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With the fast progress of infrastructure projects, super-large cross-section projects are constantly emerging, and, therefore, engineering challenges and problems are increasing. Taking the triple-arch tunnel project in the turn-back line section of Santunbei Station in Urumqi Metro Line 1# as a case study, this research applied numerical simulation software Midas GTS/NX 2022 for the analysis of tunnel force and deformation in triple-arch cross-sections under different support forms of partition wall. Following the optimization of the support design of the mixed partition wall to a single straight wall, the following analytical results were obtained: surface settlement was decreased by 21.15% at the original cross-section; maximum values of principal stress and displacement of partition wall were decreased by 6.73 and 10.64%, respectively; and corresponding values for initial support structure were decreased by 21.47% and 54.74%, respectively. Meanwhile, combined with comparative analysis of engineering measurement and numerical simulation results, surface settlement and vault deformation were found to be similar to the optimized simulation results, which not only verified the reliability of simulation results but also ensured the safe and smooth construction of the project, greatly improving construction efficiency and saving construction time and cost.

As a kind of advanced water purification technology, nanofiltration (NF) has been widely used in the treatment of water. In the NF process, scale inhibitor such as aminotris (methylenephosphonic acid) (ATMP, H6atmp, H6L) is commonly added to control scale deposition. However, the impact of ATMP on the separation performance of NF has up to now been unknown. In this study, the impact of ATMP on calcium ion (Ca2+) rejection rate and permeate flux of NF 270 membrane were investigated by permeate experiments with different ATMP concentrations. The results showed that ATMP had a significant impact on Ca2+ rejection rate, as well as the feed pH. Both a local minimum in rejection rate and a slight maximum in permeate flux appeared at 10 mg·L-1 ATMP, corresponding to the feed pH about 5.5, which may be close to the isoelectric point (IEP) of membrane. When ATMP concentration was below 8 mg·L-1 and above 10 mg·L-1, increasing ATMP concentration would both dramatically enhance Ca2+ rejection rate. The main mechanism affecting the performance of NF was electrostatic effect caused by ATMP rather than its chelation effect. Our work demonstrated that in addition to the scale inhibition effect, ATMP in water also had a certain impact on the performance of NF membrane, especially for treating low alkalinity water (contain hardness and SO42-), and aminotris (methylene phosphonic acid) (ATMP, H6atmp, H6L) is preferred to avoid precipitation and improve NF softening and desalination performance. [ABSTRACT FROM AUTHOR]

Aquatic plants are widely used for treating wastewater treatment plant secondary effluent. During this process, some residual activated sludge in the secondary effluent is intercepted and attaches to the plant roots. However, the effect of the attached activated sludge on nutrient removal in secondary effluent has up to now been unknown. Aiming at this problem, this investigation was conducted to compare the nutrient removal rates in secondary effluent by washed Pistia stratiotes (washed batch) and Pistia stratiotes with activated sludge attached to the roots (study batch). Extracellular polymeric substances (EPS) from the activated sludge attached to the roots were extracted and characterized by three-dimensional excitation emission matrix (3D-EEM) fluorescence spectroscopy. The results showed that the nutrient removal rates in the study batch were better than that in the washed batch. The 3D-EEM results showed that the protein content of EPS increased during the experiment, indicating the growth of microorganisms in the attached activated sludge. Our work demonstrated the enhanced effect of activated sludge attached to the roots of Pistia stratiotes on the removal of pollutants in secondary effluent, which is useful to guide the practical engineering of secondary effluent treatment. [ABSTRACT FROM AUTHOR]