550739
research-article2014
WMR0010.1177/0734242X14550739Waste Management & ResearchGupta et al.
Original Article
Variation in organic matter characteristics of landfill leachates in different stabilisation stages
Waste Management & Research 2014, Vol. 32(12) 1192–1199 © The Author(s) 2014 Reprints and permissions: sagepub.co.uk/journalsPermissions.nav DOI: 10.1177/0734242X14550739 wmr.sagepub.com
Abhinav Gupta1,*, Renzun Zhao1,*, John T Novak1 and C Douglas Goldsmith2
Abstract This study investigates the effect of landfill age on landfill leachate characteristics; two aspects are focused here. One is ultraviolet absorbance at 254 nm (UV254) property, as the discharge of landfill leachates to publically owned treatment works can cause interference with UV254 disinfection. The other is biorefractory organic nitrogen in leachates, as it can contribute to effluent nitrogen making it difficult to meet stringent effluent nitrogen regulations. To study variation in UV254-absorbing organic carbon and organic nitrogen, leachate samples ranging from cells with ages 2 to 30 y from a large landfill in Kentucky, were collected and fractionated on a basis of their molecular weight and chemical nature into humic acids, fulvic acids and a hydrophilic fraction. The effectiveness of long term landfilling and membrane treatment for organic matter and organic nitrogen removal was examined. Humic materials, which were the major UV254-absorbing substances, were mainly >1 kDa and they degraded significantly with landfill age. The hydrophilic organic fraction, which was the major contributor to organic nitrogen, was mainly FA > Hpi. The SUVA254 values of HA, FA and Hpi fractions ranged from 3.6–3.4, 2.4–2.0 and 1.8–1.2 L mg-1 m-1, respectively, for KY-2.5 to KY-30. This indicates that the HA fraction contains greater aromatic content than the other two fractions, the Hpi fraction has the lowest among the three fractions. However, as it accounts for more than 60% of DOM in the KY leachates in terms of TOC, the Hpi fraction contributes the most to the UV254 absorbance (cm-1) of the whole leachate sample. FA fraction is between HA and Hpi fractions regarding both SUVA254 and UV254 absorbance contribution.
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Waste Management & Research 32(12)
In the POTWs that use UV disinfection, discharging of landfill leachate adversely affects the disinfection operation. As shown in Table 4, if 5% of leachate is mixed with the waste stream in a POTW, the UV transmittance range from 0.8% to 55.7% depending on the age of the leachate. If the proportion of leachate reduces to 2%, the UV transmittance of the mixed waste stream increases to a range of 14.5%–79.1%. Usually 60%–65% of UV transmittance is required to allow the UV disinfection to work effectively in POTWs. Considering there might be possible UV absorbance contributors in sewage, discharging of studied landfill leachates will disable the UV disinfection in most cases. Figure 3 shows the MW distribution of the HA (Figure 3(a)), FA (Figure 3(b)) and Hpi (Figure 3(c)) of the organic matter in the KY leachates. The contribution of the Hpi fraction 100 kDa
350
140
KY-2.5 Total organic carbon (mg L-1)
Table 4. UV absorbance and UV transmittance of KY leachates.
400
(a)
0
Total organic carbon (mg L-1)
mainly 100 kDa 3 kDa - 100 kDa 1 kDa - 3 kDa 500 Da - 1 kDa < 500 Da
KY-2.5 KY-9 1400
(c)
1000 800
300
600
200
400
100
KY-16 KY-30 > 100 kDa 10 kDa - 100 kDa 5 kDa - 10 kDa 3 kDa - 5 kDa 1 kDa - 3 kDa 500 Da - 1 kDa < 500 Da
1200
400
KY-16 KY-30
200
0
0
KY-2.5 KY-9
KY-16 KY-30
KY-2.5 KY-9
KY-16 KY-30
Figure 3. Molecular weight distribution of total organic carbon in humic acids (a), fulvic acids (b) and hydrophilic fraction (c) in KY leachates. (left: cluster column; right: stacked column).
