Henrik Grüttner

Reduction of fecal streptococcus and salmonella by selected treatment methods for sludge and organic waste

The increasing utilization of waste water sludge and source-separated organic household waste in agriculture has brought the quality aspects into focus, among others the hygienic aspects. In this study, the reducting effect on Fecal Streptococcus (FS) and Salmonella of different methods for stabilization and methods for further treatment of sludge and organic waste has been investigated. The most common methods for stabilization, i.e. aerobic and anaerobic stabilization, only reduce the indicator organisms by approximately 1 logarithmic decade. Methods for further treatment of sludge and organic waste have shown reductions of microorganisms allowing for unrestricted utilization in agriculture, meeting the product control: FS below 100/g and no Salmonella detected. The effect of storage of sludge at summer and winter temperature respectively has been investigated. At temperatures (around 20°C) significant reductions of Salmonella were found, while the die out at low temperatures (below 10°C) was limited. FS was not reduced systematically during storage, and therefore, FS is not usable as indicator organism for the hygienic properties of sludge during storage.

Regulating industrial wastewater discharged to public wastewater treatment plants - a conceptual approach

The paper describes some of the basic principles behind the DEPA Guidelines for discharge of industrial wastewater to public sewers set in operation in 1995 and evaluates some of the experiences with the implementation. It is described how such guidelines support the approach of pollution prevention and the implementation of cleaner technology by putting a stress on the industry. Further an approach for the balance between environmental and technological considerations is introduced. The need for easily understandable environmental priorities is stressed and a concept for this is presented along with its combination with available technology. Finally expression of the environmental requirements are discussed in relation to environmental and technological considerations.