Use of the PrussiaRiskware Concept for the Construction of a Model for Risk Evaluation for the Agricultural Reuse of Sewage Sludge

Abstract

During the risk assessment of the application of sewage sludge from municipal wastewater treatment plants on agricultural areas, the question arises, if there are any resulting hazards or chances. The public reaction on their actual or just potential presence can increase the restrictions on the use of sewage sludge in agriculture. This influences both, the efforts, which have to be taken for its application and the ability for its recycling. An objectification of this matter seems certainly helpful and is therefore the target of this work. For this, the holistic concept of PrussiaRiskware shall be used. This concept incorporates a holistic risk assessment, starting with the analysis of technical risks. Emissions of these technical processes may have consequences both, for humans and the environment. A risk assessment approach, based on the Technical Guidance Document’s (TGD) approach will be introduced as a solution of one part of the chain of events. In order to assess the influence of the application of sewage sludge in agriculture on human health, the different exposure pathways wastewater/sewage sludge agricultural area- plant – human will be modeled. Based on the tolerable daily intake (TDI) of a substance the critical concentration of this substance in the soil will be calculated. By comparing the critical concentration of the substance and the PEC with each other, conclusions about the potential hazards for human health will be taken. The calculated PEC also states the basis for the environmental risk assessment. Based on the physical and chemical properties of a substance, its distribution between the different environmental compartments will be calculated. Out of results from eco-toxicological and standardized testing methods predicted no-effect concentrations (PNEC) for each environmental compartment will be derived. By comparing compartment-specific PECs and PNECs the relevance concerning the environmental impact of the substances, which are emitted through sewage sludge/wastewater, will be assessed. Nevertheless, regarding the current social situation a more detailed analysis is needed. An overall, comprehensible and transparent analysis with all its different aspects creates an atmosphere of trust. This helps solving currents conflicts and finding compromises. A trivialization will be impossible without destroying the built atmosphere again. Therefore, it is necessary to establish the kind of model which includes all the described interactions. It has to be the target to analyze all thinkable variations of compromise not just in a qualitative but in a quantitative manner.