Degradation of trichloroethylene by double dielectric barrier discharge (DDBD) plasma technology: Performance, product analysis and acute biotoxicity assessment

Trichloroethylene is carcinogenic and poorly degraded by microorganisms in the environment. Advanced Oxidation Technology is considered to be an effective treatment technology for TCE degradation. In this study, a double dielectric barrier discharge (DDBD) reactor was established to decompose TCE. The influence of different condition parameters on DDBD treatment of TCE was investigated to determine the appropriate working conditions. The chemical composition and biotoxicity of TCE degradation products were also investigated. Results showed that when SIE was 300 J L^-1, the removal efficiency could reach more than 90%. The energy yield could reach 72.99 g kWh^-1 at low SIE and gradually decreased with the increase of SIE. The k of the Non-thermal plasma (NTP) treatment of TCE was about 0.01 L J^-1. DDBD degradation products were mainly polychlorinated organic compounds and produced more than 373 mg m^-3 ozone. Moreover, a plausible TCE degradation mechanism in the DDBD reactors was proposed. Lastly, the ecological safety and biotoxicity were evaluated, indicating that the generation of chlorinated organic products was the main cause of elevated acute biotoxicity.

A short review of bioaerosol emissions from gas bioreactors: Health threats, influencing factors and control technologies

Bioaerosols have widely been a concern due to their potential harm to human health caused by the carrying and spreading of harmful microorganisms. Biofiltration has been generally used as a green and effective technology for processing VOCs. However, bioaerosols can be emitted into the atmosphere as secondary pollutants from the biofiltration process. This review presents an overview of bioaerosol emissions from gas bioreactors. The mechanism of bioaerosols production and the effect of biofiltration on bioaerosol emissions were analyzed. The results showed that the bioaerosol emission concentrations were generally exceeded 10⁴ CFU m^-3, which would damage to human health. Biomass, inlet gas velocity, moisture content, temperature, and some other factors have significant influences on bioaerosol emissions. Moreover, as a result of the analysis done herein, different inactivation technologies and microbial immobilization of bioaerosols were proposed and evaluated as a potential solution for reducing bioaerosols emissions. The purpose of this paper is to make more people realize the importance of controlling the emissions of bioaerosols in the biofiltration process and to make the treatment of VOCs by biotechnology more environmentally friendly. Additionally, the present work intends to increase people's awareness in regards to the control of bioaerosols, including microbial fragment present in bioaerosols.

Performance enhancement of a biofilter with pH buffering and filter bed supporting material in removal of chlorobenzene

Acidic substances, which produced during chlorinated volatile organic compounds, will corrode the commonly used packing materials, and then affect the removal performance of biofiltration. In this study, three biofilters with different filter bed structure were established to treat gaseous chlorobenzene. CaCO₃ and 3D matrix material was added in filter bed as pH buffering material and filter bed supporting material, respectively. A comprehensive investigation of removal performance, biomass accumulation, microbial community, filter bed height, voidage, pressure drops, and specific surface area of the three biofilters was compared. The biofilter with CaCO₃ and 3D matrix material addition presented stable removal performance and microbial community, and greater biomass density (209.9 kg biomass/m³ filter bed) and growth rate (0.033 d^-1) were obtained by using logistic equation. After 200 days operation, the height, voidage, pressure drop, specific surface area of the filter bed consisted of perlite was 27.4 cm, 0.39, 32.8 Pa/m, 974,89 m²/m³, while those of the filter bed with CaCO₃ addition was 28.2 cm, 0.43, 21.3 Pa/m, and 1021.03 m²/m³, and those of the filter bed with CaCO₃ and 3D matrix material addition was 28.7 cm, 0.55, 17.4 Pa/m, and 1041.60 m²/m³. All the results verified the biofilter with CaCO₃ and 3D matrix material addition is capable of sustaining the long-term performance of biofilters. CaCO₃ could limit the changes of removal efficiency, microbial community and filter bed structure by buffering the pH variation. And 3D matrix material could maintain the filter bed structure by supporting the filter bed, regardless of the buffering effect.

[VOCs Emission Inventory and Impact Range Simulation of Antibiotic Enterprises]

Drug production consumes a large amount of raw materials and is recognized as a "high-pollution, high-energy-consumption" industry. In consideration of the small amount of emission inventory research in the pharmaceutical industry, firstly, based on the actual monitoring data and production information of typical antibiotic enterprises, the emission factors of various volatile organic compounds (VOCs) were determined using the field measurement method. Then, combined with the activity level information of antibiotics from A to G plant in the same park, the emission factor method was used to calculate and obtain the emissions of each plant, and an emission list was established. Uncertainty analysis of the list was carried out using the Monte Carlo method. Finally, the CALPUFF model was used to simulate the environmental impact range of the A-G plants in spring, summer, autumn, and winter. The results showed that the total VOCs emission factor in the production of antibiotic enterprises was 6655.61 g·t^-1, and the crystallization process emission factor was the largest, at 3603.476 g·t^-1. The A to G plants produce 6655.610, 7454.283, 998.342, 11980.098, 4492.537, 42462.792, and 18302.928 kg, respectively, of VOCs each year for the production of antibiotics, and the four substances with the largest emissions are butyl acetate, n-butanol, n-hexane, and acetone, respectively. Through the verification of the Monte Carlo model for plant A, it was found that the emissions of plant A basically presented as a lognormal distribution, and the uncertainty of 95% confidence interval was (-60.62%, 131.78%), which was within the acceptable range. Through CALPUFF simulation, the diffusion direction and range of VOCs were found to be different in each season, and an aggregation phenomenon occurs in summer.

Protocol adherence for continuously titrated interventions in randomized trials: an overview of the current methodology and case study

Background

The standard definition for protocol adherence is the proportion of all scheduled doses that are delivered. In clinical research, this definition has several limitations when evaluating protocol adherence in trials that study interventions requiring continuous titration.

Discussion

Building upon a specific case study, we analyzed a recent trial of a continuously titrated intervention to assess the impact of different definitions of protocol deviations on the interpretation of protocol adherence. The OVATION pilot trial was an open-label randomized controlled trial of higher (75–80 mmHg) versus lower (60–65 mmHg) mean arterial pressure (MAP) targets for vasopressor therapy in shock. In this trial, potential protocol deviations were defined as MAP values outside the targeted range for >4 consecutive hours during vasopressor therapy without synchronous and consistent adjustments of vasopressor doses. An adjudication committee reviewed each potential deviation to determine if it was clinically-justified or not. There are four reasons for this contextual measurement and reporting of protocol adherence. First, between-arm separation is a robust measure of adherence to complex protocols. Second, adherence assessed by protocol deviations varies in function of the definition of deviations and the frequency of measurements. Third, distinguishing clinically-justified vs. not clinically-justified protocol deviations acknowledges clinically sensible bedside decision-making and offers a clear terminology before the trial begins. Finally, multiple metrics exist to report protocol deviations, which provides different information but complementary information on protocol adherence.

Conclusions

In trials of interventions requiring continuous titration, metrics used for defining protocol deviations have a considerable impact on the interpretation of protocol adherence. Definitions for protocol deviations should be prespecified and correlated with between-arm separation, if it can be measured.

Electronic supplementary material

The online version of this article (doi:10.1186/s12874-017-0388-3) contains supplementary material, which is available to authorized users.