Measuring the efficiency of wastewater services through Data Envelopment Analysis

Efficient water management is a priority in the European Union, since the operational efficiency of many water utilities is very low compared to best practice. Several countries are restructuring the water industry to save costs. Larger-scale operations and vertical integration are promoted to achieve scale and scope economies; however, the literature is not unanimous that such economies exist. There is also little evidence of the effect of customer density on costs. This article offers some insights into this matter, analysing the Danish water industry by a two-stage Data Envelopment Analysis approach to investigate the effects of size, scope and density in the wastewater industry. The results show that the Danish wastewater industry is positively affected by vertical integration and higher population density: firms that serve more than 100 person per km of sewer and combine water and wastewater services achieve better efficiency. Size does not have any significant influence on global efficiency, although technical pure efficiency decreases statistically with firm size.

Case study of treatment of waste water for 17α-ethinylestradiol and microorganisms with UV and photocatalysis in an on-going process of introducing AOP techniques in the Danish water sector

Failure to obtain a sufficient disinfection of waste water, initiated an investigation of the use of UV light and photocatalysis with TiO2 for treating the waste water. Furthermore, the ability of such a system to degrade endocrine disrupting chemicals was investigated through experiments with the estrogen 17α-ethinylestradiol (EE2). This study found LP UV lamps to be the optimal solution for disinfection, while photocatalysis with TiO2 was found to be the best method for removal of EE2. The experiments were carried out in a mobile test unit with solution volumes of 30 L. By use of data from the real UV system, the effect found in the experiments were extrapolated and used to evaluate the efficiency of the current system.

Experimental study of Ni adsorption on chalk: preliminary results

Nickel can cause allergic reactions so it is often considered to be a toxic metal. In some areas of Denmark and northern Europe, where drinking water comes predominantly from chalk aquifers, Ni concentrations in groundwater are higher than safety limits. The contamination is natural in the sense that it comes from oxidation of small grains of pyrite in the chalk that contain Ni as a trace element (Larsen and Postma, 1997). Because of Danish water-treatment practice, the most politically acceptable water-supply protocol is not to use secondary water treatment, so in order to minimize allergy risks for consumers, high-Ni water is either mixed with low-Ni water to bring concentrations below the Danish limit, or new, uncontaminated wells are drilled. Some recent efforts focused on finding a method to minimize nickel concentration while the water is still in the ground, before it is pumped to the primary treatment facility and distributed.Unfortunately, only a few experimental studies of the interactions between Ni and calcite have been published (Lakshtanov and Stipp, 2007; Zachara et al., 1991; Hoffmann and Stipp, 2001) and we found no previous work on Ni uptake by chalk. Experiments with calcite show that Ni forms surface complexes and it is incorporated into the solid as solid solution. Chalk aquifers often contain as much as 99% calcite, so the same processes ought to control Ni uptake, but some very preliminary experiments suggested that chalk behaviour might not be what one would expect by analogy with calcite (Stipp et al., 2005). The aim of this study was to examine the Ni-uptake capacity of chalk and compare it with that of synthetic, pure calcite.

Calibration of tipping bucket rain gauges

A tipping bucket rain gauge measures rain fall volumes with high resolution, thus enabling calculation of rain intensities. To ensure that the volume of one tipping is independent of the rain intensity a syphon is introduced. However, the syphon introduces problems with respect to both a time lag and problems when reconstructing the underlying rain intensities. This problem is studied in detail. The rain gauge in question is a RIMCO tipping bucket rain gauge, used by the Danish Water Pollution Control Committee (DWPCC). The rain gauge has been tested in the laboratory and in the field. The study shows, that it is possible to reduce the syphon volume to a level where the problems of the syphon are small and yet maintain the same accuracy with respect to volume registrations.