Stricter regulations pose a challenge for many local authorities: what to do with the sewage sludge? Stadtwerke Gießen and Mittelhessische Wasserbetriebe, in collaboration with the Technical University of Central Hesse, have developed a concept to utilise the residues from wastewater treatment for energy and material purposes. On 7 November, the two partners informed political decision-makers from the region about the current status and promoted their pioneering project.
In Germany, highly effective wastewater treatment is commonplace. The substances removed from the wastewater are still treated at great expense at the sewage treatment plants and then recycled as sewage sludge. In the Central and Northern Hesse region, the sludge was usually used as fertiliser in agriculture. However, this practice, which has been in place for decades, is now coming to an end. The Waste Sewage Sludge Ordinance, which was amended in 2017, and the Fertiliser Ordinance, which was also amended, put an end to it. "So we have to find another way to utilise the sewage sludge that is produced," said Clemens Abel, Head of Mittelhessische Wasserbetriebe (MWB), at an information event. MWB and Stadtwerke Gießen (SWG) had invited representatives from the parliaments of the surrounding municipalities on 7 November.
Ready-made concepts presented
In fact, the two regional utility companies have now been able to develop a highly interesting solution to the sewage sludge problem for the entire Central Hesse region. "We can collect, dry and incinerate the sewage sludge," explained Matthias Funk, Technical Director of SWG. This makes the sewage sludge a regenerative and therefore CO2-neutral energy source. The resulting heat can be utilised as district heating. And the ash from the incinerated sludge is an excellent raw material for the production of fertiliser due to its high content of vital phosphorus.
Many need to get involved
"In order to utilise sewage sludge for energy, special plants are required that cost a lot of money," added Clemens Abel. This is why it must be clear how many local authorities will be involved before the start of such a project. This is because in order for such a plant to cover its costs, the operators need reliable quantities of sewage sludge. The planners are currently assuming at least 50,000 tonnes per year.
This is another topic that those responsible at MWB and SWG have been working on in the run-up to the information event. In addition to a technical concept, there is already a legal model that regulates inter-municipal cooperation. Clemens Abel and Matthias Funk also presented the key points of this agreement.
Operationally reliable and economical in the future
With their approach, MWB and SWG offer the municipalities in the region a clever solution to the sewage sludge problem. The fact is: because the new, stricter regulations reduce its agricultural utilisation to a minimum, the costs of disposal have now more than doubled for many municipalities. What's more, operators of sewage treatment plants will be obliged to recover the phosphorus contained in the sludge from 2029 at the latest. This will also be associated with costs.
Municipalities that participate in the project can not only rely on the safe removal and legally compliant, environmentally friendly utilisation of their sludge. They would also have done their homework in declaring their binding sewage sludge recycling strategy to the state of Hesse by 2023 and saved the enormous expense of organising the recycling of the sludge.
Important supporters
There is therefore much to suggest that the city and municipal parliaments will make a decision in favour of the inter-municipal project. Gerda Weigel-Greilich, city councillor for Giessen, is also in favour of the project due to its sustainability and high ecological importance. Among other things, she pointed out that such a project "not only solves the sewage sludge problem, but also keeps the distances short and the added value in the region." Support for the project also came from District President Dr Christoph Ullrich: "We are aware that sewage sludge recycling under the new regulations is a challenge for many local authorities. That is why the regional council is extremely interested in a safe and practicable solution such as the Giessen concept."
With their largely finalised proposal, SWG and MWB are offering the affected towns and municipalities a coherent option. It now remains to be seen how the individual municipalities decide. In view of the alternatives available, there is a good chance that this pioneering project will soon become a reality.
08.11.2018