Parameter optimization of ferro-sonication pre-treatment process for degradation of bisphenol A and biodegradation from wastewater sludge using response surface model

Detoxification of p-nitrophenol (PNP) using Enterococcus gallinarum JT-02 isolated from animal farm waste sludge

Enterococcus gallinarum (JT-02) isolated and identified from the animal farm waste sludge was found to be capable of biodegrading p-nitrophenol (PNP), an organic compound used to manufacture drugs, fungicides, insecticides, dyes, and to darken leather. The intention of this study was to optimize the biodegradation by finding the optimal conditions for the specific strain through single-factor experiments. The bacterial strain was grown in Luria Bertani broth and various parameters were optimized to achieve the prime settings for the p-nitrophenol (PNP) biodegradation. The results indicated that the best setups for the biodegradation by the strain JT-02 was 100 mg/L of PNP; pH 7; 30 °C; 150 rpm in a shaker incubator and 3% (v/v) of inoculum dose. Once the optimal conditions were found, the bacteria were capable of degrading p-nitrophenol (98.21%) in 4 days. Intermediates produced during PNP biodegradation were identified using High Performance Liquid Chromatography (HPLC) analysis and the biodegradation pathway was elucidated. Phytotoxicity studies were carried out with Vigna radiata seeds to confirm the applicability and efficiency of PNP biodegradation.

Effect of a winter savory leaf extract obtained using high hydrostatic pressure on the quality of carrot juice

BACKGROUND

The consumption of vegetable juices has increased due to their characteristics such as freshness/naturalness, high nutritional value, low in calories, and for being a convenient way of consuming bioactive compounds. High hydrostatic pressure (HPP), which has been mainly used to replace thermal processing, is now also being successfully applied as extraction technology to recover bioactive compounds from herbs. The present work aimed to evaluate the effect of supplementation of carrot juice with winter savory leaf aqueous extract on the final juice characteristics.

RESULTS

The extract was added to raw carrot juice (1.0 mg mL^-1 ), which was then submitted to HPP and stored for 15 days under refrigeration. Microbial analyses were performed during storage time, as also were analyzed the physicochemical properties such as pH, colour, bioactive compound concentration and antioxidant activity. Supplemented juices presented lower microbial counts than the non-supplemented ones, and, generally, did not present significant changes (P > 0.05) in pH or colour. Concerning the total phenolics and total flavonoids, as well as antioxidant activity, the values were generally higher (P < 0.05) in supplemented juices, which was proven by the high correlation found between total phenolics and ABTS^●+ and FRAP assays.

CONCLUSIONS

These data suggest that the addition of winter savory leaf extract in carrot juice treated with HPP can effectively improve microbial safety throughout refrigerated storage as well as antioxidant activity, without risking other characteristics of the juice, such as the colour or the acidity. © 2020 Society of Chemical Industry.

Enhanced removal of bisphenol A from contaminated soil by coupling Bacillus subtilis HV-3 with electrochemical system

Exposure to endocrine disruptors interferes with the synthesis, release, transport and metabolic activities of hormones, thus impairing human health significantly. Bisphenol A (BpA), an endocrine disruptor, commonly released into the environment by industrial activities and needs immediate attention. This study aims at investigating the process and prospects of deploying bio-electrochemical systems (BES) for the removal of BpA from artificially contaminated soil using Bacillus subtilis HV-3. The BES was setup with desired operating conditions: initial concentration of BpA (80-150 mg/L), pH (3-11) and applied potential voltage (0.6-1.4 V). Under optimized conditions (initial BpA concentration, 100 mg/L; pH 7; and applied voltage 1.0 V), close to 98% degradation of BpA was achieved. The intermediates produced during degradation were analysed using High performance liquid chromatography-Mass spectrometry and the possible degradation pathway was elucidated. Phytotoxicity studies in the remediated soil with Phaseolus mungo confirmed the environmental applicability of the BES system.

