Wastewater recycled to make energy
According to the U.S. Geological Survey, a toilet flush uses anywhere from one to four gallons of water. What happens to all of this water? Does it all go to waste? Last Friday, Mark van Loosdrecht, professor of environmental biotechnology at the Delft University of Technology in the Netherlands, gave a lecture on “Waste-Based Biorefineries.”
Van Loosdrecht, an Association of Environmental Engineering and Science Professors (AEESP) Foundation 2013–14 distinguished lecturer, has been a professor at the Delft University of Technology for over 25 years, and is well known for his research in biofilm and granular sludge systems for wastewater treatment.
The lecture, sponsored in part by the civil and environmental engineering department at the University of Pittsburgh, discussed how wastewater is recycled into viable components, such as chemicals and cellulose fibers.
The original purpose of wastewater treatment, van Loosdrecht said, was sanitation. In the 1970s, however, many people became more environmentally aware and realized the potential of reusing wastewater and the components of biological waste to produce chemicals or even energy.
“Today we call it resource recovery, when we get things out of the water to use again, like phosphates,” van Loosdrecht said. “In the future, we think we could really integrate this into production cycles — integrate it into the chemical industry.”
Recently, the focus of wastewater recovery research has shifted to the production of energy from the associated biological waste. This research, however, is difficult to do on a large scale in an economically- and energy-efficient manner.
Van Loosdrecht began with a discussion of common resource recovery practices, such as recycling cellulose fibers from the toilet paper in wastewater.
Although these fibers can be recycled into new toilet paper, van Loosdrecht said, it would be difficult to find a market for this method. Instead, the fibers — which are separated from wastewater with sieves — are used as a component of road asphalt, where the length and quality of the fibers is irrelevant.
Van Loosdrecht discussed many of the important chemical products that can be extracted from wastewater, and the existing processes for such extraction.
Polyhydroxyalkanoates — better known as PHAs — for example, can be used for a variety of applications ranging from making plastics to paper to probiotics in fish food. PHA is produced by many of the bacteria found in the organic waste that can be separated from waste water.
“It’s an interesting compound — PHA — because almost every bacteria can make it. It’s almost more interesting to study which bacteria can’t make it,” van Loosdrecht said. “It is stored inside the cell granules, so you can easily extract it by just separating the cells, by centrifuge or other methods.”
Van Loosdrecht helped develop a new photosynthesis and feeding cycle that helps such bacteria grow and produce more PHA.
Another important byproduct of wastewater is alginates. Alginates, which are typically extracted from seaweed, are used widely in the food, textile, and pharmaceutical industries. Van Loosdrecht was also part of the research that led to the Anammox reactor. Anammox, which is short for anaerobic ammonium oxidation, was a process discovered in the late 1990s that converts nitrite and ammonium — two byproducts of wastewater refinement — into nitrogen gas.
Van Loosdrecht received his masters and Ph.D. from Wageningen University, and is a member of the Netherlands Academy of Technology and Innovation, as well as the Royal Netherlands Academy of Arts and Sciences.