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Two commercially available materials, MiraCarbon® carbon fibers (CF) and CultiSpher-S® microcarrier (CS), were used as support materials for immobilization of phosphate (P)-accumulating bacterium Acinetobacter junii. The CF are filamentous microscopic fibers intended to be used for mass adhesion of activated sludge thus preventing excess of waste sludge. The CS are macroporous gelatin spheres intended to be used as support for growth of animal cells. The immobilization of A. junii was performed by aerobically incubating the pure bacterial culture and selected materials in simulative wastewater with low P concentrations (2 mg L-1) for 24 h. After the incubation the numbers of immobilized bacteria were 1.97±0.95×109 CFU g-1 of CF and 4.96±1.0×109 CFU g-1 of CS. The materials with immobilized bacteria were now transferred to simulative wastewater with high P concentrations (20 mg L-1) to test the P-removing capacity of such prepared substrate. During 24 h of aerobic incubation a part of the cells were detaching from the surface of the CF thus bioaugmenting the surrounding media while majority of the bacteria remained firmly in the biofilm ; the bacteria were metabolically active and removed 50% of starting P from the wastewater. On the other hand, the CS dissolved after 24 h of incubation resulting in blur and gelatinous solution which excluded CS for potential usage in the treatment systems, although the bacteria were still viable and metabolically active. The CF were rigid throughout the experiment, showed great potential for implementation and should further be tested in activated sludge systems.

To test new methods of activated sludge bioaugmentation we immobilised Acinetobacter junii and Pseudomonas aeruginosa onto natural zeolitic tuff and tested their ability to remove phosphates and heavy metals (copper, zinc, nickel) from synthetic and real wastewater. A. junii strain used is a known phosphate (P)-accumulating bacterium and P. aeruginosa strain was isolated from metalworking fluids. We immobilized the bacteria (bioparticle formation) by aerobically incubating pure bacterial cultures and zeolitic tuff in nutrient medium, obtaining A. junii bioparticles (AJBP) and P. aeruginosa bioparticles (PABP). We conducted four sets of experiments in order to: i) compare heavy metal tolerance of planktonic and immobilized bacteria, ii) compare their ability to remove phosphates and heavy metals from synthetic wastewater, iii) investigate if combined system with AJBP and PABP can be as efficient as systems with only AJBP or PABP, iv) test the ability of combined AJBP and PABP to remove phosphates and metals from real wastewater. Immobilised bacteria were significantly more tolerant to heavy metal stress than planktonic bacteria and removed significantly more metals. The two bacteria in form of bioparticles can survive in the same system, multiply and remove phosphates and heavy metals more successfully than when used separately. By simultaneous use of both bioparticles in real wastewater achieved values of phosphate and metal removal were from 15.2 to 17.0 mg/L P-PO4, 1.1 to 11.4 mg/L Cu2+, 1.2 to 32.8 mg/L Zn2+ and 1.0 to 39.6 mg/L Ni2+. This high efficiency gives the opportunity to use these bioparticles in wastewater treatment plants.

Biološko uklanjanje fosfata (P) iz otpadnih voda temelji se na metabolizmu P-uklanjajućih bakterija prisutnih u aktivnom mulju. Imobilizacija P-uklanjajućih bakterija na materijale koji služe kao nosači bakterija jedna je od mogućnosti unaprjeđenja ovog procesa jer se imobilizacijom postiže veća koncentracija željenih bakterija te pojačana metabolička aktivnost u bioreaktoru. U ovom radu kao nosači P-uklanjajuće bakterije Acinetobacter junii ispitani su prirodni alumosilikatni materijali (zeolitni tufovi, bentonit i perlit), jedan prirodni magnezijev-silikat (sepiolit) te jedan sintetski alumosilikat (sintetski zeolit A). U radu su utvrđeni fizikalno-kemijski čimbenici koji utječu na rast i metabolizam bakterije A. junii i na proces imobilizacije bakterija na nosače. Svi prirodni materijali pokazali su se kao dobri nosači bakterija, a sintetski zeolit A nije bio prihvatljiv nosač. Bakterije imobilizirane na nosač zadržale su metaboličku aktivnost u pokusima sa sintetskim i realnim otpadnim vodama što ukazuje na mogućnost njihovog korištenja u postrojenjima za pročišćavanje otpadne vode.

