Microbial Activity in Various Sections of the Domestic Distribution System and the Effect of Stagnation

Abstract

The microbial activity in various sections of the domestic distribution system is studied and the effect of stagnation time is assessed. The concentration of total ATP in samples taken after 1 minute of flushing the consumers tap are generally in the range of <1-10 ng/1. The concentration of ATP in the first 500 ml sample after overnight stagnation is generally higher than the fully flushed sample whereas the second 500 ml sample in succession is always lower than the first 500ml sample: microbial activity in the domestic distribution system is most prominent present near the tap. 20 successive 50ml samples show microbial activity in certain sections of the domestic distribution system under study in more detail. The stagnation time has an effect on the concentration of ATP, but the trend was dependent on the sampling location. The stagnation time is also studied in a continuous semi-dynamic test facility. Copper, stainless steel and polypropene show decreasing concentraiton of ATP with increasing stagnation. Galvanised steel shows two different stagnation behaviours in July and September. The data allow also the assessment of the performance of the water treatment and/or problems in the mains.JRC.I.5-Physical and chemical exposure