Interstitial inorganic phosphorus concentrations in lakes Mendota and Wingra

Interstitial P levels in Lake Mendota and Lake Wingra were evaluated as a function of season and water column and sediment depth. Interstitial water was obtained by the centrifugation-filtration method. Temporal variations were observed over the entire 15 cm sediment depth interval examined in all four locations evaluated. Interstitial reactive P (IRP) levels in Lake Mendota ranged from 0.014–1.67 mg l⁻¹ at the 5–6 m water column depth and from 1.20–5.75 mg l⁻¹ at the 18–19.5 m depth. IRP levels in Lake Wingra ranged from 0.029–2.15 mg l⁻¹ at 3.5 m and from 0.191–3.96 mg l⁻¹ at 2 m. Variations in interstitial P were attributed to variations in oxidation state of Fe as influenced by oxygen transport and reduction rates.     

Oscillations of Foundations Installed on the Ground and Cast-in-Place Piles Subject to Kinematic Effects

Results are presented for experimental investigations on the traffic-induced oscillations of two full-scale foundations of a metallic tunnel, one of which is installed directly on the ground, and the other on cast-in-place piles. The foundations are close to one another with respect to mass and the load applied to them. Differences are revealed between the parameters of the actual oscillations of these foundations and their computed values.     

湿度应力场的数值模拟

基于新的湿度应力场理论,建立了湿度应力场的数值模拟方法,并用通用有限元分析软件ANSYS中的温度应力场模块,有效地模拟了圆形硐室遇水作用的湿度应力场问题.数值模拟的结果与解析解结果的一致性表明,所建立的数值模拟方法是有效的.     

Sorption of phosphorous to Filtralite-P--the effect of different scales

Sorption of P to the filter material Filtralite-P was examined at a small, medium and large scale. In the small- and meso-scale laboratory models, the sorbed amount of total phosphorus (P) was heterogeneously distributed with more P sorbed in the inlet zone and the bottom layers. The full-scale system had, on the other hand, the highest sorbed concentration in the outlet region. The overall P sorption capacity of the material was 8030, 4990 and 521 mg P kg(-1) Filtralite-P for Box 1, Box 2 and meso scale, respectively. This equals 4.4, 2.8 and 0.29 kg P m(-3) material, respectively. However, the maximum sorption capacities found were 2500, 3887 and 4500 mg P kg(-1) Filtralite-P for the two small-scale box systems and the meso-scale container, respectively. In the full-scale system the overall P sorption capacity of the material was 52 mg P kg(-1) Filtralite-P (0.029 kg P m(-3) Filtralite-P with a maximum sorbed amount of P of 249 mg P kg(-1). Results from both the small- and meso-scale system show that when a constructed wetland (CW) is saturated, i.e. when the outlet concentration has reached its maximum allowed concentration of 1.0 mg P l(-1), only parts of the filter material will have reached the sorption capacity. Sequential extractions of Filtralite-P showed that the loosely bound P, Ca-P and Al-P were the primary P sorption pools both in the small-scale models and in the full-scale CW. However, the proportion of these three fractions varied with time and change in pH. A white product precipitated in the outlet zone of both the small-scale box models as well as the onsite CW. The surface of these precipitation particles was identified by X-ray diffraction and SEM method as CaCO3 and precipitated Ca- and Mg-phosphates.     

Upgrading the Activated-Sludge Process for Total Nitrogen Removal in Hong Kong

In order to protect the sensitive waters in Tolo harbour (Hong Kong), Sha Tin and Tai Po sewage-treatment works were first designed to remove 70% of the nitrogen load from the sewage. Since then, due to continuing serious eutrophication problems in the harbour, both plants have been modified to increase the removal efficiency to 90%.
The modifications were based on the Bardenpho process. However, the designers of the two plants adopted different approaches to process intensity, complexity and control of bacterial foam. At Sha Tin, the average monthly results have shown an increase of total nitrogen removal from 60–70% to about 80% since its completion. The addition of methanol was found to be ineffective on further enhancement of the denitrification rate due to difficulties in the apportioning of the second anoxic zone. The overall monthly results for Tai Po have also shown an increase in the removal rate to about 80%, even though 90% was achieved for a short period of time. The major problem encountered at the latter plant was that the process design did not provide an effective control on bacterial foaming, which had affected the smooth operation of the process.     

Sensory evaluation of drinking water by consumer panels

The human senses play an important role in assessing the quality of food and of the environment. Particularly the chemical senses of taste and smell determine the pleasantness of foods and drinks and may provide a warning mechanism for the presence of more or less toxic contaminants. Even after the recent rapid development of powerful analytical techniques the human nose can easily detect trace amounts of chemicals at levels manytimes lower than the analytical detection limits.Although taste and odour assessment of drinking water has been practized inmany waterworks laboratories by small panels, relatively unreliable results were obtained and such sensory data played up till now only a minor role in the management of the water treatment plant. More sophisticated and reliable methods for sensory water quality evaluation are discussed. Special attention is given to the characteristics of the human senses of taste and smell, to which the methodology of sensory assessment should be better adapted. High numbers of observations on a sample are generally needed, for which purpose the use of large panels has to be realized. In this respect the help of large consumer panels is an alternative for the presently often used small laboratory groups. As an example the preliminary results of a large ongoing experiment of sensory water quality assessment by 2 consumer panels of 100 persons each in the Rotterdam area are discussed. Drinking water quality is judged at the consumer homes every week. The experiment started September 1979 and will be continued for one year.     

The direct measurement of ppm levels of uranium in soils using high-resolution Ge(Li) gamma-ray spectroscopy

The direct determination of ²³⁸U in various soil samples was done by measuring the 63.3-keV transition from the decay of the first daughter ²³⁴Th. Potential errors resulting from the chemical non-equilibrium of ²³⁸U with its daughters are thus avoided. The method sensitivity is 1 ppm compared to the 35 ppm obtainable by employing the 1001-keV gamma ray. A Ge(Li) gamma-ray spectrometer is the only analytical tool required. Examples are offered that demonstrate the usefulness of the technique for routine, inexpensive environmental monitoring of uranium. The technique also has the capability of providing information on the ²³⁸U/²³⁵U isotopic ratio.