Relationship of fluoride in drinking water with blood pressure and essential hypertension prevalence: a systematic review and meta-analysis.

BACKGROUND AND OBJECTIVE: Previous studies showed controversial results of the relationship between fluoride exposure through drinking water and elevated blood pressure. We conducted a systematic review and meta-analysis to assess the direct relationship of drinking water fluoride exposure with blood pressure and essential hypertension prevalence in general populations. METHODS: We conducted a systematic search in databases including Web of Knowledge, PubMed, Scopus, and Embase by MeSH and non-MeSH terms for relevant studies with any design published until August 2019, with no limitation in time and language. The pooled effect measure was calculated within a 95% confidence interval (CI). RESULTS: Our search retrieved 630 journal articles, six of which were eligible for data extraction. The random-effects model found significantly higher systolic blood pressure (mean difference = 6.49 mmHg; 95% CI 3.73-9.25; p value < 0.01) and diastolic blood pressure (mean difference = 4.33 mmHg; 95% CI 1.39-7.26; p value < 0.01) in groups exposed to high-fluoride drinking water than in groups exposed to normal/low-fluoride drinking water. A significant relationship was also found between high-fluoride drinking water and essential hypertension (odds ratio = 2.14; 95% CI 1.02-4.49; p value = 0.045). CONCLUSION: The risk of elevated blood pressure increases in the general population of fluoride endemic areas. However, more research is needed to make a firm conclusion about the adverse effects of excess fluoride intake on the cardiovascular system at the individual level.

Monitoring of caffeine concentration in infused tea, human urine, domestic wastewater and different water resources in southeast of Iran- caffeine an alternative indicator for contamination of human origin.

The present study was developed to evaluate the caffeine concentration in commercially high-consumed brands of dry black tea, urine of tea consumers, raw and treated wastewater, as well as water resources (WRs) in Zabol city, Iran. Furthermore, a complementary analysis was performed to evaluate the relationship between caffeine content and total coliform (TCF) and Escherichia coli (E. coli) in water sources. In this end, tea (90 samples), urine (90 samples), raw sewage (72 samples), treated sewage (72 samples), and septic tank sewage (36samples) were taken from Zabol city and analyzed in terms of caffeine content. To evaluate the correlation between caffeine and TCF and E. coli, 102 water samples were taken from WRs in Zabol city. Caffeine was measured by high-performance liquid chromatography (HPLC). Furthermore, TFC and E. coli were measured based on the procedure outlined by standard methods for water and wastewater examination and the most probable number (MPN) method. The results indicated that the caffeine concentration in different tea brands consumed by Zabol people were in the range of 12.35-18.75 mg/L. The mean caffeine level in the male group' urine (7.08 ± 1.00 µg/mL) was significantly higher than the female group (4.83 ± 1.94 µg/mL). The results showed that the total average amount of caffeine in raw and treated wastewater in Zabol city was 21.04 ± 2.22 and 19.86 ± 2.08 µg/L, respectively. Besides, the caffeine removal efficiency by the Zabol wastewater treatment plant (ZWTP) was found to be between 4.79 and 51.39%. According to the results, the environmental risk associated with caffeine through the discharge of raw and treated wastewater from ZWTP into receiving WRs was estimated to be less than the allowable limit (RQ = 1). The results showed that caffeine could be an indicator for fecal contamination with human origin.

Process modeling, characterization, optimization, and mechanisms of fluoride adsorption using magnetic agro-based adsorbent.

