Experience with algal blooms and the removal of phosphorus from sewage

The growth of algae and occurrence of algal “blooms” in a number of different waters are described.They cover the period 1930–1940 when only natural phosphates would be present.The waters were drawn from either protected catchments or from a fully treated domestic supply.Spasmotic blooms in a fully treated domestic supply suggest that the mechanism which “triggers” the start of an algal bloom may be neither nutrient concentration nor the concentration of organic matter.It is considered that the pH, alkalinity, carbon dioxide equilibrium condition is a major factor, not only in promoting, but also in maintaining algal blooms.     

Technique for measuring metallic salt effects upon the indigenous heterotrophic microflora of a natural water

The effects of several concentrations of the metallic salts Ag₂SO₄, NaAsO₃, BaCl₂2H₂O, CdCl₂2.5 H₂O, CrCl₂6H₂O, CuCl₂, HgCl₂, NaCl, NiCl₂6H₂O, PbCl₂ and ZnCl₂ upon the indigenous heterotrophic microflora of a natural water were studied. Effects of these salts upon the heterotrophic activity of the microbes were assayed using the heterotrophic technique whereas lethal effects upon the heterotrophic bacteria were determined using nutrient agar plate counts. The heterotrophic activity method is based upon the uptake and mineralization of a radioactively labeled metabolite (in these experiments ¹⁴C-glucose) by the indigenous aquatic microbes and data analysis is by Michaelis—Menten enzyme kinetics equations. Concentrations of metallic salts which resulted in bacterial death also caused erratic uptake and mineralization rates of ¹⁴C-glucose whereas sub-lethal concentrations, as determined by nutrient agar plate counts, caused a non-competitive inhibition of maximum heterotrophic activity and markedly increased the turnover time of the glucose substrate.     

Earthquake analysis of isotropic asymmetric multistory buildings

Isotropic multistory buildings are the ones characterized by the property: all load‐resisting planar frames have proportional lateral stiffness matrices. In the present paper it is proved that the modal analysis of an N‐story isotropic asymmetric, torsionally coupled, building (a problem of order 3N) can be separated into two independent sub‐problems: (a) a sub‐problem that corresponds to a single‐story asymmetric, torsionally coupled, building (a problem of order 3); and (b) a sub‐problem that corresponds to an N‐story, torsionally uncoupled, planar frame (a problem of order N). It is also demonstrated that the orientation of peak modal seismic forces of the building is independent of the orientation of seismic excitation, which affects only their size. The separation provides a better insight into the structural behavior of asymmetric multistory buildings under earthquake ground motion. Copyright © 2006 John Wiley & Sons, Ltd.     

THE INCREASING EFFECTS OF ZEBRA MUSSELS ON WATER INSTALLATIONS IN ENGLAND

The zebra mussel, Dreissena polymorpha, is a major biofouling pest of water treatment works, irrigation systems and power stations in Europe and North America. This paper documents current problems associated with zebra mussels in English waterworks. Questionnaires and manual surveys conducted between 2001 and 2003 have revealed that over 30 water treatment works in England suffer problems associated with zebra mussels. Hundreds of tonnes of mussels are being removed each year from raw water intakes, pipelines and reservoirs. Problems have increased in. the last five years, due to a spread in the range of zebra mussels around England and the cessation of chemical treatment at the intakes of many treatment facilities during the 1990s. The importance of taking control of zebra mussels into account in planning new water supply schemes is highlighted.     

广州珠江外资建筑设计院建院25周年作品回顾

对广州珠江外资建筑设计院建院25年来具有代表性的作品做了一个简要的回顾，叙述了该院在改革开放大潮中崛起，以及在25年的艰苦创业中发展壮大的历程。     

The Italian national survey of indoor radon exposure

An investigation is being developed by the Camitato Nazionale per la Ricerca e per lo Sviluppo dell'Energia Nucleare e delle Energie Alternative, ENEA, to assess the indoor exposure of the Italian population. The programme, which started in 1982, includes regional and local surveys in all the administrative districts and intensive investigations of factors which influence indoor radon levels. The survey is organized by statistical areas of sampling to obtain representative samples of houses. The definition of the areas takes into account basic parameters e.g. geolithological environments, radon soil gas from underlying soils and rocks, specific activities of local building materials, climatic and seasonal variations, building technology, types of houses and town planning. The collected data may also be used for the compilation of radon risk maps to plan special monitoring and remedial actions if needed. Preliminary results concerning the above items are discussed.     

