Microbial contamination of dental unit waterlines and effect on quality of indoor air

The microbiological quality in dental unit waterlines (DUWLs) is considered to be important because patients and dental staff with suppressed immune systems are regularly exposed to water and aerosols generated from dental units (DUs). Opportunistic pathogens like Pseudomonas, Legionella, Candida, and Aspergillus can be present in DUWLs, while during consultations, bioaerosols can be dispersed in the air, thus resulting in effects on microbiological quality of indoor air. This present study represents microbiological air and water quality in dental offices (DOs) and also concerns the relationship between the quality of DO air and dental unit water. This study aimed to assess both the microbial quality of dental unit water and the indoor air in 20 DOs and to survey the effect on the quality of the indoor air with the existing microorganisms in dental unit water. Fourteen out of 20 (70 %) DUWLs were found to be contaminated with a high number of aerobic mesophilic heterotrophic bacteria. In terms of bacterial air contamination levels, in 90 % of DOs, a medium level (<500 colony-forming units (CFU)/m³) of contamination was determined, while in terms of microfungal air contamination, in all DOs, a low level (<100 CFU/m³) of contamination was determined. Potential infection or allergen agents, such as Pseudomonas, Micrococcus, Staphylococcus, Alternaria, Cladosporium, Penicillium, Aspergillus, and Paecilomyces were isolated from water and air samples. This study’s determination of contamination sources and evaluation of microbial load in DOs could contribute to the development of quality control methods in the future.     

Multiobjective Assessment of Multipurpose Water Resources Projects for Developing Countries

Multiobjective assessments of water resource projects are useful for widening the range of impacts that are considered during the process of project planning and selection. Some of the principles and problems associated with multiobjective analyses are reviewed, as are several relatively simple information display techniques and approaches found applicable to conditions in many developing countries. These techniques can be used where data and technical expertise are limited, and where it is not possible to identify and quantify all economic, environmental or social objectives and their trade-offs during the search for the best compromise decision.     

Biosorption properties of Morus alba L. for Cd (II) ions removal from aqueous solutions

The abundantly available industrial waste product Morus alba L. pomace (MAP) is one of the cost-effective biosorbent for removal of metal ions from aqueous solutions. Hence, in the present study, we aimed to test the ability of MAP to remove Cd(II) ions through batch biosorption process. Firstly, MAP was characterized using several techniques, and then the influence of various experimental parameters such as initial pH of the aqueous solution, initial Cd(II) concentration, contact time, MAP concentration, and temperature were evaluated upon the biosorption process. It was found that the maximum uptake of Cd(II) ions occurred at initial pH 6.0 and optimum contact time was observed as 60 min. Cd(II) ions adsorption on MAP analyzed by the Langmuir and Freundlich isotherm models and the maximum monolayer biosorption capacity of MAP was found to be 21.69 mg?g^?1 by using the Langmuir isotherm model. The pseudo-first-order, pseudo-second-order, Elovich, and intraparticle diffusion models were employed to describe the biosorption kinetics. In order to investigate the thermodynamic properties of the biosorption process, the changes in the Gibbs free energy (?G), enthalpy (?H), and entropy (?S) were also evaluated and it has been concluded that the process was feasible, spontaneous, and endothermic in the temperature range of 5–40 °C.     

Determination of T‐2 toxin in grain and grain products by HPLC and TLC

Abstract

The purpose of this study was to investigate the T‐2 toxin contaminated grain and grain products consumed especially by Turkish population. The T‐2 toxin was detected using the high performance liquid chromatography (HPLC) with UV detector at 208 nm and the identify of T‐2 was further confirmed by thin layer chromatography (TLC). The recovery was 91 ±4.24% for corn flour fortified with the known amount of T‐2 toxin (1 ppm). The detection limits of T‐2 toxin for the HPLC and the TLC were 25 ng and 50 ng, respectively. A total of 30 commercially available grain and grain product samples were analyzed. Two corn flour samples were found to contain detectable levels of T‐2 toxin at a level of 1.60 ppm and 4.08 ppm.     

