Aquatic Organic Matter Fluorescence
107
Henderson et al. (2009). Limited data are available regarding the relationship with peak
C, although a correlation of 0.87 was reported by Bari and Farooq in 1985. Overall, for
both BOD and COD measurements, much stronger correlations have been found when
sewage-derived fluorescence dominates the system under investigation. For example, Wu
et al. (2006) noted that the strength of correlation between COD and peak T in river water
increased when sewage-derived DOM was more dominant (correlation coefficients rising
from 0.5 to 0.9). Strong correlations have also been found between peak T and PO 4
3–
, NO 3
–
(Baker and Inverarity, 2004), total Kjeldahl nitrogen (N k ), and NH 3 (Vasel and Praet, 2002).
These relationships are generally considered to be indirect because wastewater-derived pollution is typically characterized by high phosphate and nitrate ions when advanced nutrient removal is not undertaken at the wastewater treatment plant. Relationships between
ammonia and peak T are not always observed owing to the high removal rate of ammonia
during sewage treatment. However, ammonia can be present in significant quantities during
pollution events, as observed by Baker et al. (2003).
The monitoring of DOM levels through a treatment works allows process optimization,
and it has been estimated that as much as 40% of energy costs could be saved through efficiency gains, particularly with respect to aeration (Ahmad and Reynolds, 1998). A number
of articles by Ahmad and Reynolds (Ahmad and Reynolds, 1995, 1999; Reynolds and
Ahmad, 1997; Reynolds, 2002) have determined that a decrease in normalized fluorescence intensities of peak T is observed from influent to effluent across a treatment process.
Peak T at λ ex = 280 and λ em = 340 nm was identified as being most likely to relate to the
biodegradable material. This phenomenon has been utilized by other researchers investigating wastewater treatment processes such as sludge dewatering (Yu et al., 2010), landfill
leachates (Lu et al., 2009), membrane fouling (Moon et al., 2010), membrane bioreactors
(Wang et al., 2009), organic matter removal via coagulation–flocculation processes (Gone
et al., 2009) and the composting of municipal waste (He et al., 2011). Two of the key issues
surrounding the analysis of wastewater samples using fluorescence spectroscopy are the
correction for inner filter effects due to the highly absorbing nature of the samples and turbidity. Correction and normalization of fluorescence data are covered in Chapters 1 and 7,
and more specifically the inner filter effects exhibited in wastewater samples is discussed
by Reynolds and Ahmad (1997), Ahmad and Reynolds (1999), and Reynolds (2002).
A summary of the significant research that has established correlations between fluorescence and wastewater quality parameters over the last 25 years is shown in Table 3.3. What is
evident from previous work is that strong correlations do exist between traditional water quality parameters and fluorescence, although there are issues with directly comparing fluorescence data between geographical locations and between sites. More recent literature (Hudson
et al., 2007, 2008) indicates that future research should focus on utilizing and analyzing
fluorescence measurements as a direct and independent parameter for water/wastewater quality, rather than as a surrogate for specific water quality parameters. It is widely accepted that
further research is required to investigate fully the effects of advanced treatment process on
peaks T and C, especially if fluorescence-based techniques are to be applied to wastewater
treatment processes and the tracing of DOM within wastewater distribution systems.
107
Henderson et al. (2009). Limited data are available regarding the relationship with peak
C, although a correlation of 0.87 was reported by Bari and Farooq in 1985. Overall, for
both BOD and COD measurements, much stronger correlations have been found when
sewage-derived fluorescence dominates the system under investigation. For example, Wu
et al. (2006) noted that the strength of correlation between COD and peak T in river water
increased when sewage-derived DOM was more dominant (correlation coefficients rising
from 0.5 to 0.9). Strong correlations have also been found between peak T and PO 4
3–
, NO 3
–
(Baker and Inverarity, 2004), total Kjeldahl nitrogen (N k ), and NH 3 (Vasel and Praet, 2002).
These relationships are generally considered to be indirect because wastewater-derived pollution is typically characterized by high phosphate and nitrate ions when advanced nutrient removal is not undertaken at the wastewater treatment plant. Relationships between
ammonia and peak T are not always observed owing to the high removal rate of ammonia
during sewage treatment. However, ammonia can be present in significant quantities during
pollution events, as observed by Baker et al. (2003).
The monitoring of DOM levels through a treatment works allows process optimization,
and it has been estimated that as much as 40% of energy costs could be saved through efficiency gains, particularly with respect to aeration (Ahmad and Reynolds, 1998). A number
of articles by Ahmad and Reynolds (Ahmad and Reynolds, 1995, 1999; Reynolds and
Ahmad, 1997; Reynolds, 2002) have determined that a decrease in normalized fluorescence intensities of peak T is observed from influent to effluent across a treatment process.
Peak T at λ ex = 280 and λ em = 340 nm was identified as being most likely to relate to the
biodegradable material. This phenomenon has been utilized by other researchers investigating wastewater treatment processes such as sludge dewatering (Yu et al., 2010), landfill
leachates (Lu et al., 2009), membrane fouling (Moon et al., 2010), membrane bioreactors
(Wang et al., 2009), organic matter removal via coagulation–flocculation processes (Gone
et al., 2009) and the composting of municipal waste (He et al., 2011). Two of the key issues
surrounding the analysis of wastewater samples using fluorescence spectroscopy are the
correction for inner filter effects due to the highly absorbing nature of the samples and turbidity. Correction and normalization of fluorescence data are covered in Chapters 1 and 7,
and more specifically the inner filter effects exhibited in wastewater samples is discussed
by Reynolds and Ahmad (1997), Ahmad and Reynolds (1999), and Reynolds (2002).
A summary of the significant research that has established correlations between fluorescence and wastewater quality parameters over the last 25 years is shown in Table 3.3. What is
evident from previous work is that strong correlations do exist between traditional water quality parameters and fluorescence, although there are issues with directly comparing fluorescence data between geographical locations and between sites. More recent literature (Hudson
et al., 2007, 2008) indicates that future research should focus on utilizing and analyzing
fluorescence measurements as a direct and independent parameter for water/wastewater quality, rather than as a surrogate for specific water quality parameters. It is widely accepted that
further research is required to investigate fully the effects of advanced treatment process on
peaks T and C, especially if fluorescence-based techniques are to be applied to wastewater
treatment processes and the tracing of DOM within wastewater distribution systems.