In the past, the holiday island Usedom was mainly drained via small local water treatment plants, collecting pits and a gravity sewage channel built in the 1920ies. In 1992, the administration union „Wasserversorgung & Abwasserbeseitigung Insel Usedom“ (water supply & sewage disposal for Usedom island) was founded. Their goal was to renovate the infrastructure for water supply and sewage disposal and to centralise sewage treatment to a great extent in common water treatment plants. This is the reason why the existing sewage disposal facilities have been extended by e.g. pressure drainage systems since then. Today, 102 km of the 338 km long wastewater pipe network on Usedom are pressure pipes.

The decision for pressure drainage was mainly taken because of the topography and population density on the island. Pressure drainage allows a considerably easier and more economical drainage of remote or weakly populated areas. Drainage is mainly realised with polyethylene (PE) pressure pipes with a small pipe diameter. Compared to gravity channels, pipe dimensions are much smaller and considerable investment costs can be saved. With pressure drainage, the sewage is collected in pumps stations and then pumped through pressure pipes to the water treatment plants. WILO EMUPORT GmbH, subsidiary of the Dortmund-based pump specialist WILO SE, has already manufactured eight “tailor-made” pumps stations for the administration union. The systems are still running with the first set of pumps, which means that the two pumps in the main pumps station Karlshagen which was put into operation in 1997 have already pumped more than one million cubic metres of sewage each.

This reliability of the Wilo pumps stations on the island is owed to the so-called solids separation system. This system makes sure that during pumping, the pumps do not get in touch with solids like e.g. cellulose hygienic cloth which may be contained in the sewage. So a smaller ball passage can be chosen and the hydraulic efficiency of the pump is much higher than with conventional solutions. The pump motor consumes less power. Depending on the application, electricity costs can be cut by 50%. Moreover, clogging which can cause cost-intensive service staff deployments or a premature breakdown of the pumps is avoided. The solid separation system allows for a considerably longer service life of the pumps and increases the reliability of the installation at the same time.

The robust construction of the pump sumps in polyethylene (PE) also contributes to the reliability of the pumping stations. Compared to other materials, PE is chemically more resistant, absolutely rot-resistant and water-proof. Particularly the high resistance of the sumps plays an important role in sewage disposal on Usedom island. With roughly 760,000 guests per year (2007) which usually come only during holiday times, the sewage volume varies by an average of 40 % between the high and low season. This results in an essentially more aggressive sewage concentration during the winter months. Then the sewage is less often moved and the low inlet volume and longer stagnation times cause an increased generation of hydrogen sulphide. The resistant PE however can even handle such aggressive sewage.

Another advantage of this system is the remote controlled operation. Employees of the Usedom administration union can thus monitor the functioning of the pumping stations twenty-four-seven and take the appropriate measures if the control system emits a fault message. If repair or maintenance work becomes necessary, the pump room is clean and free of odour – thanks to the dry well installation. Due to the possibility to stop individual parts of the system, maintenance is possible without shutting down the complete installation. Furthermore, all mechanical components can be accessed from the outside which reduces time expenses for maintenance to a great extend. The smooth interaction of all system components is extremely important for the administration union. Due to the number and the great distances between the pumping stations on the island, the technicians of the union have to rely on the smooth functionality of the installations and telecontrol technology.

Wilo EMUPORT also does the planning of the pumps stations. This is a challenge as only imprecise forecasts can be made regarding the expected sewage volume. Based on the data from long-term measurements at different collection points of the island and the average per capita water consumption, Wilo develops tailor-made solutions for pressure drainage. All pumps stations are planned and constructed individually for the determined inlet volumes and inlet depths. The large range of Wilo EMU sewage pumps by the pump specialist WILO SE allows a demand-oriented choice of pumps which are exactly designed for a specific pumping need. This results in low operation and maintenance costs in relation to the life cycle of the pumps stations.