Ogii Lake is a freshwater lake located in the eastern Arkhangai province, central Mongolia, which registered as an International Ramsar Convention site in 1998. This study sought to estimate the environmental characteristics of Ogii Lake and Orkhon Valley. The authors analyzed water samples from springs, streams, the lake, and groundwater in the summer of 2017 and 2018. A questionnaire survey was undertaken in August 2018 to evaluate anthropogenic impacts on the lake’s environment. In this paper, we present two years of water analysis results, the potential waste generation derived from livestock and tourists around the lake, the normalized difference vegetation index (NDVI) surrounding the lake, and the surface area changes of Ogii Lake in the past decades. The physicochemical parameters of water samples were analyzed using the standard methods that are recommended by the American Public Health Association. Our study confirmed that the water quality of both Ogii Lake and Old Orkhon River was classified as clean; however, PO₄^3- concentrations were determined 2.7–3.4 times higher than the standard level in 2018. The observed high PO₄^3- concentration might have been attributable to livestock distribution around the lake in spatially and increasing discharge after summer intense precipitation in temporally.

To evaluate the effectiveness of gluconate as a potential hydrogen donor for reductive dechlorination of chloroethenes, we developed a trichloroethene (TCE)-dechlorinating consortium from chloroethenes-contaminated groundwater containing Dehalococcoides using gluconate as the sole hydrogen donor and characterized its chloroethenes-dechlorinating performance and microbial community composition. After repeated subculturing, we successfully developed a microbial consortium with gluconate, which showed consistent dechlorination of TCE to vinyl chloride (VC), resulting in subsequent disappearance of VC. The resultant consortium could dechlorinate 24 μmol/L TCE to VC and eliminate VC within 20 days, which was similar to or slightly longer than the required time when other hydrogen donors such as lactate or methanol were used. These results indicate that gluconate can be an effective hydrogen donor for reductive dechlorination of chloroethenes. Real-time PCR and terminal restriction fragment length polymorphism analyses of bacterial and archaeal populations revealed the establishment of a stable microbial community in the developed consortium. In addition, 16S rRNA amplicon sequencing revealed that Trichococcus and Malikia were the predominant taxa, whereas Dehalococcoides and other dechlorinating populations were minor. Our results infer that the use of gluconate as a hydrogen donor established a distinctive microbial community compared with enriched consortia developed with other hydrogen donors.

Perfluoroalkyl substances (PFASs) such as perfluorocarboxylic acid (PFCAs) and perfluoroalkane sulfonates (PFSAs) are persistent, bioaccumulative, and toxic substances that are distributed worldwide. Here we investigated the current concentrations of PFASs in the surface sediments from the Seto Inland Sea, Japan. The concentrations of PFCAs in surface sediments from the Sea ranged from 0.05 to 0.67 ng g⁻¹. Perfluoroundecanoic acid (PFUnDA) was detected at all 15 sampling stations; its concentration was 0.05–0.24 ng g⁻¹. Perfluorohexanoic acid (PFHxA), which is used as an alternative to perfluorooctanoic acid (PFOA), was detected in Osaka Bay and Kii Channel. The contamination of PFCAs in the sediment from Osaka Bay and Kii Channel is shifting to PFHxA. In contrast, only perfluorooctanesulfonic acid (PFOS) was detected at the center part of the bays in the Sea. The significant positive correlation between the PFCAs concentrations in the sediment and the sedimentation rates was observed in the Sea. Hence, the concentration of PFCAs in surface sediments from the Sea was controlled by the sedimentation rate.

Excess sludge reduction is a central challenge in wastewater treatment, requiring a cost-effective technology. Here, we report the pilot-scale implementation of two Modified Ludzack-Ettinger (MLE) processes with and without a high-pressure jet device (HPJD) as a sludge reduction method based on physically decomposing bacterial cells in activated sludge. The MLE process with an HPJD (MLE-HPJD) bifurcated the activated sludge return lines and directed them to anoxic and oxic tanks; an HPJD was incorporated in the latter. The operation of both processes by continuous municipal wastewater supply for 111 days demonstrated that HPJD application reduced the cumulative waste activated sludge amount by 56.6% without an increase in the effluent suspended solids (SS) concentration. The two MLE processes displayed comparable removal performances for organic carbon and nitrogen, indicating that sludge solubilization by HPJD does not hinder bacterial activity in activated sludge. A combination of the 16S rRNA gene amplicon sequencing and quantitative fluorescence in situ hybridization (FISH) revealed that microbial community compositions were distinct in the two processes. While still effecting excess sludge reduction, HPJD selectively lowered the relative abundance of filamentous bacteria, potentially causing sludge bulking. Further, the relative abundance and cluster structure of ammonia-oxidizing bacteria (AOB) in the MLE-HPJD and MLE processes were comparable, indicating that the application of HPJD did not impair nitrification performance. Monitoring the eukaryote community by microscopy showed that activated sludge in the MLE-HPJD had a much higher abundance of Protomastigida. Therefore, the MLE-HPJD process is an efficient sludge reduction technology that does not compromise organic carbon and nitrogen removal.

Industrial sago starch extraction from the sago palm (Metroxylon sagu) generates large volumes of wastewater, known as sago effluent that is generally discharged into nearby water bodies without proper treatment. This practice has led to severe environmental pollution that prompts the development of biotechnological treatments of sago effluent. In this study, Rhizopus oligosporus was grown in sago effluent at several initial pHs (pH 4, 5, and 6) during submerged fermentation to determine the optimum pH for high protein fungal biomass (HPFB) production while simultaneously reducing the starch content and high organic loads of sago effluent. Our results showed that the growth of R. oligosporus was the highest (3.8 g/L) when the initial pH of the sago effluent was 4. The same pH also gave the best reduction of starch, biochemical oxygen demand and chemical oxygen demand of the sago effluent following the R. oligosporus fermentations, which were 96.70%, 89.81%, and 78.30%, respectively. In addition, nitrate concentration was found to be reduced from 0.266 to 0.257 g/L, while the nitrite level dropped from 0.040 to 0.029 g/L. The present findings presented the potential of R. oligosporus for the production of HPFB as well as for treating sago effluent.

Determining the concentrations of dissolved and particulate selenium is of great importance, because it affects the toxicity, removal, recovery and reuse of selenium. For measurement, particulate selenium is usually separated from dissolved selenium by centrifugation or filtration. The reported relative centrifugation forces (rcf) used in separation are inconsistent and vary widely from 500 to 41,000 g. The 0.45 µm pore size filter is the most frequently used for the filtration. We systematically studied the effects of rcf and filter pore size on separation for typical environmental samples. We found that rcf ≥ 20,000 g and filter pore size ≤ 20 nm led to almost complete separation. The minimum rcf needed for separation could be predicted by Stokes’ law when the particulate selenium concentration was low (0.05 mg-Se/L), but could not be predicted when the particulate selenium concentration increased to ≥ 0.5 mg-Se/L probably due to aggregation of selenium nanoparticles at high concentrations. The presence of other particles (e.g., bacteria) also made the minimum rcf not predictable by Stokes’ law due to attachment of particulate selenium to bacteria. Therefore, the presence of other particles and the concentration of particulate selenium should be considered while choosing the appropriate centrifugation condition.