Separation of microalgae from bacterial contaminants using spiral microchannel in the presence of a chemoattractant

Cell separation using microfluidics has become an effective method to isolate biological contaminants from bodily fluids and cell cultures, such as isolating bacteria contaminants from microalgae cultures and isolating bacteria contaminants from white blood cells. In this study, bacterial cells were used as a model contaminant in microalgae culture in a passive microfluidics device, which relies on hydrodynamic forces to demonstrate the separation of microalgae from bacteria contaminants in U and W-shaped cross-section spiral microchannel fabricated by defocusing CO2 laser ablation. At a flow rate of 0.7 ml/min in the presence of glycine as bacteria chemoattractant, the spiral microfluidics devices with U and W-shaped cross-sections were able to isolate microalgae (Desmodesmus sp.) from bacteria (E. coli) with a high separation efficiency of 92% and 96% respectively. At the same flow rate, in the absence of glycine, the separation efficiency of microalgae for U- and W-shaped cross-sections was 91% and 96%, respectively. It was found that the spiral microchannel device with a W-shaped cross-section with a barrier in the center of the channel showed significantly higher separation efficiency. Spiral microchannel chips with U- or W-shaped cross-sections were easy to fabricate and exhibited high throughput. With these advantages, these devices could be widely applicable to other cell separation applications, such as separating circulating tumor cells from blood.

Prediction of pharmaceutical and personal care products elimination during heterogeneous catalytic ozonation via chemical kinetic model

Prediction of the removal of pollutants is important for the process design and optimization of wastewater treatment. In this study, the heterogeneous catalytic ozonation chemical kinetic model based on reaction kinetic constants between O₃ (and •OH) and pollutants, and pseudo-first order rate constants for pollutant adsorption was established. The model parameters were obtained via O₃ and p-chlorobenzonic acid decay curves, and adsorption kinetic experiments, respectively. Higher •OH exposures were obtained at the expense of lower O₃ exposures during catalytic ozonation compared to simple ozonation. Importantly, the experimentally measured and model-predicted removal ratios correlated well in all reaction systems, with correlation coefficients above 0.950 in synthetic solution and 0.893-0.979 in secondary effluent. Furthermore, the model revealed that pollutants were degraded mainly by O₃ and/or •OH oxidation during catalytic ozonation, while adsorption of pollutants on catalysts contributed negligibly. Hence, the degradation ratios of pollutants could be satisfactorily predicted using the simplified model based only on the O₃ and •OH exposures in the heterogeneous catalytic ozonation systems with low adsorption capacity catalysts.

Effects of Mechanical Drying on the Removal of Pollen Allergens

PURPOSE

Pollen may spread indoors through clothes contaminated during outdoor activities. This study aimed to evaluate the pollen removal efficacy of a mechanical dryer.

METHODS

Cotton clothes served as laundry, and fabrics measuring 2 × 5 cm served as test samples. Pollen was spread evenly on the test fabrics. The fabrics were then fixed on the cloth and left for 8 h to imitate real-life conditions. This experiment was conducted under 2 conditions, wet (after washing clothes) and dry (without washing). After drying, we counted pollen on the test fabrics to evaluate the pollen removal rate. We measured the remaining allergens in extracts from the contaminated fabrics after mechanical drying. The concentrations of allergens (Amb a 1, Bet v 1, Crp j 1, and Phl p 1) in each extracted solution were measured using 2-site ELISA.

RESULTS

For ragweed, Japanese cedar, birch, and timothy grass, the mean pollen removal ratios for the dry samples were 99.88 ± 0.09%, 99.96 ± 0.03%, 99.89 ± 0.02%, and 99.82 ± 0.11%, respectively, and those for the wet samples were 98.83 ± 0.87%, 97.91 ± 1.81%, 97.29 ± 1.19%, and 96.3 ± 0.92%, respectively. Further, for the pollen allergens Amb a 1 [ragweed], Crp j 1 [Japanese cedar], Bet v 1 [birch], and Phl p 1 [timothy grass], the mean pollen allergen removal ratios for the dry samples were 99.81 ± 0.06%, 99.94 ± 0.23%, 99.90 ± 0.11%, and 99.84 ± 0.17%, respectively, and those for the wet samples were 98.11 ± 0.14%, 96.04 ± 1.52%, 97.21 ± 0.83%, and 95.23 ± 0.92%, respectively. There was no statistically significant difference for each species.

