DAERLIGEN Wastewater Treatment Plant, Därligen, Bern, Switzerland

DAERLIGEN is a wastewater treatment plant located in Därligen, a municipality in the Bernese Oberland region of Switzerland. The plant serves a population of 1,350 and is situated near the shores of Lake Thun, a major alpine lake. As part of Switzerland's comprehensive water protection infrastructure, the facility plays a key role in maintaining water quality in this popular tourist and recreational area. The plant employs advanced treatment processes, which go beyond the secondary treatment standard required by Swiss regulations for smaller agglomerations. With a designed capacity of 1,600 cubic meters per day and a current discharge volume of approximately 613 cubic meters per day, the facility operates well within its capacity. Swiss wastewater treatment plants are subject to strict federal ordinances under the Waters Protection Act, which mandate nutrient removal (nitrogen and phosphorus) for plants in sensitive lake catchments like Lake Thun. Treated effluent from DAERLIGEN is discharged into the local drainage network that ultimately flows into Lake Thun, a deep oligotrophic lake known for its high water quality. Lake Thun drains via the Aare River, which flows through Bern and eventually joins the Rhine. The plant's advanced treatment helps protect the lake from eutrophication, preserving its ecological health and supporting diverse aquatic life, including fish species such as lake trout and Arctic char.

DAERLIGEN discharges into the catchment of Lake Thun, a large alpine lake in the Bernese Oberland. The lake drains via the Aare River, a major tributary of the Rhine, which flows through Switzerland and Germany to the North Sea. The watershed is ecologically sensitive due to the lake's oligotrophic status and its importance for recreation and biodiversity. Advanced treatment at the plant helps minimize nutrient loading, protecting the lake's clear waters and supporting a healthy aquatic ecosystem.