Applications of natural organic matter optical properties for assessing drinking water disinfection and distribution

The task of providing safe drinking water requires proper monitoring of water quality and treatment performance from source to tap. Accordingly, the demand for online monitoring is increasing both at treatment plants a nd within distribution networks. Some of the available techniques use correlations between the optical properties of dissolved organic matter (DOM), mainly absorbance, and other water quality parameters. Fluorescence spectroscopy is significantly more sensitive than absorbance spectroscopy and gives comprehensive information about the composition and concentration of organic matter, so it has a strong potential for online monitoring applications. In this thesis, the application of fluorescence spectroscopy was investigated for two locations in the drinking water treatment system: the ultraviolet (UV) disinfection chambers and the distribution network. With respect to UV254disinfection, fluorescence spectroscopy was investigated as a proxy of potential unwanted by-products (assimilable organic carbon (AOC) and disinfection by products (DBPs), in addition to the administered UV dose. The UV254 irradiation increased assimilable organic carbon (AOC) concentration, with the estimated AOC production induced by UV254irradiation at a dose of 40 mJ cm-2being 0.4 % of the dissolved organic carbon. The concentration of adsorbable organic chlorine (AOCl), a subset of adsorbable organic halogens (AOX), generally increased following UV254 irradiation at the typical disinfection dose. Weak but statistically-significant correlations were found between the UV-induced fluorescence reduction and increases in both AOC and AOCl concentrations. Compared to absorbance, greater reductions were observed in fluorescence intensity following sequential UV irradiation and chlorination and these correlated more strongly with AOCl production. Following UV254disinfection, a linear relationship was observed between UV254dose and changes in long-wavelength fluorescence (> 400 nm) intensities at doses up to 200 mJ cm-2. However, the application of fluorescence as a proxy of the UV254dose is limited due to the relatively small and unpredictable direction of change of fluorescence intensity. In the distribution network, the sensitivity of fluorescence to detect contamination caused by entrainment was compared to the sensitivity of other common water quality parameters including several trace elements and microbial indicator species abundances. Of these, fluorescence was the most sensitive tracer for distinguishing contamination from natural variation, followed by absorbance. The relationship between fluorescence and microbial regrowth was also examined; however, no correlation was observed. The results of this thesis imply that although fluorescence might not always correlate with the chemical and microbial water parameters, its prompt response to treatment-induced modifications and fluctuations, together with high analytical precision and sensitivity of fluorescence measurements, make it a useful parameter for real-time monitoring of water quality changes in drinking water treatment plants and distribution systems

A frequency and molecular typing study of methicillin-resistant staphylococcus aureus isolates in teaching hospitals in Shahrekord, southwestern Iran

Methicillin-resistant Staphylococcus aureus (MRSA) remains a significant public health problem and treatment challenge. Objectives: This study was conducted to determine the frequency, molecular types, and drug resistance of S. aureus isolated from nasal carriers in two teaching hospitals (Hajar and Kashani) in Shahrekord, southwestern Iran. Methods: In this cross-sectional study, 262 nasal specimens were obtained from healthcare staff. The disk-diffusion method was used to detect MRSA. Nine antibiotic disks were used to determine the antibiotic susceptibility pattern. Staphylococcal cassette chromosome mec (SCCmec) types were identified by the multiplex polymerase chain reaction (PCR). The data analysis was performed using Fisher’s exact test with SPSS software. Results: Forty-eight (18.8%) specimens were identified as S. aureus, of which 30 (11.45%) specimens were methicillin resistant. The nasal colonization rate of the MRSA isolates was not associated with age or gender (P > 0.05). The highest resistance (33%) recorded was to rifampin, and all the isolates were susceptible to quinupristin-dalfopristin, vancomycin, and linezolid. The SCCmec results showed that 16.7%, 6.7%, 20%, and 56.6% of MRSA isolates were types I, II, III, and IV, respectively. Conclusions: Nasal isolates of MRSA were prevalent among hospital staff. The highest level of resistance was to rifampin, and all the isolates were susceptible to quinupristin-dalfopristin, vancomycin, and linezolid. SCCmec type 4 was the most frequent MRSA isolate. © 2016, Ahvaz Jundishapur University of Medical Sciences

Molecular investigation of methicillin-resistant Staphylococcus epidermidis and Staphylococcus saprophyticus isolated in Shahrekord training hospitals

