| Summary: | Groundwater is an important source of fresh water on earth. A source that is also affected by climate change. Climate change is expected to influence both the groundwater quality and the groundwater level, where elevated levels of iron and manganese in the groundwater are to be expected. In Sweden guideline values are set for iron and manganese in drinking water, which means that waterworks that use groundwater as raw water must treat the water when the guidline values are exceeded. A common treatment step to remove iron and manganese is abiotic oxidation with a chemical oxidant. A relatively new method is biological oxidation where microorganisms oxidize the metals. Biological oxidation has proven to be a faster process than chemical oxidation and better adapted to variations in raw water quality. In this work the possibility of biological oxidation of iron and manganese at smaller groundwater plants with day-to-day production breaks has been studied. The study also concern how seasonal variations in raw water quality might affect the oxidation ability of the microorganisms. During the study a pilot filter for biological oxidation was constructed where the efficiency of the filter and the raw water quality was measured during a one-year test. After a short start-up time for iron oxidation the pilot filter reduced iron in the raw water up to 92 % and after a longer start-up time for manganese oxidation the pilot filter reduced manganese from the raw water up to 97 % during the rest of the test period. The results show that biological oxidation is possible at smaller groundwater plants despite production breaks. The results also show that biological oxidation is not affected by the vaiations i raw water quality that was measured during the test period. Furthermore, the results show that biological oxidation is equally efficient as the chemical oxidation, at the investigated groundwater plant, in terms of removing iron and even more efficient in terms of removing manganese. In addition the biological oxidation do not require pH adjustment or addition of any chemicals. The results indicate that biological oxidation of iron and manganese is a more favorable alternative to chemical oxidation in smaller groundwater plants on the impact of climate change on raw water quality.
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