Downloaded from wmr.sagepub.com at NORTHERN ARIZONA UNIVERSITY on June 1, 2015
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Gupta et al. 6
500 Da - 1 kDa
6
2
< 500 Da
4
1
2
0
0 KY-2.5
KY-9
KY-16
KY-30
KY-2.5
KY-9
12
(b)
UV254 abs. cm-1
2
KY-30
3 kDa - 100 kDa
8
1 kDa - 3 kDa
6
500 Da - 1 kDa < 500 Da
4
1
KY-16
> 100 kDa
10
3
2 0
0 KY-2.5
8
1 kDa - 3 kDa
8
3
9
3 kDa - 100 kDa
10
4
4
> 100 kDa
12
UV254 abs. cm-1
5
14
(a)
KY-9
KY-16
KY-2.5
KY-30
KY-9
20 18 16 14 12 10 8 6 4 2 0
(c)
UV254 abs. cm-1
7 6 5 4 3 2 1 0 KY-2.5
KY-9
KY-16
KY-30
KY-16
KY-30
> 100 kDa 10 kDa-100k Da 5 kDa - 10 kDa 3 kDa - 5 kDa 1 kDa - 3 kDa 500 Da - 1 kDa < 500 Da
KY-2.5
KY-9
KY-16
KY-30
Figure 4. MW distribution of UV254-absorbing substances in humic acids (a), fulvic acids (b) and hydrophilic fraction (c) in KY leachates (left, cluster column; right: stacked column).
older leachates, the FA fraction contributes up to 92% (KY-30) of the humic substances. The greatest decrease from young to older leachate can be seen for the HA fractions with most of organic matter left in the HA fraction consisting of the higher MW (>100 kDa) fraction for the older leachates. For the FAs however, it is the 1 kDa showed an increasing tendency from KY-2.5 to KY-30. The trend for the distribution of the organic matter in the FAs varies in the sense that fraction of the FAs >1 kDa dominates in the younger leachates, but is in the minority in the older leachates. Thus, membrane filtration with a MWCO of 1 kDa would be effective for the removal of HAs for landfills of all ages, but for the older leachates it would be less effective for the removal of FAs. Also, for the older leachates, KY-30 and KY-16, membrane filtration is not attractive for the removal of the total
organic matter, because the fraction >1 kDa for KY-30 and KY-16 is quite low in amount. For the Hpi fraction in the younger leachates, the MW fraction 1 kDa organics increases. The maximum decrease over a landfilling period of 30 y in the landfill was 98% for HAs and around 80% for the FA and Hpi fractions. However, the contribution of the Hpi fraction remains significant in the older leachates and thus tends to persist over long term landfilling. Also, while considering the effectiveness of the membrane filtration with a MWCO of 1 kDa for the removal of the Hpi fraction, it is suitable only for the older leachates where the fraction of the Hpi >1 kDa is relatively high as compared with the younger leachates. Figure 4 shows the MW distribution of the UV254-absorbing substances in the HA (Figure 4(a)), FA (Figure 4(b)) and Hpi (Figure 4(c)) for the KY leachates. The distribution of
Downloaded from wmr.sagepub.com at NORTHERN ARIZONA UNIVERSITY on June 1, 2015
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Waste Management & Research 32(12)
Organic Nitrogen mg L-1 - N
300
(a)
250
Total ON
Hpi ON
200 150 100 50 0 KY-2.5
KY-9
KY-16
KY-30
120
(b)
Protein mg L-1 - N
100
Total Protein
Hpi Protein
80 60
age, however, the degradability of the protein fraction increases with age. The contribution of the Hpi fraction to the ON is around 78% for KY-2.5, which is the youngest leachate, whereas it is around 50% for all the other leachates. Hence, the Hpi fraction is the biggest contributor to the ON among the various hydrophobic fractions. The Hpi fraction is the biggest contributor to the proteins among the HA, FA and Hpi fractions. Its contribution increases for the older leachates, especially for KY-30 where it contributes 86% of the proteins. The higher proportion of the Hpi protein’s contribution to the total protein in the KY-30 leachate is owing to the predominance of the Hpi fraction in the sample. These results suggest that most of the ON and proteins come from the Hpi fraction, which is mostly 1 kDa dominate, as opposed to the 1 kDa, with the absorption due to fractions >1 kDa ranging from 44%–55% for the different leachates. Thus, membrane filtration with a MWCO of 1 kDa will be helpful for the removal of UV254-absorbing substances.
The results indicated that Hpi fraction contributes the most UV254 absorbance to the whole leachate samples, while HA fraction contains the greatest SUVA254. Discharging a small proportion (2%–5%) of leachate may adversely affect a POTW where UV disinfection is used. Membrane treatment with a 1 kDa MWCO can significantly decrease the UV254 absorbance owing to the leachates in the POTW effluents. A significant decrease in humic substances with long term landfilling indicated that age is important in determining potential for leachates to impact UV disinfection in POTWs. Hpi fraction (mostly
research-article2014
WMR0010.1177/0734242X14550739Waste Management & ResearchGupta et al.
