RESUMO
Background: Human exposure to antibiotic resistant bacteria [ARB] is a public health concern which could occur in a number of ways. Wastewaters seem to play an important role in the dissemination of bacteria and antibiotic resistant genes [ARGs] in our environment. The aim of this study was to evaluate the occurrence of three groups of ARB and their resistance genes in hospital and municipal wastewaters [MWs] as possible sources
Methods: A total of 66 samples were collected from raw MWs and hospital wastewaters [HWs] and final effluents of related wastewater treatment plants [WWTPs]. Samples were analyzed for the detection of three groups of ARB including gentamicin [GM], chloramphenicol [CHL] and ceftazidime resistant bacteria and their ARGs [aac [3]-1, cmlA1 and ctx-m-32, respectively]
Results: The mean concentration of GM, CHL and ceftazidime resistant bacteria in raw wastewater samples was 1.24 × 10[7], 3.29 × 10[7] and 5.54 × 10[7] colony forming unit/100 ml, respectively. There is a variation in prevalence of different groups of ARB in MWs and HWs. All WWTPs decreased the concentration of ARB. However, high concentration of ARB was found in the final effluent of WWTPs. Similar to ARB, different groups of ARGs were found frequently in both MWs and HWs. All genes also detected with a relative high frequency in effluent samples of MWs WWTPs
Conclusions: Discharge of final effluent from conventional WWTPs is a potential route for dissemination of ARB and ARGs into the natural environment and poses a hazard to environmental and public health
RESUMO
Drinking water quality can be deteriorated by microbial and toxic chemicals during transport, storage and handling before using by the consumer. This study was conducted to evaluate the microbial and physicochemical quality of drinking water from bottled water coolers. A total of 64 water samples, over a 5-month period in 2012-2013, were collected from free standing bottled water coolers and water taps in Isfahan. Water samples were analyzed for heterotrophic plate count [HPC], temperature, pH, residual chlorine, turbidity, electrical conductivity [EC] and total organic carbon [TOC]. Identification of predominant bacteria was also performed by sequence analysis of 16S rDNA. The mean HPC of water coolers was determined at 38864 CFU/ml which exceeded the acceptable level for drinking water in 62% of analyzed samples. The HPC from the water coolers was also found to be significantly [P < 0.05] higher than that of the tap waters. The statistical analysis showed no significant difference between the values of pH, EC, turbidity and TOC in water coolers and tap waters. According to sequence analysis eleven species of bacteria were identified. A high HPC is indicative of microbial water quality deterioration in water coolers. The presence of some opportunistic pathogens in water coolers, furthermore, is a concern from a public health point of view. The results highlight the importance of a periodic disinfection procedure and monitoring system for water coolers in order to keep the level of microbial contamination under control
RESUMO
Partial nitrification was reported to be technically feasible and economically favorable, especially for wastewater with high ammonium concentration or low C/N ratio. In this study, the effect of dissolved oxygen [DO] and influent ratio of chemical oxygen demand to nitrogen [COD/N] ratio on biological nitrogen removal from synthetic wastewater was investigated. Experiments were conducted in moving bed biofilm reactors [MBBRs] on partial nitrification process in pilot-plant configuration for 300 days. DO levels were changed from 0.04 to 0.12 and 0.42 to 3.4 mg/l in the anoxic [R1] and aerobic [R2] reactors, respectively. The optimum DO for partial nitrification was between 1-1.5 mg/l in the aerobic reactor [R2]. Influent COD/N ratios between 20 and 2 g COD/g-N were tested by changing the nitrogen loading rate [NLR] supplied to the pilot plant. During operational conditions when the DO concentration in aerobic reactor was above 1 mg/l, near complete organic carbon removal occurred in the total MBBRs system. The effluent total nitrogen concentration in the operational conditions [1.7-2.1 mg O2/l and NH+4-N=35.7 mg N/l] was obtained in the range of 0.85-2 mg/l. The highest nitrite accumulation [50%-52%] took place at the DO concentration of 1-1.5 mg/l and increased with decreasing COD/N ratio in aerobic reactor [R2]. This study showed that the average nitrification rate at various COD/N ratios is about 0.96 gN/m[2] per day while the maximum nitrification rate is about 2 gN/m[2] per day at COD/N ratios lower than 6. The experimental COD/N ratio for denitrification was close to complete sum of NO2- and NO3- [NOx] removal efficiency [about 99%] at COD/N ratio equal 14 in the operational conditions in the anoxic reactor [R1]
RESUMO
In this research, an experimental study to evaluate nutrient removal from synthetic wastewater by a lab-scale moving bed biofilm process was investigated. Also, kinetic analysis of the process with regard to phosphorus and nitrogen removal was studied with different mathematical models. For nutrient removal, the moving bed biofilm process was applied in series with anaerobic, anoxic and aerobic units in four separate reactors that were operated continuously at different loading rates of phosphorus and nitrogen and different hydraulic retention times. Under optimum conditions, almost complete nitrification with an average ammonium removal efficiency of 99.72% occurred in the aerobic reactor. In the aerobic reactor, the average specific nitrification rate was 1.92 g NOx-N [NOx-N=NO2-N +NO3-N] produced/kg volatile suspended solids. hour [VSS.h]. Denitrification rate increased with increasing NOx-N loading in the second anoxic reactor. The aerobic phosphate removal rate showed good correlation with the anaerobic phosphate release rate. Under optimum conditions, the average total nitrogen and phosphorus removal efficiencies were 80.9% and 95.8%, respectively. As a result of the moving bed biofilm process [MBBR] kinetic analysis, the Stover-Kincannon model was chosen for modeling studies and experimental data analysis. The Stover-Kincannon model gave high correlation coefficients for phosphorus and nitrogen removal, which were 0.9862 and 0.986, respectively. Therefore, this model could be used in predicting the behavior or design of the moving bed biofilm process
Assuntos
Insetos , Fósforo , Nitrogênio , Esgotos , Biofilmes , Modelos TeóricosRESUMO
In recent years, chitosan and Moringa oleifera Coagulant Protein a natural coagulant were used in order to reduce the problems occure from chemical coagulants. This investigation was done to determine effectiveness of Moringa Oleifera Coagulant Protein and Chitosan as natural coagulant aids in removal of colloidal particles and bacteria from turbid waters. In this interventional- quasi experimental study, the experiments were run by using synthetic water having low [10-20NTU], medium [100-120NTU] and high [200-220NTU] initial turbidities. In order to determine optimum pH and dosage of coagulant and coagulant aids, a conventional jar test apparatus was employed. Turbidity reading were carried out using a Hach model 2100P Turbidimeter. The samples were taken from the top four inch of the suspension for turbidity and bacteria removal measurement. Optimum dose of alum for waters with three different initial turbidities were 20, 40, and 20 mg/1, respectively. Optimum pH was between 7-7.5. Moringa oleifera Coagulant Protein and chitosan were reduced the required dosage of alum from 12.5% to 62.5% and from 50% to 87.5%, respectively, in different turbidities and residual aluminum was reduced to standard limit [0.2mg/l]. The bacteria removal efficiency were from 90% to 99.9999%. It was found when samples were stored during 24 hours; regrowth of E.coli was not observed. This study showed that natural coagulant aids can reduce the turbidity to below 5NTU without filtration in optimum condition