Biodegradation of the endocrine disrupter 4-t-octylphenol by the non-ligninolytic fungus Fusarium falciforme RRK20: Process optimization, estrogenicity assessment, metabolite identification and proposed pathways

4-t-octylphenol (4-t-OP), a well-known endocrine disrupting compound, is frequently found in various environmental compartments at levels that may cause adverse effects to the ecosystem and public health. To date, most of the studies that investigate microbial transformations of 4-t-OP have focused on the process mediated by bacteria, ligninolytic fungi, or microbial consortia. There is no report on the complete degradation mechanism of 4-t-OP by non-ligninolytic fungi. In this study, we conducted laboratory experiments to explore and characterize the non-ligninolytic fungal strain Fusarium falciforme RRK20 to degrade 4-t-OP. Using the response surface methodology, the initial biomass concentration and temperature were the factors identified to be more influential on the efficiency of the biodegradation process as compared with pH. Under the optimized conditions (i.e., 28 °C, pH 6.5 with an initial inoculum density of 0.6 g L^-1), 25 mg L^-1 4-t-OP served as sole carbon source was completely depleted within a 14-d incubation; addition of low dosage of glucose was shown to significantly accelerate 4-t-OP degradation. The yeast estrogenic screening assay further confirmed the loss of estrogenic activity during the biodegradation process, though a longer incubation period was required for complete removal of estrogenicity. Metabolites identified by LC-MS/MS revealed that strain RRK20 might degrade 4-t-OP as sole energy source via alkyl chain oxidation and aromatic ring hydroxylation pathways. Together, these results not only suggest the potential use of non-ligninolytic fungi like strain RRK20 in remediation of 4-t-OP contaminated environments but may also improve our understanding of the environmental fate of 4-t-OP.

Nanoferrosonication: A novel strategy for intensifying the methanogenic process in sewage sludge

In this work, the effect of coupling ultrasonic pretreatment with dosing of zero-valent iron nanoparticles (nanoferrosonication, "NFS") to improve the anaerobic digestion of sewage sludge was studied. Biochemical methane potential tests were conducted at 15,000 and 25,000 kJ/kg_TS and their combinations with 2 and 7 mgFe⁰/g_VS. The biogas yield increased from 106 (control) to 143 (25,000 kJ/kg_TS) and 308 mL/g_VS with NFS (7 mgFe⁰/g_VS + 15,000 kJ/kg_TS). The methane content increased from 55.6 to 66%, and the maximum VS removal was 11.5% at 7 mgFe⁰/g_VS + 15,000 kJ/kg_TS. The results demonstrated that NFS was effective in intensifying the process.

Removal of polycyclic aromatic hydrocarbons (PAHs) from textile dyeing sludge by ultrasound combined zero-valent iron/EDTA/Air system

This paper proposes a combined ultrasound (US) and zero-valent iron/EDTA/Air (ZEA) system to remove polycyclic aromatic hydrocarbons (PAHs) from textile dyeing sludge. The removal efficiencies of 16 PAHs using ZEA, US/Air (air injected into the US process), and US/ZEA treatments were investigated, together with the effects of various operating parameters. The enhanced mechanisms of US and the role of reactive oxygen species (ROS) in removing PAHs in the US/ZEA system were explored. Results showed that only 42.5% and 32.9% of ∑16 PAHs were removed by ZEA and US/Air treatments respectively, whereas 70.1% were removed by US/ZEA treatment, (with favorable operating conditions of 2.0 mM EDTA, 15 g/L ZVI, and 1.08 w/cm³ ultrasonic density). The US/ZEA system could be used with a wide pH range. US led to synergistic improvement of PAHs removal in the ZEA system by enhancing sludge disintegration to release PAHs and promoting ZVI corrosion and oxygen activation. In the US/ZEA system, PAHs could be degraded by ROS (namely OH, O₂^-/HO₂, and Fe(IV)) and adsorbed by ZVI, during which the ROS made the predominant contribution. This study provides important insights into the application of a US/ZEA system to remove PAHs from sludge.

