Publikasjoner
NIBIOs ansatte publiserer flere hundre vitenskapelige artikler og forskningsrapporter hvert år. Her finner du referanser og lenker til publikasjoner og andre forsknings- og formidlingsaktiviteter. Samlingen oppdateres løpende med både nytt og historisk materiale. For mer informasjon om NIBIOs publikasjoner, besøk NIBIOs bibliotek.
2005
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Controlled experiments were carried out in a meso-scale sub-surface flow constructed sand filter treating municipal wastewater from a single household. The system consisted of a 50 cm high vertical flow column (pre-filter) with unsaturated flow and a 3 m long horizontal sub-surface flow unit (main filter) with saturated flow. Fluxes of nitrogen and carbon were analysed in four different operating conditions (low and high loading, with and without the pre-filter unit). Water samples were taken from the inlet, the outlet and within the sand filter at different depths and locations and analysed for water quality (Tot N, NO3-N, NH4-N, TOC, DOC, CODcr, BOD5, SS, pH and EC) and dissolved gas content (N2O, CH4 and CO2). Emissions of N2O, CH4 and CO2 were measured with the closed-chamber technique adjacent to water quality sampling points. The results show that pre-filtering in a vertical, unsaturated flow column changed the incoming ammonium to nitrate during low loading. During high loading part of the ammonium nitrified in the pre-filter was lost by denitrification. Within the horizontal main filter there were two pathways for the incoming nitrate: denitrification and dissimilatory nitrate reduction to ammonium (DNRA).
Sammendrag
The suitability of shell sand as a P sorbent has been tested both with laboratory batch experiments as well as in a sub-surface flow (SSF) meso-scale constructed sand filter treating municipal wastewater from a single household. The batch experiments suggest that retention of P in shell sand occurs both as sorption and precipitation. The soil-water ratio was found to be a crucial parameter when performing laboratory batch experiments. The maximum retention capacity was about 8000 and 800 mg P kg-1 sand, and the Kd was 33.7 and 82.9 L kg-1 for soil-water ratios of 5 g "75 mL and 50 g " 50 mL, re-spectively. The average total accumulated P concentration in samples from the SSF sand filter was 335 mg P kg-1. The Kd value based on [PO43-] and accumulated concentration of inorganic P in the SSF filter was 89.8 L kg-1. Thus the batch experiments overestimated the retention capacity of shell sand in real sand filter systems, however, a ratio of 50-50 gave a more reasonable estimate than a ratio of 5-75. The Kd value from batch samples with a ratio of 50-50 also gave a good estimate of the Kd value in the constructed sand filter. Ca-P was found to be the predominant form of P mineral in samples col-lected from the SSF sand filter. Some Al-P, loosely bounded P and occluded P were also present in the sand.
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Det er ikke registrert sammendrag
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Laboratory incubations with varying O2 and NO3 concentrations were performed with a range of filter materials used in constructed wetlands (CWs). The study included material sampled from functioning CWs as well as raw materials subjected to laboratory pre-incubation. 15N-tracer techniques were used to assess the rates of denitrification versus dissimilatory nitrate reduction to ammonium (DNRA), and the relative role of nitrification versus denitrification in producing N2O. The N2O/(N2+N2O) product ratio was assessed for the different materials. Sand, shell sand, and peat sustained high rates of denitrification. Raw light weight aggregates (LWA) had a very low rate, while in LWA sampled from a functioning CW, the rate was similar to the one found in the other materials. The N2O/(N2+N2O) ratio was very low for sand, shell sand and LWA from functioning CWs, but very high for raw LWA. The ratio was intermediate but variable for peat. The N2O produced by nitrification accounted for a significant percentage of the N2O accumulated during the incubation, but was dependent on the initial oxygen concentration. DNRA was significant only for shell sand taken from a functioning CW, suggesting that the establishment of active DNRA is a slower process than the establishment of a denitrifying flora.
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Erosjonsmodellen GIS avrenning beregner flateerosjon fra landbruksarealer ved å kombinere data om erosjonsrisiko med data om jordarbeiding og driftspraksis. I løpet av 2003-2005 er modellen videreutviklet til også å beregne retensjon i fangdammer og vegetasjonssoner og koble dette opp mot totale effektberegninger for disse tiltakene. Denne rapporten beskriver det teoretiske grunnlaget for å beregne retensjonen av suspendert stoff og fosfor i fangdammer og vegetasjonssoner i GIS avrenning.
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