Electrochemical sensor amplified with cellulose nanofibers/Fe3O4 composite to the monitoring of hydrazine as a pollutant in water and wastewater samples.

A quite swift and sensitive analytical instrument was designed in this work to detect and monitor hydrazine in various water and wastewater samples. The glassy carbon electrode (GCE) was amplified using cellulose nanofibers/Fe3O4 composite (CNF-Fe3O4/NC) for monitoring hydrazine in the concentration range of 0.001 - 140 M with a superior detection limit of 0.5 nM. Results showed a diffusion control process for the oxidation of hydrazine at the surface of CNF-Fe3O4/NC/GCE. Under the optimum condition (pH=8.0), the oxidation current of hydrazine was improved by about 2.3 times and the oxidation potential was reduced by about 60 mV at the surface of CNF-Fe3O4/NC/GCE compare to unmodified GCE. A standard addition method was employed to assess CNF-Fe3O4/NC/GCE's capability for the detection of hydrazine in water and wastewater samples, and a recovery range of 97.6 % to 104.9 % was noted.

Water-carbon trade-off for inter-provincial electricity transmissions in China.

Electricity transmissions have been utilized in China to balance its spatially mismatched development needs and natural resources endowments. However, it has led to spatial shifts of negative environmental impacts induced by electricity generations, including water consumption and carbon emissions. This study calculates that, from 2010 to 2016, carbon emissions and water consumption to produce the transmitted electricity have grown from 507 Mt and 2.7 km3 respectively to 642 Mt and 6.5 km3. Applying a structural decomposition model coupled with a Quasi-Input-Output model to quantify the driving factors of such increases, we find that GDP increase has played the dominant role in driving the increase of both factors. Our results also highlight the potential conflicts between carbon reduction and water conservation in developing future electricity transmission infrastructure systems. Changing the electric power sector's energy portfolio and the transmission structure by increasingly utilizing hydropower productions have both contributed to national total carbon emissions reductions, but at the expenses of increased national water consumption. As a result, on a national level, in 2016, due to the inter-provincial differences in energy portfolios and technologies, electricity transmissions have led to 155.27 Mt of net carbon reduction and 3.4 km³ of additional net water consumption compared to the counterfactual scenario where no electricity transmission were facilitated. The future expansion of electricity transmission network needs to consider such trade-offs, particularly within the contexts of global climate change mitigation and emergent challenges posed by water stresses.

Enrichment and application of nitrifying activated sludge in membrane bioreactors.

In this study, nitrifying bacteria were enriched in a membrane bioreactor (MBR, R1) and their bioaugmentation effectiveness was evaluated in another two MBRs (R2 and R3). Nitrifying activated sludge (NAS) with high nitrification activity of up to 3,000 mg-N/(L·d)-1 was successfully enriched in R1. The results showed that chemical oxygen demand concentration of 100-200 mg/L had no negative effect on NAS enrichment but reduced the ratio of bacterial nitrifiers. Moreover, the cell concentration of nitrifying bacteria in NAS, which was 3.1 × 1011 cells/L, was similar to that of the commercial bacterium agent. For the bioaugmentation test, the reactor inoculated with 14% NAS achieved a 23% higher NH4+-N removal efficiency than that of the uninoculated reactor. Along with the improvement of nitrification performance, the bacterial nitrifiers abundance and microbial richness remarkably increased after bioaugmentation. These results suggested that the MBR system could efficiently enrich nitrifying bacteria using organic carbon containing culture medium, and potentially act as a side-stream reactor to enhance the nitrification function of the wastewater treatment plant.

[Enhanced Pollutants Removal in a Municipal Wastewater Treatment Plant with Multistage A/O Process].

Removal of conventional pollutants as well as genotoxicity was studied along a multistage A/O process, which was based on the monitoring data in a Municipal Wastewater Treatment Plant (MWWTP) of Yixing City. The results showed that the multistage A/O process removed (67.3±7.0)% of COD, (93.7±1.5)% of NH4+-N, (65.3±7.9)% of TN and (60.0±18.7)% of TP, respectively, which played a dominant role in the removal performance of the whole wastewater treatment process. The multistage A/O process showed significant ability to reduce alkanes, halogenated hydrocarbons and alcohols in the municipal wastewater, while it failed to remove the aromatic proteins which were the main fluorescent substances of this wastewater. Furthermore, the process removed 82.8% genotoxicity from its influent. Low organic load, single-phase influent and undesirable carbon source feeding pattern, which caused the downstream A/O stages being not fully utilized, were considered as the predominant reasons for the relatively low performance of the multistage A/O process. Multi-phase feeding and adjusting carbon source feeding pattern were thereby proposed. The results were considered to be helpful for improving the operational performance of the MWWTP and useful for performance evaluation of MWWTPs with similar process.