This paper studied Beijing sanitary wastewater and investigated phosphorus removal effect and related factors under PFS and polyacrylamide (PAM) synergistic effect. The results show that the effect of phosphorus removal would be improved to a certain extent when the PFS combined with the PAM. The optimum dosage of PAM, the best mixing intensity and time, and the best pH are all defined and the order of coagulation influencing factors is: stirring intensity> pH> stirring time> dosage.

As the coal mine gets deeper and the stopes’ structures become more complex, gas and coal spontaneously burned composite disaster seriously threatens the efficient operation of coal mines. To study the interaction process and disaster-causing mechanism of gas and coal spontaneous combustion (GCSC), this paper establishes a numerical model to study the influence of drilling location/pressure and N2 injection on the evolution of gas and coal spontaneously burned composite disaster in the goaf. The simulation shows that in the central part of the goaf, a combined area of gas and coal combustion poses a possibility of spontaneous combustion calamity, and the length of the compound disaster area is about 20 m. The methane (CH4) explosion zone and the dioxygen(O2) temperature rise zone do not overlap in the air entrance roadway and return air roadway, indicating that there is no risk of compound disasters. The optimal nitrogen (N2) injection rate for this working face is 2000 m3/h, and the N2 port should be located 25 m profound into the goaf, which can effectively drive the diffusion of N2 and narrow the O2 zone’s breadth. The findings have considerable engineering applications for revealing the evolution process, risk assessment and control for GCSC compound disasters in coal mines.

The deformation and failure features of rock formation in deep coal mines are basic mechanical problems in the complex geology environment and complicated excavation process. Under the effect of cyclic loading and unloading, the bearing capacity weakens and damage degree exacerbates significantly, which seriously threatens the safety and stability of the working face. To study the damage characteristics of sandstone, especially the precursor characteristics of acoustic emission (AE), this paper conduct the AE response experiments on sandstone under cyclic loading and unloading. The results show that with the increasing number of cycles, the loading modulus, unloading modulus, total strain energy, elastic energy, and dissipation energy of sandstone in the cycle stage all increase continuously. In the initial loading stage, the sandstone has fewer cycles and lower stress levels, fewer AE ringing counts and energy, and less rock damage. With the increasing cyclic times and loading stress, the damage degree of sandstone increases rapidly in a very short time. The damage variable represented by ringing count is more sensitive than by energy. Just before rock failure, the ringing count and the energy value increase significantly, and the damage curve rises sharply. In addition, AE waveform signals have obvious aggregation characteristics and four main bands. Just before sandstone failure, the main frequency band becomes wider, the low frequency bands f1 and f2 become connected, and the main signal frequency appears abnormally low and high. The waveform signals before sandstone instability and failure show a phenomenon where the low-frequency amplitude is generally at a high level, the high-frequency signal decreases, the amplitude becomes low, and the multipeak phenomenon weakens. The above characteristics of the AE time domain and waveform analysis can be used as the precursor characteristics of sandstone failure and instability. This study can reveal the process of the sandstone deterioration and AE response under the cyclic loading and unloading condition, and has certain guiding significance for roof and floor control in deep roadway, instability warming monitor of working faces, and guarantees for safety production.

The 10 organophosphorus pesticides in fish can be rapidly extracted and separated by gel permeation chromatography, and the lipin and organophosphorus pesticides of fish can be seperated. The interfering matters can be well eliminated in this condition, and analysis is more rapid than other methods. The residues of 10 organophosphorus pesticides at same time can be identified and quantified simultaneously by GC-PFPD. This method is simple, rapid, and the average recovery ratios were 71.7%-80.9%.Good repeatability was obtained in all the cases with relative standard deviations (RSDs) lower 11%, and limit of detection was0.0003-0.004 mg·kg-1.