A new method (NMM, using acetic acid fiber filter and 90% ethanol) was established to determine chlorophyll in freshwater algae, and it was compared with US standard method (USM, using glass fiber filter and 90% acetone) and the method recommend by EPA of China (CHM, using acetic acid fiber filter and 90% acetone). The precision and repeatability of NMM is equivalent to that of USM, but NMM is safer to laboratory workers than USM and CHM because ethanol was used as solvent in NMM instead of acetone used in USM and CHM, and time and money were also greatly saved by the new method. The precision and repeatability of CHM was much less than USM and NMM, and the advice improving the method was proposed that the extraction time must be prolonged.
High power and good beam quality of two-dimensional bottom-emitting vertical-cavity surface-emitting laser array with GaAs microlens on the substrate is achieved. Uniform and matched convex microlens is directly fabricated by one-step diffusion-limited wet-etching techniques on the emitting windows. The maximum output power is above 1 W at continuous-wave operation at room temperature, and the far-field beam divergence is below 6.6° at a current of 4 A. These properties between microlens-integrated and conventional device at different operating current are demonstrated.
In order to effectively remove the Microcystis from drinking-water sources, pre-pressure treatment was first used to make the Microcystis lose buoyancy, and then it is easily removed by coagulation and sedimentation processes. The Microcystis-containing water from Taihu Lake was taken for the pre-pressure coagulation and sedimentation treatments in this study. Both intermittent laboratory experiment and continuous-flow field experiment were conducted. Experimental results showed that the optimum pre-pressure condition was pressuring at 0.6-0.8 MPa for at least 10 s, and 60 s was the best. Comparing with the pre-oxidation, pre-pressure could obviously increase the removal efficiency of Microcystis by following coagulation and sedimentation, and would not increase the dissolved microcystins. The mechanism of pre-pressure treatment was that the pre-pressure destroys the gas vesicles in Microcystis cells and the gas diffuses out of the cells, which leads the Microcystis to lose buoyancy and make them to sink. The recovery time of gas vesicles was longer than the sludge discharge period of sedimentation tank; therefore, the sinking Microcystis would not re-float in the sedimentation tank. In the practical application of drinking water treatment plant, the continuous-flow pressure device could be chosen, with the energy consumption of about 22.9 kw·h per 10,000 m.
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