NEWS

Soil-based wastewater treatment plants get rid of leftover residue

Processing sludge from waste treatment plants has long been a difficult problem to solve in practice. This is mainly because the huge task of constructing, maintaining and operating the installations for sludge combustion and fermentation calls for an enormous outlay and consumes large amounts of energy. Other solutions, such as using the sludge for agricultural purposes or depositing it in landfills, is problematic and prohibitive, mainly for reasons of hygiene and environmental pollution. A purely ecological technology exists, however, to dessicate, stabilize and reconstruct the sludge, without consuming energy apart from solar energy, based on the action of plants. It was developed by Professor Reinhold Kickuth, who talked to Kathimerini about the technology of turning organic sludge into soil, a method that can be used to process every kind of industrial waste. After processing, the sludge is transformed into a moisture-free, soil-improving product with a dry weight of 40-50 percent and free of toxic and organic pollutants. What is the origin of these toxic substances in sludge? Sludge consists of the microbe mass that is produced during wastewater treatment, whereby the organic pollutants in the waste are destroyed. These microorganisms, once their life cycle is complete, die and settle on the bed of the waste treatment tanks. The water at the surface is clean but a deposit remains in the form of sludge, containing more than 50 percent of the original pollutants, and has to be processed further. That is the secret of the wastewater treatment plants that no one talks about. To a great extent, pollutants in the effluent are turned into sludge and the pollution problem is perpetuated. So wastewater treatment only cleans the waste of half of its pollutants? From measurements we have done over the past 30 years, we have shown that the percentage of treatment of waste in traditional plants is just 38 percent. The remaining 62 percent has to undergo further processing, which is much more expensive than the first stage, and includes the processing of sludge. Isn’t the production of sludge and the enormous problems it involves a self-evident by-product, and therefore not even a necessary evil? Under no circumstances. This is a problem that originates in the technical installations of waste treatment plants. Everyone knows the way farmers fertilize their fields with manure from their stables. In no way do these quantities of manure concentrate over time into sludge, but they are completely reconstructed. This is a continuous natural form of waste treatment without by-products or any production of sludge. One hundred percent of the waste is treated. Of course, these natural processes have now lost their usefulness because people have congregated in large cities, leaving behind their villages and fields. Yet similar solutions have already been developed since the 1960s within the framework of environmental technology. For the treatment of waste there are the so-called land treatment systems for waste from communities or factories. These are soil-based, fixed-bed reactors that do not produce sludge. On the contrary, these kinds of soil-bed reactors can treat waste produced by conventional waste treatment plants as mentioned above. Systems like these have been operating very successfully for the past 20 years now in Europe. How does the system work? To begin with, it is a natural method that requires little or no human intervention. The installations consist of soil-based fixed beds planted with specific reed strains. It is the plants and their root systems that undertake the processing of the waste by desiccating and decomposing the organic and toxic material and rendering the solid parts of the sludge with qualities similar to those of soil. All this happens simultaneously and is self-regulated. No chemicals or technology are required. The result is truly incredible. However, there is always a great deal of energy and valuable substances in waste, and we should not lose it, as happens now, but we should try to recycle it. How much space is required for such an installation and at what cost? About 0.2-0.3 square meters per person is required for sludge processing, but the population density is also important. The greater the population the smaller the area required. The life cycle of these plants is at least 50 years. The cost is about the same as that for the equipment for a conventional technical installation. But from then on there are almost no operating or maintenance costs, or energy consumption. The product can be used for soil improvement in parks and farms, so as not to end up in a landfill. A system like that has the advantage of conserving energy. Extreme climatic conditions, and the direct effects of overconsumption of energy are now upon us. We are not somewhere else, we are in the midst of energy disasters. Central Europe has to face up to the problem. Last year we were flooded, this year we were on fire. There is no time left for anyone. We have to act immediately and at local level rather than waiting for decisions to be taken somewhere far away, whether in Kyoto or elsewhere – and in a simple and economical way, which is also the only ecological way.