The technically sophisticated treatment of sewage sludge is also becoming increasingly important. Because sewage sludge can not only be a problem, but also a solution. In addition to sludge composting, which generates topsoil for the expansion of agricultural land, the treatment of sewage sludge as a carrier of valuable substances and sewage sludge incineration are in the spotlight. For example, sewage sludge contains phosphorus, a vital mineral without which neither plants could thrive nor animals live. Humans need phosphorus above all to build bones and teeth. But the Earth's naturally occurring phosphate rock reserves have already become scarce. Phosphorus recovery by WTE therefore contributes to solving important questions for the future. And in the future, we will have even greater experience in sewage sludge incineration, resulting from the construction of smaller plants such as in Utena (Lithuania), medium-sized ones such as in Halle-Lochau (Saxony-Anhalt) and large ones such as in Tubli (Bahrain), where our own share of the investment varies.
The disposal problems with sewage sludge, triggered by new regulations in the Sewage Sludge Ordinance and the Fertiliser Law, have drawn attention to possibilities that will soon be common process practice at many plants planned and built by WTE: In this case, sewage sludge incineration is used for thermal utilisation of the previously dried sludge to generate heat. This can be used in turn for sludge drying, as in a cycle. But it can also be used for district heating or to supply electrical energy via steam and turbine drive. Knowing that WTE guarantees zero emissions during incineration, operators have long been reducing their energy consumption and are thus already complying with the regulation for 100 per cent thermal sewage sludge utilisation, including possible phosphorus recovery, which will apply in many places from 2029.
Another important aspect of thermal utilisation is the prevention of further addition of microplastics, hormones and other undesirable substances to the water bodies. Because while today's treatment stages are not able to filter such substances, they can be eliminated when the sewage sludge is incinerated. If we consider that, according to studies by the University of Newcastle (Australia), humans ingest up to five grams of microplastics per week through drinking water, food and breathing, depending on their living conditions, sewage sludge incineration is an important and responsible contribution to reducing this environmental pollution.