gov.au (retrieved 2010). Mermaid Marine Australia Limited – Port Information Hand Book.

Dampier Port Authority website www.dpa.wa.gov.au (retrieved 2010). Environment and Heritage, Ecological Values.

Dampier Port Authority website www.dpa.wa.gov.au (retrieved 2010). Port – Development/Port – Development Plan 2008.

DAL (2002). Perth Seawater Desalination Project Seawater Quality Assessment. Report No. 02/267/1 IDB (2004) Water quality investigation for PSDP drinking water: review of seawater reverse osmosis

plant in terms of elements 2 to 6 of the NHMRC Framework for the management of drinking water, Infrastructure Development Branch.

NHMRC (2004) Australian Drinking Water Guidelines (ADWG) and Framework for the management



of Drinking Water Quality, 2004 National Health & Medical Research Council, Australian Government.

Water Corporation (2002) Perth Seawater Desalination Plant – Water Quality Assessment 2002. Water Corporation, (2004). Perth Seawater Desalination Plant-Basis for design and construction. Water Corporation (2004). Source Protection Operations Manual, Drinking Water Quality Branch. Water Corporation, DWQB (2005). Water Safety Plan. Perth Seawater Desalination Plant. Water Corporation (2010) Drinking water quality annual report, Water Corporation

http://www.watercorporation.com.au/W/waterquality_annualreport.cfm?uid=2377-9937-9579-7091 .

Water Corporation (2011) Memorandum of Understanding with the Department of Health, http://www.watercorporation.com.au/_files/PublicationsRegister/13/MoU_WC_DoH.pdf

WHO (2004) Guidelines for Drinking Water Quality, 3rd Ed., World Health Organization, Geneva. WHO (2005) Water Safety Plans, Managing drinking water quality from catchment to consumer, Water

sanitation and health protection and the human environment, World Health Organization, Geneva, 2005.

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