Degradation of chlortetracycline in wastewater sludge by ultrasonication, Fenton oxidation, and ferro-sonication

Residual emerging contaminants in wastewater sludge remain an obstacle for its wide and safe applications such as landfilling and bio-fertilizer. In this study, the feasibility of individual ultrasonication (UlS) and Fenton oxidation (FO) and combined, Ferro-sonication processes (FO) on the degradation of chlortetracycline (CTC) in wastewater sludge was investigated. UlS parameters such as amplitude and sonication time were optimized by response surface methodology (RSM) for further optimization of FS process. Generation of highly reactive hydroxyl radicals in FO and FS processes were compared to evaluate the degradation efficiency of CTC. Increasing in the ratio of hydrogen peroxide and iron concentration showed increased CTC degradation in FO process; whereas in FS, an increase in iron concentration did not show any significant effect (p>0.05) on CTC degradation in sludge. The estimated iron concentration in sludge (115mg/kg) was enough to degrade CTC without the addition of external iron. The only adjustment of sludge pH to 3 was enough to generate in-situ hydroxyl radicals by utilizing iron which is already present in the sludge. This observation was further supported by hydroxyl radical estimation with adjustment of water pH to 3 and with and without the addition of iron. The optimum operating UlS conditions were found to be 60% amplitude for 106min by using RSM. Compared to standalone UlS and FO at 1:1 ratio, FS showed 15% and 8% increased CTC degradation respectively. In addition, UlS of sludge increased estrogenic activity 1.5 times higher compared to FO. FS treated samples did not show any estrogenic activity.

Fungal laccases degradation of endocrine disrupting compounds

Over the past decades, water pollution by trace organic compounds (ng/L) has become one of the key environmental issues in developed countries. This is the case of the emerging contaminants called endocrine disrupting compounds (EDCs). EDCs are a new class of environmental pollutants able to mimic or antagonize the effects of endogenous hormones, and are recently drawing scientific and public attention. Their widespread presence in the environment solicits the need of their removal from the contaminated sites. One promising approach to face this challenge consists in the use of enzymatic systems able to react with these molecules. Among the possible enzymes, oxidative enzymes are attracting increasing attention because of their versatility, the possibility to produce them on large scale, and to modify their properties. In this study five different EDCs were treated with four different fungal laccases, also in the presence of both synthetic and natural mediators. Mediators significantly increased the efficiency of the enzymatic treatment, promoting the degradation of substrates recalcitrant to laccase oxidation. The laccase showing the best performances was chosen to further investigate its oxidative capabilities against micropollutant mixtures. Improvement of enzyme performances in nonylphenol degradation rate was achieved through immobilization on glass beads.

Partial ozonation pre-treatment for sludge solubilization and simultaneous degradation of bisphenol A: quantification studies

Ozonation pre-treatment was investigated for the enhancement of sludge solids and organic matter solubilization and simultaneous degradation of bisphenol A (BPA), an endocrine disruptor compound from wastewater sludge (WWS). The ultrafast method (15 s per sample) used for the analysis of BPA in WWS is based on Laser Diode Thermal Desorption/Atmospheric Pressure Chemical Ionization coupled to tandem Mass Spectrometry. The statistical methods used for optimization studies comprised the response surface method with fractional factorial designs and central composite designs. The ozonation pre-treatment process was carried out with four independent variables, namely WWS solids concentration (15-35 g l(-1)), pH (5-7), ozone dose (5-25 mg g(-1) SS) and ozonation time (10-30 min). It was observed that among all the variables studied, ozone dose had more significantly (probability (p) < 0.001) affected the efficiency of the ozonation pre-treatment by increasing sludge solids (suspended solids (SS) and volatile solids) solubilization and organic matter (soluble chemical oxygen demand and soluble organic carbon) increment and BPA degradation from WWS. During the optimization process, it was found that higher BPA degradation (100%) could be obtained with 24 g l(-1) SS, 6.23 pH with an ozone dose of 26.14 mg g(-1) SS for 16.47 min ozonation time. The higher ozone dose used in this study was observed to be cost effective on the basis of solids and organic matter solubilization and degradation of BPA.