Jasna Hrenović

Surfactants in the Environment

Surfactants in the Environment Surfactants are a diverse group of chemicals that are best known for their wide use in detergents and other cleaning products. After use, residual surfactants are discharged into sewage systems or directly into surface waters, and most of them end up dispersed in different environmental compartments such as soil, water or sediment. The toxic effects of surfactants on various aquatic organisms are well known. In general, surfactants are present in the environment at levels below toxicity and in Croatia below the national limit. Most surfactants are readily biodegradable and their amount is greatly reduced with secondary treatment in wastewater treatment plants. The highest concern is the release of untreated wastewater or wastewater that has undergone primary treatment alone. The discharge of wastewater polluted with massive quantities of surfactants could have serious effects on the ecosystem. Future studies of surfactant toxicities and biodegradation are necessary to withdraw highly toxic and non-biodegradable compounds from commercial use and replace them with more environmentally friendly ones. Surfaktanti u Okolišu Surfaktanti ili površinski aktivne tvari raznolika su skupina molekula najpoznatijih po uporabi u sastavu deterdženata i ostalih sredstava za pranje i čišćenje. Nakon uporabe u kućanstvu ili industriji, surfaktanti se ispuštaju u kanalizacijski sustav ili izravno u površinske vode te većina surfaktanata završi raspršena u vodi, sedimentu ili tlu. Toksični utjecaj surfaktanata na vodne organizme dobro je istražen i opisan u literaturi. U većini slučajeva surfaktanti su u okolišu prisutni u koncentracijama nižim od toksične te nižim od maksimalne koncentracije dopuštene hrvatskim zakonskim odredbama. Većina surfaktanata klasificirana je kao biološki razgradiva i njihova se koncentracija znatno smanjuje biološkom obradom otpadne vode pa je najveći rizik za okoliš ispuštanje prethodno pročišćene ili nepročišćene otpadne vode. Takva otpadna voda opterećena visokim koncentracijama surfaktanata može nepovoljno utjecati na okoliš. Potrebno je proučavati toksičnost i biološku razgradnju surfaktanata u svrhu uklanjanja visoko štetnih i biološki nerazgradljivih surfaktanata iz komercijalne uporabe te njihovu zamjenu tvarima manje štetnim za okoliš.

Interaction of surfactant-modified zeolites and phosphate accumulating bacteria

The aim of this study was to determine the interaction of surfactant-modified zeolites (SMZ) and orthophosphate (P)-accumulating bacteria in the process of P removal from wastewater. The SMZ were prepared from the natural zeolite (NZ) of size fractions <0.122 mm and 0.25-0.5 mm. The hexadecyltrimethylammonium (HDTMA) bromide was used to modify the NZ surface from partial monolayer to the bilayer coverage. The surface modification of NZ resulted in the change of zeta potential of particles from negative to positive and great enhancement of the P-adsorption capacity. Only in reactors containing <0.122 mm fraction of partial monolayer coverage of the SMZ, the P was efficiently removed from wastewater by combined adsorption onto the SMZ and bacterial uptake in the biomass. The SMZ with bilayer or patchy bilayer coverage showed the bactericidal effect. To enhance the P removal from wastewater in the aerated biological system, the SMZ can be used, but the special attention should be given to the configuration of sorbed HDTMA molecules and its potential desorption.

Antibacterial activity of heavy metal-loaded natural zeolite

The antibacterial activity of natural zeolitized tuffs containing 2.60wt.% Cu(2+), 1.47 Zn(2+) or 0.52 Ni(2+) were tested. Antibacterial activities of the zeolites against Escherichia coli and Staphylococcus aureus were tested after 1h and 24h of exposure to 1g of the zeolite in 100mL of three different media, namely Luria Bertani, synthetic wastewater and secondary effluent wastewater. The antibacterial activities of the zeolites in Luria Bertani medium were significantly lower than those in the other media and negatively correlated with the chemical oxygen demand of the media. The Ni-loaded zeolite showed high leaching of Ni(2+) (3.44-9.13wt.% of the Ni(2+) loaded) and weak antibacterial activity in the effluent water. Since Cu-loaded zeolite did not leach Cu(2+) and the leaching of Zn(2+) from Zn-loaded zeolite was low (1.07-1.61wt.% of the Zn(2+) loaded), the strong antibacterial activity classified the Cu- and Zn-loaded zeolite as promising antibacterial materials for disinfection of secondary effluent water.

