Volatile fatty acid impacts on nitrite oxidation and carbon dioxide fixation in activated sludge

Batch test were performed to assess nitrite removal, nitrate formation, CO2 fixation, gaseous nitrogen production and microbial density in activated sludge exposed to volatile fatty acid (VFA) mixtures. Nitrite removal and nitrate formation were both affected by the presence of VFAs, but to different degrees. Nitrate formation rates were reduced to a greater extent (79%) than nitrite removal rates (36%) resulting in an apparent unbalanced nitrite oxidation reaction. Since the total bacterial density and the nitrite oxidizing bacteria (NOB, Nitrospira) concentration remained essentially constant under all test conditions, the reduction in rates was not due to heterotrophic uptake of nitrogen or to a decrease in the NOB population. In contrast to the nitrogen results, VFAs were not found to impact CO2 fixation efficiency. It appeared that nitrite oxidation occurred when VFAs were present since the oxidation of nitrite provides energy for CO2 fixation. However, nitrate produced from the oxidation of nitrite was reduced to gaseous nitrogen products. N2O gas was detected in the presence of VFAs which was a clear indication that VFAs stimulated an alternative pathway, such as aerobic denitrification, during biotransformation of nitrogen in activated sludge.     

Effect of dentin and fiber post surface treatments with fumaric acid on the bonding ability of fiber posts

This study investigated the effects of fumaric acid on push‐out bond strength when applied to dentin surfaces and fiber posts. The root canals of 60 mandibular premolar teeth were instrumented and obturated. After removing two thirds of filling material, teeth were prepared according to six randomized groups (n = 10/group) defined by two fiber post surface treatments (0.7% fumaric acid or 9% hydrofluoric acid) and three dentin conditioning treatments [control (no conditioning); 17% ethylenediamine tetraacetic acid (EDTA); or 0.7% fumaric acid]. After fiber post‐cementation, three 1‐mm thick discs were obtained from each tooth by transverse sectioning, and each disc underwent push‐out bond strength testing. Data were analyzed with a one‐way analyses of variance (anova ) and t tests; p < .05 was considered statistically significant. Failure modes were determined by stereomicroscopy, and the surface characteristics of dentin and fiber posts were observed by scanning electron microscopy. Push‐out bond strength was greater for the group in which the post surface treated with hydrofluoric acid and the dentin surface treated with fumaric acid than the nontreated dentin and hydrofluoric acid‐treated post group (p < .05). There were no significant differences between other comparison pairs (p > .05). A combination of fumaric acid dentin conditioning and hydrofluoric acid fiber post treatment strengthened the bonding ability of fiber posts.     

Exergoeconomic analysis of a solar assisted tea drying system

Abstract

In this study, an integrated system which consists of a batch type tea dryer and a PV/T unit is developed and analyzed through the exergoeconomic approach. The EXCEM method based on mass, energy, exergy, and cost balances is performed to find out the exergoeconomic performance of the drying system. The parametric studies are used to see the effect of changing properties utilized in the system on performance. The results of the present study show that the capital cost and the capital productivity of the system are $5953 and 1.54, respectively. The energetic and exergetic loss ratios are calculated as 76.45?MJ/$ and 72.63?MJ/$, respectively. The exergy efficiency and exergy destruction for the whole system are found to be 74% and 201.6?GJ, respectively.     

Preparation,Characterization, and Separation Performances of Novel Surface Modified LbL Composite Membranes from Polyelectrolyte Blends and MWCNT

Here, it was aimed to modify the surface of NF90 with layer by layer (LbL) blended poly(allylamine hydrochloride) (PAH)-chitosan (CHI) and poly(acrylic acid) (PAA) with/without functionalized multiwalled carbon nanotube (fMWCNT) for reverse-osmosis applications. Using Quartz Crystal Microbalance Dissipation monitoring, it was observed that PAH-CHI/PAA LbL films grew linearly after a few bilayers and no LbL film degradation occurred during synthetic seawater treatment. Thermal degradation of all LbL blended membranes was similar. NF90 had a heterogeneous surface while the surface of LbL blend membranes exhibited some agglomerations due to the polyelectrolyte (PE) complex formation and fibrillary appearance depending on the use of fMWCNT. [(PAH50-CHI50/(PAA-fMWCNT)]₃₀ indicated the highest flux with 14.5 L m² h⁻¹ at 40 bar. The sodium and chlorine ion rejections were 75% and 87%, respectively, for the same membrane. The use of fMWCNT led to a significant enhancement in flux with a slight decay in ion rejections. On the other hand, chlorine ion rejection of [(PAH50-CHI50/(PAA-fMWCNT)]₃₀ decreased by 25% at 40 bar while 60 and 90 bilayers of [(PAH50-CHI50/(PAA-fMWCNT)] disintegrated after NaOCl treatment. Briefly, the flux and ion rejections of the LbL blended membranes can be controlled depending on the use of fMWCNT and different PE couples without multilayer decomposition against synthetic seawater. POLYM. ENG. SCI., 60: 341–351, 2019. © 2019 Society of Plastics Engineers     

A new exposure route to trace elements in indoor particulate matter

Concentrations and emission rates of sixteen trace elements in emitted PM during heating soybean oil using three types of pans, including Teflon, granitium, and cast-iron, were investigated. Statistically significant decreases in Mn and Co emission rates were observed when the oil was heated in the cast-iron pan compared to Teflon and granitium pans. Among the released trace elements, Ni, Ba, Zn, and Cr had more contribution to the emission rate. The concentrations of Fe in the emitted PM₁ were found to be higher when cast-iron pan (8.49 ± 3.35 µg/m³) was utilized compared to Teflon (8.05 ± 2.27 µg/m³) and granitium (7.45 ± 1.38 µg/m³). However, these increases were statistically insignificant. The results of our study support the hypothesis that the trace elements translocate from cooking pans into the heated oil and subsequently to the particulate phase. This translocation creates a new inhalation exposure route to trace elements in indoor environments.     

Effect of Strontium and Magnesium Additions on the Microstructure and Mechanical Properties of Al–12Si Alloys

Metals and Materials International - In this study, a binary Al–12Si, eight ternary Al–12Si–Sr, and six quaternary Al–12Si–0.1Sr–(0.2–1)Mg alloys were...     

Functional implications of bound phenolic compounds and phenolics–food interaction: A review

Sizeable scientific evidence indicates the health benefits related to phenolic compounds and dietary fiber. Various phenolic compounds-rich foods or ingredients are also rich in dietary fiber, and these two health components may interrelate via noncovalent (reversible) and covalent (mostly irreversible) interactions. Notwithstanding, these interactions are responsible for the carrier effect ascribed to fiber toward the digestive system and can modulate the bioaccessibility of phenolics, thus shaping health-promoting effects in vivo. On this basis, the present review focuses on the nature, occurrence, and implications of the interactions between phenolics and food components. Covalent and noncovalent interactions are presented, their occurrence discussed, and the effect of food processing introduced. Once reaching the large intestine, fiber-bound phenolics undergo an intense transformation by the microbial community therein, encompassing reactions such as deglycosylation, dehydroxylation, α- and β-oxidation, dehydrogenation, demethylation, decarboxylation, C-ring fission, and cleavage to lower molecular weight phenolics. Comparatively less information is still available on the consequences on gut microbiota. So far, the very most of the information on the ability of bound phenolics to modulate gut microbiota relates to in vitro models and single strains in culture medium. Despite offering promising information, such models provide limited information about the effect on gut microbes, and future research is deemed in this field.