A non-relativistic limit of NS-NS gravity.

We discuss a particular non-relativistic limit of NS-NS gravity that can be taken at the level of the action and equations of motion, without imposing any geometric constraints by hand. This relies on the fact that terms that diverge in the limit and that come from the Vielbein in the Einstein-Hilbert term and from the kinetic term of the Kalb-Ramond two-form field cancel against each other. This cancelling of divergences is the target space analogue of a similar cancellation that takes place at the level of the string sigma model between the Vielbein in the kinetic term and the Kalb-Ramond field in the Wess-Zumino term. The limit of the equations of motion leads to one equation more than the limit of the action, due to the emergence of a local target space scale invariance in the limit. Some of the equations of motion can be solved by scale invariant geometric constraints. These constraints define a so-called Dilatation invariant String Newton-Cartan geometry.

Reuse and recycling of secondary effluents in refineries employing advanced multi-barrier systems.

In this paper the reclamation and reuse of municipal secondary effluents, as well as the reclamation and recycling of refinery secondary effluents, are technically and economically evaluated. It is shown that both practices are feasible and sustainable, and that the reclamation costs depend largely on specific circumstances such as legal requirements, price policy, reuse application, raw water composition, etc. The reclaimed water is reused, or respectively recycled, as boiler make-up. Therefore both reclamation plants employ advanced multi-barrier systems including ultra-filtration and reverse osmosis. The employed processes have shown excellent performance with regard to the removal of critical parameters such as silica. For example, this parameter was reduced from 13 mg/l in the raw water to 7 µg/l in the boiler make-up.

Ozone treatment of organic micro-pollutants in sewage sludge.

Organic micro-pollutants accumulate to a certain extent in sewage sludge and are therefore ecologically relevant if the sludge is to be reused in both agriculture and landscaping applications. This paper describes the degradation of endocrine-disrupting compounds and other micro-contaminants by means of ozone and ultrasonic treatment. One of the findings is that, as expected, aromatic compounds such as polycyclic aromatic hydrocarbons can be degraded easily by ozone. Thus it could be shown that, apart from enhanced VSS reduction and increased biogas production, sludge disintegration processes using ozone provide an additional benefit, i.e. the degradation of micro-pollutants, which is practically unattainable with ultrasonic treatment.

MARAPUR--a new process combination for the optimization of MBR.

The MARAPUR concept is a biological wastewater treatment process based on the MBR functional principle. The ultrafiltration of activated sludge takes place in pressure-driven hollow fiber membranes. The vertical membrane modules are installed compactly in a MEGAMODUL. The permeate extraction is accomplished in the cross-flow, which is supported by rinsing aeration. The main process advantages are high filtration performance, excellent operation reliability provided by wastewater fine sieving and reduced cleaning chemicals demand. Wastewater fine sieving with a mesh size of 0.25 mm is an effective measure against membrane clogging by hair and fibers.

Water management in Windhoek, Namibia.

For decades, the city of Windhoek in Namibia succeeded in stretching their limited potable water resources through strict water management, latterly including wastewater reclamation and direct potable reuse. An integrated approach was followed and proper policies were put in place. This was followed up with appropriate legislation, education, policing and technical and financial measures with the result that extreme water shortages were overcome even in times of severe droughts.