NURSECOAST-II

Managing seasonal pressure on coastal wastewater systems

Coastal towns, villages and tourist destinations around the Baltic Sea experience strong seasonal changes in population and wastewater generation. During the summer tourism season, wastewater loads can be significantly higher than in the off-season, while many local wastewater systems are designed primarily around the needs of permanent residents.

These fluctuations can put pressure on smaller wastewater treatment systems, making them more difficult to operate and potentially increasing nutrient discharges and other environmental impacts in the Baltic Sea region.

The challenge is not only limited treatment capacity. Small and seasonal wastewater systems can also face gaps in data, monitoring, maintenance, technical support and local expertise. At the same time, Baltic Sea coastal areas differ considerably in their geographical and technical conditions, meaning that a solution that works in one location may not be suitable for another.

Testing solutions in real coastal conditions

NURSECOAST-II brought together 16 partner organisations from eight Baltic Sea Region countries to develop and test approaches for managing wastewater in areas affected by seasonal tourism.

Rather than looking for one universal technology, the project tested different approaches in different local settings and examined how they perform under real conditions. Six pilot solutions in Denmark, Poland, Latvia and Finland explored approaches including constructed wetlands, nanobubble technology and the reuse of treated wastewater.

The pilots were supported by data collection, environmental and technical assessments, knowledge exchange and guidance for decision-makers. The project also mapped small wastewater systems across the Baltic Sea Region, reviewed technologies suitable for seasonal conditions and developed tools, business approaches and policy recommendations to support wider uptake of the results.

What the pilots showed

The six pilots provided practical evidence that different technologies can help address seasonal wastewater challenges.

Testing showed that constructed wetlands and nanobubble technology can improve wastewater quality and help manage peak pollution loads. The results also highlighted the strengths and limitations of individual approaches. For example, nanobubble technology can provide highly efficient oxygen transfer — in some cases up to four times higher than conventional aeration — but this needs to be considered alongside its additional energy requirements.

The results therefore point to technologies with potential for further development and testing, rather than to a single solution for all locations.

The pilots also demonstrated the importance of adapting solutions to local conditions. The six sites covered different settings in Denmark, Poland, Latvia and Finland, providing experience that can be compared and transferred across the Baltic Sea Region.

Building the conditions for long-term solutions

The project showed that technology alone cannot solve the challenge. For small and seasonally loaded wastewater systems to work reliably, regular maintenance, monitoring, technical support and the knowledge and skills of local stakeholders are equally important.

NURSECOAST-II also strengthened the evidence base for small wastewater systems. Mapping work revealed significant differences between Baltic Sea countries in the availability of data on small wastewater treatment plants and their operation.

Together, these results shift the focus from simply asking “Which technology should we use?” to a broader question: how can local wastewater systems be designed, operated and supported so that they can cope with seasonal tourism?

The project has produced practical tools, studies, recommendations and pilot experience that can help authorities, wastewater operators and tourism areas make these decisions.

From regional cooperation to lasting impact

NURSECOAST-II shows how cooperation across the Baltic Sea Region can help coastal communities respond to a shared challenge while recognising that local solutions need to reflect local conditions.

Interreg enabled 16 organisations from eight countries to combine their knowledge, test solutions in different settings and share the results across borders. The project has created not only pilot experience, but also a shared evidence base, practical tools and policy recommendations that can support future action.

The long-term vision is that coastal tourism can develop without putting unnecessary pressure on local wastewater systems and the Baltic Sea. By combining appropriate technologies with better data, maintenance, monitoring, skills and cooperation, communities can become better prepared for seasonal wastewater peaks.