Antimicrobial activity of metal oxide nanoparticles supported onto natural clinoptilolite

The antimicrobial activity of Cu(2)O, ZnO and NiO nanoparticles supported onto natural clinoptilolite was investigated in the secondary effluent under dark conditions. After 24h of contact the Cu(2)O and ZnO nanoparticles reduced the numbers of viable bacterial cells of Escherichia coli and Staphylococcus aureus in pure culture for four to six orders of magnitude and showed consistent 100% of antibacterial activity against native E. coli after 1h of contact during 48 exposures. The antibacterial activity of NiO nanoparticles was less efficient. The Cu(2)O and NiO nanoparticles showed 100% of antiprotozoan activity against Paramecium caudatum and Euplotes affinis after 1h of contact, while ZnO nanoparticles were less efficient. The morphology and crystallinity of the nanoparticles were not affected by microorganisms. The metal oxide nanoparticles could find a novel application in the disinfection of secondary effluent and removal of pathogenic microorganisms in the tertiary stage of wastewater treatment.

Toxicity of anionic and cationic surfactant to Acinetobacter junii in pure culture

The harmful effects of surfactants to the environment are well known. We were interested in investigating their potential toxicity in a pure culture of Acinetobacter junii, a phosphate (P)-accumulating bacterium. Results showed a high acute toxicity of sodium dodecyl sulfate (SDS) and hexadecyltrimethylammonium bromide (HDTMA) against A. junii. The estimated EC50 values of the HDTMA for the inhibition of CFUs in the pure culture of A. junii was 3.27 ± 1.12 × 10−7 mol L−1 and for the inhibition of the P-uptake rates 2.47 ± 0.51 × 10−6 mol L−1. For SDS, estimated EC50 values for the inhibition of CFUs in the pure culture of A. junii was 5.00 ± 2.95 × 10−6 mol L−1 and for the inhibition of the P-uptake rates 3.33 ± 0.96 × 10−4 mol L−1. The obtained EC50 values in the standardised yeast toxicity test using Saccharomyces cerevisiae were 3.03 ± 0.38 × 10−4 and 4.33 ± 0.32 × 10−5 mol L−1 for SDS and HDTMA, respectively. These results emphasized the need to control concentrations of surfactants entering the activated sludge system. The negative effects of these toxicants could greatly decrease populations of P-accumulating bacteria, as well as eukaryotic organisms, inhabiting activated sludge systems, which in turn could result in the decrease of the system efficiency.

The effect of mineral carrier composition on phosphate-accumulating bacteria immobilization.

The goal of this study was to determine the dynamics and yield of immobilization of the phosphate-accumulating bacterium Acinetobacter junii on mineral carriers. As mineral carriers natural clinoptilolite tuff from Turkey (T) and Serbia (S) and natural bentonite (TER), in original and magnesium (Mg)-exchanged form were used. The key feature which determined the extent of immobilization of A. junii was the type of carrier; the immobilization yield decreased in order T>TER>S. The number of immobilized cells was significantly higher for the Mg-exchanged carriers when compared to their original counterparts (95 and 75 x 10(8)CFU g(-1) for T, 74 and 58 x 10(8)CFU g(-1) for TER, 19 and 6 x 10(8)CFU g(-1) for S). The Mg-exchanged T and S displayed a prolonged biofilm growth up to 24h, while the original counterparts reached the mature biofilm after 12h of incubation. Both forms of TER reached the mature biofilm after 24h of incubation, due to swelling property of the material. The number of immobilized cells correlated significantly negatively with particle size of the carrier, indicating that particle size is another important feature which determined the extent of immobilization. The Mg-exchange of original carriers resulted in significant increase of the zeta potential. When all of the materials were compared, the increase of the zeta potential of carriers correlated negatively with the number of immobilized cells, suggesting that the zeta potential of material is not a crucial factor which determined the immobilization of cells.