In this study, fluoride removal from polluted potable water using magnetic carbon-based adsorbents derived from agricultural biomass was thoroughly investigated. An experimental matrix is designed considering the interactive effects of independent process variables (pH, adsorbent dose, contact time, and initial fluoride concentration) on the removal efficiency. Isotherms and kinetics studies, as well as anions interactions, were also investigated to understand the adsorption mechanisms further. The model parameters of isotherms and kinetics are estimated using nonlinear differential evolution optimization (DEO). Approaches like adaptive neuro-fuzzy inference system (ANFIS) and response surface methodology (RSM) are implemented to predict the fluoride removal and identify the optimal process values. The optimum removal efficiency of GAC-Fe3O4 (89.34%) was found to be higher than that of PAC-Fe3O4 (85.14%). Kinetics experiments indicated that they follow the intraparticle diffusion model, and adsorption isotherms indicated that they follow Langmuir and Freundlich models. Both PAC-Fe3O4 and GAC-Fe3O4 adsorbents have shown an adsorption capacity of 1.20 and 2.74 mg/g, respectively. The model predictions from ANFIS have a strong correlation with experimental results and superior to RSM predictions. The shape of the contours depicts the nonlinearity of the interactive effects and the mechanisms in the adsorption process.

Antibiotic resistance and antibiotic-resistance genes of Pseudomonas spp. and Escherichia coli isolated from untreated hospital wastewater.

Hospitals are considered an important factor in the spread of antibiotic-resistant bacteria (ARBs) and antibiotic-resistance genes (ARGs). The purpose of this research was to characterize the microbial populations in hospital wastewater and investigated the prevalence of ß-lactamase, SulІ and QnrS resistance genes. In the first step, culture method was used to isolate Pseudomonas aeruginosa and Escherichia coli. In the next step, accurate identification of isolated bacteria was carried out using the polymerase chain reaction (PCR) method, then the resistance of the bacteria at different concentrations of antibiotics (8-128 µg/mL) was examined. Finally the ARGs were detected using the PCR method. The averages of heterotrophic plate count (HPC) and ARB concentration in wastewater samples were 1.8 × 108 and 4.3 × 106 CFU/100 mL, respectively. The highest resistance rates were found for sulfamethoxazole and the highest resistance rates in the ß-lactamase group were for ceftazidime, while highest sensitivity was for gentamicin and there was no isolate that was sensitive to the studied antibiotics. SulІ and QnrS were the highest and lowest abundance of all ARGs in samples respectively and blaSHV was the highest ß-lactam resistance gene. Our results indicated an increase in the resistance of identified bacteria to several antibiotics. So it can be concluded that numerous antibiotic-resistant pathogens and vast numbers of ARGs exist in the human body so that their release from hospitals without effective treatment can cause many dangers to the environment and human health.

Gamma radiation in the mineral hot springs of Ardabil, Iran: Assessment of Environmental Dose Rate and health risk for swimmers.

The main aim of this study was to evaluate gamma radiation level in the mineral hot springs of Ardabil province in Iran. In addition, the cancer risk of gamma radiation was assessed for swimmers. Natural gamma radiation was measured using Ion Chamber Survey Meter 451B in 22 springs throughout the province. Gamma was measured at 20 cm and 100 cm above the ground level in 15 locations of each spring. Excess lifetime cancer risk was calculated to investigate the risk of exposure to gamma radiation. The highest and lowest annual absorbed dose rate of gamma were found to be 1.17(10-3) and 1.99(10-3) Sv/y at the height of 20 cm above the ground level and 5.26(10-4) and 1.52(10-3) Sv/y at the height of 100 cm above the ground level, respectively. Excess lifetime cancer risk ranged from 4.57(10-4) to 7.76(10-4) at the height of 20 cm and from 2.06(10-4) to 5.94(10-4) at the height of 100 cm which are lower than global average of 1.45(10-3) declared by the United Nations. Although the risk level in this study is lower than the global average, protective and preventive measures should be considered by individuals and authorities in these areas to reduce the effects of gamma radiation on the health of the swimmers.

Prevalence of diarrheal illness and healthcare-seeking behavior by age-group and sex among the population of Gaza strip: a community-based cross-sectional study.

