Occurrence, characteristics, and microbial community of microplastics in anaerobic sludge of wastewater treatment plants.

Wastewater treatment plants (WWTPs) usually contain microplastics (MPs) due to daily influents of domestic and municipal wastewater. Thus, the WWTPs act as a point source of MPs distribution in the environment due to their incapability to remove MPs completely. In this study, MPs occurrence and distribution in anaerobic sludge from WWTPs in different regions (Kaifeng "KHP", Jinan "JSP", and Lanzhou "LGP") were studied. Followed by MPs identification by microscopy and Fourier transform infrared (FTIR) spectrum. The microbial communities associated with anaerobic sludge and MPs were also explored. The results showed that MPs concentrations were 16.5, 38.5, and 17.2 particles/g of total solids (TS) and transparent MPs accounted for 49.1%, 58.5%, and 48.3% in KHP, JSP, and LGP samples, respectively. Fibers represented the most common shape of MPs in KHP (49.1%), JSP (56.0%), and LGP (69.0%). The FTIR spectroscopy indicated the predominance of polyethylene polymer in 1-5 mm MPs. The Proteobacteria, Chloroflexi, Actinobacteria, Bacteroidetes, and Planctomycetes were the abundant phyla in all anaerobic sludge. The bacterial genera in KHP and LGP were similar, in which Caldilinea (>23%), Terrimonas (>10%), and Ferruginibacter (>7%) formed the core bacterial genera. While Rhodococcus (15.3%) and Rhodoplanes (10.9%) were dominating in JSP. The archaeal genera Methanosaeta (>69%) and Methanobrevibacter (>10%) were abundant in KHP and LGP sludge. While Methanomethylovorans accounted for 90% of JSP. Acetyltransferase and hydratase were the major bacterial enzymes, while reductase was the key archaeal enzyme in all anaerobic sludge. This study provided the baseline for MPs distribution, characterization, and MPs associated microbes in WWTPs.

Supplementation of micro-nutrients to growth media of microalgae-induced biomass and fatty acids composition for clean energy generation.

The presence of harmful heavy metals (HMs) in the aquatic environment can damage the environment and threaten human health. Traditional remediation techniques can have secondary impacts. Thus, more sustainable approaches must be developed. Microalgae have biological properties (such as high photosynthetic efficiency and growth), which are of great advantage in the HMs removal. In this study, the effect of various concentrations (2×, 4×, and 6×) of copper (Cu), cobalt (Co), and zinc (Zn) on microalgae (C. sorokiniana GEEL-01, P. kessleri GEEL-02, D. asymmetricus GEEL-05) was investigated. The microalgal growth kinetics, HMs removal, total nitrogen (TN), total phosphor (TP), and fatty acids (FAs) compositions were analyzed. The highest growth of 1.474 OD680nm and 1.348 OD680nm was obtained at 2× and 4×, respectively, for P. kessleri GEEL-02. P. kessleri GEEL-02 showed high removal efficiency of Cu, Co, and Zn (38.92-55.44%), (36.27-68.38%), and (32.94-51.71%), respectively. Fatty acids (FAs) analysis showed that saturated FAs in C. sorokiniana GEEL-01 and P. kessleri GEEL-02 increased at 2× and 4× concentrations while decreasing at 6×. For P. kessleri GEEL-02, the properties of biodiesel including the degree of unsaturation (UD) and cetane value (CN) increased at 2×, 4×, and 6× as compared to the control. Thus, this study demonstrated that the three microalgae (particularly P. kessleri GEEL-02) are more suitable for nutrient and HMs removal coupled with biomass/biodiesel production.

Biochar addition augmented the microbial community and aided the digestion of high-loading slaughterhouse waste: Active enzymes of bacteria and archaea.

The biogas production (BP), volatile fatty acids (VFAs), microbial communities, and microbes' active enzymes were studied upon the addition of biochar (0-1.5%) at 6% and 8% slaughterhouse waste (SHW) loadings. The 0.5% biochar enhanced BP by 1.5- and 1.6-folds in 6% and 8% SHW-loaded reactors, respectively. Increasing the biochar up to 1.5% caused a reduction in BP at 6% SHW. However, the BP from 8% of SHW was enhanced by 1.4-folds at 1.5% biochar. The VFAs production in all 0.5% biochar amended reactors was highly significant compared to control (p-value < 0.05). The biochar addition increased the bacterial and archaeal diversity at both 6% and 8% SHW loadings. The highest number of OTUs at 0.5% biochar were 567 and 525 in 6% and 8% SHW, respectively. Biochar prompted the Clostridium abundance and increased the lyases and transaminases involved in the degradation of lipids and protein, respectively. Biochar addition improved the Methanosaeta and Methanosphaera abundance in which the major enzymes were reductase and hydrogenase. The archaeal enzymes showed mixed acetoclastic and hydrogenotrophic methanogenesis.

Protein biomethanation: insight into the microbial nexus.

