1991-4

Phosphorus and nitrogen mass balances for Lake Vänern show that ca 70 % of the total phosphorus input accumulates in the sediments, while 25 to 40 % of the total nitrogen input was lost via sedimentation and denitrification. These results are based on total input calculations for the period 1970 to 1989, and transport via […]

P removal and chlorination of artificial wastewaters by electrocoagulation – flotation and Cl2 generation were investigated. The Cl2 generation by carbon electrodes and the Al generation by Al electrodes, employing alternating current, were combined into a recirculation system.

Full scale tests with nitrogen removal have been performed at the Klagshamn wastewater treatment plant in Malmö, Sweden. Characterization of the wastewater and earlier tests at the plant have shown that the organic material in the primary effluent was limiting the overall nitrogen removal. The organic material in the raw wastewater measured as BOD7 was […]

A simple model for calculation of nitrogen transports and the effect of wetlands on nitrogen retention is presented. Model input data were taken from an inventory of potential wetlands in the county of Halland (Wessling 1991, Wessling and Skage 1991). Nitrogen retention was calculated according to a relationship between areal nitrogen load and areal nitrogen […]

There are several ways to obtain information about land use and vegetation for an area. In this project we have used satellite images to calculate statistics for the drainage area of River Fyrisån in Uppland, Sweden. A Landsat TM (Thematic mapper) image registered on the 7th of July, 1989 was used. The spectral information in […]

The creation and restoration of wetlands has been suggested as an efficient method for the reduction of the transport of nitrogen to the Swedish coastal waters. In the paper, which is written from a hydrological viewpoint, a few critical questions are identified which require further clarification. The questions concern our knowledge about retention processes, dynamics […]

There are diverging opinions on nitrogen retention in wetlands. In southern Sweden, wetlands contribute to limit nitrogen leaching. In forest wetlands in central and northern Sweden there are only indications on small or no retention effects. Wetland types as well as the nitrogen load vary. Outflow of nitrogen from forested watersheds, including considerable wetland areas, […]

The role of wetlands, ponds and lakes in the retention of nitrogen and thus in the decrease of nitrogen transport to the sea is under discussion in Sweden. In this paper nitrogen budgets for Lake Björkaren during four years are presented. The lake is very shallow and almost covered with higher vegetation and the water […]

From September 1988 up to June 1991 a full-scale experiment was conducted using a submerged macrophyte pond and a root-zone for wastewater treatment. The mean removal was 32 % and 46 % of nitrogen and 62 % and 61 % of phosphorus respectively. The major removal mechanism for N was denitrification and for P assimilation, […]

The concentration of nitrous oxide in the atmosphere increases with 0.25 % per year. Nitrous oxide degrades ozone and it also increases the green-house effect. Many biological processes can produce nitrous oxide. The three most important processes are nitrification, denitrification and dissimilatory ammonium production. These biological processes are of importance in development of systems for […]

In southern Sweden, changes in agricultural practices have affected the streamland interface increasing nutrient transport to the sea. Results from ongoing studies suggest that these areas surrounding Scanian streams are important in nutrient removal. In artificially induced surface runoff through a riparian buffer strip, 66 % of the PO4-P was retained during the first 8 […]

Recent studies show that anthropogenic acid surges provide the major acidification problem for lakes and watercourses in northern Sweden. Anthropogenic acid episodes may occur in around 20-40 % of all watercourses and in around 15-30 % of all lakes. Anthropogenic acidification throughout the year is a lesser problem. Predictions for the future using mathematical models […]

Scandinavian freshwater acidification was observed at the end of the nineteen sixties and was thought to be a result of the observed pH-decreasing in the precipition over north-western and northern Europe (Oden and Ahl 1970). These results were obtained from the monitoring of the water quality in the Swedish rivers started in 1965 and a […]

Soil acidification has not as yet been observed in upper Norrland. Possibly the investigations mostly carried out in well drained soils may not be relevant however as an early stage of surface water acidification should concern the discharge zones. In these zones the flow is channelled to restricted soil volumes both depthwise and sideways. This […]

Current practice in Swedish environmental policy treats most acid surface waters as likely cases of acidification resulting from acid deposition that are suitable objects for liming. That approach to the management of acidity in surface waters is based largely on the understanding of surface water acidification in the clear water lakes and streams of southern […]

Benthos from lakes and running waters has been used to assess the extent of surface water acidification in Sweden 1969-1991. Altogether 2,861 different waters have been investigated. The acidification status was determined by classifying the different taxa into two groups – acid sensitive, i.e. do not tolerate pH below 5.5 and acid tolerant, i.e. tolerate […]