BACKGROUND: In the Gaza strip, diarrhea is one of main reasons for children visiting primary healthcare centers. Hence, we investigate predictors of the diarrheal illness and health care-seeking behavior among different age groups. METHODS: This community-based cross-sectional survey was conducted from August 2017 to June 2018 among 1857 households. A pretested structured questionnaire included information about socio-demographic, sanitation, hygiene, source of water, diarrheal illness, and seeking healthcare in households was administered to head of household. To achieve representativeness for the five Gaza's governorates, a cluster random sampling was applied. RESULTS: Of the 1857 household's heads, 421 (22.7%) reported an episode of diarrhea during the 48 h preceding the interview resulting an overall prevalence rate of 3.8 per 100 individuals. The prevalence of diarrhea was statistical significant greater in males (5.4/100) compared to females (1.3/100) in all age groups (p <  0.05). Socio-demographic, economic, water, sanitation, and hygiene factors were predictors of the diarrheal illness and seeking of non-professional healthcare for diarrhea illness treatment among. A transition behavior from professional to non-professional and vice versa in seeking healthcare in each diarrheal episode was found. CONCLUSIONS: We recommend improving the status of water, sanitation, and hygiene in the Gaza strip's households to reduce diarrhea among the population of Gaza strip. Community sensitization about the importance of seeking care at primary health centers because treatment of children is available for free or in low costs.

Advantages and disadvantages of different pre-cooking and cooking methods in removal of essential and toxic metals from various rice types- human health risk assessment in Tehran households, Iran.

The aim of present study was to evaluate the effects of different pre-cooking and cooking methods on the concentration of toxic (As, Cd and Pb) and essential (Fe, Cu, Co and Zn) metals in widely consumed rice types by Tehran households, Iran. In this regard, a total of 90 samples were obtained from Iranian, Pakistani and Indian rice brands (30 samples from each brand), and were examined in order to determine the concentration of toxic metals including As, Cd, Pb, Fe, Zn, Co and Cu using ICP-OES. Among these rice brands, the most contaminated one was selected in order to evaluate the effects of washing and soaking processes in different time points (1, 5 and 12 h), as well as different cooking methods (Rinsing and Kateh) in reducing the concentration of subjected metals. Nine samples were analyzed for each process, which were 54 samples in total. Our results show that the preparation and cooking methods applied for all rice brands (except for Indian rice) could effectively reduce the non-carcinogenic risk associated with these metals to the acceptable level; however, this is not true about the carcinogenic risk associated with arsenic. Finally, according to our findings it can be concluded that all cooking methods can lead to considerable removal of rice toxic metals (this is partially true about all available rice brands in Iran), however, a large amount of essential metals were also eliminated by these methods. Moreover, after cooking of different rice types in Iran, this food has still carcinogenic risk associated with arsenic.

A systematic literature review for some toxic metals in widely consumed rice types (domestic and imported) in Iran: Human health risk assessment, uncertainty and sensitivity analysis.

In present study we aimed to investigate the literature in the form of systematic review to determinate the concentrations of some toxic metals (arsenic, lead, and cadmium) in widely consumed rice brands in Iran and their related health risks. International and Iranian national databases were searched carefully with appropriate keywords for papers on toxic metal contamination of rice from Agust-2000 to Agust-2018. Initially, 560 articles were found, of which only the 50 papers fit the inclusion criteria and were selected for further analysis. The Monte Carlo Simulation was applied to generate missing data (mean, standard deviation, data distribution and sample size) of toxic metal concentration in some papers. Then, statistical analysis, health risk assessment, and uncertainty and sensitivity analysis were performed. The results indicated that approximately 88% of rice consumed in Iran (including Iranian, Pakistani and Indian rice) do not meet the national standard and WHO/FAO guideline requirements and their related health risks are unacceptable. The risks of arsenic and lead in Indian rice and cadmium in Iranian rice were considerably higher than others. In conclusion, according to our findings, In conclusion, it is necessary to prevent toxic metals contamination of rice by modifying cultivation patterns and, also, prevent low-quality rice brands to be imported.

