Urban water systems face a multitude of challenges, Stanford University Professor Richard Luthy told delegates at last week’s Water Research Conference in Singapore.
These challenges include everything from having less water that they can import to dealing with larger populations using more water to less runoff that can help provide enough water.
To reinvent urban water systems, Luthy and his team of collaborators from UC Berkeley, the School of Mines and New Mexico State University are working with corporations and utilities on solutions that include urban systems integration, efficient engineered systems and natural water infrastructure systems.
Luthy cited future hybrid systems as one example of this. His team is looking at how to shift from centralized systems and treatment plants that are often far away from users to thinking about satellite systems and tailored water solutions that can provide water for different uses. Tailored water reuse can leverage a distributed infrastructure to provide water for irrigation, groundwater recharge or other uses.
Another is unit process wetlands, which offer opportunities to use organic removal, de-nitrification, filtration, solar treatment, pathogen predation or other processes for water treatment.
Managed aquifer recharge and recovery can offer an opportunity for stormwater that has been treated to be put into the ground for storage and water reuse, although barriers such as operational standards, efficiency and footprint do exist. Luthy said stormwater harvesting for distributed recharge faces several issues, including the effects of herbicides and discharge from automobile tires.
His team is looking at vertical infiltration systems and perhaps using iron oxides and trap compounds to operate systems that are internet-enabled, and to couple them with weather prediction.
Another solution the team has been studying is coupled aerobic-anoxic nitrous decomposition operation (CANDO) to generate energy; it plans to test this by working with the Delta Diablo and South Bayside System Authorities in California.
University of Innsbruck professor Wolfgang Rauch told the conference that urban water management is changing rapidly, citing his base of Innsbruck, Austria as an example.
Rauch said he found three especially interesting changes in Innsbruck that were probably unexpected in the past and that affected water management. First, there has been a shift in demographics and the population in the city is not growing. Second, the number of single households increased starting in about the 1960s. And lastly, the city nearly halved per-capita urban water use since the 1980s. What these changes demonstrate, he said, is that urban development is highly dynamic, there are things we cannot anticipate, and what he called “mystic technology” – technology we don’t know – may become available to handle changes.
He saw six drivers for urban water management. One is energy, although it is not a key factor because water management accounts for less than one percent of total energy usage. A second is economic, and with his calculations showing that water management accounts for about one percent of the city’s budget, it is significant. A third is dealing with the aging infrastructure. The fourth is climate change, which introduces pressure on urban water management decisions and which can be unpredictable, since extreme event models do not give a good prediction of the impact
A fifth is urban development, with the impact coming from rising populations that are increasingly living in urban areas and putting pressure on the water system as urban sprawl increases. And finally, technology development is rising exponentially and there is no reason it should stop.
It is no longer enough just to discuss infrastructure, he said. Cities also need to take integrated socio-economic issues into account. Researchers can use digital tools like Google Earth to build and extract the information needed to drive the computational models for sewer systems, wastewater treatment and on-site solutions. And simulation software can also help researchers make predictions, look at technology transition, understand how technology diffusion works, and evaluate how technology is linked to society.