Kinetics of microbial nitrification: nitrite-nitrogen oxidation

The kinetics of nitrite-nitrogen oxidation by enriched Nitrobacter cultures were examined under various temperatures (9°–35°C), pH (6.0–8.5), and microbial concentrations. For the substrate concentrations examined (100–1100 mg N1⁻¹) the reaction was zero order and correlations between temperature, pH, microbial concentrations and reaction rates were formulated. Inhibition by free ammonia and nitrous acid is discussed. This study of enriched cultures of nitrobacter organisms also provide some insight into the growth characteristics of this fastideous organism under conditions of dense population and severe environmental conditions (temperature and pH).     

The impact of preoxidation of SAS on biosorption efficiency on activated carbon

We have studied the process of a prolonged dynamic filtration on activated carbon in two biosorption systems — without preoxidation treatment of the initial matter and after ozonization. It has been shown that given the uniform load on activated carbon terms of the organic matter the efficiency of the biosorption process after preozonization is 2.3 times as small compared with that that without pretreatment, which correlates with the change of adsorption free energy.     

Distortional buckling of monosymmetric I-beams

A finite element method which is applicable to studying the distortional buckling of fabricated monosymmetric I-beams is briefly described. The method is used to demonstrate the effects of web slenderness on a monosymmetric I-beam whose smaller flange is in compression. A study is also made of the effects of monosymmetry on the distortional buckling of an I-beam with a slender web in uniform moment and moment gradient. Based on parameter studies using the finite element method, a design equation is developed which may be used to determine the distortional buckling stress of a monosymmetric I-beam under moment gradient.     

Probabilistic Modelling in the Water Industry

The water authorities in England and Wales, which have now become water companies, recently had to provide anticipated costs for maintaining the water supply and sewerage systems over the next 20 years. Probabilistic models and statistical inference provide an opportunity to quantify the uncertainty in such exercises. Their use in a study undertaken by a water authority in the north-east of England is described and illustrated with interim data which were available at an early stage in the exercise.