Coble, Spencer, Baker, and Reynolds
106
DOM related to natural systems is derived predominantly from plant material and where
microbial activity is slow and weak but nevertheless sustained. The unique origins of
wastewater DOM are highlighted in their associated EEMs, which are most notably different from EEMs of DOM from marine and freshwater systems, where peak C predominates (Hudson et al., 2007). The unique spectral characteristics of wastewater DOM have
facilitated the tracking of sewage contamination in aquatic systems (Galapate et al., 1998;
Baker, 2001; Baker et al., 2003, 2005; Chen et al., 2003; Holbrook et al., 2005; Hudson
et al., 2008; Carstea, 2010).
The intense fluorescence intensity associated with sewage-derived DOM has led to the
investigation of fluorescence as a marker for existing biochemical and chemical parameters
commonly used to determine wastewater quality and monitor wastewater treatment processes (Reynolds and Ahmad, 1997; Ahmad and Reynolds, 1999; Reynolds, 2002; Vasel and
Praet, 2002; Lee and Ahn, 2004; Cumberland and Baker, 2007; Hudson et al., 2008; Hur
et al., 2008). Relationships between the fluorescence intensity of various peaks (A, B, T,
and C) and water quality parameters have been investigated. The most common wastewater quality parameters investigated include the 5-day BOD; COD of filtered and unfiltered
samples; total organic carbon (TOC); dissolved organic carbon (DOC); nitrate (NO 3
–
) and
phosphate (PO 4
3–
) ions; UV absorption at 254 nm, 340 nm, and 450 nm; dissolved oxygen
levels (DO); and ammonia (NH 3 ).
Correlations of Pearson’s coefficient (r or r
2
) values of between 0.77 and 0.98 have
been reported between BOD and peaks T and A T (Reynolds and Ahmad, 1997; Ahmad and
Reynolds, 1999; Baker, 2001; Ahmad et al., 2002; Hudson et al., 2008; Hur et al., 2008).
The correlations of peaks A C and C (which represent humic and fulvic-like fluorescence)
with the 5-day BOD were lower (r
2
= 0.72–0.77) (Baker, 2001; Hudson et al., 2008). The
strong correlation between the 5-day BOD and the tryptophan-like fluorescence at around
340–350 nm is expected, as BOD is an indirect measure of microbial growth. Furthermore,
the tryptophan-like fluorescence has been associated with wastewater microbial activity
(Reynolds, 2002; Elliott et al., 2006; Hudson et al., 2008), whereas fulvic and humic-like
fluorescence has been reported to represent the nonreadily biodegradable organic fraction
of wastewaters (Reynolds, 2002).
Reported correlations of Pearson’s coefficient for peak T and the COD and DOC values
of wastewaters typically range from values between 0.42 and 0.97 (Reynolds, 2002; Vasel
and Praet, 2002; Lee and Ahn, 2004; Wu et al., 2006). This is unsurprising given the well
established chemical relationships between TOC and DOC. The wide range of correlations
that have been observed for fluorescence (especially peak T) and DOC, COD, and TOC are
explained by the ratio of refractory DOM to labile DOM, of fluorescent and nonfluorescent
character. Correlations can exhibit greater variation depending on the ratio of both humic/
fulvic-like/tryptophan-like material and fluorescent/nonfluorescent DOM. For this reason,
some investigators have found it useful to examine the T/C ratio in relation to wastewater
and effluent samples. Baker (2001) found that the T/C ratios for rivers (1.0) were far lower
than that of untreated sewage (2.7–31). A comprehensive data set representing the T/C
ratios of waste, rivers, and drinking and deionized water is shown in the recent review by
106
DOM related to natural systems is derived predominantly from plant material and where
microbial activity is slow and weak but nevertheless sustained. The unique origins of
wastewater DOM are highlighted in their associated EEMs, which are most notably different from EEMs of DOM from marine and freshwater systems, where peak C predominates (Hudson et al., 2007). The unique spectral characteristics of wastewater DOM have
facilitated the tracking of sewage contamination in aquatic systems (Galapate et al., 1998;
Baker, 2001; Baker et al., 2003, 2005; Chen et al., 2003; Holbrook et al., 2005; Hudson
et al., 2008; Carstea, 2010).
The intense fluorescence intensity associated with sewage-derived DOM has led to the
investigation of fluorescence as a marker for existing biochemical and chemical parameters
commonly used to determine wastewater quality and monitor wastewater treatment processes (Reynolds and Ahmad, 1997; Ahmad and Reynolds, 1999; Reynolds, 2002; Vasel and
Praet, 2002; Lee and Ahn, 2004; Cumberland and Baker, 2007; Hudson et al., 2008; Hur
et al., 2008). Relationships between the fluorescence intensity of various peaks (A, B, T,
and C) and water quality parameters have been investigated. The most common wastewater quality parameters investigated include the 5-day BOD; COD of filtered and unfiltered
samples; total organic carbon (TOC); dissolved organic carbon (DOC); nitrate (NO 3
–
) and
phosphate (PO 4
3–
) ions; UV absorption at 254 nm, 340 nm, and 450 nm; dissolved oxygen
levels (DO); and ammonia (NH 3 ).
Correlations of Pearson’s coefficient (r or r
2
) values of between 0.77 and 0.98 have
been reported between BOD and peaks T and A T (Reynolds and Ahmad, 1997; Ahmad and
Reynolds, 1999; Baker, 2001; Ahmad et al., 2002; Hudson et al., 2008; Hur et al., 2008).
The correlations of peaks A C and C (which represent humic and fulvic-like fluorescence)
with the 5-day BOD were lower (r
2
= 0.72–0.77) (Baker, 2001; Hudson et al., 2008). The
strong correlation between the 5-day BOD and the tryptophan-like fluorescence at around
340–350 nm is expected, as BOD is an indirect measure of microbial growth. Furthermore,
the tryptophan-like fluorescence has been associated with wastewater microbial activity
(Reynolds, 2002; Elliott et al., 2006; Hudson et al., 2008), whereas fulvic and humic-like
fluorescence has been reported to represent the nonreadily biodegradable organic fraction
of wastewaters (Reynolds, 2002).
Reported correlations of Pearson’s coefficient for peak T and the COD and DOC values
of wastewaters typically range from values between 0.42 and 0.97 (Reynolds, 2002; Vasel
and Praet, 2002; Lee and Ahn, 2004; Wu et al., 2006). This is unsurprising given the well
established chemical relationships between TOC and DOC. The wide range of correlations
that have been observed for fluorescence (especially peak T) and DOC, COD, and TOC are
explained by the ratio of refractory DOM to labile DOM, of fluorescent and nonfluorescent
character. Correlations can exhibit greater variation depending on the ratio of both humic/
fulvic-like/tryptophan-like material and fluorescent/nonfluorescent DOM. For this reason,
some investigators have found it useful to examine the T/C ratio in relation to wastewater
and effluent samples. Baker (2001) found that the T/C ratios for rivers (1.0) were far lower
than that of untreated sewage (2.7–31). A comprehensive data set representing the T/C
ratios of waste, rivers, and drinking and deionized water is shown in the recent review by