Coping with COPA II: Actions to Improve Effluent Quality

The paper outlines some of the actions taken by Severn Trent Water to achieve compliance with consent limits since the implementation of the Control of Pollution Act (Part II) in 1985.
Prior to and since 1985, Severn Trent Water has undertaken an extensive programme to analyse the reasons for failure and carry out remedial work. A major feature of this programme, which has been further stimulated by privatization, has been the need to reduce the lead time for carrying out improvements.
The paper discusses the means by which this has been achieved, including the introduction of the 'fast-track'initiative and the 'process matrix'.
Other aspects are outlined including initiatives to develop more robust processes, computerized work scheduling, extensive training programmes and best practice studies.     

Structural analysis of assemblages of thin-walled members

A matrix method for the analysis of structural systems composed of thin-walled members is presented. The matrix displacement analysis includes the effects of thin-walled non-uniform torsion theory, cross-section asymmetry, eccentric restraint as well as joint types peculiar to thin-walled members. The method is used for a prediction of the elastic behaviour of a set of representative test frames. The test frames were pitched-roof portals constructed from channel sections bent about their major-axis and supported by eccentric restraints simulating purlins and girts.     

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.     

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.     

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.