On the zinc sorption by the Serbian natural clinoptilolite and the disinfecting ability and phosphate affinity of the exhausted sorbent

The Serbian natural zeolite is moderately effective in removing the zinc(II) ions from aqueous solutions. At 298 K the sorption capacity varies from 13 to 26% for the initial Zn(II) solution concentration of 100 and 600 mg Zndm(-3), respectively. The sorption isotherm at 298-338 K is best represented by the Langmuir model and the sorption kinetics by the pseudo-second-order model. The sorption involves a combination of film diffusion, intra-particle diffusion, and a chemical cation-exchange between the Na(+) ions of clinoptilolite and Zn(2+) ions. The sorption was found to be endothermic and spontaneous in the 298-338 K range. The exhausted sorbent can remove phosphate ions and it exhibits an excellent antibacterial activity towards Acinetobacter junii. By dehydration at about 500 °C it transforms to a ZnO-containing product featuring nano-sized wurtzite ZnO particles widespread over the clinoptilolite surface.

Carbapenem-resistant isolates of Acinetobacter baumannii in a municipal wastewater treatment plant, Croatia, 2014.

Acinetobacter baumannii is an emerging hospital pathogen. Whereas A. baumannii isolated from patients or hospitals has been reported, there are few data regarding propagation of viable A. baumannii in the natural environment. This study investigates the occurrence and antimicrobial susceptibility of viable A. baumannii in municipal wastewater and its persistence through the wastewater treatment process. A total of 21 A. baumannii isolates were recovered at a secondary type of municipal wastewater treatment plant in Zagreb, Croatia: 15 from raw influent wastewater and six from final effluent. All isolates were carbapenem- and multidrug-resistant. Among 14 isolates tested for blaOXA genes, all harboured the constitutive blaOXA-51-like gene, while the acquired blaOXA-23-like and blaOXA-40-like genes were found in 10 and three isolates respectively. Six A. baumannii isolates recovered from effluent wastewater multiplied and survived in sterilised effluent wastewater up to 50 days. These findings support the idea that multidrug-resistant A. baumannii can occur and have the ability to survive in the environment.

Toxicity of dodecylpyridinium and cetylpyridinium clorides against phosphate-accumulating bacterium

The antibacterial effect of cationic surfactants against the pure culture of phosphate (P)-accumulating bacterium Acinetobacter junii was investigated. The estimated EC50 values of the N-dodecylpyridinium chloride (DPC) for growth inhibition was 1.4±0.5 × 10−6 mol L−1 and for the inhibition of the P-uptake rates 7.3±2.6 × 10−5 mol L−1. The estimated EC50 values of the N-cetylpyridinium chloride (CPC) for growth inhibition was 4.9±1.3 × 10−7 mol L−1 and for the inhibition of the P-uptake rates 7.7±2.9 × 10−6 mol L−1. This suggests the importance of controlling the amounts of cationic surfactants in influent of the wastewater treatment systems in order to avoid the possible failure of the biological P removal from wastewaters.

Occurrence of an Environmental Acinetobacter baumannii Strain Similar to a Clinical Isolate in Paleosol from Croatia

ABSTRACT Over the past decade, bacteria of the genus Acinetobacter have emerged as a leading cause of hospital-acquired infections. Outbreaks of Acinetobacter infections are considered to be caused exclusively by contamination and transmission in hospital environments. The natural habitats of clinically important multiresistant Acinetobacter spp. remain to be defined. In this paper, we report an incidental finding of a viable multidrug-resistant strain of Acinetobacter baumannii, related to clinical isolates, in acid paleosol from Croatia. The environmental isolate of A. baumannii showed 87% similarity to a clinical isolate originating from a hospital in this geographic area and was resistant to gentamicin, trimethoprim-sulfamethoxazole, ciprofloxacin, and levofloxacin. In paleosol, the isolate was able to survive a low pH (3.37), desiccation, and a high temperature (50°C). The probable source of A. baumannii in paleosol is illegally disposed waste of external origin situated in the abandoned quarry near the sampling site. The bacteria could have been leached from waste by storm water and thus infiltrated the paleosol.