Povećane količine željeza mogu ući u uređaje za biološko pročišćavanje s industrijskim i procijednim otpadnim vodama ili korištenjem željeznih soli za precipitaciju fosfata u tercijarnom stupnju pročišćavanja. U ovom radu istražen je utjecaj dodatka željeza u obliku FeSO4 na rast i metabolizam čiste kulture fosfatakumulirajuće bakterije Acinetobacter junii. Pokazalo se da je za uspješan rast i metabolizam A. junii dovoljna prisutnost Fe2+ u tragovima (≤0,02 mg L-1). U otpadnoj vodi koncentracije Fe2+ od 1,31 mg L-1 pokazuju negativan utjecaj na rast i metabolizam bakterija, a koncentracije veće od 24,16 mg L-1 uzrokuju

odumiranje bakterijske biomase. Postoji opasnost da povišene koncentracije Fe2+ djeluju toksično prema fosfat-akumulirajućim bakterijama i drugim mikroorganizmima u aktivnom mulju i tako dugoročno naruše sposobnost uređaja za tercijarno pročišćavanje da uspješno uklanjaju fosfate iz otpadnih voda.; Increased iron concentrations may enter biological treatment plants through industrial and seepage wastewater or use of iron salts for phosphate precipitation in tertiary treatment. This paper investigated the impact of iron addition in the form of FeSO4 on the growth and metabolism of the pure culture of phosphate-accumulating bacteria Acinetobacter junii. It was determined that the presence of Fe2+ in traces (≤0.02 mg L-1) was sufficient for successful growth and metabolism of A. junii. In wastewater, concentrations of Fe2+ starting from 1.31 mg L-1 adversely impact the growth and metabolism of the bacteria, whereas concentrations over 24.16 mg L-1 cause dying off of bacterial biomass. There is a danger that increased Fe2+ concentrations will have a toxic impact on phosphateaccumulating bacteria and other microorganisms in active sludge, with consequential long-term reduction of the tertiary treatment plant's ability to successfully remove phosphates from wastewater.