Municipal, industrial and storm waste water from the municipalities of Domžale, Kamnik, Mengeš, Trzin, Komenda and Cerklje na Gorenjskem flows through the sewerage system into the Domžale-Kamnik treatment plant, where it is cleansed and from where it flows into the Kamniška Bistrica river. The treatment plant receives waste water from nearby populations and large industrial sources. The capacity of the plant is one hundred and fort-nine thousand population equivalent.
At the Domžale – Kamnik plant, waste water treatment is carried out in three stages. The first stage involves mechanical waste water treatment, which removes the coarse solids and larger debris. Then follows the second aerobic biological stage, which removes the carbon, nitrogen and phosphorus compounds. The third stage is anaerobic biological digestion, which converts the sludge into biogas.
The Domžale – Kamnik waste water treatment plant can receive up to nine million cubic metres of waste water per year. It can also receive septic tank sludge from small waste water treatment plants and liquid waste in compliance with the environmental permit. The treatment plant produces approximately four thousand tons of waste sludge and approximately three million kilowatt hours of electricity annually.
All technological treatment processes are automated and constantly under control. Regular measurements and monitoring of waste water make sure the treated water at the outflow is suitable for discharge into the river and measured quality parameters are below the allowed limit values. This means, under seventy milligrams per litre for chemical oxygen demand, under fifteen milligrams per litre of biochemical oxygen demand, under ten milligrams per litre of total nitrogen, under one milligram per litre of total phosphorus and under twenty-five milligrams per litre of suspended solids.
The wastewater treatment plant operates in such a way that its emission influence on water and soil, air and noise connected with its operation is within the legal limits.
Od leta 2014 do 2016 je potekala nadgradnja čistilne naprave z namenom odstranitve dušikovih in fosforjevih spojin.