CONCLUSIONS

Mechanical drying effectively removed pollen and allergens from dry and wet fabrics. We expect that further studies on the removal of other indoor allergens would contribute to improved environmental control for allergy patients.

A hybrid method for synthesis of integrated water and regeneration networks with variable removal ratios

This work presents a systematic optimization framework that integrates graphical insights with mathematical modelling to reduce both model complexity and computational time. The graphical technique adopted in this work is Composite Table Algorithm (CTA), which is improved to determine an optimal regenerator removal ratio (RR) that simultaneously minimizes the freshwater requirement and wastewater generation within the water network. The improved CTA is demonstrated using literature examples for both fixed load and fixed flowrate problems. It is further adapted to solve a multiple contaminant problem using the reference contaminant approach. The mathematical model developed includes a detailed design of a reverse osmosis (RO) unit to allow for simultaneous optimization of water and energy used by the regenerator. This provides accurate cost estimation of the water network rather than the linear cost functions associated with the use of blackbox representations in graphical targeting. Upon integrating the graphical and mathematical techniques in this study, results show that there was a reduction of about 85% in CPU time. This implies that the model converges faster and therefore favours the use of insight-based techniques as a preprocessing step for mathematical modelling.

New use for spent coffee ground as an adsorbent for tetracycline removal in water

Spent coffee grounds (SCG-1 and SCG-2) were used to study the adsorption of tetracycline (TC) antibiotics and the effects of adsorption time, initial pH, amount of adsorbent and ionic strength were detected. The TC adsorption isotherm on SCG-1 was compared with SCG-2. The results showed that the removal efficiencies of TC (50 mg/L) of SCG-1 and SCG-2 were 83.1% and 97.2%, respectively, shake for 2 h. The probability of adsorption is high and balances in about 20 min. The estimate of parameters got for TC from the Langmuir isotherm saturated adsorption quantity and adsorption balance constant were 64.89 mg/g, 0.0557 L/mg, respectively for SCG-1 and 123.46 mg/g, 0.4735 L/mg, respectively for SCG-2. The adsorption mechanism might be a π-π interaction that occurs in the interface by hydrogen bonding and the between the TC molecular and the SCGs. At last, we found that SCG has a high adsorption size for TC.

The occurrence and removal of selected fluoroquinolones in urban drinking water treatment plants

Fluoroquinolones (FQs) are a widely prescribed group of antibiotics. They enter the aqueous environment, where they are frequently detected, and can lead to a threat to human health. Drinking water treatment plants (DWTPs) play a key role in removing FQs from potable water. This study investigated the occurrence and removal of four selected FQs (norfloxacin (NOR), ciprofloxacin (CIP), enrofloxacin (ENR), and ofloxacin (OFL)) in three urban DWTPs in China. The treatment efficacy for each system was simultaneously evaluated. Two of the examined DWTPs used conventional treatment processes. The third used conventional processes followed by additional treatment processes (ozonation-biologically activated carbon (ozonation-BAC) and membrane technology). The average concentrations of the four FQs in the source water and the finished water ranged from 51 to 248 ng/L and from <5 to 46 ng/L, respectively. Based on residual concentrations, the conventional treatment system had a low removal of FQs. In contrast, the addition of advanced treatment processes such as the ozonation-BAC and membranes, substantially improved the removal of FQs. The finding of this study has important implications: even though coagulation-sedimentation and chlorination treatment processes can remove most target FQs, the typical practice of advanced treatment processes is necessary for the further removal.