Turning waste into treasure: How can wastewater treatment surplus sludge become valuable?

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Professor Mark van Loosdrecht is a Chair Professor in the Department of Environmental Biology at Delft University of Technology in the Netherlands. In short, his research focuses on the use of microorganisms to treat sewage. As a pioneer and technology master of sewage recycling, he will share some of his insights and views on sludge resource recycling in this lecture, following a brief interview with AIWW.

Professor Mark said: "You can use sewage to do three things, the first is the cliché of water shortages as drinking water; the second is to get energy from sewage, from the perspective of integrated environmental impact can make the sewage plant greener and more sustainable; the third is also often overlooked and very headache, that is, sewage plant sludge, however, sludge is the raw material for many high value-added products." ”

The sludge is almost worthless... Is it? Despite the general recognition that we need to dispose of sludge efficiently and rationally, there is still a major obstacle to be overcome, namely that no one is willing to invest in the disposal of sludge. From this point alone, the sludge is almost worthless.

Professor Mark said: "I am very interested in microbial ecology, especially how it is used in the design of processes such as wastewater treatment and waste utilization and product conversion. One of the key points of the study is the biofilm process, including the migration and conversion of nitrogen and phosphorus in sewage and the formation of polymers inside and outside the microbial cell, and most of these potentially recyclable substances are present in the form of sludge and wasted, and are not well disposed of. In the Netherlands, about 15 kilograms of residual sludge are produced per person per year. And we are just a small country, imagine how much waste is caused in Europe and even on a global scale! Of course, in some countries or regions, sludge is allowed to be used as fertilizer for agricultural land, which is a very sustainable and easy way to reuse resources. But what to do in countries where laws and regulations do not allow sludge for agricultural use? If sewage treatment plants are still avoided, how will we create value? ”

Kaumera, the latest representative multi-functional product extracted from the sludge, however, the understanding of sludge as a resource carrier has slowly begun to form, for example, about 2 to 4% of the phosphorus in the sludge, if recycled in the form of guano stone, can be sold to agricultural users for 300 pounds per ton for fertilizer, resulting in economic and socio-environmental benefits. Recently, Professor Mark and his team developed and recycled a new material from sludge called Kaumera (https://kaumera.com/english/). Professor Mark said: "This is our latest discovery of a material that can be extracted from sludge, has a great potential market value, and can make the sewage treatment plant itself financially self-supporting, rather than relying on the government's tax input. (There are many introductions to Kaumera at home and abroad, and will not be repeated in the next time)

Results of industry-university-research on sludge resource recovery

In addition, Professor Mark also stressed the importance of government-university-enterprise tripartite cooperation to promote sludge resource recovery. Currently, the Sludge Recovery Kaumera project is planned in close cooperation with the Water Authority of the Cantons of Valais and Veluwe, the Rhine and Ijssel Water Authority, the Netherlands Foundation for Applied Research in Water Management (STOWA), the Royal Haskoning DHV Engineering Consultancy and the Delft University of Technology.

Each party contributes some of the knowledge and expertise required to recycle, process and market Kaumera's new materials, whether financially, marketally or technologically. Through this tripartite collaboration, water authorities, scientific institutions and businesses can work together to build a sustainable circular economy.

The sludge industry is booming

Resources, new materials are extracted from sewage, and then sold; from this perspective, the sewage plant looks like a hidden gold mine. Can sewage treatment plants become millionaires now? Professor Mark also gave his own answer: "Who knows, but this may still be too far away from us." However, the fact that sewage plants can be fully self-sufficient is an exciting outcome. Of course, we are not quite there yet, for several reasons. At present, extracting such new materials from sludge is still more expensive than petroleum-based products. Most importantly, due to psychological reasons, it is difficult for people to accept the sewage that has just been flushed over the toilet, even if the water quality is already very good, even if the extracted material, acceptance also needs a process. Moreover, the complexity of laws, regulations, protocols and standards has led to a very complex legislative framework, which also limits the resource recovery process of sludge to a certain extent. In short, sludge resources are easier said than done, and not many investors are keen on investing money in this area. But I hope that the value of sludge can be widely recognized, we can actively reuse it, the key is that we need innovative research, can really develop and extract high value-added products, in order to ensure the market and customers.

Disclaimer: The above content is reproduced from Polaris Environmental Protection Network, and the content posted does not represent the position of this platform.

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