1.
Stress-strain relationship and seismic performance of cast-in-situ phosphogypsum.
Zhang, Y, Dai, S, Weng, W, Huang, J, Su, Y, Cai, Y
Journal of applied biomaterials & functional materials. 2017;(Suppl. 1):e62-e68
Abstract
BACKGROUND Phosphogypsum is a waste by-product during the production of phosphoric acid. It not only occupies landfill, but also pollutes the environment, which becomes an important factor restricting the sustainable development of the phosphate fertilizer industry. Research into cast-in-situ phosphogypsum will greatly promote the comprehensive utilization of stored phosphogypsum. The aim of this study was to clarify the mechanical properties of phosphogypsum. METHODS Stress-strain relationships of cast-in-situ phosphogypsum were investigated through axial compressive experiments, and seismic performance of cast-in-situ phosphogypsum walls and aerated-concrete masonry walls were simulated based on the experimental results and using finite element analysis. RESULTS The results showed that the stress-strain relationship fitted into a polynomial equation. Moreover, the displacement ductility index and the energy dissipation index of cast-in-situ phosphogypsum wall were 6.587 and 3.425, respectively. CONCLUSIONS The stress-strain relationship for earthquake-resistant performance of cast-in-situ phosphogypsum walls is better than that of aerated-concrete masonry walls. The curve of stress-strain relationship and the evaluation of earthquake-resistant performance provide theoretical support for the application of cast-in-situ phosphogypsum in building walls.
2.
[Characteristics and Mechanism of Biological Nitrogen and Phosphorus Removal Granular Sludge Under Carbon Source Stress].
Qin, SY, Chen, W, Ma, ZR, Liu, XY, Chen, XG, Yu, WT, Xia, YY, Huang, J
Huan jing ke xue= Huanjing kexue. 2017;(6):2461-2469
Abstract
In SBR reactor, the mature granular sludge fed with sodium acetate was gradually cultivated with different carbon sources (sodium acetate/glucose ratio was 1:0, 3:1, 1:1, 1:3 and 0:1, in terms of COD, respectively). During the five stages, the physical, biochemical properties, extracellular polymeric substances (EPS), phosphorus fractions and nitrogen and phosphorus removal efficiency of granular sludge were studied. 705 days' experimental results were showed as follows. At stage Ⅳ, the granular sludge had the smallest diameter of 0.5 mm; moreover the phosphorus release/uptake rate, denitrification rate and the total phosphorus (TP) content were the lowest. While at stages Ⅰ and Ⅱ, the phosphorus release/uptake and denitrification rates were the highest, meanwhile, the TP content reached up to 72.36 mg·g-1, and the EPS content was about 350 mg·g-1, as a result, the nitrogen and phosphorus removal efficiencies were both over 94%. Nevertheless at stage Ⅴ, the biochemical rates were slightly slower than values of stages Ⅰ and Ⅱ, simultaneously the TP, glycogen and EPS contents in sludge were maintained at 69.60 mg·g-1, 224.18 mg·g-1 and 200 mg·g-1, respectively, while high nitrogen and phosphorus removal efficiency was obtained. During all stages, Ca-P was the main phosphorus fraction, and inorganic phosphorus(IP) was closely related to phosphorus removal of granular sludge.