Watershed Management and Optimization for Membrane Treatment Facilities

My research seeks to learn how water treatment managers can optimize treatment processes through improved watershed management. I hypothesize that watershed management will gain renewed relevance as newer membrane technologies increase treatment costs downstream. In recent years, we have observed how water managers increasingly select membrane treatment in order to meet new water demand and to improve water quality. These new technologies imply significant changes to various aspects of the treatment process. The high energy use and costs associated with membrane treatment create new optimization equations. Pollutants such as dissolved salts -- previously untreatable using standard treatment methods -- now will directly increase treatment costs. Thus the technological innovation should change how water treatment managers engage with upstream polluters who degrade water supplies. More precisely, the high operating costs associated with membrane treatment may uncover new economic arguments that favor of watershed management.

To understand how membrane treatment plants should respond to upstream polluters I will draw from the fields of urban planning, environmental economics, and environmental engineering. In particular, I am interested in learning if the adoption of membrane treatment will create new opportunities to align economic incentives with environmental goals. Do the increased treatment costs generate new incentives to address point source pollution at their source? If so, what are the quantifiable economic benefits associated with specific surface water quality improvements? These questions are of interest to a broad community of environmental engineers, urban planners, and environmentalists. They also are questions that move us forward in our quest for sustainability because they simultaneously address
economic and environmental goals.

This research is inspired by the experience in New York City where water managers saved millions of dollars by investing in strategic land use management in the Catskill watershed. The investment in land conservation helped them protect drinking water supplies and avoid installing an expensive filtration system (Chichilnisky & Heal 1998). New York is one of the most well studied examples of integrated land and water management (National Research Council 2000). While my research follows the spirit of the New York case, it adds two important twists. First, the treatment technology is vastly different. Instead of seeking to avoid new technologies, my research embraces the most advanced membrane treatment and yet searches for efficient and environmentally sound practices within this new technological context. Second, I will study the benefits of restoration, not conservation. I will quantify the real savings derived from improving surface water quality instead of speculating on the avoided costs that resulted from land conservation. Furthermore, the technological and environmental conditions at my research site are more representative of urban water challenges globally. Most treatment facilities have already installed the filtration systems that New York avoided. My research site reflects conditions that water managers are likely to face in the future, whereby poor water sources will be treated with newer technologies.

Research Site
The Llobregat River near Barcelona, Spain offers a special opportunity to study the new relationship between membrane treatment and watershed management. Over 4 million residents in the Barcelona metropolitan region depend on the Llobregat River for their drinking water (Saurí 2003).Two major treatment plants draw water from the Llobregat: the public water agency Aigües Ter-Llobregat (ATLL) and the private water company Aigües de Barcelona (AGBAR). Motivated by upstream pollution and new drinking water standards, both facilities will begin to operate new desalination systems starting in 2009. The publicly managed ATLL plant has purchased a reversible electrodialysis system from General Electric. The private water company AGBAR has chosen to install a reverse osmosis system.

For decades, both facilities have had difficulties managing trihalomethanes (THM) produced during disinfection (Esteban & Prat 2006). THM formation is especially high in water from the Llobregat River because mine tailings upstream release salts and bromides. These contaminants have also contributed to poor odor and taste. While several measures have mitigated the mines’ impact, public officials have always claimed that effective management of river pollution in the Llobregat implied unbearable financial costs. This scenario may change under the new technological and economic conditions. Clearly, the new treatment systems will generate additional operation costs per cubic meter. Therefore the transition to membrane treatment and the high operating costs that come with it may change the economic calculus to make investments in upstream pollution financially viable. And while no one disputes that cleaner surface water would reduce treatment costs, it is unclear how much the savings really are, if they would materialize under actual operating conditions, and if watershed investments truly make economic sense in a restoration context.

Method
I will collect and analyze one year’s worth of data from the treatment plants in order to define the relationship between surface water quality and treatment cost under actual operating conditions. In particular, I would like to learn how marginal improvements in water quality can reduce treatment costs. Regression analysis of a time series data set will help isolate the relationship between pollutant concentrations and treatment costs. Water treatment managers are already collecting water quality data at different points in their treatment process. In collaboration with them, I will compile a database of water qualities at three critical stages: (1) raw surface water quality, (2) water quality following the standard treatment process, and prior to desalination and (3) final water quality following desalination. At each stage, I will track parameters such as temperature, pH, dissolved oxygen, total organic matter, conductivity, and total THMs. When I have established how a marginal improvement in water quality reduces treatment costs, I will be able to conduct a Cost/Benefit Analysis of restoration options available to watershed managers.

Completed Research
I have conducted preliminary order of magnitude calculations to test if my research is viable. Thus far, these calculations have yielded encouraging results. The literature asserts that the operating costs for both desalination plants will be approximately €0.36 / m3 (Avlontis 2002, Karagiannis and Soldatos 2008). Nearly 75 percent of these operation costs are from energy expenditures (Valderi-Perez et al. 2001). To estimate the potential savings derived from improvements in surface water quality, I have calculated the savings associated with a 3 percent (€0.01/m3) reduction in water treatment cost. This hypothetical reduction would result in savings of over € 2 million per year. This represents a Net Present Value of €36 million over 20 years and using a discount rate of 5 percent. These are significant savings for a reasonably small reduction (3%) in water treatment cost, and suggest that there are real opportunities to align the economic and environmental goals. It means that watershed management proposals under €36 million will make financial sense if they can reduce treatment costs by only €0.01 / m3. With such a large amount of money in play, there may be several measures that can simultaneously help restore the Llobregat River and reduce treatment costs.