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.     

Dynamic modelling and control applications in water quality maintenance

The purpose of this paper is to develop and illustrate a unified, systematic approach to problems of water quality management. In order to achieve this a water quality system is defined as the following group of component features: the abstraction, purification, and supply of potable water from a river: consumer effluent, rainfall-runoff from an urban land surface, and the sewer network; the wastewater treatment plant: the river itself. A systems analysis approach to the study of the dynamic and control aspects of the system is discussed, with particular reference to the practical limitations of instrumentation and technology. In an attempt to blend the theory with the practice recent studies on the dynamic modelling and control of parts of the water quality system are reviewed. Special attention is paid to the practical application of techniques of system identification and parameter estimation. Finally, piecing together several individual results, it is possible to give a good indication of the manner in which control studies should be directed in the near future.     

Contamination bacterienne d'une zone balneaire liee a sa frequentation

The bacterial contamination from bathers in the water and sand at a beach was investigated. Measurements were made of the composition of the cutaneous bacterial flora released by two bathers as well as the sensitivity of the main contaminants to solar radiation. The variations in bacterial concentration of the sea water and sand were determined at the sea shore over three complete day cycles. Broadly speaking, the concentration of some bacteria increases with the frequency with which the beach is used. Nevertheless, short-period variations seem to be masked by the opposing effects of solar radiation and bathers.     

Effects of adding organic materials to an acid sulfate soil on the growth of cocoa (Theobroma cacao L.) seedlings

Acid sulfate soils having a pH of less than 3.5 are widespread in Malaysia. Some of these soils are planted to cocoa, but the yield is reported to be low due to soil infertility related to Al toxicity. Cocoa growth is sensitive to the presence of Al in the soil. To a certain extent, Al toxicity in soils can be reduced by organic matter application and to a greater extent in iron-poor acid sulfate soil. A study was conducted to determine the efficacy of various types of organic materials easily available in the country to ameliorate acid sulfate soil infertility for growing cocoa seedlings. The treatments were control (nil), lime (3 t/ha), peat (10% w/w), peat plus green manure (10% w/w), peat plus rice straw (10% w/w), peat plus chicken dung (10% w/w) and peat plus POMS (Palm oil mill sludge) (10% w/w). The growth of cocoa seedlings was affected significantly by the presence of Al in the cocoa tissues. As the amount of Al in the leaves increased, the relative top dry weight of cocoa seedlings decreased. Likewise, the relative plant height was negatively correlated with Al in the leaves. Peat as well as peat in combination with green manure, rice straw, chicken dung or palm oil mill sludge was able to reduce Al toxicity in acid sulfate soil; the highest top dry weight of cocoa seedlings were obtained in the peat plus green manure treatment. The best cocoa seedlings root growth was found for the peat treatment alone. The relative top dry weight of cocoa seedlings was negatively correlated with Al(3+) as well as Al(3+)+Al(OH)(2+)+Al(OH)(2)(+) activity in the soil solution. The critical values for Al(3+) and the combination of Al(3+)+Al(OH)(2+)+Al(OH)(2)(+) activity in the soil solution were 10 microM and 15 microM, respectively.     

Noise impact caused by electrical energy substations in the city of Curitiba, Brazil

This survey is intended to characterize the noise impact due to electrical energy substations in the city of Curitiba over the population living in their vicinity. This impact has been studied with the aid of a computational tool capable of mapping the acoustical field of substations and their vicinity. Several factors have been considered in this survey: (1) sound power of the transformers; (2) vehicle flow on the surrounding roads; (3) positioning of the firewalls, buildings and walls; and (4) terrain topography. Four substations have been analyzed, and an acoustical map has been traced for each of them. With these maps it was possible to visualize what was the incident noise level on the building facades. The predicted noise levels have been compared to the environmental legislation of the noise emissions in effect in the city.     

Experience with the preconstruction of thawing of soils in the foundation bed of the main building of the Neryungrinsk state area power plant

Conclusions 1. The scheme that we developed is efficient and ensures thawing over a period of 40–45 days. 2. To accelerate thawing by 8–10 days when using two electric heaters in each hole, it is necessary to raise the heaters by 3–4 m after 25 days and continue thawing. 3. An 8–10-day reduction in the thaw time is also possible by using three 1.25-kW electric heaters in each hole in place of two heaters of the same capacity, installing them at depths of 20, 14, and 8 m from the surface. Taking the results of the experimental work account, the State Institute for Special Design developed a plan for the production preconstruction thawing of soils over a area of 12,380 m². The volume of soil thawed was 324,400 m³. Translated from Osnovaniya, Fundamenty i Mekhanika Gruntov, No. 3, pp. 7–8. May–June, 1982.     

Activated charcoal and microflora in water treatment

Significant sanitation was achieved by using 0.5% activated charcoal in influent and effluent of a wastewater treatment plant. The drastic reduction in the microorganisms was confirmed for twelve tester strains, including gram-positives, gram-negatives, Candida albicans, Vahlkampfia avara, Leptospira biflexa and Trichomonas foetus. The removal of microflora correlates positively with the quality of the activated charcoal used. Once adsorbed, the bacteria could not be eluted by salt, alkalinization or citric acid. Diatomaceous earth also eliminated some of the microflora, but white clay (Bolus alba) and zinc dust are inefficient. The activated carbon may be reused several times after regeneration by heat (2 h at 160°C), but eventually a slight decrease in adsorbing capacity occurs.