Development of a methodology to assess the footprint of wastes.

The ecological footprint (EF) is a widely used indicator to assess the sustainability of people, regions or business activities. Although this metric has grown in interest and popularity over the years, it has also been the subject of criticism and controversy. The advantages of an aggregated indicator are often overshadowed by the shortcomings of its corresponding methodology. One weakness of the EF is that it does not account for toxic or hazardous pollutants and wastes, which cannot be part of a closed biological cycle. The methodology developed in the present work estimates the EF of toxic and hazardous wastes considering a closed cycle modeled through a plasma process; a phenomenon that naturally occurs in stars and volcanoes. Wastes from industry can be treated in a thermal plasma gasification process, and, by developing a methodology to describe this process, the EF of hazardous wastes was calculated. A value of 56.5 gha was obtained, a figure on the same order of magnitude as that obtained in a previous study where a conventional ecological footprint methodology was applied to the same production process.

Advanced monitoring and supervision of biological treatment of complex dairy effluents in a full-scale plant.

The operation of a wastewater treatment plant treating effluents from a dairy laboratory was monitored by an advanced system. This plant comprises a 12 m(3) anaerobic filter (AF) reactor and a 28 m(3) sequential batch reactor (SBR) coupled in series and is equipped with the following on-line measurement devices: biogas flow meter, feed and recycling flow meters, temperature sensor, dissolved oxygen analyzer, and redox meter. Other parameters such as chemical oxygen demand (COD), volatile fatty acids (VFA), etc. were determined off-line. The plant has been in operation for 634 days, the influent flow rate being 6-8 m(3)/d. COD concentration of the influent ranged between 8 and 12 kg COD/m(3), resulting in COD values in the effluent around 50-200 mg/L. The behavior of the system was studied using the set of measurements collected by the data acquisition program especially developed for this purpose. Monitoring of variables such as anaerobic reactor temperature permitted the detection and prevention of several failures such as temperature shocks in the AF reactor. Besides, off-line measurements such as the alkalinity or the VFA content, together with the on-line measurements, provided immediate information about the state of the plant and the detection of several anomalies, such as organic overloads in the SBR, allowing the implementation of several fast control actions.