Drinking Water Through Recycling The benefits and costs of supplying direct to the distribution system Dr Stuart Khan School of Civil & Environmental Engineering, University of New South Wales Project aim “To define in objective scientific, economic and social terms, the potential place of recycling directly to the drinking water distribution system, in the spectrum of available water supply options” Target audience “The report will be directed towards policy makers, regulators, researchers, the water industry at large and the consuming public” Indirect potable reuse Water treatment plant Indirect potable reuse Water treatment plant Role of the ‘environmental buffer’ • Opinions of 80 Australian stakeholders: – – – – – – To provide an additional treatment barrier for pathogenic and/or trace chemical substances To provide dilution of contaminants in recycled water To stabilise/equilibrate highly purified reverse osmosis permeates To provide ‘time to respond’ to treatment malfunctions or unacceptable water quality Buffering the production and use of recycled water / storage Maintenance of aquifer integrity and/or groundwater quality – To provide a ‘perception’ of increased water quality or safety / public confidence – To provide a perception of a disconnection between treated effluent and raw drinking water / To reduce the “yuck factor” Goreangab Water Reclamation Plant, Windhoek, Namibia • • • Pioneer DPR Project (since 1968) Goreangab WTP converted to not only treat water from Goreangab Dam, but also reclaimed effluent New plant completed in 2002 (NGWRP) – – – Capacity: 7.5 GL/year (~20 ML/day) Provides 35% of total supply Can do 50% in severe drought conditions Cloudcroft, New Mexico, USA • • • • • • Small, high altitude skiing village Permanent population <1000, but more than doubles on weekends and holidays Potable water from springs and wells, but during drought has been tankered in on weekends DPR system began operation in 2011 Operating license requires slightly greater fraction (51%) of surface or groundwater to be used. DPR capacity: 0.1 ML/day Big Spring, West Texas, USA • • • • Permian Basin city of around 30,000 population Severe drought during much of last 15 years Surface water (from Colorado River) and available groundwater insufficient for future needs IPR considered but: – – – • • • Current raw water sources are distant and lower in elevation High evaporative losses High dissolved solids in current surface water (and in available effluent sources) DPR began operation April 2013. Capacity: 10 ML/day Contributes up to 15% of blended raw water in the pipeline Treatment energy costs offset by energy savings from avoided raw water and effluent pumping Beaufort West Municipality, South Africa • • • • • • • Situated in Central Karoo, one of the driest areas in South Africa Population: ~40,000 (spread across three towns) Severe drought in 2010/2011 led to daily water trucking to >8000 homes Increased water demand forecast in coming years DPR plant commissioned in January 2011 Design capacity: 2 ML/day Contributes 20% of blended raw water in the pipeline (will increase to 25%) Health risk assessment and risk management • Broad range of harmful substances in untreated sewage – Pathogens (viruses, bacteria, protozoa) – Chemicals (carcinogenic, endocrine disrupting, other toxicities) • Objectives – Reduce concentrations to levels of acceptable risk (treatment) – Ensure that the above is achieved (monitoring) – Engineer system reliability • Hazard Analysis and Critical Control Points (HACCP) • Multiple-barrier approach • Probabilistic reliability analysis – Foster operator reliability • High levels of expertise and training within the Australian water industry • Supported by mechanisms to ensure compliance with requirements to only use appropriately skilled operators and managers Cost, energy and GHG emissions • Illustrative hypothetical case study – Undertaken by GHD Four scenarios based on alternative water supply options for a hypothetical coastal Australian city: • Seawater desalination • Indirect potable reuse • Direct potable reuse • Dual-pipe systems Model (including uncertainty): • Financial (capital and operating) costs • Potential environmental impacts Cost, energy and GHG emissions Power consumption Flow-specific Power Use Breakdown, based on Product Water Flow (kWh/ML) 5,000 4,500 Error bars denote indicative range between 5%ile (lower) & 95%ile (upper) for total 4,000 Product Water Distribution Production Raw Water Intake Power Use (kWh/ML) 3,500 3,000 2,500 2,000 1,500 1,000 500 0 1 - SWRO 2 - IPR 3 - DPR Option 4 - Dual Pipe Greenhouse gas emissions Flow-specific GHG Emissions Breakdown, based on Product Water Flow (kg CO2-e/ML) 6.0 Error bars denote indicative range between 5%ile (lower) & 95%ile (upper) for Total (Scopes 2 & 3) 50%ile values plotted in columns GHG emissions (tonnes CO2-e/ML) 5.0 Scope 3 - Sludge Disposal Scope 3 - Membranes (negligible) Scope 3 - Chemicals 4.0 Scope 3, Electricity Scope 2 3.0 2.0 1.0 0.0 1 - SWRO 2 - IPR 3 - DPR Option 4 - Dual Pipe Social acceptance of DPR • A significant challenge • Numerous important factors – – – – – – – Trust in organisations involved Protection of public health is clear The ‘Yuck factor’ Participation in planning Timing of information Religion? Prior knowledge and understanding of urban water cycles • But some interesting recent research on DPR – Context and language – Effect of Prior Knowledge of Unplanned Potable Reuse on the Acceptance of Planned Potable Reuse Report findings • DPR can safely supply drinking water directly into the water distribution system, but needs to be designed correctly and operated effectively with appropriate oversight. – Current Australian regulatory arrangements can already accommodate soundly designed and operated DPR systems. – Australian Guidelines for Water Recycling provide an appropriate framework for managing community safety and for guiding responsible decision-making. • High levels of expertise and workforce training within the Australian water industry are critical. – These must be supported by mechanisms to ensure provider compliance with requirements to use appropriately skilled operators and managers in their water treatment facilities. • Planning, decision-making and post-implementation management processes should acknowledge and respond to community concerns. – Public access to information and decision-making processes needs to be facilitated. Report findings (cont). • The relative merits of water supply options should be based on quantifiable or evidence-based factors – Public safety, cost, GHG emissions and other environmental impacts, as well as public attitudes. – There is little value in distinguishing DPR from other water supply options, unless specific proposals are compared using these criteria. • ATSE considers there can be considerable environmental, economic, and community benefits of DPR in suitable circumstances. • ATSE concludes that DPR should be considered on its merits – among the range of available water supply options for Australian towns and cities. • Governments, community leaders, water utilities, scientists, engineers and other experts will need to take leadership roles to foster the implementation and acceptance of any DPR proposal in Australia.