The new machine reduces costs

A new wastewater treatment plant in Domžale-Kamnik has significantly reduced operational costs through advanced technology and energy efficiency. The facility, operated by the Central Wastewater Treatment Plant (CČN), completed a major investment in a new sludge dryer this summer, marking a key step in improving sustainability and cost-effectiveness. According to local reports, the plant processed 8.26 million cubic meters of wastewater in 2025 and achieved 120 percent energy self-sufficiency, with surplus electricity generated primarily from biogas and partially from solar power. This year, in August, the new sludge drying unit was officially taken into operation, further enhancing the plant’s capacity and reducing expenses. The plant serves approximately 82,400 residents, about 88 percent of the population in the municipalities of Domžale, Kamnik, Mengeš, Trzin, Komenda, and Cerklje. In 2025, the facility produced around 3.53 million kilowatt-hours of electricity, meeting its own energy demands and contributing excess to the grid. Despite challenging operating conditions, including multiple instances of toxic substance inflows and high levels of foreign water from rainfall and infiltration, the plant managed to remove nearly all organic load and a significant portion of nitrogen and phosphorus. Emissions remained within regulatory limits, with two minor exceedances of phosphorus thresholds that did not cause environmental harm. Operating challenges were notable during the past year, particularly due to the influx of contaminated substances and the large volume of non-local water. Nevertheless, the plant successfully maintained high cleaning standards. Director Dr. Marjetka Levstek noted that the results of 2025 confirmed the ability to achieve high-level purification even under demanding operational conditions. She emphasized that the goal remains efficient wastewater treatment with minimal environmental impact. One of the main advantages of the new system is the utilization of available heat sources already present at the central treatment plant. Fifty-five percent of the required heat comes from a biomass boiler, while the remaining is recovered from exhaust air during the drying process and supplemented by excess heat from biogas engines. This integration of renewable resources contributes to the plant's overall energy independence and reduces reliance on external energy supplies. The introduction of the new sludge dryer has had a substantial effect on waste management practices. Last year, approximately 4,820 tons of sludge were transported abroad for incineration, costing around €6.4 million without VAT. With the new dryer, which has a capacity of 8,000 tons per year, the amount of sludge sent overseas has been drastically reduced. From mid-February to the end of July, the plant dried approximately 2,057 tons of dehydrated sludge, resulting in about 617 tons of dry sludge, a reduction of over 70 percent. As a result, transportation costs have dropped by approximately 60 percent, and the cost of sludge disposal has fallen by about 80 percent. The sludge dryer was fully integrated into operations by August. The success of the new system reflects broader efforts to enhance environmental protection and economic efficiency in regional wastewater management. The plant continues to monitor performance and adjust strategies to ensure compliance with environmental regulations while maintaining operational effectiveness. The ongoing implementation of innovative technologies underscores a commitment to sustainable resource management and long-term ecological responsibility.