NITROGEN REMOVAL IN CREATED PONDS

The role of nitrogen as an environmental hazard has become increasingl y important since World War II. Emissions, and increased use of nitrog en compounds, e.g. fertilizers, have an impact on eutrophication, acid ification, production of greenhouse gases and on the stratospheric ozo ne layer. Decreasing the supply of nitrogen to coastal waters by half by 1995 has been adopted as a national goal in Sweden, However, this d ecrease appears to be unrealistic to attain for many years. In 1989, a n interdisciplinary project in the Laholm Bay drainage basin pointed o ut that the goal can be attained if decreased emissions and teaching i s combined with increased removal during runoff. This paper presents s tudies on nitrogen removal/retention in created ponds. Annual removal per area unit varied about two orders of magnitude between the differe nt ponds studied. Highest removal was obtained in ponds with high nitr ogen loads.