An innovative swimming pool water quality index (SPWQI) to monitor and evaluate the pools: design and compilation of computational model.

This research aimed to develop an index known as swimming pool water quality index (SPWQI) for quantifying the water pollution potential. The index is a quantitative tool to show the data on the water quality of swimming pools consistently. It makes summarizing the complex data on water quality possible and paves the way for its communication to the general public and decision makers. In this study, the SPWQI has been formulated according to the literature review and Delphi method. According to literature review and the total judgment of the panelist (23 experts specialized in environmental health engineering), 13 physicochemical and biological parameters along with their weights were selected for inclusion in the SPWQI. The results indicated the possibility of calculating a single numerical value (i.e., SPWQI), which indicates the combined effect of significant selected parameters on water quality. In addition, biological composition (47%) had a strong preference weighting than physical and chemical parameters in evaluating the index. Next, it was attempted to implement a novel and user-friendly mathematical model for evaluating the SPWQI. Then, the model accuracy and performance was confirmed by a case study. Overall, it could be said that the assessment of SPWQI sheds light on the concurrent power of several pollutants and can help the authorities to decide upon water quality management and treatment approaches.

Studies on influence of process parameters on simultaneous biodegradation of atrazine and nutrients in aquatic environments by a membrane photobioreactor.

A Lab scale algal-bacterial membrane photobioreactor (MPBR) was designed and operated under 12-h light and 12-h dark conditions with a light intensity of 8000lx, in order to investigate the effects of initial concentrations of atrazine, carbon concentration, and hydraulic retention time on the ability of this photobioreactor in simultaneous removal of atrazine and nutrients in the continuous mode. The removal efficiencies of atrazine (ATZ), chemical oxygen demand (COD), phosphorus (PO43--P) and nitrogen (NOx) in optimum condition was more than 95%, 99%, 98% and 97% when the maximum removal rates were 9.5 × 10-3, 99.231, 11.773 and 7.762mg/L-day, respectively. Results showed that the quality of the effluent was reduced by the increase of atrazine concentration. The outcomes on the hydraulic and toxic shocks indicated that the system has a relatively good resistance to the shocks and can return to the stable conditions. Microalgae showed a great deal of interest and capability in cultivating and attaching to the surface of the membrane and bioreactor, and the total biomass accumulated in the system was greater than 6g/L. The kinetic coefficients of atrazine removal were also studied using various kinetic models. The maximum atrazine removal rate was determined by the modified Stover-Kincannon model. The results approved the ability of the MPBR reactor in wastewater treatment and microalgae cultivation and growth. The decline of atrazine concentration in this system could be attributed to the algal-bacterial symbiosis and co-metabolism process. Accordingly, the MPBR reactor is a practical, simple, economical and therefore suitable process for simultaneous biodegradation of chlorinated organic compounds and nutrients removal from aquatic environments.

Characteristics and health effects of BTEX in a hot spot for urban pollution.

This study reports a spatiotemporal characterization of toluene, benzene, ethylbenzene, and xylenes concentrations (BTEX) in an urban hot spot in Iran, specifically at an bus terminal region in Shiraz. Sampling was carried out according to NIOSH Compendium Method 1501. The inverse distance weighting (IDW) method was applied for spatial mapping. The Monte Carlo simulation technique was applied to evaluate carcinogenic and non-carcinogenic risk owing to BTEX exposure. The highest average BTEX concentrations were observed for benzene in the morning (at 7:00-9:00 A.M. local time) (26.15 ±â€¯17.65 µg/m3) and evening (at 6:00-8:00 P.M. local time) (34.44 ±â€¯15.63 µg/m3). The benzene to toluene ratios in the morning and evening were 2.02 and 3.07, respectively. The main sources of BTEX were gas stations and a municipal solid waste transfer station. The inhalation lifetime cancer risk (LTCR) for benzene in the morning and evening were 1.96 × 10-4 and 2.49 × 10-4, respectively, which exceeds the recommended value by US EPA and WHO. The hazard quotient (HQ) of all these pollutants was less than 1. The results of this work have implications for public health near 'hot spots' such as IKBT where large populations are exposed to carcinogenic emissions.

