Kakovostno stanje Rakiškega stržena po obnovi Centralne čistilne naprave Postojna

Clanek obravnava kakovostno stanje Rakiskega stržena. Predstavljeni so rezultati meritev fizikalno-kemijskih parametrov na stirih merilnih mestih v obdobju oktober 2016–junij 2017 ter rezultati monitoringa iztocnih voda iz Centralne cistilne naprave Postojna, ki kažejo, da se je kakovost potoka po prenovi cistilne naprave izboljsala. To potrjuje tudi primerjava rezultatov s starejso raziskavo, opravljeno v hidroloskem letu 2014, ki kaže na znižanje koncentracij nitrata in nitrita ter nasprotno, majhno povisanje koncentracij amonija in fosfata, kar razlagamo s slabsim ucinkom redcenja v hidroloskem letu 2017, ki je bilo manj vodnato. K celotnemu obremenjevanju najvec prispevajo preciscene odpadne vode iz cistilne naprave ter nepreciscene odpadne vode iz Rakitnika. //   The article deals with water quality of the Rakiski stržen brook. Results of the measurements of physico-chemical parameters in the period from October 2016 to June 2017 at four sampling points and the results of the monitoring of the treated wastewater effluent from the Central Wastewater Treatment Plant Postojna are presented. The results show, that the quality of the brook improved after the upgrading of the wastewater treatment plant. Comparison of the gained results with a former study, conducted in the hydrological year 2014, also confirms this finding, showing lower concentrations of nitrate and nitrite, but on contrary, slightly higher concentrations of ammonium and phosphates. The latter is most likely associated with lower dilution effect, since the hydrological year 2017 was significantly less wet. Treated wastewater effluent and untreated wastewaters from the Rakitnik village contribute the greatest part to the overall pollution burden of the brook.