Interview of Dr. Valentina Lazarova for Water Network Expert Interview

Dr. Valentina Lazarova is an international expert with over 30 years of research and practical experience in the field of Environmental Engineering. She is the former chair of the IWA (International Water Association) Water Reuse Specialist Group. She is a member of the International Water Academy and International Desalination academy. The Water Network research team had the pleasure of interviewing Dr. Lazarova, as she shares her expert opinion on wastewater reuse. Dr. Lazarova's overview on global milestones and advancements in water reuse published in Water21 magazine can be found in the attached file.

1. Treated waste water reused to provide drinking water is being considered as a viable option in many urban areas facing water shortage. What are the constraints involved in reuse of waste water to provide potable water supply?

The main constraints for the development of potable water reuse are inadequate communication, misunderstanding of the efficiency and reliability of the available treatment technologies and water quality control tools. As a consequence, public opposition and concerns of unknown micropollutants or pathogens were the key arguments against the development of some potable reuse projects. In fact, unplanned potable reuse is a wide uncontrolled practice worldwide associated with higher health risks compared to planned water reuse.

For these reasons, the major challenges for indirect potable reuse remain the public support, regulatory approval, high capital and operation costs, including very high monitoring costs for emerging micropollutants.

2. In many countries waste water is reused for agriculture or for lawn irrigation but not as drinking water due to fears of pathogens, also due to the mental block many have against drinking treated waste water. How can we move beyond these fears?

We have also many examples where misunderstanding of water reuse is blocking the development of projects for irrigation with well treated wastewater, while many rivers used for irrigation are much more polluted that recycled water.

Independent of the type of reuse application and the country, the public’s knowledge and understanding of the safety and suitability of recycled water is a key factor for the success of any water reuse programme. Consistent communication and easy to understand messages need to be developed for the public and politicians explaining the benefits of water reuse for the long term water security and sustainable urban water cycle management.

There are few proven solutions available to convince the public at large and the project stakeholders regarding the safety and relevance of water reuse. Undoubtedly, the use of a clear and positive terminology and simple explanations on water quality, treatment technology and water reuse benefits are necessary to build-up credibility and trust in water reuse. Existing experience and lessons learned are very important to convince decision makers. Finally, the most important recommendation is to inform and involve the public, politicians and all stakeholders from the beginning of any water reuse project. The increasing media impact and the new communication tools via internet should also be taken into account.

3. What are the current research projects at Suez in understanding these constraints and solving them?

For more than 20 years, Suez is actively involved in national and international projects on water reuse in collaboration with leading academic institutions, public and private research organizations, SMEs and manufacturers. Not only innovative technologies, monitoring tools and smart remote control strategies were developed, but also decision making tools, public outreach and education programs and methodologies for improvement of economic and energy efficiency of water reuse schemes. However, each water reuse project is case specific and the key factors of success are the good understanding of local constraints and the development of its unique most efficient solution.

4. Can you recount the most exciting technology that was successfully implemented in the last 15 years that has revolutionized the waste water industry?

Without any doubt, membrane technologies have revolutionized the water industry during the last 15 years.

The combination of microfiltration (MF) and reverse osmosis (RO - recognised as a “multiple barriers” polishing of municipal effluents - is considered as the best available technology for potable water reuse applications (Water Replenishment Project in Orange County, California; Wulpen Aquifer Recharge Project in Belgium, NeWater Project in Singapore; Western Corridor in Australia, etc.). The main advantages of double membranes systems are the high efficiency of removal of organic micropollutants and desalination.

The high reliability of membrane treatment and the decreasing membrane costs favoured the implementation of membrane tertiary treatment for non-potable applications such as urban uses for landscape irrigation, toilet flushing and fire protection (Sydney Olympic Park and Rouse Hill, Australia; Olympic Oark in Beijing, China; in-building recycling in Japan, United States, Australia), as well as industrial uses as cooling or boiler water (West Basin Water Recycling Project, California; Luggage Point, Australia; Panipat and Chennai reclamation plants in India).

Among the membrane processes used for wastewater treatment, membrane bioreactor (MBR) technology had advancing the most rapidly. It is important also to underline that MBRs are becoming the state-of-the-art technology for decentralised systems, in particular in-building wastewater treatment and recycling. Recent studies demonstrated that the combination of membrane bioreactors (MBR) and RO could be a competitive option for advanced water reuse, ensuring improved removal of micropollutants.

5. Waste water/Direct potable reuse (vs.) Desalination are often compared with each other as alternative water supply sources. What are the pros and cons of the two and which of the two would you recommend under which conditions?

Forward looking water utilities consider desalination and water reuse as two integral components of the water cycle, with a number of synergies and mutual benefits in terms of water production capacity, product water quality and energy use.

Until recently, the use of seawater desalination was limited to desert-climate dominated regions. Latest technological advances and associated decrease in water production costs and energy demand have expanded its use in coastal areas traditionally supplied with fresh water resources. The key advantage of seawater water desalination compared to potable water reuse is the better acceptance from society. Nevertheless in some countries, public opposition against desalination is higher compared to water reuse because potential adverse environmental impacts. On the other hand, public acceptance of indirect potable reuse would not be a major issue, as shown by the implementation of the NEWater brand in Singapore, if adequate policies and communication were applied to improve the tolerance towards water reuse.

The selection of the most appropriate type of alternative water sources depends on the local framework conditions and the expected economic and ecological impacts. For example, water reuse for irrigation can be done at very limited costs, which is not the same for desalination. Moreover, water reuse is easy to be implemented near each urban or industrial center where wastewater is available. In terms of energy demand, water reuse is always more advantageous than desalination, at the exception when brackish water is available.

In any case, synergies between desalination and water reuse have to be strengthened as there should be an incentive to keep desalted water in the water use loop as long as possible, minimising “freshwater” discharges to the sea.

6. How should direct potable supply network be designed? Should it be integrated to the drinking water supply network or dealt with using separate lines?

The main advantage of direct potable reuse is its fast integration to the drinking water supply network. Compared to indirect potable reuse, two major advantages have to be underlined: preservation of high water quality from diffuse pollution and cost saving from construction and operation of dual distribution system. Health risk control could be ensured by on-line control of process performance and water quality parameters, as well as by means of well-designed engineered buffer to check the compliance of water quality.

7. In your opinion, which are the areas in which more thought and research money needs to be spent in to improve the efficiency in treatment and supply of drinking water?

I think that the development of smart systems with on-line and remote control will greatly contribute to the improvement of treatment efficiency and water quality control in distribution systems. Since many years, one of the major challenges for water quality control remains the development of reliable broad spectrum methods/sensors for toxicity measurement. New sensors and surrogates have to be developed for monitoring of pathogens and emerging pollutants. For process performance control and membrane integrity testing it is necessary to develop and implement simple, cheap and easy to use sensors. In addition to intensive monitoring, smart systems are requiring new approaches for data treatment and analysis, secure data transmission and remote control.

In few words, I am convinced that water management and the mobilization of alternative resources is giving tremendous opportunities for research and innovation.

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Taxonomy

• Wastewater Use
• Wastewater Treatment
• Drinking Water
• Water & Wastewater