Russian Railways (RZD) and St. Petersburg Mining University are working together to implement a technology for managing wastewater residuals. The core of the technology is the heat treatment of sludge, after which it becomes an ingredient for making concrete products, such as flagstones, for instance. For now, these residuals end up in landfills, which incurs financial costs for a waste producer and also harms the environment.
There has been a common misperception – largely thanks to Western eco-activists who declared war on coal, oil, and natural gas, too – that preserving nature is confined to a net-zero target. However, the concept of nature conservation is much broader. It encompasses a raft of measures to develop and protect the biosphere sustainably, with the following amongst them:
- Elimination of so-called objects of accumulated environmental damage, i.e. landfill sites, also unauthorised ones.
- Tree-planting.
- Reduction of plastic use.
- Energy-saving.
- Training staff to understand how to minimise the anthropogenic impact.
RZD's environmental strategy up to 2030 comprises the plan of action on the above-listed and several other measures. It also sets forth the target indicators as to each of the areas of work. The company's primary focus will be on minimising the discharge of insufficiently treated wastewater and increasing the share of recycled waste.
"Many stations or depots, especially far from the big cities, are not connected to the centralised sewage system but equipped with in-house treatment facilities. They gradually produce sewage sludge, a class IV waste material that has to be disposed of or buried in specially designated landfills. Whilst the first option entails certain costs, the second one, in contrast, can be profitable. We have already field-tested our technology, and it enables its users to recycle 100% of the sludge and turn this raw material into a marketable product," says Denis Suchkov, a graduate student in the Department of Geoecology at Mining University.
The new method incorporates two stages. First, the waste goes to an incinerator, a powerful furnace equipped with burners that raise the temperature inside its primary chamber to 800-1200 degrees and burn the sludge to ashes. Then the flue gases produced during this process enter the secondary combustion chamber, where they get treated and cleaned from harmful impurities. As a result, the number of pollutants dispersed into the atmosphere significantly decreases.
This solution is by no means revolutionary. Different companies and enterprises are using it to reduce the amount of their non-metallic waste, including, for example, MSW or animal by-products. The point is that incinerated ash takes about ten times less space than the original material, making it much cheaper to landfill. Representatives of Mining University consider this technology as being transitional, though.
"We have obtained a patent for the development of lightweight concrete. Part of the cement that goes into concrete production is replaced with the ash produced by burning wastewater residuals and other waste materials. It does not affect the product's strength, as production testing confirms. Based on its characteristics, the concrete is of no use in residential construction but is perfect for building amenities — flags, kerbs, gutters, and other products," notes Yury Smirnov, associate professor of the Department of Geoecology.
The university's research team presented their development – potentially allowing to recycle 100% of sewage sludge – to RZD at the first meeting of the project office. The company set up the latter to ensure the implementation of its environmental strategy at the Oktyabrskaya Railway. Russian Railways' executives warmly welcomed the breakthrough solution delivered by the scientists and thereupon decided to establish joint working groups to put this idea into practice.
The Oktyabrskaya Railway will shortly provide Mining University with samples of the sludge from its wastewater treatment plants. The researchers will then conduct laboratory tests to confirm that the material is suitable for manufacturing lightweight concrete. After completing the studies, which may take up to several months, it will become possible to develop the technology commercially.
Sewage sludge treatment is not the only joint initiative of Mining University and the Oktyabrskaya Railway to reduce the burden on the environment. There is also a way to utilise the technology to recycle wooden sleepers treated with creosote or other antiseptic agents. They fall under the class II definition of hazardous waste and emit toxic substances when incinerated.
