Rödfärgade utfällningar i dammanläggningar orsakade av G. ferruginea och L. ochracea - Problemstatistik och mikrobiella levnadsförutsättningar

Sammanfattning: Hydropower is an extensive national industry which supplies Sweden with about 45 % of its total energy produced (Molin 2016). A problem which the industry is currently fighting is the presence of ochre-colored precipitations that clog vital measuring tools and drainage pipes at the dams, commonly called red mud. The red mud is produced by iron-oxidizing bacteria, FeOB, which oxidize Fe(II) to Fe(III) (Hamrén 2013). The particles of oxidized iron accumulate in the microbial mat, with other particles, and build up the red mud. Gallionella ferruginea and Leptothrix ochracea are two FeOB which have been connected to the foremost production of red mud (Hamrén 2013). This article examines the occurrence of red mud in dam facilities, the severity of the problems caused, which FeOB produces the main amount of red mud, which are the living conditions of these FeOB and are there any measures which you can take to halt the growth of the FeOB. The scope of the problem within different facilities across Sweden is examined through a survey. A visit to a facility with problems with red mud was realized, where samples of water was collected from different problem areas. Further, a literature study was done with the focus on the ironoxidizing bacteria. 7 out of 8 respondents confirmed that they had problems with red mud within their facilities, where they cause small to considerable problems. The red mud is reported to severely complicate monitoring measurements and cause clogging of drainage pipes. From the analysis of the water-samples elevated amounts of iron was found in the areas which contained the most amount of red mud, compared to those which contained less or no amount of red mud. It is assumed that L. ochracea is responsible for the main production of red mud, and it is confirmed that L. ochracea is better suited for the environment within a dam compared to G. ferruginea. The growth of L. ochracea is limited by high levels of salt, the addition of sodium azide and the absence of potassium and magnesium (Fleming et al. 2018; Eggerichs et al. 2020).