Determination of assimilable organic carbon in humus-rich drinking waters

The potential for microbial growth in drinking waters is considered to be a ssociated with the content of easily assimilable organic carbon (AOC). The bacterial test for the determination of the AOC concentration presumes that microbial growth in the test is limited by the availability of organic car bon. However, in the northern latitudes inorganic nutrients, particularly p hosphorus, may limit the microbial growth in drinking waters. In our studie s, addition of an inorganic nutrient mixture (N, P, K. S. Ca. Mg) to soft, humus-rich drinking waters increased the AOC yield in most of the drinking waters. The assimilable organic carbon determined with the addition of nutr ients describes that pool of organic carbon potentially available for micro bial growth (AOC(potential)). The AOC yield when there is no without additi on of inorganic nutrients describes that part of organic carbon (AOC(native )) which bacteria can utilize in the prevailing conditions and it is compos ed of the availability of both organic substrates and inorganic nutrients. We found that the bacterial strains, Pseudomonas fluorescens P 17 and Aquas pirillum NOX, used in the standard, AOC method, can also be applied in humu s-rich drinking waters. (C) 1999 Elsevier Science Ltd. All rights reserved.