Microbial flora included in activated sludge in which a water treatment is performed is analyzed accurately. A computer of a microbial community analysis system includes an input unit configured to input a plurality of data groups including information indicating a nucleotide sequence of a gene of each of a plurality of microorganisms included in activated sludge in which a water treatment is performed; a similarity calculating unit configured to calculate a similarity between data groups on the basis of the nucleotide sequences included in the input data groups, and a coordinates calculating unit configured to calculate coordinates in a multidimensional space of each of the data groups on the basis of the calculated similarity.
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