The tail of two models: Impact of circularity and biomass non-homogeneity on UV disinfection of wastewater flocs.

The effects of floc structural characteristics, i.e. shape and dense biomass distribution, were evaluated on ultraviolet (UV) disinfection resistance, represented by the tailing level of the UV dose response curve (DRC). Ellipsoid-shaped flocs of similar volume and different projected circularities were constructed in-silico and a mathematical model was developed to compare their UV DRC tailing levels (indicative of UV-resistance). It was found that floc shape can significantly influence tailing level, and rounder flocs (i.e. flocs with higher circularity) were more UV-resistant. This result was confirmed experimentally by obtaining UV DRCs of two 75-90 µm floc populations with different percentages (20% vs. 30%) of flocs with circularities higher than 0.5. The population enriched in less circular flocs (i.e. 20% flocs with circularities >0.5) had a lower tailing level (at least by 1-log) compared to the other population. The second model was developed to describe variations in UV disinfection kinetics observed in flocs with transverse vs. radial biomass non-homogeneity, indicative of biofilm-originated vs. suspended flocs. The varied-density hemispheres model and shell-core model were developed to simulate transverse and radial non-homogeneity, respectively. The UV DRCs were mathematically constructed and biofilm-originated flocs showed higher UV resistance compared to suspended flocs. The calculated UV DRCs agreed well with the experimental data collected from activated sludge and trickling filter flocs (no fitting parameters were used). These findings provide useful information in terms of designing/modifying upstream processes for reducing UV disinfection energy demand.

Comparative study of chemical and physical methods for distinguishing between passive and metabolically active mechanisms of water contaminant removal by biofilms.

In this study, physical and chemical approaches were employed to distinguish between passive and active mechanisms in biofilms removing contaminants in waste waters and their relative merits were assessed. Respiration, post-exposure recovery and scanning electron microscopic analysis demonstrated that both ultraviolet (UV) treatment (300 mJ/cm(2)) and sodium azide (10 mM) completely inhibited metabolic activity at 5 and 24 h exposure, respectively, whilst not damaging the integrity of the biofilms. Amongst the commonly used chemical inhibitors, only sodium azide showed complete inhibition after 24 h incubation with only about 10% (±4%) of biofilm carbon released into the bulk solution, compared to 33-41% (±8%) when exposed to 5 mM and 10 mM 2,4-dinitrophenol (DNP) and 69-80% (±5%) when exposed to 2% and 5% w/v formalin, respectively. Biofilm inhibition with UV and sodium azide was found to be equally effective at inhibiting biofilms for treatment of triethanolamine (TEA) and benzotriazole (BTA): the results confirming that the dominant removal mechanism was biodegradation. However, the rates of glucose removal by sodium azide-inhibited biofilms were similar to controls, suggesting that chemical inhibitors were not effective for distinguishing the removal mechanisms of simple sugars. Statistically similar amounts of metal were removed by biofilms treated with UV and sodium azide in zinc, copper and cadmium single-systems: the results indicated that the removal mechanism is predominantly a passive biosorption process.

Prevalence of chronic pulmonary aspergillosis in patients with tuberculosis from Iran.

In patients with preexisting lung disease, especially a cavity, Aspergillus can infect the surface of the cavity, causing chronic cavitary pulmonary aspergillosis (CCPA), and may form an aspergilloma, collectively called chronic pulmonary aspergillosis (CPA). In the present study, we assessed tuberculosis (TB) patients for CPA based on culture and serological methods. During a period of 1 year (from March 2013 to March 2014), we studied 124 patients with TB (94 with current TB and 30 with previous TB) at Masih Daneshvari Hospital in Tehran, Iran. Sputum specimens were analyzed by direct microscopic examination (DME) and fungal culture. The clinical and radiological features of all patients were recorded, to categorize the patients into CCPA and aspergilloma. All patients were screened for serum-specific IgG against A. fumigatus, by enzyme-linked immunosorbent assay (ELISA). Out of 124 patients with TB (66 male, age range: 10-91 years), 48 patients (38.7 %) exhibited residual cavities. Eighteen (14.5 %) patients had cavities with pleural thickening. A round-shaped mass lesion was detected in six patients (6.8 %). DME was positive in ten patients for septate fungal hyphae. A. fumigatus was grown from 14 samples. Fifty-five (44.3 %) cases were positive for serum-specific IgG against A. fumigatus. Of 124 patients with TB, 3 (2.4 %) met criteria for aspergilloma and 14 (11.3 %) for CCPA. CPA is a common clinical presentation in individuals with healed TB in Iran, as reported by previous studies from other countries.