Performance Enhancement of a Beta Type Rhombic Drive Stirling engine

ABSTRACT

Stirling engines maintain attraction because of their high energy conversion efficiencies. In this study, experimental comparison of a beta-type Stirling engine for two different rhombic-drive mechanisms was presented. In one of the rhombic mechanisms, spur gears were used and the gear shaft was supported in bearings from one side. In the other mechanism, two helical gears were placed on crankshafts and the crankshafts were supported in bearings from both sides. Rhombus lengths of the mechanisms were determined as 66 mm and 80 mm to provide same constant compression ratio of 2.5 for both configurations. Both mechanisms were used in the same beta-type Stirling engine having same cylinder, piston and displacer dimensions. Performance parameters of the engines were evaluated at different helium charge pressures (2–4 bar) and hot-end temperatures (400–600°C). The hot-end of the displacer cylinder was heated by a liquefied petroleum gas (LPG) burner. The engine power increased by 132%, friction losses and gear noses were reduced by supporting the rhombic-drive mechanism from both side and using helical gears. The maximum output torque and power of the engine were obtained as 13.14 Nm at 428 rpm engine speed and 663 W at 800 rpm engine speed, respectively, at 600°C hot-end temperature and 4 bar charge pressure.     

Investigation of the bacterial load and antibiotic susceptibility of dental units

The aim of this study was to evaluate the bacterial contamination level and to determine the antibiotic susceptibility of the isolated bacteria from dental unit waterlines (DUWLs) in Istanbul. Bacterial quality of DUWLs is very important, as patients and dental staff are regularly exposed to water and aerosols generated by the unit. If opportunistic pathogens such as Staphylococcus aureus, Pseudomonas aeruginosa, and Legionella pneumophila are present in DUWLs, patient and dental staff can be infected. One hundred water samples were collected from high-speed drills and input waters from 50 dental units. Aerobic heterotrophic bacteria counts and the presence of Legionella, Pseudomonas, oral streptococci, and Staphylococcus were investigated in dental unit waters and aerosol samples. In addition, the antibiotic susceptibility of the isolated and identified bacteria from DUWLs was examined. This research found that 37 out of 50 dental unit water samples exceeded the American Dental Association’s limit of 200 colony-forming units (CFU)/mL^?1. Legionella, oral streptococci, and S. aureus were not detected in any water or aerosol samples, but P. aeruginosa was isolated in three DUWLs. Also, Pseudomonas and Staphylococcus were found in water and aerosol samples. Cefoperazone, ofloxacin, gentamicin, ciprofloxacin, and piperacillin were the most effective antibiotics against the isolated bacteria from DUWLs.     

Adsorptive removal of Cd(II) and Pb(II) ions from aqueous solutions by using Turkish illitic clay

The ability of Turkish illitic clay (TIC) in removal of Cd(II) and Pb(II) ions from aqueous solutions has been examined in a batch adsorption process with respect to several experimental conditions including initial solution pH, contact time, initial metal ions concentration, temperature, ionic strength, and TIC concentration, etc. The characterization of TIC was performed by using FTIR, XRD and XRF techniques. The maximum uptake of Cd(II) (11.25 mg g⁻¹) and Pb(II) (238.98 mg g⁻¹) was observed when used 1.0 g L⁻¹ of TIC suspension, 50 mg L⁻¹ of initial Cd(II) and 250 mg L⁻¹ of initial Pb(II) concentration at initial pH 4.0 and contact time of 240 min at room temperature. The experimental data were analyzed by the Langmuir, Freundlich, Temkin and Dubinin Radushkevich (D-R) isotherm models. The monolayer adsorption capacity of TIC was found to be 13.09 mg g⁻¹ and 53.76 mg g⁻¹ for Cd(II) and Pb(II) ions, respectively. The kinetics of the adsorption was tested using pseudo-first-order, pseudo-second-order, Elovich and intraparticle diffusion models. The results showed that the adsorption of Cd(II) and Pb(II) ions onto TIC proceeds according to the pseudo-second-order model. Thermodynamic parameters including the Gibbs free energy (ΔG), enthalpy (ΔH), and entropy (ΔS) changes indicated that the present adsorption process was feasible, spontaneous and endothermic in the temperature range of 5–40 °C.     

