Water scarcity is a growing issue. Today, over two billion people live in areas with high water stress, and many major cities, like Barcelona, are increasingly facing drought conditions. Yet, in our daily lives, we still rely on potable water for non-drinking uses, such as flushing toilets, cooling towers/air conditioning, and most urban irrigation. Potable water requires an extensive, multi-step process (especially in urban environments), with Europe having one of the strictest standards globally.
Instead of relying on such highly treated water for all out water consumption, why not use recycled wastewater? Water reuse programs have been launched in the EU, with the European Commission stating that wastewater is an effective alternative water supply. However, this practice is still far deployed below its potential and currently only looks at using recycled wastewater for agricultural irrigation, leaving the potential for water reuse in the urban landscape untapped.
At the same time, architecture interacts with water every day—through facades, surfaces, and runoff. However, these surfaces remain passive (sometimes even further adding pollutants to urban wastewater). What if instead, architecture itself could play an active role in water recycling? Helping bring water filtration out from underneath us, and visible to the public.
This led me to my research question:
Last term, I tested chitosan-based tiles made with mussel shells. I started off with chitosan as my main filtering agent due to its potential for filtering out organic pollutants (such as phenols, dyes, pesticides, and herbicides) and heavy metals (such as chromium and cobalt) from wastewater.
Chitosan can be extracted from mussel shells, creating a potential circular material process by utilizing the same source for both filtering agent and aggregate. For this reason I started with mussel shells as my main aggregate. Mussel shells are an abundant waste product, especially in many coastal regions undergoing water stress. When ground up, they help neutralize acidic water, adsorb some heavy metals, and can provide mechanical reinforcement.
The key finding was that the material increased pH and alkalinity, which raised questions about its potential applications in filtration. What contaminants does high-pH water remove? Where is high-alkalinity irrigation beneficial?
This term, my research shifted toward improving material performance, mainly focusing on improving filtration with a consideration towards the material’s structural integrity and the environmental impact of the ingredients used.
I continued prototyping, testing different aggregates, investigating binders (reducing sodium hydroxide and increasing chitosan), and experimenting with sulfur additions to counteract alkalinity.
material test recipes & filtration results:
Since the tiles can’t fully filter water alone, they need to be part of a larger filtration system. The question is: Where in the water management system should they be implemented?
However, before resolving that, what would the feasibility of implementing a water management and filtration system be? How much water would such a system help save?
typical “business-as-usual” plumbing system:
proposed grey-water filtration plumbing system:
If we filter and reuse greywater from showers, sinks, and laundry for toilet flushing, this building could save nearly 12 million liters of potable water per year—a 20% reduction in total water consumption.
There’s also potential to reuse excess greywater for irrigation and cooling towers, though this depends on regulations and further estimating and calculating water demand for these uses.
design exploration & application:
