Water quality and waterborne diseases are increasing concerns in rapidly growing cities. Municipal wastewater from households and industries must be properly treated before it can be safely released in the water system. The global market for wastewater recycling and reuse reached nearly US$12.2 billion in 2016 and is expected to reach over US$22 billion by 2021. Wastewater treatment plants often require high capital costs and requires high energy consumption. Two new technologies are emerging to address some of these pain points.
Murdoch University in Germany has developed a new wastewater treatment system that is set to reduce energy consumption to half. Dr Ralf Cord-Ruwisch and Dr Liang Cheng, together with two Phd students are working to commercialize this more energy-efficient approach.
“At present, the majority of the electricity consumed by the nation’s wastewater treatment plants is used to oxygenate wastewater as part of the treatment process, and this design has the potential to revolutionise this,” Dr Cord-Ruwisch said. He also stated that an added benefit to employing this new system is a lower carbon footprint.
The breakthrough came with a deeper understanding of the microorganisms that break down waste materials. The bacteria that digests organic matter forms what is called biofilm. In traditional methods, a huge amount of electricity was needed to pump air bubbles thereby introducing oxygen to allow the bacteria to breathe. However, the bubbles only contain 20 percent oxygen making the process inefficient and wasteful. The team found a way to bring oxygen to the microorganisms more effectively.
The method relies on ‘passive aeration’ wherein water is removed from the treatment reactors allowing the bacteria to thrive on a supported ‘biofilm’ allowing them to breathe directly from the air. The exposure lets them take in the needed amount of oxygen to function. They are then brought back into the sewage sludge to digest more organic wastes. The new process results in less greenhouse gases and odours.
“This is similar to the way in which a whale floats on the surface of the water, taking in enough oxygen from the air into its lungs to sustain itself before it submerges,” Dr Cord-Ruwisch said.
The team is currently fabricating the processing plant on an industrial scale and is looking for investors to help commercialize the technology.
Another promising discovery was done by a team of scientists from the National University of Singapore (NUS). They have developed a new approach to treat industrial wastewater using electricity as a reagent for purification. The process can take out up to 99 percent of hard-to-treat organic compounds in industrial wastewater. It only requires low electrical power and does not result in sludge thereby eliminating the need for incineration.
The treatment entails moving the wastewater into the system’s chamber. As electric current goes through the electrodes in the chamber that generates hydrogen peroxide and hydroxyl radical (one of the most powerful oxidizing agents). It will react with the complex organic compounds which will be broken down into simpler molecules, until they are degraded into water and carbon dioxide.
“Despite the great advances in wastewater treatment technologies, the removal of refractory organic compounds remains a costly and challenging process. Our invention provides an environmentally-friendly solution and helps to raise the overall standard of industrial wastewater treatment,” said Assistant Professor Olivier Lefebvre from the Department of Civil and Environmental Engineering at NUS Faculty of Engineering, who is the leader of the research team.
Waste and residues from the electronics industry, pharmaceuticals and agriculture consists of toxic substances that pose a danger to human health and the environment. This innovation can completely mineralize any organic pollutant by degrading them into water and carbon dioxide. Since the system only requires low energy, it can be utilized with solar power and other purification methods such as using membranes and biological treatments. This electrochemistry process does not need chemicals to be incorporated into the system.
Asst Prof Lefebvre and his team have applied for two patents for the technology and they continue to test it on various kinds of industrial wastewater to further improve the design and maximize the utility of the system.
If you are a municipality in Ontario and in need of a biosolids management solution, please feel free to contact us at 1 (877) 479-1388.
Sources:
https://phys.org/news/2018-04-scientists-cheaper-greener-wastewater-treatment.html
https://phys.org/news/2017-12-energy-cost-effective-wastewater-purification.html