Original Article
Variation in organic matter characteristics of landfill leachates in different stabilisation stages
Waste Management & Research 2014, Vol. 32(12) 1192–1199 © The Author(s) 2014 Reprints and permissions: sagepub.co.uk/journalsPermissions.nav DOI: 10.1177/0734242X14550739 wmr.sagepub.com
Abhinav Gupta1,*, Renzun Zhao1,*, John T Novak1 and C Douglas Goldsmith2
Abstract This study investigates the effect of landfill age on landfill leachate characteristics; two aspects are focused here. One is ultraviolet absorbance at 254 nm (UV254) property, as the discharge of landfill leachates to publically owned treatment works can cause interference with UV254 disinfection. The other is biorefractory organic nitrogen in leachates, as it can contribute to effluent nitrogen making it difficult to meet stringent effluent nitrogen regulations. To study variation in UV254-absorbing organic carbon and organic nitrogen, leachate samples ranging from cells with ages 2 to 30 y from a large landfill in Kentucky, were collected and fractionated on a basis of their molecular weight and chemical nature into humic acids, fulvic acids and a hydrophilic fraction. The effectiveness of long term landfilling and membrane treatment for organic matter and organic nitrogen removal was examined. Humic materials, which were the major UV254-absorbing substances, were mainly >1 kDa and they degraded significantly with landfill age. The hydrophilic organic fraction, which was the major contributor to organic nitrogen, was mainly FA > Hpi. The SUVA254 values of HA, FA and Hpi fractions ranged from 3.6–3.4, 2.4–2.0 and 1.8–1.2 L mg-1 m-1, respectively, for KY-2.5 to KY-30. This indicates that the HA fraction contains greater aromatic content than the other two fractions, the Hpi fraction has the lowest among the three fractions. However, as it accounts for more than 60% of DOM in the KY leachates in terms of TOC, the Hpi fraction contributes the most to the UV254 absorbance (cm-1) of the whole leachate sample. FA fraction is between HA and Hpi fractions regarding both SUVA254 and UV254 absorbance contribution.
Downloaded from wmr.sagepub.com at NORTHERN ARIZONA UNIVERSITY on June 1, 2015
1196
Waste Management & Research 32(12)
In the POTWs that use UV disinfection, discharging of landfill leachate adversely affects the disinfection operation. As shown in Table 4, if 5% of leachate is mixed with the waste stream in a POTW, the UV transmittance range from 0.8% to 55.7% depending on the age of the leachate. If the proportion of leachate reduces to 2%, the UV transmittance of the mixed waste stream increases to a range of 14.5%–79.1%. Usually 60%–65% of UV transmittance is required to allow the UV disinfection to work effectively in POTWs. Considering there might be possible UV absorbance contributors in sewage, discharging of studied landfill leachates will disable the UV disinfection in most cases. Figure 3 shows the MW distribution of the HA (Figure 3(a)), FA (Figure 3(b)) and Hpi (Figure 3(c)) of the organic matter in the KY leachates. The contribution of the Hpi fraction 100 kDa
350
140
KY-2.5 Total organic carbon (mg L-1)
Table 4. UV absorbance and UV transmittance of KY leachates.
400
(a)
0
Total organic carbon (mg L-1)
mainly 100 kDa 3 kDa - 100 kDa 1 kDa - 3 kDa 500 Da - 1 kDa < 500 Da
KY-2.5 KY-9 1400
(c)
1000 800
300
600
200
400
100
KY-16 KY-30 > 100 kDa 10 kDa - 100 kDa 5 kDa - 10 kDa 3 kDa - 5 kDa 1 kDa - 3 kDa 500 Da - 1 kDa < 500 Da
1200
400
KY-16 KY-30
200
0
0
KY-2.5 KY-9
KY-16 KY-30
KY-2.5 KY-9
KY-16 KY-30
Figure 3. Molecular weight distribution of total organic carbon in humic acids (a), fulvic acids (b) and hydrophilic fraction (c) in KY leachates. (left: cluster column; right: stacked column).