Evaluation of kenaf fibers as moving bed biofilm carriers in algal membrane photobioreactor.

In this lab-scale study, the feasibility of using kenaf fibers as moving bed biofilm carriers in hybrid microalgal membrane photobioreactors (HMPBR) in organic matter and atrazine elimination from real secondary effluent was evaluated. For evaluating the kinetics of biofilm substrate consumption, an experimental model was proposed. Inoculation of wastewater samples with free carriers resulted in the greater removal of target pollutants. Removal efficiency of atrazine and chemical oxygen demand (COD) increased to 27% and 16%, with respect to the control, respectively. The total biomass accumulation in HMPBR exceeded 5g/L, and the microalgae tended to aggregate and attached to biofilm carriers. The removal efficiency of HMPBR improved significantly via inoculation of kenaf fiber carriers with bioremediation microalgal strains (p < 0.01). A lower stabilization ratio (VSS/TSS) was also recorded. The biomass in HMPBR included more lipids and carbohydrates. The results revealed that kenaf fibers could improve and upgrade the biological activity of different wastewater treatment applications, considering the great potential of biofilm carriers and their effluent quality.

Biodegradation of atrazine from wastewater using moving bed biofilm reactor under nitrate-reducing conditions: A kinetic study.

In this study employed an anoxic moving bed biofilm reactor (AnMBBR) to evaluate the effects of hydraulic and toxic shocks on performance reactor. The results indicated a relatively good resistance of system against exercised shocks and its ability to return to steady-state conditions. In optimal conditions when there was the maximum rate of atrazine and soluble chemical oxygen demand (COD) removal were 74.82% and 99.29% respectively. Also, atrazine biodegradation rapidly declines in AnMBBR from 74% ±â€¯0.05 in the presence of nitrate to 9.12% only 3 days after the nitrate was eliding from the influent. Coefficients kinetics was studied and the maximum atrazine removal rate was determined by modified Stover & Kincannon model (Umax = 9.87 gATZ/m3d). Results showed that AnMBBR is feasible, easy, affordable, so suitable process for efficiently biodegrading toxic chlorinated organic compounds such as atrazine. Also, its removal mechanism in this system is co-metabolism.

Simultaneous removal of atrazine and organic matter from wastewater using anaerobic moving bed biofilm reactor: A performance analysis.

In this study, an anaerobic moving bed biofilm reactor (AMBBR) was designed to biodegrade atrazine under mesophilic (32 °C) condition and then it was evaluated for approximately 1 year. After biofilm formation, acclimation, and enrichment of microbial population within the bioreactor, the effect of various operation conditions such as changes in the concentration of influent atrazine and sucrose, hydraulic retention time (HRT), and salinity on the removal of atrazine and chemical oxygen demand (COD) were studied. In optimum conditions, the maximum removal efficiency of atrazine and COD was 60.5% and 97.4%, respectively. Various models were developed to predict the performance of atrazine removal as a function of HRT during continuous digestion. Also, coefficients kinetics was studied and the maximum atrazine removal rate was determined by Stover - Kincannon model (rmax = 0.223 kgATZ/m3d). Increasing salinity up to 20 g/L NaCl in influent flow could inhibit atrazine biodegradation process strongly in the AMBBR reactor; whereas, the reactor could tolerate the concentrations less than 20 g/L easily. Results showed that AMBBR is feasible, easy, affordable, so suitable process for efficiently biodegrading toxic chlorinated organic compounds such as atrazine. There was no accumulation of atrazine in the biofilm and the loss of atrazine in the control reactor was negligible; this shows that atrazine removal mechanism in this system was due to co-metabolism.