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.

Cilj ovog rada je bio istražiti i usporediti kako fosfat-akumulirajuća bakterija Acinetobacter junii preživljava nepovoljne vrijednosti pH u planktonskoj formi (slobodne stanice) i imobilizirana na mineralni nosač, u ovom slučaju prirodni zeolitni tuf, (biočestice), te kako to utječe na njenu sposobnost uklanjanja fosfata iz sintetske otpadne vode. Imobilizirane bakterije su bile otpornije na nepovoljne vrijednosti pH od planktonskih, a njihova stopa umnožavanja je bila značajno veća. Metaboličku aktivnost su zadržale i planktonske i imobilizirane bakterije, no postotak uklonjenog fosfata je bio veći u slučaju biočestica. Rezultati pokazuju da je prirodni zeolitni tuf obečavajući nosač fosfat-akumulirajućih bakterija u svrhu korištenja u postrojenjima za pročišćavanje otpadnih voda. The aim of this study was to determine and compare how phosphate-accumulating bacterium Acinetobacter junii survives unfavorable pH levels in planktonic form (free cells) and immobilised on a mineral carrier, in this case natural zeolitic tuff, (biosolids), and also how this affects the ability to remove phosphate from synthetic wastewater. Immobilised bacteria were better at withstanding unfavorable pH levels than planktonic, and their reproduction rates were signifcantly higher. Both planktonic and immobilised bacteria remaind metabolically active, but percentage of removed phosphate was higher for biosolids. Results show that natural zeolitic tuff is a promising carrier for phosphate accumulating bacteria to be used in wastewater treatment plants.

Mnoge bakterije mogu postojati kao zajednice vezane na površinu poznate kao biofilmovi. Bakterijski biofilm je sesilna zajednica čije su stanice ireverzibilno povezane sa supstratom i međusobno, te uronjene u matriks izvanstanične polimerne tvari (eng. extracellular polymeric substance, EPS) koji su same stvorile. Istraživanje je bilo usmjereno na statičke sustave biofilma koji su posebno korisni za ispitivanje ranijih stadija formiranja biofilma. Za istraživanje su korištene bakterije Bacillus cereus i Acinetobacter junii. Cilj istraživanja bio je odrediti model rasta biofilma kojeg tvore te vrste bakterija u stacionarnim uvjetima, kao i vizualizirati biofilm, usporediti količine nastalog EPS-a, te usporediti rast planktonskih i imobiliziranih bakterija kroz vrijeme u stacionarnim uvjetima (batch culture) te uvjetima kontinuiranog rasta (continuous culture). Budući da se pratila biomasa bakterija kroz vrijeme i količina nastalog EPS-a, bakterije su se bojale bojilom Alcian blue i Karbol-fuksinom. Zaključeno je da u stacionarnim uvjetima model rasta bakterijskog biofilma koji se odvija u pet faza nije primjenjiv za bakteriju B. cereus, dok je primjenjiv za bakteriju A. junii. Također je zaključeno da stacionarni uvjeti pogoduju vrsti B. cereus, dok kod bakterije A. junii nema značajne razlike u uvjetima kontinuiranog rasta i u stacionarnim uvjetima. Many bacteria may exist as surfaces-related communities known as biofilms. Bacterial biofilm is a sessile community whose cells are irreversibly linked to the substrate and mutually, and immersed in the matrix of extracellular polymeric substances (EPS) that they have created. The research was focused on static biofilm systems that are particularly useful for the early stages of biofilm formation. Bacteria Bacillus cereus and Acinetobacter junii were used for the study. The goal was to determine a model of biofilm created by these bacteria species in stationary conditions. Also, visualize the biofilm, compare the amount of produced EPS and compare the growth of planktonic and immobilized bacteria over time in batch culture and continuous culture. Given that we monitored bacterial biomass through the time and the amount of produced EPS, bacteria were stained with Alcian-blue which dye the EPS and Carbol-fuchsin which dye the cells. It was concluded that in stationary conditions the five stage model of biofilm development is not applicable to B. cereus, but is applicable to A. junii. It was also concluded that stationary conditions were beneficial for the growth of B. cereus, whereas in comparison with A. junii there was no significant difference in the stationary assay relative to the continuous growth assay.