Biomethanation of carbohydrates (e.g., lignocellulosic biomass) and lipids (e.g., waste oils) has been well studied. However, investigations on the biomethanation of protein-rich biowastes (PRBs) and associated microbial communities have not been reported. This review summarizes the challenges in the metabolic process of anaerobic digestion of PRBs and the microbial instability associated with it. We discuss the diversity of bacterial and archaeal communities via metagenomics under PRB mono- and codigestion. A stable community structure with enhanced metabolic activity is a core factor in PRB biomethanation. The application of strategies such as codigestion of PRBs with carbon-rich biomass and microbial stimulation/augmentation would make PRB biomethanation more feasible.

Appraising the factors favouring uranium mobilization and associated health risk assessment in groundwaters of north-western India.

An attempt has been made in this study to evaluate the factors favoring the uranium mobilization into the groundwater of Northwest India using uranium isotope activity ratio (234U/238U), radon (222Rn) and environmental isotopes of water (2H, 18O and 3H). The values range from 23 - 597 µg/L for total uranium and 634-3210 Bq/m3 for radon and the corresponding annual effective dose is estimated to be 18.9-490 µSv/a and 6.2-31.5 µSv/a respectively. Uranium activity ratio (UAR) varies from 0.68 - 1.17 and maximum samples indicate secular equilibrium. Environmental isotopic data indicates that the source to groundwater is vertical percolation of rainwater in the case of shallow zone while regional flows from outcrop areas recharge the deep groundwater. A wide scatter is noticed in environmental 3H content (0.23-6.62 TU) indicating both fast and sluggish water flows. The UAR phase diagram suggests that leaching process controls the uranium mobilization into the groundwater. The correlations among UAR, uranium and Uexcess further indicate oxidative nature of leaching process. Statistical treatment of the obtained data along with available geochemical and isotope evidences suggest that source of uranium is common but the driving processes are different for shallow and deep zone. Influences of root zone CO2, oxic species from irrigation return flows and water level fluctuations are also evaluated. Low uranium, low UAR, low 3H and high 222Rn activity in deep zone suggest uranium being released from the roll front as well as transported from outcrop regions. This study highlights the application of uranium isotope ratio, radon and environmental isotopes in assessing vulnerability of alluvial aquifers towards uranium contamination.

Evaluation of various waste cooking oils for biodiesel production: A comprehensive analysis of feedstock.

Biodiesel production from edible sources faces several challenges such as food security and cost issues. Waste cooking oils (WCOs) can be an alternative feedstock due to their large production. The comprehensive characterization of WCOs has been rarely reported in previous studies. In this study, six different WCOs including chicken oil (CO), fat, oil, and grease (FOG), beef hotpot oil (BHP), mixed waste cooking oil (MWO), duck oil (DO), and vegetable hotpot oil (VHP) were assessed for the biodiesel production. Lipid content of WCOs ranged from 73 to 84.5% with the highest C16 in DO (32.1%) and C18 in VHP (71.4%). The highest saturated (such as C16:0 and C18:0), monounsaturated (such as C18:1) and poly unsaturated (such as C18:2, and C18:3) fatty acids were 58%, 59%, and 21% in BHP, VHP, and MWO, respectively. The diverse nature of fatty acids in WCOs makes it highly recommended for biodiesel production, as its derived biodiesel complied with international standards. Fourier transform infrared spectroscopy confirmed the presence of linkages specific to lipid and thermogravimetric analysis showed high volatile matter content (>97%). Biochemical composition, fatty acids profile, and the properties of the produced biodiesel demonstrated that these WCOs could be promising candidates for biodiesel production, solving waste management and socio-economic challenges of conventional feedstocks. However, the commercialization of WCOs' biodiesel requires further investigation of produced biodiesel and their petro-diesel blends on the engine performance, efficiency, and emissions (SO×, NO×, and CO×) parameters to produce quality and cost-effective biodiesel.

Distribution and correlation of radon and uranium and associated hydrogeochemical processes in alluvial aquifers of northwest India.

The spatial and vertical distributions of radon and uranium are evaluated in relation to the hydrogeology, geomorphology, and hydrochemistry of southwest Punjab. Radon activity of the groundwater ranges from 580 to 3633 Bq/m3 (shallow groundwater 580 to 2438 Bq/m3 and deep groundwater 964 to 3633 Bq/m3), and uranium concentration varies from 24.4 to 253 µg/L (shallow groundwater 24.4 to 253 µg/L and deep groundwater 27.6 to 76.3 µg/L). Shallow groundwater shows higher U concentration compared with deeper ones, which can be attributed to the presence of dissolved oxygen (DO) and NO3- as oxidants and HCO3- as stabilizing agent in shallow zone. Unlike uranium, the radon activities were found to be similar in both shallow and deep groundwater. Rnexcess over secular equilibrium was used to confirm the possibility of additional sources of radon, such as secondary minerals present in the subsurface. Surface manifestations show significant influence on radon and uranium distributions in the shallow zone but not in deep zone due to limited hydraulic connectivity. Depth profiles and correlations of radon and uranium with trace elements and hydrochemical parameters indicate that groundwater exhibits different redox characteristics in shallow (younger and oxidizing) and deep zones (older and reducing). The present study provides critical information that can be helpful for planning sustainable groundwater development in this region and other similar regions without contaminating the relatively safer deep aquifers.