زمینه و هدف: استافیلوکوکوس های کوآگولاز منفی یکی از مهم ترین عوامل عفونت های بیمارستانی هستند. مقاومت به متی- سیلین در این گروه از باکتری ها مشاهده شده است. این مطالعه با هدف بررسی و مقایسه مقاومت به متی سیلین به دو روش فنوتیپی و ژنوتیپی در باکتری های استافیلوکوکوس اپیدرمیدیس و استافیلوکوکوس ساپروفیتیکوس جدا شده از نمونه های بیمارستان های آموزشی شهرکرد طراحی و اجرا گردید. روش بررسی: در این مطالعه توصیفی- تحلیلی تعداد 2900 نمونه مختلف شامل خون، ادرار و غیره از بیماران بستری در بیمارستان‌ های هاجر (س) و آیت الله کاشانی شهرکرد از آذر ماه سال 1391 تا مهر ماه سال 1392 جمع آوری شد؛ سپس با انجام آزمایشات میکروبیولوژی، تعداد 150 ایزوله استافیلوکوکوس های کوآگولاز منفی انتخاب شد. در مرحله بعد به طور همزمان مقاومت فنوتیپی به روش انتشار از دیسک (Disk diffusion) و مقاومت ژنوتیپی (ژن مقاومت به متی سیلین) با روش واکنش زنجیره ای پلیمراز بررسی گردید. یافته ها: از بین 150 ایزوله مورد بررسی، در بررسی فنوتیپی 70 ایزوله (66/46 درصد با فاصله اطمینان 95 درصد برابر با 98/54-49/38 درصد) و در بررسی ژنوتیپی 64 ایزوله (66/42 درصد با فاصله اطمینان 95 درصد برابر با 51-63/34 درصد) به متی سیلین مقاوم بودند. توزیع مقاومت فنوتیپی و مقاومت ژنوتیپی در دو بیمارستان مورد مطالعه برابر بود. نتیجه گیری: نتایج ژنوتیپی نشانگر حضور ژن مقاومت به متی سیلین می‌باشد. بررسی ژنوتیپی به کمک واکنش زنجیره پلیمراز مرکب، ابزاری مطمئن برای نشان دادن میزان مقاومت به متی سیلین در استافیلوکوکوس های اپیدرمیدیس و ساپروفیتیکوس می باشد

New applications of fluorescence spectroscopy for monitoring drinking water disinfection and distribution

The task of providing safe drinking water requires proper monitoring of water quality and treatment performance from source to tap. Accordingly, the demand for online monitoring is increasing both at treatment plants and within distribution networks. Some of the available techniques use correlations between the optical properties of dissolved organic matter (DOM), mainly absorbance, and other water quality parameters. Fluorescence spectroscopy is significantly more sensitive than absorbance and gives comprehensive information about the composition and concentration of organic matter, so has a strong potential for online monitoring applications. In this thesis, the application of fluorescence spectroscopy was investigated at two locations in the drinking water treatment system: the distribution network and the ultraviolet (UV) disinfection chambers. In the distribution network, the sensitivity of fluorescence to detect contamination caused by entrainment was compared to the sensitivity of other common water quality parameters including several trace elements and microbial indicator species abundances. Of these, fluorescence was the most sensitive tracer for distinguishing contamination from natural variation, followed by absorbance. The relationship between fluorescence and microbial regrowth was also examined, however, no correlation was observed. Following UV disinfection, the application of fluorescence as a proxy of the UV dose was examined. Fluorescence was sensitive enough to detect changes in the fluorescent fraction of organic matter due to UV irradiation at disinfection doses. A linear relationship was observed between UV dose and changes in humic-like fluorescence intestines at doses up to 350 mJ/cm2

a review of airq models and their applications for forecasting the air pollution health outcomes

Even though clean air is considered as a basic requirement for the maintenance of human health, air pollution continues to pose a significant health threat in developed and developing countries alike. Monitoring and modeling of classic and emerging pollutants is vital to our knowledge of health outcomes in exposed subjects and to our ability to predict them. The ability to anticipate and manage changes in atmospheric pollutant concentrations relies on an accurate representation of the chemical state of the atmosphere. The task of providing the best possible analysis of air pollution thus requires efficient computational tools enabling efficient integration of observational data into models. A number of air quality models have been developed and play an important role in air quality management. Even though a large number of air quality models have been discussed or applied, their heterogeneity makes it difficult to select one approach above the others. This paper provides a brief review on air quality models with respect to several aspects such as prediction of health effects

