The apparatus and methods of the present invention enable efficient and appropriate treatment of Urban Water Runoff, so that the treated Urban water Runoff can be can be introduced into public waterways without contaminating such waterways. The device further includes a unit for modularly reducing a first product of the numerator and the factor using a modulus equaling a sum of a second product of the denominator and the factor and of an integer to obtain an auxiliary quantity having the result. A second device runs a computer program that generates log files for storage on the second device. The inertia can take into account the extent to which the process accepts external connections; the greater the extent to which the process accepts external connections is, the greater the inertia.