Microbial contamination of dental unit waterlines in Istanbul, Turkey

The water used in dental unit waterlines (DUWLs) acts as a coolant for the high-speed equipment and as an irrigant during dental treatments. There are kind of water tanks. DUWLs provide a favorable environment for microbial biofilm and multiplation primarily due to the high surface in the tubing and the character of fluid dynamics in narrow, smooth-walled waterlines. Biofilms can harbour opportunist pathogens such as Legionella sp., Pseudomonas sp. Several studies have shown that DUWLs have high levels of microbial contamination. Presence of high level of microbial contamination is an important problem for dentists and dental patients who are immunocompromised. We collected water samples from DUWLs of 20 private dental offices. We have determined that only 2 (3.4%) out of 59 dental unit water samples were found to meet the standard (<200 CFU.ml(-1)) for DUWLs water quality by American Dental Association (ADA). Of the 59 water samples examined, 14 (24%) were positive for Pseudomonas sp. and 18 (30.5%) were positive for fungi. The most common 14 bacterial strains and seven fungi were isolated. Of bacterial strains, 57.1% were identified: Majority of the bacterial species isolated from our samples was identified as Pseudomonas fluorescens, Pasteurella haemolytica, Photobacterium damsela, Ochrobacter anthropi, Moraxella sp., Aspergillus flavus, Penicillium expansum. Legionella sp. were not detected in all water samples.     

Biosorption of Cr(VI) by free and immobilized Pediastrum boryanum biomass: equilibrium, kinetic, and thermodynamic studies

Background and purpose

The biosorption of Cr(VI) from aqueous solution has been studied using free and immobilized Pediastrum boryanum cells in a batch system. The algal cells were immobilized in alginate and alginate?Cgelatin beads via entrapment, and their algal cell free counterparts were used as control systems during biosorption studies of Cr(VI).

Methods

The changes in the functional groups of the biosorbents formulations were confirmed by Fourier transform infrared spectra. The effect of pH, equilibrium time, initial concentration of metal ions, and temperature on the biosorption of Cr(VI) ion was investigated.

Results

The maximum Cr(VI) biosorption capacities were found to be 17.3, 6.73, 14.0, 23.8, and 29.6?mg/g for the free algal cells, and alginate, alginate?Cgelatin, alginate?Ccells, and alginate?Cgelatin?Ccells at pH?2.0, which are corresponding to an initial Cr(VI) concentration of 400?mg/L. The biosorption of Cr(VI) on all the tested biosorbents (P. boryanum cells, alginate, alginate?Cgelatin, and alginate?Ccells, alginate?Cgelatin?Ccells) followed Langmuir adsorption isotherm model.

Conclusion

The thermodynamic studies indicated that the biosorption process was spontaneous and endothermic in nature under studied conditions. For all the tested biosorbents, biosorption kinetic was best described by the pseudo-second-order model.     

Evaluation of microbial contamination and distribution of sulphate-reducing bacteria in dental units

Although bacterial contamination is widely researched in dental unit water systems, we have been unable to find any published reports to date about the presence and distribution of sulphate-reducing bacteria (SRB) in dental unit waterlines (DUWLs). The aim of this study was to evaluate microbial contamination and to determine the presence and distribution of SRB in DUWLs. One hundred twenty-three water samples were collected from the air–water syringes, high-speed drills and water sources from 41 dental units in Istanbul, Turkey. The counts of aerobic heterotrophic bacteria and SRB were investigated in the water samples. In addition, the presence of free-living amoebae (FLA) was examined. In this work, we evaluated microbial contamination and reported for the first time the distribution of SRB in DUWLs. We determined that only ten out of 123 water samples were able to meet the American Dental Association’s limit (≤200 CFU ml^− 1). SRB were observed in 102 out of 123 samples (82.9%). In addition, SRB were detected in all of the air–water syringes and high-speed drills. FLA were established in 103 out of 123 samples (83.7%).