Optimization of biostimulant for bioremediation of contaminated coastal sediment by response surface methodology (RSM) and evaluation of microbial diversity by pyrosequencing

Adsorption of paratoluic acid on MIL-53 (Al) metal-organic framework, and response surface methodology optimization

In this study, an organic metal framework adsorbent was used to remove paratoluic acid from aqueous solutions. The effect of various parameters such as pH, initial concentration of paravoluic acid, contact time, and amount of adsorbent was investigated by experimental design method. Central composite design (CCD) was used to optimize paratoluic acid uptake. Initially, MIL-53 (Al) was synthesized, and characterized by X-ray diffraction (XRD), Fourier transforms infrared spectroscopy (FTIR), spectroscopy, and thermogravimetry (TGA). The results of central composite design showed that pH is the most essential factor in the removal of paratoluic acid with MIL-53 (Al). The maximum removal efficiency of paratoluic acid by MIL-53 (Al) adsorbent is 93.67%, the optimal amount of adsorbent is 0.396 g, the optimal time is 35.67 min, the initial concentration is 11.12 mg L−1. The pH is 6.6 with the desired amount 1 is. Isothermal, and kinetic models have also examined. The maximum adsorption capacity was 132.05 (mg g−1), and the adsorption data of MIL-53 (Al) were well consistent with the quasi-second order, and Langmuir isotherm models.

Biostimulants application for bacterial metabolic activity promotion and sodium dodecyl sulfate degradation under copper stress

In this study, the metabolic activity (adenosine triphosphate, ATP; electron transfer system, ETS; and dehydrogenase activity, DHA) response of a sodium dodecyl sulfate (SDS) degrading bacterium Pseudomonas sp. SDS-N2 to copper stress conditions were investigated. Results showed that the ATP content, ETS activity, and DHA activity of strain SDS-N2 were significantly correlated with substrate removal efficiency and bacterial growth under copper stress conditions. Based on the metabolic response patterns of strain SDS-N2, biostimulants citric acid, proline as well as FeSO₄ were used to promote the metabolic activity of strain SDS-N2 at 0.8 mg L^-1 copper stress condition. Plackett-Burman design and analysis proved that citric acid and FeSO₄ were significant factors for enhanced SDS removal; and the optimum biostimulation conditions (FeSO₄ 72 mg L^-1 and citric acid 100 mg L^-1) for SDS removal were obtained by using steepest ascent experiment and central composite design. Under the optimum biostimulation conditions, ATP, ETS, DHA activity as well as bacterial growth were 14.1, 45.5, 0.5 and 2.3-fold higher than that of the control (without FeSO₄ and citric acid addition) after 12.5 h biodegradation, and the substrate removal efficiency was increase by 37.6%.

Enhanced methane production of vinegar residue by response surface methodology (RSM)

As the by-product of the vinegar production process, a large number of vinegar residue has been abandoned and caused a serious environmental pollution. Anaerobic digestion has been proved to be able to dispose and convert vinegar residue into bioenergy but still need to improve the efficiency. This study applied central composite design of response surface methodology to investigate the influences of feed to inoculum ratio, organic loading, and initial pH on methane production and optimize anaerobic digestion condition. The maximum methane yield of 203.91 mL gVS⁻¹ and biodegradability of 46.99% were obtained at feed to inoculum ratio of 0.5, organic loading of 31.49 gVS L⁻¹, and initial pH of 7.29, which was considered as the best condition. It has a very significant improvement of 69.48% for methane production and 52.02% for biodegradability compared with our previous study. Additionally, a high methane yield of 182.09 mL gVS⁻¹ was obtained at feed to inoculum ratio of 1.5, organic loading of 46.22 gVS L⁻¹, and initial pH of 7.32. And it is more appropriate to apply this condition in industrial application owing to the high feed to inoculum ratio and organic loading. Besides, a significant interaction was found between feed to inoculum ratio and organic loading. This study maximized the methane production of vinegar residue and made a good foundation for further study and future industrial application.

Evaluation methods for assessing effectiveness of in situ remediation of soil and sediment contaminated with organic pollutants and heavy metals

Soil and sediment contamination has become a critical issue worldwide due to its great harm to the ecological environment and public health. In recent years, many remediation technologies including physical, chemical, biological, and combined methods have been proposed and adopted for the purpose of solving the problems of soil and sediment contamination. However, current research on evaluation methods for assessing these remediation technologies is scattered and lacks valid and integrated evaluation methods for assessing the remediation effectiveness. This paper provides a comprehensive review with an environmental perspective on the evaluation methods for assessing the effectiveness of in situ remediation of soil and sediment contaminated with organic pollutants and heavy metals. The review systematically summarizes recent exploration and attempts of the remediation effectiveness assessment based on the content of pollutants, soil and sediment characteristics, and ecological risks. Moreover, limitations and future research needs of the practical assessment are discussed. These limitations are not conducive to the implementation of the abatement and control programs for soil and sediment contamination. Therefore, more attention should be paid to the evaluation methods for assessing the remediation effectiveness while developing new in situ remediation technologies in future research.

Bioremediation of contaminated coastal sediment: Optimization of slow release biostimulant ball using response surface methodology (RSM) and stabilization of metals from contaminated sediment

The aim of the present study is to optimize the slow release biostimulant ball (BSB) for bioremediation of contaminated coastal sediment using response surface methodology (RSM). Metals contamination and stabilization of metals in coastal sediments using BSB were investigated. The effects of BSB size (1-5cm), distance (1-10cm), and time (1-4months) on the stabilization of metals including Fe, Cd, Cu, and Pb were determined. The maximum stabilization percentages of Fe, Cd, Cu, and Pb, of 64.5%, 54.9%, 63.8%, and 47.6%, respectively, were observed at a 3cm ball size, 5.5cm distance, and a period of 4months; these values are the optimum conditions for effective treatment of contaminated coastal sediment. The determination coefficient of the R² value suggests that >91.55%, 89.97%, 96.10%, and 86.40% of the variance is attributable to the variables of Fe, Cd, Cu, and Pb, respectively.

Influence of applied voltage on the performance of bioelectrochemical anaerobic digestion of sewage sludge and planktonic microbial communities at ambient temperature

The influence of applied voltage on the bioelectrochemical anaerobic digestion of sewage sludge was studied at ambient temperature (25±2°C). The stability of the bioelectrochemical anaerobic digestion was considerably good in terms of pH, alkalinity and VFAs at 0.3V and 0.5V, but VFA accumulation occurred at 0.7V. The specific methane production rate (370mLCH4/L.d) was the highest at 0.3V, but the methane content (80.6%) in biogas and the methane yield (350mLCH4/gCODr) were higher at 0.5V, significantly better than those of 0.7V. The VS removal efficiency was 64-66% at 0.3V and 0.5V, but only 31% at 0.7V. The dominant species of planktonic microbial communities was Cloacamonas at 0.3V and 0.5V, but the percentage of hydrolytic bacteria species such as Saprospiraceae, Fimbriimonas, and Ottowia pentelensis was much higher at 0.7V. The optimal applied voltage for bioelectrochemical anaerobic digestion was 0.3-0.5V according to digestion performance and planktonic microbial communities.