3.1.1. Ideal wastewater contamination indicator parameter
Pitt (2004) defined an ideal indicator for detecting wastewater
contamination in stormwater as a parameter having the following
properties: (i) occurring in wastewater and stormwater at considerably
different concentrations, which only slightly vary within
each flow stream; (ii) possess conservative properties; and, (iii)
measurable by simple, reliable, accurate, and safe methods. Scott
et al. (2002) focused on ideal indicator microorganisms, which
should be: (i) non-pathogenic (ii) present in sufficient quantities to
be detectable; (iii) easily countable; (iv) exist in a constant ratio to
pathogens; (v) possessing survival characteristics similar to those
of pathogens; (vi) unable to reproduce outside the host; and, (vii)
able to enter the environment only from the faeces of warmblooded
animals. Both references concluded that there was no
ideal indicator parameter available (Pitt, 2004; Scott et al., 2002)
and, consequently, one needs to look for an indicator, which in the
given circumstances mimics the essential characteristics of the
ideal indicator as closely as possible.