Impact of calcium and TOC on biological acidification assessment in Norwegian rivers

Acidification continues to be a major impact in freshwaters of northern Europe, and the biotic response to chemical recovery from acidification is often not a straightforward process. The focus on biological recovery is relevant within the context of the EU Water Framework Directive, where a biological monitoring system is needed that detects differences in fauna and flora compared to undisturbed reference conditions. In order to verify true reference sites for biological analyses, expected river pH is modeled based on Ca and TOC, and 94% of variability in pH at reference sites is explained by Ca alone, while 98% is explained by a combination of Ca and TOC. Based on 59 samples from 28 reference sites, compared to 547 samples from 285 non-reference sites, the impact of calcium and total organic carbon (TOC) on benthic algae species composition, expressed as acidification index periphyton (AIP), is analyzed. Rivers with a high Ca concentration have a naturally higher AIP, and TOC affects reference AIP only at low Ca concentrations. Four biological river types are needed for assessment of river acidification in Norway based on benthic algae: very calcium-poor, humic rivers (Ca < 1 mg/l and TOC > 2 mg/l); very calcium-poor, clear rivers (Ca < 1 mg/l and TOC < 2 mg/l); calcium-poor rivers (Ca between 1 and 4 mg/l); moderately calcium rich rivers (Ca > 4 mg/l). A biological assessment system for river acidification in Norway based on benthic algae is presented, following the demands of the Water Framework Directive.     

Buckling of tube-stiffened prolate domes under external water pressure

The paper describes experimental tests carried out on three tube-stiffened prolate hemi-ellipsoidal domes under external water pressure.The tubes were stuck to the internal surfaces of these three domes, in their flanks, and the experimental tests showed that the tubes increased the buckling pressures of these domes, especially in one case, when the tube was subjected to an initial internal pressure.All three domes failed by lobar buckling, in their flanks, and showed buckling resistances much larger than similar unstiffened domes.     

Prediction of the effectiveness of rolling dynamic compaction using artificial neural networks and cone penetration test data

Rolling Dynamic Compaction(RDC),which is a ground improvement technique involving non-circular modules drawn behind a tractor,has provided the construction industry with an improved ground compaction capability,especially with respect to a greater influence depth and a higher speed of compaction,resulting in increased productivity. However,to date,there is no reliable method to predict the effectiveness of RDC in a range of ground conditions. This paper presents a new and unique predictive tool developed by means of artificial neural networks(ANNs) that permits a priori prediction of density improvement resulting from a range of ground improvement projects that employed 4-sided RDC modules;commercially known as"impact rollers". The strong coefficient of correlation(i.e. R0.86) and the parametric behavior achieved in this study indicate that the model is successful in providing reliable predictions of the effectiveness of RDC in various ground conditions.     

Ultraviolet light inactivation of protozoa in drinking water: a Bayesian meta-analysis

To assess the dose of UV light needed to achieve specified levels of Giardia spp. cysts and Cryptosporidium spp. oocysts inactivation in drinking water, a Bayesian meta-analysis is used to analyze experimental data from several studies. Of the 20 studies identified by an extensive data collection effort, 14 (five reported experiments on Giardia and nine on Cryptosporidium) were selected for analysis based on a set of criteria. A substantial amount of the log inactivation data are reported as greater than a given inactivation level (i.e., censored data). The Bayesian hierarchical modeling approach used in this study not only properly addresses the common concerns in a meta-analysis but also provides a robust method for incorporating censored data. Different statistical models will result in different estimates of the UV doses needed to achieve a specific inactivation level. The Bayesian approach allows us to present the uncertainty in terms of risk, which is better suited for supporting US EPA in developing regulations.