Simultaneous removal of cationic methylene blue and anionic reactive red 198 dyes using magnetic activated carbon nanoparticles: equilibrium, and kinetics analysis.

For the simultaneous adsorption of cationic dye (methylene blue, MB) and anionic dye (reactive red 198, RR198) from aqueous solution, magnetic activated carbon (MAC) nanocomposite as a promising adsorbent was prepared and used. The concentration of MB at different time intervals was determined using a UV-Vis spectrophotometer while the concentration of RR198 was determined using a high performance liquid chromatography (HPLC) system. The effect of solution pH, contact time, adsorbent amount, and dye concentration were investigated. Also, both kinetic and isotherm experiments were studied. The optimum pH was 10 and 5.5 for adsorption of MB and RR198, respectively, and the equilibrium status was achieved after 120 min. The adsorption kinetics was controlled by the pseudo-second order kinetic model more than pseudo-first order. The best-fitted isotherms were Freundlich and Langmuir models for MB and RR198, respectively. The higher values of Freundlich adsorption capacity (Kf) for MB in comparison with RR198 refer to MAC affinity to remove cationic dyes more than anionic dyes. Apparently, there was no substantial change in the adsorption efficiency among the 10 adsorption-desorption cycles. Overall, MAC can be considered as an effective and efficient viable adsorbent for cationic and anionic dyes removal from industrial wastewaters.

Optimization of the synthesis and operational parameters for NOM removal with response surface methodology during nano-composite membrane filtration.

The aim of this study was to investigate membrane synthesis by interfacial polymerization methods, the application of synthesized nano-composite membrane for natural organic matters (NOMs) removal from water, evaluation of fouling mechanism and antifouling properties. Polysulfone (PSf) was selected as a porous ultrafiltration membrane support and interfacial polymerization was done using tannic acid (TA) and Trimesoyl chloride (TMC) with central composite design (CCD). The effects of TA and TMC monomer concentrations, reaction time and post treatment temperature was evaluated. The synthesized membrane was characterized by field emission scanning electron microscope (FESEM), atomic force microscopy (AFM), attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR) and water contact angle. Based on the results, the optimum conditions for synthesizing nano-composite were: TA concentration of 0.27 g/L, TMC concentration of 0.22 g/L, reaction time of 68.29 min and temperature of 25.23 °C. The predicted optimum operational conditions were a NOM concentration of 6.429 mg/L; time of 10.931 min and applied pressure of 1.039 bar. The potential applications of the synthesized nano-composite membranes with interfacial polymerization can enhance water treatment.

A new recycling technique for the waste tires reuse.

In this series of laboratory experiments, the feasibility of using fixed bed biofilm carriers (FBBC) manufactured from existing reclaimed waste tires (RWTs) for wastewater treatment was evaluated. To assess polyamide yarn waste tires as a media, the fixed bed sequence batch reactor (FBSBR) was evaluated under different organic loading rate (OLRs). An experimental model was used to study the kinetics of substrate consumption in biofilm. Removal efficiency of soluble chemical oxygen demand (SCOD) ranged by 76-98% for the FBSBR compared to 71-96% in a sequencing batch reactor (SBR). Removal efficiency of FBBC was significantly increased by inoculating these RWTs carriers. The results revealed that the sludge production yield (Yobs) was significantly less in the FBSBR compared to the SBR (p < 0.01). It also produced less sludge and recorded a lower stabilization ratio (VSS/TSS). The findings show that the Stover-Kincannon model was the best fit (R2 > 99%) in a FBSBR. Results from this study suggest that RWTs to support biological activity for a variety of wastewater treatment applications as a biofilm carrier have high potential that better performance as COD and TSS removal and sludge settling properties and effluent quality supported these findings.

Application of novel Modified Biological Aerated Filter (MBAF) as a promising post-treatment for water reuse: Modification in configuration and backwashing process.