Enhancing disinfection by advanced oxidation under UV irradiation in polyphosphate-containing wastewater flocs.

In this paper, the role of naturally occurring polyphosphate in enhancing the ultraviolet disinfection of wastewater flocs is examined. It was found that polyphosphate, which accumulates naturally within the wastewater flocs in the enhanced biological phosphorus removal process, is capable of producing hydroxyl radicals under UV irradiation and hence causing the photoreactive disinfection of microorganisms embedded within flocs. This phenomenon is likely responsible for the improved UV disinfection of the biological nutrient removal (BNR) effluent compared to that of conventional activated sludge effluent by as much as 1 log. A mathematical model is developed that combines the chemical disinfection by hydroxyl radical formation within flocs, together with the direct inactivation of microorganisms by UV irradiation. The proposed model is able to quantitatively explain the observed improvement in the UV disinfection of the BNR effluents. This study shows that the chemical composition of wastewater flocs could have a significant positive impact on their UV disinfection by inducing the production of oxidative species.

UV disinfection of wastewater flocs: the effect of secondary treatment conditions.

Activated sludge flocs that are carried to the final effluent can significantly decrease the effectiveness of ultraviolet (UV) disinfection of wastewater. This effect is detected in a typical UV dose-response curve, where at higher UV doses there is a decrease in the inactivation rate (tailing). In this study, the effect of activated sludge process conditions on the UV inactivation kinetics of flocs was investigated. The conditions compared were nitrifying vs. non-nitrifying vs. an enhanced biological nutrient removal-University of Cape Town (BNR-UCT) system. The results showed that the flocs generated in the BNR-UCT process were easier to disinfect. The final effluent from the BNR-UCT process also showed improved kinetics of inactivation and reached higher levels of disinfection. The nitrifying system's final effluent had a lower number of initial fecal coliforms, which contributed to reaching higher disinfection levels compared to the non-nitrifying system.

Kinetics of UV inactivation of wastewater bioflocs.

Ultraviolet disinfection is a physical method of disinfecting secondary treated wastewaters. Bioflocs formed during secondary treatment harbor and protect microbes from exposure to ultraviolet (UV) light, and significantly decrease the efficiency of disinfection at high UV doses causing the tailing phenomena. However, the exact mechanism of tailing and the role of biofloc properties and treatment conditions are not widely understood. It is hypothesized that sludge bioflocs are composed of an easily disinfectable loose outer shell, and a physically stronger compact core inside that accounts for the tailing phenomena. Hydrodynamic shear stress was applied to the bioflocs to peel off the looser outer shell to isolate the cores. Biofloc and core samples were fractionated into narrow size distributions by sieving and their UV disinfection kinetics were determined and compared. The results showed that for bioflocs, the tailing level elevates as the biofloc size increases, showing greater resistance to disinfection. However, for the cores larger than 45µm, it was found that the UV inactivation curves overlap, and show very close to identical inactivation kinetics. Comparing bioflocs and cores of similar size fraction, it was found that in all cases cores were harder to disinfect with UV light, and showed a higher tailing level. This study suggests that physical structure of bioflocs plays a significant role in the UV inactivation kinetics.

Husband-wife communication and family planning practices among Malay married couples in Mukim Rusila, Terengganu.

The role of husband-wife communication in the practice of family planning was studied among the rural Malay couples in Mukim Rusila, Terengganu. It was a cross-sectional study in which a cluster sampling was used to select the study sample. A total of 193 (100.0%) wives and 74 (38.3%) husbands responded to a face-to-face interview. Visual Analogue Scale was used to measure the level of husband-wife communication. Husband-wife communication score was lower on family planning compared to other matters. There was a significant fair agreement on the scores between the husbands and the wives (p > 0.05) on family planning. There was a significant association between husband-wife communication on family planning and the current practice of family planning (p = 0.002). The 'likelihood' that couples who had had good husband-wife communication to practice family planning was about 2.8 times higher compared to those couples with poor husband-wife communication (95% C.I.: 1.4, 5.3). Further research need to be carried out, as the study was limited by certain constraints.