The effect of pH on the competition between polyphosphate-accumulating organisms and glycogen-accumulating organisms

In enhanced biological phosphorus removal (EBPR) processes, glycogen-accumulating organisms (GAOs) may compete with polyphosphate-accumulating organisms (PAOs) for the often-limited carbon substrates, potentially resulting in disturbances to phosphorus removal. A detailed investigation of the effect of pH on the competition between PAOs and GAOs is reported in this study. The results show that a high external pH ( approximately 8) provided PAOs with an advantage over GAOs in EBPR systems. The phosphorus removal performance improved due to a population shift favouring PAOs over GAOs, which was shown through both chemical and microbiological methods. Two lab-scale reactors fed with propionate as the carbon source were subjected to an increase in pH from 7 to 8. The phosphorus removal and PAO population (as measured by quantitative fluorescence in situ hybridisation analysis of "Candidatus Accumulibacter phosphatis") increased in each system, where the PAOs appeared to out-compete a group of Alphaproteobacteria GAOs. A considerable improvement in the P removal was also observed in an acetate fed reactor, where the GAO population (primarily "Candidatus Competibacter phosphatis") decreased substantially after a similar increase in the pH. The results from this study suggest that pH could be used as a control parameter to reduce the undesirable proliferation of GAOs and improve phosphorus removal in EBPR systems.     

利用极化电阻测试混凝土模拟孔隙溶液中钢筋锈蚀临界氯离子浓度

从钝化膜破坏标志钢筋锈蚀开始的本质出发,通过建立极化电阻与钢筋钝化膜间的对应关系,得到了钢筋钝化膜破坏时的极化电阻变化规律,研究了不同pH值下钢筋钝化膜破坏的临界氯离子浓度值,得到了pH值与临界氯离子摩尔浓度的关系,分析了pH值对钢筋钝化膜的影响。结果表明:当钢筋极化电阻值低于2.7×105Ω.cm2并持续下降时钢筋钝化膜已经破坏,在pH值为12.5~13.4之间,混凝土模拟孔隙溶液中临界氯离子浓度为[Cl-]/[OH-]比值0.1,pH值与临界氯离子摩尔浓度呈对数关系,pH值为11.7时临界氯离子浓度值接近为零,高pH值对维持钢筋钝化膜稳定效果明显。     

Effects of pH and precipitation on autohydrogenotrophic denitrification using the hollow-fiber membrane-biofilm reactor

Experiments carried out in a hollow-fiber, membrane-biofilm reactor (HFMBR) showed that the optimum pH for autotrophic denitrification was in the range 7.7-8.6, with the maximum efficiency at 8.4. Increasing the pH above 8.6 caused a significant decrease in nitrate removal rate and a dramatic increase in nitrite accumulation. The pH rose by 1.2 units when a large buffer was not added, suggesting that some field applications may require pH control. Precipitation of Ca(2+) occurred in every experiment. Precipitation was the largest sink for carbonate, and it also offset alkalinity production by denitrification. Although the alkalinity increased in most cases, systems with a high carbonate buffer and high pH accentuated precipitation, and the net change in alkalinity was negative. The long-term success of field applications of the HFMBR may depend upon the interactions among calcium concentration, total carbonate concentration, pH, and alkalinity changes.     

化学沉淀法对水中钼、钴金属污染物的应急处理技术研究

通过混凝试验,研究了化学沉淀法去除钼、钴金属污染物的可行性、最佳处理条件及最大应对能力。结果表明,采用三氯化铁作混凝剂,混凝前原水pH值调至7.0～7.6,可有效去除钼,其最佳pH值为7.0,且在钼标准限值10倍浓度条件下依然有良好的去除效果,但钼标准限值50,100倍浓度条件下,混凝沉淀后上清液钼浓度均无法达标;采用聚合氯化铝作混凝剂则无法有效去除钼。采用三氯化铁和聚合氯化铝作混凝剂,混凝前将水样pH值分别调至9.6～10.0和9.25～9.5,均可有效去除钴,其最佳pH值分别为9.75和9.5;在钴标准限值10,50和100倍高浓度条件下,聚合氯化铝作为混凝剂的去除效果明显优于三氯化铁,混凝沉淀后上清液钴浓度均能达标。     

pH值对溶胶-凝胶法制备La0.65Sr0.35MnO3的影响

利用溶胶-凝胶法制备亚锰酸盐化合物La0.65Sr0.35MnO3,通过XRD和SEM研究不同pH值对合成粉体相组成和微观形貌的影响。结果发现:在pH值为0.5的酸性环境和pH为8.0的弱碱性环境中,均可以获得具有钙钛矿结构且尺寸均匀的La0.65Sr0.35MnO3粉体。在pH值为0.5的酸性环境中,有利于形成二维层状结构的凝胶,而在pH为8.0的弱碱性环境中,有利于形成三维空间网络结构的凝胶,金属离子可以有效地分散于这两种凝胶中,避免了后期热处理过程中化学组分的偏差及团聚的生成。     

镁合金表面植酸转化膜研究Ⅱ.pH值对镁合金植酸转化膜的影响

通过SEM观察、AES元素深度分析、成膜增重实验、动电位极化曲线和EIS电化学测试，研究了植酸处理液的pH值对AZ91D镁合金转化膜生长速度及耐蚀性的影响.结果表明：溶液在pH=8时，转化膜生长速度最快，膜层较厚，且完整，无碎裂；pH=12时，转化膜生长速度较慢，膜层较薄；pH=5时，转化膜生长速度最慢，有碎裂.当植酸溶液的pH值在5～12时，镁合金表面形成的转化膜均可提高其耐蚀性，且pH=8时形成的膜耐蚀性最好.     

超声波辅助硫精矿回收萃铟废水中的锌

研究了一种通过控制pH值和以超声波为辅助手段,利用硫精矿溶解所产生的硫离子对锌的沉淀作用从萃铟废水中回收锌的新方法。试验结果表明：在pH值为2,硫精矿用量为理论量的1.05倍及常温条件下,用频率为40 kHz,功率为150 W的超声波辅助反应50 min,可从含铁61.23 g/L,含锌28.23 g/L的广东某锌铟冶炼厂萃铟废水中获得锌品位为50.36%的锌精矿产品,锌的回收率达到95.29%;有超声波辅助作用与无超声波辅助作用相比,锌精矿锌回收率提高了23.67个百分点,锌品位提高了18.52个百分点,且锌精矿颗粒比较均匀,粒径明显减小。     

核黄素在废水处理过程中的荧光光谱特性研究

废水处理过程中会产生核黄素,其含量在一定程度上能够反映生物反应器的运行状态。本文采用荧光光谱法,针对废水处理过程中核黄素的自身的浓度效应、pH值和离子强度与核黄素的荧光光谱特性之间的关系进行了相关研究,为废水处理过程中生物反应器的参数控制提供相关数据,以进一步提高厌氧降解效率。     

混凝土碳化试验与碳化深度测定方法的对比分析

利用不同的混凝土碳化试验方法和碳化深度测定方法测试得到的混凝土碳化深度存在差异。通过对自然碳化和实验室加速碳化两种碳化试验方法的对比分析,以及酚酞指示剂法、红外光谱法、热分析法和 X射线物相分析法等碳化深度测定方法的对比,分析研究了各混凝土碳化试验方法与碳化深度测定方法的原理和各自的特点,可以为混凝土结构碳化分析的试验方法选择提供参考。