Downloaded from wmr.sagepub.com at NORTHERN ARIZONA UNIVERSITY on June 1, 2015
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Gupta et al. 6
500 Da - 1 kDa
6
2
< 500 Da
4
1
2
0
0 KY-2.5
KY-9
KY-16
KY-30
KY-2.5
KY-9
12
(b)
UV254 abs. cm-1
2
KY-30
3 kDa - 100 kDa
8
1 kDa - 3 kDa
6
500 Da - 1 kDa < 500 Da
4
1
KY-16
> 100 kDa
10
3
2 0
0 KY-2.5
8
1 kDa - 3 kDa
8
3
9
3 kDa - 100 kDa
10
4
4
> 100 kDa
12
UV254 abs. cm-1
5
14
(a)
KY-9
KY-16
KY-2.5
KY-30
KY-9
20 18 16 14 12 10 8 6 4 2 0
(c)
UV254 abs. cm-1
7 6 5 4 3 2 1 0 KY-2.5
KY-9
KY-16
KY-30
KY-16
KY-30
> 100 kDa 10 kDa-100k Da 5 kDa - 10 kDa 3 kDa - 5 kDa 1 kDa - 3 kDa 500 Da - 1 kDa < 500 Da
KY-2.5
KY-9
KY-16
KY-30
Figure 4. MW distribution of UV254-absorbing substances in humic acids (a), fulvic acids (b) and hydrophilic fraction (c) in KY leachates (left, cluster column; right: stacked column).
older leachates, the FA fraction contributes up to 92% (KY-30) of the humic substances. The greatest decrease from young to older leachate can be seen for the HA fractions with most of organic matter left in the HA fraction consisting of the higher MW (>100 kDa) fraction for the older leachates. For the FAs however, it is the 1 kDa showed an increasing tendency from KY-2.5 to KY-30. The trend for the distribution of the organic matter in the FAs varies in the sense that fraction of the FAs >1 kDa dominates in the younger leachates, but is in the minority in the older leachates. Thus, membrane filtration with a MWCO of 1 kDa would be effective for the removal of HAs for landfills of all ages, but for the older leachates it would be less effective for the removal of FAs. Also, for the older leachates, KY-30 and KY-16, membrane filtration is not attractive for the removal of the total
organic matter, because the fraction >1 kDa for KY-30 and KY-16 is quite low in amount. For the Hpi fraction in the younger leachates, the MW fraction 1 kDa organics increases. The maximum decrease over a landfilling period of 30 y in the landfill was 98% for HAs and around 80% for the FA and Hpi fractions. However, the contribution of the Hpi fraction remains significant in the older leachates and thus tends to persist over long term landfilling. Also, while considering the effectiveness of the membrane filtration with a MWCO of 1 kDa for the removal of the Hpi fraction, it is suitable only for the older leachates where the fraction of the Hpi >1 kDa is relatively high as compared with the younger leachates. Figure 4 shows the MW distribution of the UV254-absorbing substances in the HA (Figure 4(a)), FA (Figure 4(b)) and Hpi (Figure 4(c)) for the KY leachates. The distribution of
Downloaded from wmr.sagepub.com at NORTHERN ARIZONA UNIVERSITY on June 1, 2015
1198
Waste Management & Research 32(12)
Organic Nitrogen mg L-1 - N
300
(a)
250
Total ON
Hpi ON
200 150 100 50 0 KY-2.5
KY-9
KY-16
KY-30
120
(b)
Protein mg L-1 - N
100
Total Protein
Hpi Protein
80 60
age, however, the degradability of the protein fraction increases with age. The contribution of the Hpi fraction to the ON is around 78% for KY-2.5, which is the youngest leachate, whereas it is around 50% for all the other leachates. Hence, the Hpi fraction is the biggest contributor to the ON among the various hydrophobic fractions. The Hpi fraction is the biggest contributor to the proteins among the HA, FA and Hpi fractions. Its contribution increases for the older leachates, especially for KY-30 where it contributes 86% of the proteins. The higher proportion of the Hpi protein’s contribution to the total protein in the KY-30 leachate is owing to the predominance of the Hpi fraction in the sample. These results suggest that most of the ON and proteins come from the Hpi fraction, which is mostly 1 kDa dominate, as opposed to the 1 kDa, with the absorption due to fractions >1 kDa ranging from 44%–55% for the different leachates. Thus, membrane filtration with a MWCO of 1 kDa will be helpful for the removal of UV254-absorbing substances.
The results indicated that Hpi fraction contributes the most UV254 absorbance to the whole leachate samples, while HA fraction contains the greatest SUVA254. Discharging a small proportion (2%–5%) of leachate may adversely affect a POTW where UV disinfection is used. Membrane treatment with a 1 kDa MWCO can significantly decrease the UV254 absorbance owing to the leachates in the POTW effluents. A significant decrease in humic substances with long term landfilling indicated that age is important in determining potential for leachates to impact UV disinfection in POTWs. Hpi fraction (mostly
