Determination and discussion hydraulic retention time in membrane bioreactor system

Based on the microorganism kinetic model, the formula for computing hydraulic retention time in a membrane bioreactor system (MBR) is derived. With considering HRT as an evaluation index a combinational approach was used to discuss factors which have an effect on MBR. As a result, the influencing factors were listed in order from strength to weakness as: maximum specific removal rate K, saturation constant Ks, maintenance coefficient m, maximum specific growth rate ,ua and observed yield coefficient Yobs. Moreover, the formula was simplified, whose parameters were experimentally determined in petrochemical wastewater treatment. The simplified formula is θ= 1.1( 1/β -1)(Kｓ S)/KXo , for oetroehemical wastewater treatment K and Ko eaualed 0.185 and 154.2, resoectively.     

Effects of Fireplace Use on Forest Vegetation and Amount of Woody Debris in Suburban Forests in Northwestern Switzerland

Urban forests are popular recreation areas in Europe. Several of these temperate broad-leaved forests also have a high conservation value due to sustainable management over many centuries. Recreational activities, particularly the use of fireplaces, can cause extensive damage to soil, ground vegetation, shrubs, and trees. Firewood collection depletes woody debris, leading to a loss of habitat for specialized organisms. We examined the effects of fireplace use on forest vegetation and the amount of woody debris by comparing disturbed and control plots in suburban forests in northwestern Switzerland. At frequently used fireplaces, we found reduced species densities in the ground vegetation and shrub layer and changes in plant species composition due to human trampling within an area of 150–200 m². Picnicking and grilling also reduced the height and changed the age structure of shrubs and young trees. The amount of woody debris was lower in disturbed plots than in control plots. Pieces of wood with a diameter of 0.6–7.6 cm were preferentially collected by fireplace users. The reduction in woody debris volume extended up to a distance of 16 m from the fire ring, covering an area of 800 m² at each picnic site. In order to preserve the ecological integrity of urban forests and to maintain their attractiveness as important recreation areas, we suggest depositing logging residues to be used as firewood and to restrict visitor movements near picnic sites.     

一种改进的多学习教与学优化算法

针对传统教与学算法在解决复杂多峰函数优化问题时,具有局部最优且搜索开发能力较差的缺点,提出了一种改进的多学习教与学优化算法,新算法为学员的每一维加入不同的教学因子,设计了基于学员均值比较的教师选择策略和向教师及学员学习的多学习策略。基于多个单峰和多峰函数的仿真结果表明,新算法跟传统的、改进的教与学算法相比,在稳定性、寻优精度和收敛速度方面更具优势。     

Emerging conservation challenges and prospects in an era of offshore hydrocarbon exploration and exploitation

Globally, extensive marine areas important for biodiversity conservation and ecosystem functioning are undergoing exploration and extraction of oil and natural gas resources. Such operations are expanding to previously inaccessible deep waters and other frontier regions, while conservation‐related legislation and planning is often lacking. Conservation challenges arising from offshore hydrocarbon development are wide‐ranging. These challenges include threats to ecosystems and marine species from oil spills, negative impacts on native biodiversity from invasive species colonizing drilling infrastructure, and increased political conflicts that can delay conservation actions. With mounting offshore operations, conservationists need to urgently consider some possible opportunities that could be leveraged for conservation. Leveraging options, as part of multi‐billion dollar marine hydrocarbon operations, include the use of facilities and costly equipment of the deep and ultra‐deep hydrocarbon industry for deep‐sea conservation research and monitoring and establishing new conservation research, practice, and monitoring funds and environmental offsetting schemes. The conservation community, including conservation scientists, should become more involved in the earliest planning and exploration phases and remain involved throughout the operations so as to influence decision making and promote continuous monitoring of biodiversity and ecosystems. A prompt response by conservation professionals to offshore oil and gas developments can mitigate impacts of future decisions and actions of the industry and governments. New environmental decision support tools can be used to explicitly incorporate the impacts of hydrocarbon operations on biodiversity into marine spatial and conservation plans and thus allow for optimum trade‐offs among multiple objectives, costs, and risks.     

