Changes in material flows, treatment efficiencies and shifting of environmental loads in the wastewater treatment sector. Part I: case study of the Netherlands.

The material that is separated from wastewater in wastewater treatment plants has to be transferred from the water phase to the atmosphere, lithosphere, and/or biosphere (and also the technosphere). After the initial discharges into the different environmental media (and the technosphere), there are further 'inter-sphere' leakages or redirections. However, these happen over protracted periods of time and have not been accounted for in this paper. The paper presents a case study on the wastewater treatment plants in the Netherlands, examines how the degree of separation of COD (BOD), nitrogen, phosphorus and heavy metals from the wastewater have increased over time, and studies the changes in proportions separated out to the atmosphere and lithosphere. The hydrosphere has benefited from a decline in the degree of eutrophication and marine/fresh water toxicity, owing to the favourable combination of higher degrees of separation, over time, and source control, especially in the industrial sector. Global warming is a major concern owing to the increasing conversion of COD to carbon dioxide (and methane). Heavy metal and nitrogen emissions have been curbed thanks to source reduction within industries. Technologies have, of course, enabled some mitigation of the problems associated with atmospheric (global warming and toxicity) and lithospheric (toxicity) pollution, though these are beyond the scope of this paper, which assumes a hypothetical worst-case scenario in this regard for the study period 1993-2005.