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821.
822.
Kinetics of enzymatic unhairing by protease in leather industry 总被引:2,自引:0,他引:2
In leather industry, unhairing is a heavy pollution operation. The conventional lime-sulfide process produces a large amount of sulfide which is toxic to health and difficult to dispose. Moreover, conventional lime-sulfide process leads to the destruction of the hair causing increased COD, BOD and TDS loads in the effluent. As an alternative method, enzymatic unhairing is a promising clean technology. The main utilized enzyme preparations are proteases.There are many reports about enzymatic unhairing, most of which are qualitative. The kinetics of enzymatic unhairing by protease was discussed in this article. It will provide useful information to enzymatic unhairing. In our research, by analysis of the concentrations of released total protein in enzyme bath during protease unhairing, the good linearity between released total protein and square root of time (min1/2) was obtained at the initial stage. The good linearity suggests that enzymatic unhairing by protease is a diffusion-controlled process at the initial stage. The analysis of kinetics of released saccharides also confirms the same conclusion. On the other hand, the same characteristics between the kinetics of released saccharides and that of released total protein further confirms that it is the hydrolysis of core protein by protease that leads to the degradation of proteoglycans and the release of protein and saccharides. However, in our tests, the kinetics of released collagen indicates that the injury to skin took place in 3-6 h. Therefore, it’s necessary to control the time of protease unhairing within an appropriate limit. 相似文献
823.
基于格网的太湖生态环境质量空间评价 总被引:1,自引:0,他引:1
将GIS格网空间分析技术应用于太湖生态环境综合评价,实现了全湖范围内多因素的综合评价,揭示太湖生态环境状况的空间分布规律。首先将太湖分为800个格网单元,在2002~2003年实测样点的水体、底泥、水生生物特征数据基础上,通过空间插值获得全部单元模拟值,然后进行格网叠加计算,通过层次分析法得出各单元综合评价值,将太湖分为好、较好、中等、较差、差5个等级区,生成太湖生态环境空间综合评价图。结果显示,评价结果与太湖实际情况基本相符,太湖生态环境质量基本上由东南向西北逐渐降低,中等以下地区占全部湖区的一半以上,整体状况偏差。 相似文献
824.
825.
应用景观生态学原理构建城市河道生态护岸 总被引:19,自引:0,他引:19
首先分析了传统水工设计中护岸的弊端,然后从景观生态学角度介绍了岸坡生态系统的主要特征、生态护岸的多种功能和景观生态学内涵;介绍了国内外生态护岸的研究现状,提出了城市河道在生态护岸设计中应在保证稳定安全的前提下,坚持生态优先的原则,重视其景观性和亲水性;最后对生态护岸的材料与植物群落的选择进行了分析。旨在探讨河流生态治理的方法,为生态护岸的构建与河流、洪泛区的治理提供一定的思路和参考。 相似文献
826.
中国旅游业空间集聚与集群化发展研究 总被引:13,自引:0,他引:13
旅游产业集聚与集群是联系密切而又有明显区别的一组概念,旅游产业集聚是集群形成的前提,但旅游产业集聚不一定形成集群,影响旅游产业空间集聚和集群发展的因素较多。选择行业集中度、基尼系数、赫芬代尔系数等指标,以相关数据为依据,探讨了中国旅游业的空间集聚问题,指出中国旅游业具有明显的空间集中分布与分散相结合的集聚特征。分析了中国旅游业集群发展现状与存在的问题并提出了相应对策,认为我国旅游业集群化发展是非常必要而且有可能的。 相似文献
827.
828.
Tao Zhang Qiucheng Li Lili Ding Hongqiang Ren Ke Xu Yonggang Wu Dong Sheng 《环境科学学报(英文版)》2011,23(6):881-890
Chemical precipitation to form magnesium ammonium phosphate (MAP) is an effective technology for recovering ammonium
nitrogen (NH4
+-N). In the present research, we investigated the thermodynamic modeling of the PHREEQC program for NH4
+-N
recovery to evaluate the effect of reaction factors on MAP precipitation. The case study of NH4
+-N recovery from coking wastewater
was conducted to provide a comparison. Response surface methodology (RSM) was applied to assist in understanding the relative
significance of reaction factors and the interactive effects of solution conditions. Thermodynamic modeling indicated that the saturation
index (SI) of MAP followed a polynomial function of pH. The SI of MAP increased logarithmically with the Mg2+/NH4
+ molar ratio
(Mg/N) and the initial NH4
+-N concentration (CN), respectively, while it decreased with an increase in Ca2+/NH4
+ and CO3
2??/NH4
+
molar ratios (Ca/N and CO3
2??/N), respectively. The trends for NH4
+-N removal at different pH and Mg/N levels were similar to the
thermodynamic modeling predictions. The RSM analysis indicated that the factors including pH, Mg/N, CN, Ca/N, (Mg/N) (CO3
2??/N),
(pH)2, (Mg/N)2, and (CN)2 were significant. Response surface plots were useful for understanding the interaction effects on NH4
+-N
recovery. 相似文献
829.
Effect of C/N ratio, aeration rate and moisture content on ammonia and greenhouse gas emission during the composting 总被引:3,自引:0,他引:3
Gaseous emission (N2O, CH4 and NH3) from composting can be an important source of anthropogenic greenhouse gas and air pollution. A laboratory scale orthogonal experiment was conducted to estimate the effects of C/N ratio, aeration rate and initial moisture content on gaseous emission during the composting of pig faeces from Chinese Ganqinfen system. The results showed that about 23.9% to 45.6% of total organic carbon (TOC) was lost in the form of CO2 and 0.8% to 7.5% of TOC emitted as CH4. Most of the nitrogen was lost in the form of NH3, which account for 9.6% to 32.4% of initial nitrogen. N2O was also an important way of nitrogen losses and 1.5% to 7.3% of initial total nitrogen was lost as it. Statistic analysis showed that the aeration rate is the most important factor which could affect the NH3 (p = 0.0189), CH4 (p = 0.0113) and N2O (p = 0.0493) emissions significantly. Higher aeration rates reduce the CH4 emission but increase the NH3 and N2O losses. C/N ratio could affect the NH3 (p = 0.0442) and CH4 (p = 0.0246) emissions significantly, but not the N2O. Lower C/N ratio caused higher NH3 and CH4 emissions. The initial moisture content can not influence the gaseous emission significantly. Most treatments were matured after 37 days, except a trial with high moisture content and a low C/N ratio. 相似文献
830.
Polyaspartic acid (PASP) has been extensively studied in recent years as a green scale inhibitor. PASP was synthesized by thermal polycondensation of maleic anhydride and ammonium carbonate in this study. The optimal polycondensation reaction conditions were the raw material (maleic anhydride and ammonium carbonate) molar ratio of 1.0:1.2, the polymerization temperature of 180°C and reaction time of 2.0 hr. The results showed that PASP exhibits very good scale inhibiting performance. The inhibition rate was 95% for calcium carbonate and 90% for calcium sulfate by the application of 5 mg/L PASP. 相似文献