Keith Hanna from Fluent News recently interviewed Herve Buisson, Head of the Research Center at Vivendi Water in Paris, France and Christelle de Traversay, CFD Program Manager at Vivendi Water about the trends and challenges facing the environmental industry's use of CFD.

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Wastewater treatment plant of Nevers, France, certified ISO 14001, Courtesy of Générale des Eaux - Marcel Chevret

Herve Buisson

KH: Vivendi has become a world famous industrial conglomerate over the last decade or so - where does the Vivendi Environnement (VE) group fit into the mix?

HB: Vivendi, as a company, really started off in 1853 as Generale des Eaux, a French municipal water company. Over time, it extended its activities to other environmental sectors, such as waste management and transportation, and evolved to become the world's largest environmental company. In the 1990s, the company diversified into print and broadcast media, eventually buying out Universal Studios in America, and in 1998, it changed its name to Vivendi. In 2002, Vivendi Environnement separated from Vivendi Universal to focus again on its original core competencies as the world leader in environmental services.

KH: Can you describe the scope of your environmental company today?

HB: We turned over about $29 billion in 2001 with operations in over 100 countries worldwide and some 295,000 employees. Vivendi Environnement is the only company in the world that operates across the entire range of environmental services, with our four divisions covering water (Vivendi Water, which accounts for nearly half of our total revenues), waste management (Onyx), energy services (Dalkia), and public transportation (Connex). US Filter is a leading supplier of water industry equipment and services in the USA. Because of our diversity we can develop integrated service packages that offer a comprehensive, tailored response to the environmental problems our customers face in both private and public utilities. We have a strong customer focus, and are proud of our long-term commitment to protecting the environment through ethical operating standards.

KH: You both work in Vivendi Environnement's Anjou Recherche R&D Center - what are the important technical issues for the water industry from your perspective? HB: The industry today is driven by stronger and stronger regulations, and consumer demands, and our research is geared as much to new or potential legislation as it is to process and equipment improvements. Water is, for the most part, a high volume, low end-value product, typically costing less than $1/ton with typical city plants treating over 100,000 t/yr. In the past, our new product development cycles were around 10 to 15 years in duration, but with frequent regulatory changes and a growing demand for cost efficiency and more compact plants, Research & Development has come very much to the forefront. Today, new process and equipment development cycles are typically three to five years in duration. Through optimization of existing products and processes, our research group aims to supply Vivendi plant operators with solutions that are cost-effective (from a Life Cycle Costs perspective) and tailored to specific water applications.

Sludge volume fraction in a secondary settling tank during dry weather conditions (top) and after a storm event (bottom)

KH: Where does CFD fit into your rapidly shortening product development cycles?

CdT: CFD is a key component of all of our R&D work, in operations, engineering applications, and equipment design. Over the years it has been validated for modeling many processes and pieces of equipment. In some instances, we have seen cost savings of up to 30% over conventional pilot study approaches. CFD has given us a fundamental understanding of many of our unit processes that have been viewed as "black boxes" in the past. The flow visualization capabilities have been invaluable for demonstrating process behavior to our senior management and clients. Today, we see a greater need to optimize our processes, which means that CFD usage has increased. Our use of other software, such as AUTOCAD®, FLOWMASTER®, MATLAB®, and InfoWorks® is also on the rise.

KH: What sort of CFD work do you do at Anjou Recherche?

Christelle de Traversay

CdT: In addition to modeling unit processes, we tend to do standard fluid flow simulations in ducts and pipework. Increasingly, we are doing multiphase simulations with two or three phases, because such systems are very common in the water industry. Once we test and validate CFD for a given flow application, we pass our know-how on to plant engineers and to our partners at Vivendi Water Systems and US Filter. We have an internal CFD club where we share our experiences with CFD engineers throughout the company. CFD offers us significant advantages over experimental methods during pilot plant scale-up tests, where we want to investigate full-scale effects before a plant is constructed. Our newer water treatment processes tend to be more compact than older ones, because they are cheaper to build and operate. Smaller equipment means reduced hydraulic residence times, however, so we are faced with lower over-engineering margins for our equipment designs. To accurately predict behavior, CFD is critical to our design processes.

KH: Why did you choose FLUENT as your CFD code and what benefits does it provide?

CdT: Fluent is the clear leader in CFD and has a strong presence here in France. We like FLUENT's ease of use, range of turbulence models and customization capabilities. We were one of the first users in France when we licensed FLUENT in 1991 and we have stayed with Fluent France ever since. Early on when we decided that we needed CFD, we also decided not to develop our own CFD codes in-house because it is just not cost-effective. Instead, we wanted CFD software that allowed us to attach our know-how to the code and FLUENT provides that.

Research Center hall at Maisons-Laffitte, France (Anjou Recherche): bubble columns for ozone transfer

KH: How do you foresee CFD being used in the water & environmental industry in the long term?

HB: At Vivendi, we aim to give the best local access to our global development, and therefore want to deploy hydraulic modeling tools in an easy-to-use template format locally at every major water plant, so that plant operators will be able to get dynamic fluid flow information that allows them to make informed decisions in real time. Ideally, we would want very few buttons on the interface and background software that is foolproof. The CFD code may be transparent and do multiple CFD simulations on a neural network for instance, or perhaps pick out answers from a database of pre-calculated simulations to display to the operator as needed. In essence, we are envisioning an advanced process control flow modeling tool that has CFD (and maybe other software tools) integrated into it as necessary. In addition, we want faster, better, and cheaper software!

We want to be able to model biological and chemical phenomena in conjunction with our CFD calculations. We work with a range of world-class universities and colleges around the world and would like to integrate the latest biological and chemical research findings into our software modeling tools. We hope to put more and more of these models into FLUENT through user-defined functions (UDFs) or through couplings with other software programs.

On the waste management and energy side of our company we see a lot of potential for applying CFD, especially in incinerator modeling and solid waste management processes. Our R&D colleagues dealing with these issues are using the same CFD tools, to optimize intercompany transfers of know-how and synergies. We anticipate doing more two- and threephase simulations with CFD, and anticipate such advanced uses as multivariable analyses through Monte Carlo simulations using FLUENT output. While not underestimating the inherent complexity of our raw material, water, with its complex chemical, biochemical, seasonal, and geographical variations, we strive to optimize our services, standardize our equipment, and customize our engineering plants using software tools like FLUENT as powerful and "smart" templates to embed our know-how.

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