EM enrichment culture liquid was immobilized on nano-silica carrier to form microbial nano ball, so as to investigate the reaction kinetics of ammonia nitrogen (NH4+-N) by microbial nano ball. The results showed that first order reaction kinetics model could describe NH4+-N removal by different diameter microbial nano-silica balls well. And the microbe could keep higher biological activity between 0-72h. Reaction kinetic equations of NH4+-N were: (1) when diameter was 10mm, (0-48h), (48-72h); (2) when diameter was 20mm, (0-48h), (48-72h); (3) (0-48h), (48-72h).
Through real-time monitoring of chemical oxygen demand (COD), ammonia nitrogen (NH 4 + -N), total nitrogen (TN) and total phosphorus (TP) in the aquaculture wastewater, the purification effects of EM techniques by applying EM active calcium, Microbial nanoSilica Ball and both of them were studied. The results showed that the purification effect of solid preparation for Microbial nanoSilica Ball was better than that of the liquid preparation for EM active calcium. Moreover, the purification effect with the technological cooperation of Microbial nanoSilica Ball with EM active calcium reached best, indicating that the removal rate of COD, NH 4 + -N, TN and TP in the aquaculture wastewater was 72.12% , 73.85% , 64.99% and 67.87% respectively.
To form microbial nanoball, EM active calcium was immobilized on nano-silica carrier consisting of pond sediment, zeolite powder and nanosilica. Through real-time monitoring of pH, dissolved oxygen (DO), chemical oxygen demand (COD) and ammonia nitrogen (NH 4 + -N) aquaculture wastewater, the purification effects of Microbial nanoSilica Ball on aquaculture wastewater under different mud-water ratio condition were studied. The results showed that the purification effect reached best in 3-6 days for all treatments and was better for mud-water ratio of 1:2.7. In this mud-water ratio, it was indicated that pH was maintained at 7-8.5 which was an optimum value for the aquaculture, the content of DO was increased by 82.16% compared with the initial value and the removal rate of COD and NH 4 + -N was 57.80% and 54.60% respectively.
In view of the harm of residual film retention to soil environment in Xinjiang which even affected the germination of seeds and hindered the growth of crop roots in severe cases, in this paper, a 4SGMS-220 plough layer residual film recovery machine with a ground preparation device is designed. The main part of the machine is composed of a filming mechanism, a conveying mechanism, a soil crushing roller, and a film collecting box. The machine can achieve simultaneous film lifting, film stripping, collecting membrane and suppression operations. In this paper, primary focus is placed on the design of the filming mechanism, while the movement trajectory of the comb teeth and the filming condition are analysed in detail. In order to obtain the optimal combination of equipment and operating parameters, the equipment traveling speed, the filming device rotational speed, and the comb teeth depth are used as the influencing factors. Furthermore, the residual film recovery rate and impurity rates are employed as test indicators for three-factor three-level response surface experiment and optimization via Design-Expert software. The results indicate that optimal operation is achieved for the machine travel speed of 4.1 km/h, the filming device speed of 106 min-1, and the comb tooth soil penetration depth of 139.2 mm. The residual film recovery rate is equal to 74.32%, while the residual film impurity rate is equal to 7.11%. The difference between the test results and the predicted values is relatively small. Thus, it can be concluded that the optimized model is reliable.
To address the issue of uneven shear strength distribution in dredged sediment during electroosmosis treatment, a grouting system was employed to inject CaCl2 into the anode region and Na2SiO3 solution into the central region. An experimental study was conducted to examine the effect of injection timing on the electrochemical treatment of dredged sediment. Five experimental groups, each with different Na2SiO3 injection timings, were established. The impact of injection timing on the macroscopic electrochemical reinforcement was assessed based on current, drainage volume, settlement, moisture content, and shear strength. Additionally, the ion concentration of effluent from the cathode was measured, and scanning electron microscopy (SEM) and mercury intrusion porosimetry (MIP) were employed to analyze ion migration and pore characteristics. The results indicated that when CaCl2 was injected into the anode at the start of the experiment and Na2SiO3 was injected into the central region after the current had decayed by 70% from its peak, the drainage volume reached its maximum. Under these conditions, the average shear strength increased from nearly 0 kPa to 48.2 kPa, yielding the optimal reinforcement effect. The strength in both the central and cathode regions also improved, and the strength distribution between the anode and cathode became more uniform, with the strength ratio decreasing from 1.91 to 1.65, thereby enhancing the overall soil strength distribution. The Na+ concentration in the cathode effluent was highest, suggesting that Na+ migration played a predominant role in electroosmotic drainage. Furthermore, the electrochemical reactions generated cementitious materials that effectively filled the soil pores. SEM imaging and MIP pore size analysis revealed a reduction in porosity and an increase in soil compaction.
The secondary salinized greenhouse soil was provided with subsurface pipe drainage system with drainage spacing 6 m and drain depth 0.4m to study the movement of salt and water. The field investigations indicated that the resalination rates of the surface soil with subsurface drainage system were lower than those with non-drained system (CK) in an irrigation circle of the crop. The resalination rate of the surface soil right above the drainage tubes (T1) was significantly lower than that between the two drainage tubes (T2). At the 5th day after irrigation, the soil volumetric moisture contents of different treatments were significantly decreased and the resalination of surface soil were obvious. The results showed a considerable increase of resalination rate after irrigation that was varied at the 5th day as following sequence: CK(10.6%) > T2(8%) > T1(7%).
Recent research shows that there is a serious need for accurate methods to evaluate the deformation resistance of asphalt mixtures at high temperatures, especially for stone-skeleton mixtures. To reflect the interlocking angle between coarse aggregates, confining pressure should be considered during testing. The dynamic loading test has been developed for applying different repetitive loads to a limited area of the specimen. This test can measure permanent deformation indices under different loads to evaluate the deformation resistance of asphalt mixtures at high temperatures. The dynamic loading test is conducted on samples with different compaction rates and gradations. Further, the rutting resistance of two types of gradation is compared with a wheel tracking test and a dynamic loading test. The test results indicate that the dynamic loading test can apparently distinguish the influence of gradations on rutting resistance. It is also derived from this test that dense-graded mixtures have higher permanent deformation susceptibility than coarse-graded mixtures, which is consistent with experience in the field and validated by experiments. This test can reflect the entire permanent deformation and separate the compactive deformation and shear flow deformation. Furthermore, this test can simulate heavy and repeated loads to fully exhibit the deformation resistance of asphalt mixtures, especially for coarse-graded mixtures. However, this test is limited by the effects of rigid confinement, which can be improved by changing the confining pressure.
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