Influencing factors of microplastic generation and microplastic contamination in urban freshwater.

This research analyzes data on the microplastic (MP) contamination in the environmental systems (atmosphere, lithosphere, hydrosphere) and the levels of MPs in freshwater of cities with different levels of national income. This study investigates the influencing factors of MP generation, i.e., mismanaged plastic waste, untreated wastewater, number of registered motor vehicles, and stormwater runoff. The statistical correlations between the MP contamination in urban freshwater and the four influencing factors of MP generation are determined by linear regression. The results indicate that MPs are most abundant in aquatic systems (i.e., hydrosphere) and pose a serious threat to the human food chain. The regression analysis shows a strong correlation between mismanaged plastic waste and microfragment smaller than 300 µm in particle size in urban freshwater with high goodness-of-fit (R2 = 0.8091). A strong relationship with high goodness-of-fit also exists between untreated wastewater and microfragment of 1000-5000 µm in particle size (R2 = 0.9522). The key to mitigate the MP contamination in urban freshwater is to replace improper plastic waste management and wastewater treatment with proper management practices.

Life cycle impact assessment and life cycle cost assessment for centralized and decentralized wastewater treatment plants in Thailand.

This research investigates the cost-effectiveness of four sludge treatment scenarios for centralized (C) and decentralized (D) wastewater treatment plants (WWTP) using life cycle cost assessment (LCCA). The environmental impacts and costs are quantified by Stepwise2006. The most environmentally and financially viable WWTP construction option for Bangkok, Thailand (2022-2031) is determined in terms of LCCA and net present value (NPV). The environmental costs of D-treatment scenarios are lower than those of C-treatment scenarios. The total environmental costs of C- and D-fertilizer scenarios are lower than those of C- and D-dewatering scenarios. The net cash flow per functional unit of C-WWTPs is higher than that of D-WWTPs. The C-fertilizer scenario is the most environmentally and economically viable treatment scenario due to the lowest LCCA deficit (-5.58 THB2020 per m3 treated effluent). Composting should thus be adopted for treating sludge. The most environmentally and financially viable WWTP construction option is option I (building four C-WWTPs within 10 years) due to the lowest LCCA deficit (-19925 million THB2020) and smallest financial loss (NPV = -6309.96 million THB2020). Essentially, the local administration of the capital should adopt option I as a guideline in formulating the wastewater treatment management policy of 2022-2031.

Hollow porous cobalt oxide nanobox as an enhanced for activating monopersulfate to degrade 2-hydroxybenzoic acid in water.

As 2-hydroxybenzoic acid (HBA) represents a typical pharmaceutical and personal care product (PPCP), constant releasing of HBA into the environment poses threats to the ecology, and thus it is critical to develop effective techniques to remove HBA from water. Recently, sulfate radical (SO4‒)-based advanced oxidation processes involved with monopersulfate (MPS) activation are proven as effective approaches for eliminating PPCPs from water, and Co3O4 is recognized as a capable catalyst for activating MPS. Therefore, great interests have arisen to develop Co3O4-based catalysts with advantageous morphologies and characteristics for enhancing catalytic activities. Therefore, a special Co3O4-based material is proposed in this work. Through a surfactant-assisted strategy, a cubic Co-MOF is prepared and used as a precursor, which is etched to afford hollow structure, and then transformed into hollow porous Co3O4 nanobox (PCNB). PCNB can exhibit distinct reactive surface with abundant surface oxygen vacancy as well as physical properties in comparison to the commercial Co3O4 NPs (com-Co3O4 NP), thereby leading to the outstanding catalytic activity of PCNB for activating MPS to degrade HBA. The activation energy (Ea) of 46.2 kJ/mol is also calculated using PCNB + MPS system, which is much lower than most of recent reported studies for activating MPS. PCNB could be also reusable over 5 consecutive HBA degradation cycles. The activation mechanism of MPS by PCNB and HBA degradation pathway are also comprehensively elucidated via experimental evidences and the theoretical calculation to offer insightful information of development of Co3O4 for HBA degradation.

Nitrogen removal of anammox cultures under different enrichment conditions.

Anammox bacteria in sludge from an anoxic tank of a municipal wastewater treatment plant at Nongkhaem, Bangkok, Thailand were enriched in two sequencing batch reactors (SBRs; SBR-1 and SBR-2), under different conditions. SBR-1 was open to the atmosphere, while SBR-2 was closed and flushed with a mixture of 95% argon and 5% CO(2) during the fill period in order to provide strict anaerobic conditions. The specific nitrogen removal rates of SBR-1 and SBR-2 were 0.43 g N/g VSS-d and 2.59 g N/g VSS-d, respectively. Denaturing gradient gel electrophoresis (DGGE) analyses showed differences in band patterns among the Nongkhaem sludge and the two enrichment cultures. Based on fluorescent in situ hybridization (FISH), the anammox bacteria in both systems were either "Candidatus Brocadia anammoxidans" or "Candidatus Kuenenia stuttgartiensis". The results from this study demonstrate the potential of alternative anammox systems for nitrogen removal and provide information on the microbial communities of anammox cultures under different enrichment conditions.

Dispersion and ecological risk assessment of di (2-ethylhexyl) phthalate (DEHP) in the surface waters of Thailand.

Previous environmental monitoring indicated that di (2-ethylhexyl) phthalate (DEHP) was released into the environment. This study collected both water and sediment samples from the source area, deltas of major rivers discharging into the Gulf of Thailand, and 2 tourist beaches from February 2007-August 2009. The analyses showed that the highest DEHP concentrations were 8.64 microg l(-1) and 14.51 microg g(-1) for water and suspended sediment samples, respectively. Nevertheless, the monitoring results indicated that the dispersion of DEHP was limited to the source area. The ecological risk assessment indicated that the ecological risk did not exceed the acceptable level for the current degree of contaminations.