The estimation of PAH bioavailability in contaminated sediments using hydroxypropyl-beta-cyclodextrin and Triton X-100 extraction techniques

A study was conducted to investigate whether cyclodextrins and surfactants can be used to predict polycyclic aromatic hydrocarbon (PAH) bioavailability in contaminated sediments. Two sediment samples were extracted with aqueous solutions of hydroxypropyl-beta-cyclodextrin (HPCD) and Triton X-100. PAH removal during extraction was compared with PAH removal during biodegradation and solid-phase extraction. The latter two methods were used as reference methods to establish which part of the PAHs could be biodegraded and to what extent biodegradation was governed by bioavailability limitations. It was demonstrated that HPCD extraction followed solid-phase extraction and removed primarily readily bioavailable PAHs, while Triton X-100 extracted both readily and poorly bioavailable PAHs. Moreover, HPCD did not affect the degradation of PAHs in biodegradation experiments, while Triton X-100 enhanced the degradation of low molecular weight PAHs. It was concluded that HPCD extraction may provide a good method for the prediction of PAH bioavailability. Triton X-100 extraction is unfit for the prediction of PAH bioavailability.     

The building materials decree: an example of a Dutch regulation based on the potential impact of materials on the environment

Some 20 years ago Dutch society became very aware of the problem of the increasing production of waste materials and of the need to find solutions. Technical solutions had to be developed and introduced into society. Due to the discovery of many soil pollution problems and other environmental calamities, people asked for clear criteria on which proper and safe solutions could be based. Therefore a large number of environmental aspects had to be taken into account in the developing field of environmental policy. The Dutch building materials decree is one of the steps on the road towards a sustainable society. The decree is based on the soil protection act and the surface water protection act. The decree gives quality criteria for the application and re-use of stony materials and earth used as building materials. No difference is made between primary materials, secondary materials and waste materials. The decree is applicable in case these materials are used in constructions where they are in contact with rain, surface water and ground water (e.g. in embankments, road building, outside walls of buildings, foundations and roofs). For implementation of the decree in the construction industry it was necessary to develop standards, methods for testing and certification schemes. In order to guarantee independent testing and judgement, laboratories had to meet quality standards put forward in an accreditation scheme. Although this legislation does not cover all environmental aspects, it has proved to be an important element in judging the environmental quality of construction materials in a direct or indirect way, and a contribution to the management of waste materials. The question of clear and fair criteria was easily put forward. Answering this question, however, turned out to be a complex task in which a great number of aspects had to be considered and a great many tools had to be developed, checked and thoroughly discussed. In some cases practical choices had to be made in order to prevent an unclear situation continuing too long. After an introduction period of three years, the decree came into full operation on 1 July 1999.     

蠕虫在膜生物反应器和活性污泥法中的污泥减量研究

通过长达345d的中试规模试验,研究比较了蠕虫在膜生物反应器(MBR)和活性污泥法(CAS)的生长状况及其导致的污泥减量效果.CAS中的蠕虫生长状况明显优于MBR的蠕虫生长状况.MBR曝气池中平均蠕虫密度(10条·mg-1)远低于CAS曝气池中平均蠕虫密度(71条·mg-1),并且CAS中蠕虫连续保持高密度(>30条·mg-1)生长达172d.CAS中红斑瓢体虫和仙女虫交替成为优势蠕虫.蠕虫生长对MBR的污泥产率(0 40kg·kg-1)和污泥沉降性能(污泥沉降指数133mL·g-1)影响很小,但却能显著减少CAS的污泥产率(0 17kg·kg-1)和改善污泥沉降性能(污泥沉降指数为60mL·g-1).仙女虫比红斑瓢体虫能更大地减少污泥产量和更好地改善污泥沉降性能.蠕虫生长不影响MBR的COD去除率和出水水质,但却显著影响CAS的COD去除率和出水水质.