Closing the nutrient loop between urban and rural area – wastewater and sludge utilization in Ner River Valley

For decades an area of 4 500 ha of Ner River valley was used as a part of Łódź municipality wastewater treatment system. Sandy alluvial soils were irrigated with nutrient rich river water for high hay crop production.Nowadays wastewater treatment plant in Łódź discharges 2 m3s−1 of wastewater and produces daily 30–35 t of dry matter of sludge which can be utilized in the valley for energy biomass production.Of a great importance for sustainable development is the recirculation of nutrients between urban and rural areas. Reuse nutrient rich wastewater and sludge results in saving natural resources (mining rocks, forest wood) and protection of receiving water bodies.