Guro Hensel
Seniorrådgiver
(+47) 977 29 995
guro.hensel@nibio.no
Sted
Ås - Bygg O43
Besøksadresse
Oluf Thesens vei 43, 1433 Ås (Varelevering: Elizabeth Stephansens vei 23)
Sammendrag
WebGIS avløp er et fagsystem for private avløpsløsninger i kommunene. Applikasjonen beregner utslipp til resipient og effekter av planlagte tiltak. I tillegg kan WebGIS avløp også brukes til administrativ oppfølging, tilsyn, pålegg og rapportering.
Sammendrag
Artikkelen tar for seg levetid for infiltrasjonsanlegg for avløpsvann og ser spesielt på binding av fosfor og gjentetting som kan begrense levetiden. Det refereres til norske og internasjonale undersøkelser. I Norge er det generelt gode erfaringer med infiltrasjon som rensemetode og regnes som en robust metode som tåler variasjoner i hydraulisk belastning og oppnår rensing på mange viktige parametere. Undersøkelser av eldre anlegg, etablert før 1985, viser imidlertid at anleggene ofte er plassert på dårlige egnede masser, har for lite areal eller mangelfull utforming i forhold til dagens krav. Infiltrasjonsanlegg i gode masser, og spesielt med nyere design, kan forventes å ha lang levetid (mer enn 20 ‐ 25 år), men lokale forhold kan begrense levetiden. Artikkelen har forslag til tema som bør undersøkes nærmere i forhold til å vurdere levetid på norske infiltrasjonsanlegg.
Sammendrag
Norwegian constructed wetlands (CWs) that treat domestic wastewater are classified as horizontal subsurface flow constructed wetlands (HSFCWs). Over the years of continuous performance, the HSFCWs operating under cold climate conditions have shown a high and stable treatment efficiency with regard to the removal of organic matter (>90 % BOD), nutrients (>50 % N and >90 % P) and microbes (>99 % bacteria). The majority of Norwegian HSFCWs are categorised as small (<50 pe) on-site, decentralised wastewater treatment systems. The Norwegian systems consist of three fundamental elements: a septic tank, a pre-filter (i.e. an aerobic vertical flow biofilter) and a horizontal flow saturated filter/wetland bed. The first, primary treatment step begins in the septic tank from which effluents are pre-treated in the second step occurring in the pre-filter/biofilter section and further in the third, final step taking place in the filter bed/HSFCW. The first and third treatment steps are quite common in systems with CWs, but the pre-treatment in biofilter(s) is mainly known from Norway. The main purpose of using the pre-treatment phase is to supply air during the cold season, to enhance nitrification processes, and to reduce the load of organic matter before entering the filter/wetland bed. If constructed and maintained correctly, the biofilters alone can remove 90 % BOD and 40 % N. Various filter/CW beds have been introduced for treatment of domestic wastewater (as complete or source-separated streams) in Norway, but the most common feature is the use of specific filter media for high phosphorus (P) removal. A few Norwegian municipalities also have limits with respect to nitrogen (N) discharge, but the majority of municipalities use 1.0 mg P/l as the discharge limit for small wastewater treatment systems. This particular limit affects the P retention lifetime of the filter media, which varies from system to system depending on the filter media applied, the type of wastewater treated, and the system design and loading rates. An estimated lifetime of filter media with regard to P removal is approximately 15–18 years for a filter/CW bed of a single household. After completing the lifetime, the filter media is excavated and replaced with new/fresh materials, allowing the system to operate effectively for another lifespan. Since the exploited media are P-rich materials, the main intention is their reuse in a safe and hygienic way, in which P could be further utilised. Therefore, the Norwegian systems can represent a complex technology combining a sustainable technique of domestic wastewater treatment and a bio-economical option for filter media reuse. This is a quite challenging goal for reclamation and recycling of P from wastewater. Thus, there are some scenarios of reusing the P-rich filter media as a complementary P fertiliser, a soil amendment or a conditioner, provided the quality is acceptable for utilisation in agriculture. Alternatively, the filter media could be reused in some engineering projects, e.g. green roof technology, road screening or construction of embankments, if the quality allows application in the environment. The core aspect of the reuse options is the appropriate quality of the filter media. As for the theoretical assumption, it should not be risky to reuse the P-rich media in agriculture. In practice, however, the media must be proven safe for human and environmental health prior to introducing into the environment.