Germany is more popular as a tourist destination than ever before. The number of overnight stays by visitors from Germany and abroad rose by three per cent in 2017 to a new record level of 459.6 million (Federal Statistical Office). The percentage of international guests even rose by four percent to 83.9 million overnight stays by visitors. There are a variety of reasons for this: business travellers and tourists from all over the world are attracted to Germany due to the exceptional infrastructure, which makes it easy to reach, together with very good value for money, many sights and impressive landscapes. Winterberg, a winter sports region in the Sauerland region, has also recorded significant growth in terms of overnight stays. However, the effects of the tourism boom have posed specific challenges for the municipality. We have resolved these together.
Winterberg, a centre of tourism in the Sauerland region with about 13,000 inhabitants in 15 districts, has experienced a development boom in recent years and, from the point of view of tourism, has all the features of a typical destination in the central German uplands. The municipality is home to the largest interconnected ski area north of the Alps and thus doesn’t just attract German holidaymakers. Winterberg is particularly popular with our Dutch neighbours. The central location ensures a quick journey, the landscape is beautiful in all seasons, even more so in winter, and invites you to participate in a number of outdoor activities. To give winter sports enthusiasts 80 days of guaranteed snow a year, a plan to make snow was drawn up in the 1990s against the backdrop of a weather-related slump in winter sports tourism. This scheme worked: in 2012, Winterberg recorded more than 1 million overnight stays for the first time - and that was in commercial hotels alone. Unrecorded overnight stays with small and private accommodation providers and about 1.5 million day visitors a year should be added to this.
Of course, this had consequences for the local sewage system. Stadtwerke Winterberg AöR (Winterberg Public Utilities) operates two sewage treatment plants which struggle especially in winter with sudden additional loads because of the increase in tourism.
Winterberg Public Utilities built on our expertise to overcome two particular challenges in this connection:
On the one hand, the large number of day visitors and tourists has changed WC usage and the quantity of urea in sewage has increased significantly. As a result, the amounts of carbon and nitrogen in the sewage are out of proportion. In normal public sewage, the ratio of carbon to nitrogen is 100:20, while in Winterberg it hovers around 80:40. This disproportionate ratio leads to a shortage of carbon in the denitrification period. Acetic acid is added to the sewage as a source of carbon to compensate for this. This supports the breakdown of nitrates into elemental nitrogen and the ratio of carbon to nitrogen is restored to the level required.
On the other hand the sewage also has very low temperatures as a result of weeks of snow melting in Winterberg, which cause poor settling behaviour of the sewage sludge in the secondary clarification process. The addition of polymer flocculating agents improves the bonding and settling behaviour.
sera provided a suitable solution for both challenges: The two Winterberg sewage treatment plants were each supplied with a complete solution in an insulated hazardous material container with ventilation and heating, which in turn included two dosing systems. A DAV2 dosing system with spray protection doses the acetic acid from a container into the denitrification system. Two iSTEP S50 dosing pumps (delivery range of 0.1 ml/h to 50 l/h each), supported by a controller, ensure that very large quantities of acetic acid can be added if necessary, but it is also possible to add small quantities of acetic acid continuously in the denitrification process.
Both turn-key containers also have a smart CTD dosing system to prepare and dose polymer flocculating agents. The polymer is prepared from a concentrate and water, and is added to the feed for the secondary clarification system. The polymer is added automatically, depending on the turbidity in the secondary clarification system. Here, too, we used two iSTEP S50 pumps in order to offset fluctuations as effectively as possible. And this also facilitates easy maintenance and parts supply.
The customer's requirements were very unusual in this case. However, the container solutions developed jointly with Stadtwerke Winterberg now ensure perfect wastewater treatment. These solutions also ensure that tourism continues to boom in Winterberg.