Detection of antiseptic resistance genes among Staphylococcus aureus colonising nurses and coagulase-negative staphylococci isolated from clinical specimens at teaching hospitals in southwest of Iran

Background: The wide application of antibiotics and antiseptics for patient therapy and medical equipment and surfaces disinfection has resulted in the emergence of resistant microorganisms. Staphylococcus aureus and coagulase-negative Staphylococci (CoNS) are found as a part of the normal resident flora in human so that up to two-thirds of the healthy populations are permanently or transiently colonized by S. aureus and CoNS. Chlorhexidine is an antiseptic agent particularly effective against Gram-positive bacteria. It is widely used for hygienic hand wash to prevent transmission of Staphylococci nosocomial infections. The plasmid-borne qacA/B, qacC, and smr genes confer resistance to cationic antiseptic agents in S. aureus and CoNS. Objectives: The objective of the current study was to characterize the antibiotic resistance and susceptibility to quaternary ammonium compounds (QACs) in methicillin-sensitive S. aureus (MSSA), methicillin-resistant S. aureus (MRSA), methicillin-sensitive coagulase-negative staphylococci (MSCoNS), and methicillin-resistant coagulase-negative Staphylococci (MRCoNS). Methods: In this study, the antibiotic susceptibility and resistance to Chlorhexidine in 120 Staphylococcal strains were evaluated by disc diffusion and Minimum inhibitory concentration (MIC) of Chlorhexidine gluconate (CHG) methods, respectively. The MICs of CHG were determined in triplicate by broth micro-dilution, and the presence of mecA, qacA/B, qacC, and smr genes was examined by PCR assay. Results: Of total 60 S. aureus isolates, 51 (85%) were MRSA, and of 60 CoNS, 7 (11.66%) were MRCoNS. The results showed that the MIC of Chlorhexidine for all 120 isolates was 1-16 _g/mL. 15 (12.5%) isolates carried qacA/B gene, 26 (21.7%) carried qacC gene, and 38 (31.7%) carried smr gene. Conclusions: Maintenance of MRSA isolates in the attendance of low amounts of antiseptics could result in the decreased susceptibility to antiseptics

Water quality changes during the first meter of managed aquifer recharge

The capacity of an artificial recharge field to alter organic matter and the bacterial flora of surface water was assessed by following changes in bacterial communities and composition of natural organic matter (NOM) over the first meter of infiltration depth. The sampling strategy applied in this study ensured that water samples consisted only of infiltrated water, excluding natural groundwater. Water was sampled at 50 and 100 cm below the surface of an infiltration basin divided into two halves; one side was dried and frozen and one was infiltrating water during the winter period prior to the sampling period. Bacterial cell counts, proportions of intact cells and community fingerprints were determined by flow cytometry, and NOM was characterized using total organic carbon (TOC), UV254 nm-absorbance (UVA) and fluorescence spectroscopy. Around 40% of the NOM was removed after only 50 cm. Protein-like components were reduced to a larger extent (45-50%) than the humic-like components (25%), suggesting removal of mostly biodegradable fractions of NOM. After only 50 cm of infiltration, about 99% total cell count (TCC) was removed. The flow cytometric data revealed that the bacterial communities collected after infiltration from the basin area that had been dried and frozen were more similar to those in the raw water. This suggests that drying and freezing the basin negatively impacted its treatment capacity. The results from this study highlight the importance of a well-developed biofilm and unsaturated zone for artificial recharge

Assessment of drinking water quality at the tap using fluorescence spectroscopy

Treated drinking water may become contaminated while travelling in the distribution system on the way to consumers. Elevated dissolved organic matter (DOM) at the tap relative to the water leaving the treatment plant is a potential indicator of contamination, and can be measured sensitively, inexpensively and potentially on-line via fluorescence and absorbance spectroscopy. Detecting elevated DOM requires potential contamination events to be distinguished from natural fluctuations in the system, but how much natural variation to expect in a stable distribution system is unknown. In this study, relationships between DOM optical properties, microbial indicator organisms and trace elements were investigated for households connected to a biologically-stable drinking water distribution system. Across the network, humic-like fluorescence intensities showed limited variation (RSD = 3.5-4.4%), with half of measured variation explained by interactions with copper. After accounting for quenching by copper, fluorescence provided a very stable background signal (RSD

Mutation screening of exons 7 and 13 of the TMC1 gene in autosomal recessive non-syndromic hearing loss (ARNSHL) in Iran

Mutation screening of exons 7 and 13 of th