Biological Aerated Filter (BAF) reactors due to their plentiful biomass, high shockability, high efficiency, good filtration, availability and lack of need for large land areas, are enjoying from great importance in advanced wastewater treatment. Therefore, in this study, Polystyrene Coated by Sand (PCS) was produced as a novel media and its application in a modified down-flow BAF structure for advanced wastewater treatment was assessed in two steps. In step one, the backwash effluent did not return to the system, while in step two backwash effluent returned to increase the water reuse efficiency. The backwash process was also studied through three methods of Top Backwashing (TB), Bottom Backwashing (BB), as well as Top and Bottom Backwashing Simultaneously (TBBS). The results showed that return of backwash effluent had no significant effect on the BAF effluent quality. In the second step similar to the first one with slight differences, the residual average concentrations of TSS, BOD5, and COD at the effluent were about 2.5, 8.2, and 25.5 mg/L, respectively. Additionally, in step two, the mean volume of disposal sludge/volume of treated water (vds/vtw) decreased a large extent to about 0.088%. In other words, the water reuse has increased to more than 99.91%. The backwash time in methods of TB and BB were 65 and 35 min, respectively; however, it decreased in TBBS methods to 25 min. The concentrations of most effluent parameters in this system are in concordance with the 2012 EPA Agriculture Standards, even for irrigation of Non-processed agricultural crops and livestock water consumption.

Hybrid coagulation-UF processes for spent filter backwash water treatment: a comparison studies for PAFCl and FeCl3 as a pre-treatment.

In this study, the reclamation of clean water from spent filter backwash water (SFBW) was investigated through pilot-scale experiments. The pilot plant consisted of pre-sedimentation, coagulation, flocculation, clarification, and ultrafiltration (UF). Two coagulants of PAFCl and FeCl3 were investigated with respect to their performance on treated SFBW quality and UF membrane fouling. At the optimum dose of PAFCl and FeCl3 turbidity removal of 99.6 and 99.4% was attained, respectively. PAFCl resulted in an optimum UV254, TOC, and DOC removal of 80, 83.6, and 72.7%, respectively, and FeCl3 caused the removal of those parameters by 76.7, 80.9, and 65.9%, respectively. PAFCl removed hydrophilic and transphilic constituent better than FeCl3, but FeCl3 had, to some extent, higher affinities to a hydrophobic fraction. It was concluded that PAFCl showed a better coagulation performance in most cases and caused a lower membrane fouling rate compared to FeCl3. Finally, the treated SFBW with both coagulant-UF systems met the drinking water standards.

Evaluation of volcanic pumice stone as media in fixed bed sequence batch reactor for atrazine removal from aquatic environments.

Atrazine (2-chloro-4-ethylamino-6-isopropylamino-1,3,5-triazine) is a component of S-triazine. Its characteristics make it a pollutant of ecosystems and a probable human carcinogen. The present study evaluated volcanic pumice stone as a suitable media for biological growth and biofilm development in a fixed-bed sequencing batch reactor (FBSBR) for atrazine removal from aquatic environments. The FBSBR was fed with synthetic wastewater containing sucrose and atrazine at four hydraulic retention times to assess biodegradation of atrazine by a microbial consortium for removal from aquatic environments. The maximum efficiency for atrazine and soluble chemical oxygen demand removal were 97.9% and 98.9%, respectively. The results of this research showed that the Stover-Kincannon model was a very good fit (R2 > 99%) for loading atrazine onto the FBSBR. Increasing the initial concentration of atrazine increased the removal efficiency. There was no significant inhibition of the mixed aerobic microbial consortia by the atrazine. Atrazine degradation depended on its initial concentration in the wastewater and the amount of atrazine in the influent. Although this system shows good potential for atrazine removal from aqueous environments, that remaining in the effluent does not yet meet international standards. Further research is required to make this system effective for removal of atrazine from the environment.