Impact of Filters to Reduce Phosphorus Losses: Field Observations and Modelling Tests in Tile-Drained Lowland Catchments

Andreas Bauwe,Bernd Lennartz,Petra Kahle

doi:10.3390/w11122638

Abstract

In this study, we analyzed Dissolved Reactive Phosphorus (DRP) and Total Phosphorus (TP) concentration dynamics over two years in surface waters of five nested catchments in northeastern Germany. Based on this, we constructed a filter box filled with iron-coated sand for Phosphorus (P) removal at the edge of a tile-drained field. Results of the filter box experiment were used for a model scenario analysis aiming at evaluating the P removal potential at catchment scale. DRP and TP concentrations were generally low but they exceeded occasionally target values. Results of the filter box experiment indicated that 28% of the TP load could be retained but the DRP load reduction was negligible. We assume that DRP could not be reduced due to short residence times and high flow dynamics. Instead, particulate P fractions were probably retained mechanically by the filter material. The scenario analysis revealed that the P removal potential of such filters are highest in areas, in which tile drainage water is the dominant P source. At a larger spatial scale, in which other P (point) sources are likewise important, edge-of-field P filters can only be one part of an integrated catchment strategy involving a variety of measures to reduce P losses.

Highlights

Phosphorus (P) as an essential nutrient for plant production can cause eutrophication with negative ecological and economic consequences when excessively introduced into lakes, rivers and oceans [1]
P losses have been reduced by 72% in recent decades, in particular due to technical improvements of wastewater treatment plants, the ecological status of many surface waters is still unsatisfactory [3]
We considered the two most important P forms: Dissolved Reactive Phosphorus (DRP) and Total Phosphorus (TP)

Summary

Introduction

Phosphorus (P) as an essential nutrient for plant production can cause eutrophication with negative ecological and economic consequences when excessively introduced into lakes, rivers and oceans [1]. P pollution of surface water bodies is considered a widespread and serious problem [2]. In Germany, 23,000 t P are discharged into surface waters every year. P losses have been reduced by 72% in recent decades, in particular due to technical improvements of wastewater treatment plants, the ecological status of many surface waters is still unsatisfactory [3]. Only 8.2% of German water bodies achieve the “good ecological status” according to the EU Water Framework Directive [4]. Agriculture is to be considered the main driver of nutrient pollution in surface waters [5]

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