A case study of regional catchment water quality modelling to identify pollution control requirements.

There are four ecologically important river catchments that contain candidate Special Areas of Conservation (cSACs) under the Habitats Directive in the Lake District National Park located in the North of England. These are the rivers Ehen, Kent, Derwent and Eden. For each cSAC, there are defined ecological criteria that include water quality targets to protect the designated species. Stretches of the riverine cSACs in each catchment are failing to meet these and other water quality targets. The Environment Agency commissioned a study of each catchment to provide the underpinning scientific knowledge to allow it to deliver its statutory obligations under the Habitats Directive. SIMCAT river water quality models were produced and used to predict the water quality impacts resulting from a number of water quality planning scenarios aimed at achieving full compliance with the Habitats Directive and other national and EEC water quality targets. The results indicated that further controls on effluent discharges will allow the majority of targets to be met but other sources of pollution will also need to be controlled. The outcome of the study also recognised that water quality improvements alone will not necessarily produce the required improvement to the ecological interest features in each cSAC.     

Disc filtration for separation of flocs from a moving bed bio-film reactor.

A Discfilter with 10 and 18 microm filter openings, respectively, was placed in parallel to a flotation plant for separation of biological flocs from a post-denitrifying Kaldnes Moving Bed Process, the last treatment step at the municipal wastewater treatment plant at Sj?unda, Malm?, Sweden. The effluent concentrations from the 10 and 18 microm filter were 2-5 and 2-8 mg SS L(-1), respectively, which is comparable to, or better than, the flotation plant. Comparison with experiences from activated sludge plants shows that the Discfilter works especially well after the Kaldnes process. Particle size distribution (PSD) studies show that particles larger than the filter openings of 10 and 18 microm are separated with approximately 90% efficiency, whereas most of the smaller particles pass the filter. This fact indicates that the major particle separation mechanism is physical blocking. These findings point to the possibility of improving the prediction of the separation efficiency by combining measurements of turbidity and suspended solids with particle size analysis.     

Modelling biological processes under anaerobic conditions through integrating titrimetric and off-gas measurements-applied to EBPR systems.

An innovative method for modelling biological processes under anaerobic conditions is presented and discussed. The method is based on titrimetric and off-gas measurements. Titrimetric data is recorded as the addition rate of hydroxyl ions or protons that is required to maintain pH in a bioreactor at a constant level. An off-gas analysis arrangement measures, among other things, the transfer rate of carbon dioxide. The integration of these signals results in a continuous signal which is solely related to the biological reactions. When coupled with a mathematical model of the biological reactions, the signal allows a detailed characterisation of these reactions, which would otherwise be difficult to achieve. Two applications of the method to the enhanced biological phosphorus removal processes are presented and discussed to demonstrate the principle and effectiveness of the method.     

Foreign Factor Ownership and Optimal Tariffs

In the presence of foreign factor ownership tariffs change not only the terms of (goods) trade but also income flows between countries. Assume that only the home country owns factors abroad. Then the optimal tariff is negative if and only if foreign factor ownership entails trade-pattern reversals. Trade-pattern reversals are neither a necessary nor a sufficient condition for a negative optimal tariff if the foreign country owns factors in the home country. Changes in the home country's tariff shift the foreign country's offer curve. This adds a new dimension to optimal tariff analysis.     

Day-of-the-Week Effects in the Long-Run Performance of Initial Public Offerings

This study examines the influence of day-of-the-week patterns in security returns on long-run IPO underperformance. Comparisons are made between the IPOs in Ritter's [20] database, and a constructed set of matching firms based on SIC code and size, using NYSE, AMEX, and NASDAQ securities. It is found that virtually all of the IPO underperformance occurs on Mondays and Tuesdays and that the degree of underperformance significantly differs from other days. Thus, a common explanation may exist for the general day-of-the-week pattern in security returns and IPO long-run underperformance.     

Believing in employment discrimination: The case of Forrest Mims,Scientific American,and title VII protection

This article reviews the law regarding Title VII employment discrimination protection from religious discrimination. The issues surrounding the principal legal protection in this regard are explored in the context of a recent controversial case in which an author, Forrest Mims, was not hired as a regular contributor forScientific American magazine, ostensibly because of his belief in the theory of creation over the theory of evolution. The definition of what constitutes a protected religious belief or practice is seen to have expanded over time. However, a belief in creationism is not necessarily seen as being tantamount to a religious belief under present legal interpretation of Title VII. The implications of this finding for future needed Title VII revision are discussed.     

From Phillips curve to wage curve

Summary In most traditional macroeconomic models for The Netherlands the wage equation is specified by a Phillips curve, in which wage growth is negatively related to the unemployment rate. This paper shows, however, that wage formation can better be described by the so-called wage curve, in which the wage level, instead of wage growth, depends negatively on the unemployment rate.The author thanks S.K. Kuipers and D.A.G. Draper and other colleagues of the Central Planning Bureau for their useful comments.