Nitrogen elimination from landfill leachates using an extra carbon source in subsurface flow constructed wetlands.

A three-stage constructed wetland for leachate treatment was monitored on a landfill at a pilot scale. The plant had been designed to achieve at least 75% nitrogen removal. NH4-N input concentration was 240 (median) up to 290 mgl(-1) and COD concentration was 455 to 511 mgl(-1), respectively. A 14 m2 vertical flow sand filter plus a 14 m2 horizontal flow sand filter followed by a 3.3 m2 vertical flow sand filter was chosen. Acetic acid was added to the horizontal flow system for denitrification. The results showed a very stable nitrification rate within the vertical flow system of 94% (median) at NH4-N loading rates of about 10 (median) up to 17 gm(-2)d(-1). Denitrification was mainly dependent on the dosing of acetic acid and could reach a maximum of 98%. One interesting effect was the production of nitrite in the horizontal flow sand filter. This could efficiently be eliminated by the subsequent vertical flow sand filter. The chosen concept proved to be very effective for nitrogen removal. In combination with a final activated carbon filter the COD effluent concentrations could be easily and safely controlled. The design of denitrification reed beds showed a further potential for optimization.

Investigations on phosphorus retention in subsurface flow constructed wetlands.

62 SSF sand-based constructed wetlands in Germany, Austria and Switzerland have been evaluated for their phosphorus performance. In addition intensive investigations on the removal of phosphorus and its accumulation within the filter bed were conducted at five wetlands. For the performance of horizontal flow (HF) reed beds a regression equation could be derived. This was not possible for vertical flow (VF) reed beds. The best removal efficiency was observed from HF systems with hydraulic loading rates of 10 mm d(-1) or less. 50 percent of all investigated HF wetlands had an average P output concentration of less than 2.1 mg l(-1) in comparison to 3.3 mg l(-1) of VF wetlands. Saturation, seasonal and redox effects could be derived from time series analysis of the performance rate and further investigations of a well monitored VF reed bed. The retention of phosphorus was highest during the warm season. A small positive effect on phosphorus removal was observed with intermittent low redox levels. Soil analyses showed the highest accumulation of P within the influent zone of either HF or VF wetlands.

Nutrient removal in subsurface flow constructed wetlands for application in sensitive regions.

One of the most interesting sites for research on CWs in Germany has been established in Wiedersberg (Saxonia). The multi-stage concept with primary settling, vertical and horizontal flow reed bed followed by UV-disinfection and a special phosphorus filter bed, allows numerous ways of operation and investigations. Denitrification can be improved by recirculation through VF bed and sedimentation tank or by means of adding carbonaceous water from the primary stage to a second level within the VFB or directly to the following HF bed. In order to investigate the efficiency of P-elimination four kinds of natural sands containing different amounts of iron have been used. To maintain a long-term capacity for P-reduction an additional filter bed is filled with gravelly sand which had been used for the precipitation of iron from drinking water before. After saturating with P this filter medium can be exchanged easily. A result of more than one year of operation is the high performance rate for adsorption of phosphorus by enriched iron on drinking water filter sand. At a total loading rate of 350 g P/m3 filter medium 250 g P/m3 have been adsorbed. Design considerations can not be given yet. The median denitrification rate at VFB is 1.3 g N m(-2) d(-1) and at HFB is 0.25 g N m(-2) d(-1). The low denitrifcation rate of HFB might be due to a very high quota of wastewater dilution by storm- and ground-water of 100 to 200 percent. The investigations on this wastewater treatment plant will be continued until June 2001 and experiments with filter columns will be added.

[Procedures for the isolation and characterization of human antithrombin III]. / Möglichkeiten der Isolierung und Charakterisierung des menschlichen Antithrombin III.

Antithrombin III, the most important inhibitor of activated coagulation factors (IIa, IXa, Xa, XIa, XIIa) was isolated from human plasma by affinity chromatography. The biochemical characterization of this highly purified inhibitor showed, that is was uniform by means of HPLC and PAA gradient gel electrophoresis. The molecular weight was determined to 70000 daltons and the isoelectric point was pH 4,5. The inhibition of factor Xa by AT III had been proofed as competitive by kinetic studies. AT III works as a "dead end inhibitor". Heparin seems to form a ternary complex with AT III and activated coagulation factors, so acting as a catalyst. The therapeutic value of AT III-concentrates will be discussed.