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The present work used the coagulative colloidal gas aphron (CCGA)-involved flotation as a robust technology to efficiently remove the typical engineered nanoparticles – silica nanoparticles (SNPs) from water. The inorganic polymer coagulant – polyaluminum chloride (PACl) was used to surface-functionalize the zwitterionic surfactant (C15B)-based CGAs. Results denote that the physicochemical conditions of PACl/C15B mixed solution markedly influenced the flotation behaviors by changing the properties of CCGAs. The C15B molecules showed different dissociated states and interaction behaviors with Al species with the variation of pH. The addition of salt into the PACl/C15B mixed solution decreased the foamability of solution, and the bubbles collapsed before they could efficiently capture SNPs in their rising trajectory. The optimum SNP removal (87.2%) was obtained when the pH and the additional ionic strength of PACl/C15B mixed solution were ∼4.7 and ≤ 1.0 g NaCl/L, individually, and the pH of SNP suspension was ∼9.4. Importantly, modifying PACl on microbubbles took greater advantages than directly using it as coagulant in terms of SNP removal and PACl utlization. The CCGAs were robust since their colloidal attraction and collision efficiency with SNPs were simultaneously enhanced. The PACl was more efficiently utilized during flotation whilst the regular chemical-dosing unit was omitted.

The ambient noise in controlled-source electromagnetic (CSEM) data seriously affects the accuracy and reliability of the exploration result. Traditional correlation-based data selection method requires manually setting the threshold. To overcome the deficiency, we analyze the typical noises in CSEM data and find that normalized cross-correlation (NCC), absolute maximum value of the amplitude (Max), and detrend fluctuation analysis (DFA) can be used to accurately identify high-quality time series. Based on this discovery, we replace traditional manually intervention with unsupervised machine learning and propose a novel CSEM data processing method. We applied the newly proposed method to synthetic and measured CSEM data to verify the feasibility and effectiveness. Experimental results demonstrate that the newly proposed method is superior to the conventional data selection method because it accurately selects the best data fragments from noisy data automatically. The newly proposed method requires no human intervention which makes the results obtained free of subjective distortion caused by the operator.

A novel modified pilot scale anaerobic oxidation ditch with additional internal anoxic zones was operated experimentally, aiming to study the improvement of biological nitrogen and phosphorus removal and the effect of enhanced denitrifying phosphorus removal in the process. Under all experimental conditions, the anaerobic-oxidation ditch with additional internal anoxic zones and an internal recycle ratio of 200% had the highest nutrient removal efficiency. The effluent NH + 4 -N, total nitrogen (TN), PO 3− 4 -P and total phosphorus (TP) contents were 1.2 mgL −1 , 13 mgL −1 , 0.3 mgL −1 and 0.4 mgL −1 , respectively, all met the discharge standards in China. The TN and TP removal efficiencies were remarkably improved from 37% and 50% to 65% and 88% with the presence of additional internal anoxic zones and internal recycle ratio of 200%. The results indicated that additional internal anoxic zones can optimize the utilization of available carbon source from the anaerobic outflow for denitrification. It was also found that phosphorus removal via the denitrification process was stimulated in the additional internal anoxic zones, which was beneficial for biological nitrogen and phosphorus removal when treating wastewater with a limited carbon source. However, an excess internal recycle would cause nitrite to accumulate in the system. This seems to be harmful to biological phosphorus removal.

A pilot-scale, pre-anoxic-anaerobic oxidation ditch was used in this study to treat municipal wastewater with limited carbon source. A novel return activated sludge (RAS) pre-concentration tank was adopted for improving the phosphorus removal efficiency and the effects of RAS pre-concentration ratio were studied. Under the optimal operational condition, the suspended total phosphorus (STP) and the total phosphorus (TP) removal efficiencies were around 58.9% and 63.9% respectively and the effluent PO3-4 -P was lower than 0.8 mg·L−1. The reason is that with the optimal RAS pre-concentration ratio, nitrate is completely removed with endogenous carbon source and the secondary phosphorus release is strictly restrained in the pre-anoxic tank. Therefore, the anaerobic phosphorus release and the carbon source uptake by phosphorus accumulation organisms (PAOs) in the sludge, which are extremely important to the phosphorus removal process, can be fully satisfied. Furthermore, the oxidation-reduction potential is proved to be suitable for controlling the RAS pre-concentration ratio due to influent fluctuation and varied conditions. The novel modified system is also beneficial for PAO accumulation.