Full proceedings at: http://www.extension.org/72736 Residual antibiotics in land-applied manure and biosolids present a potential threat to public and ecological health, so it is important to determine antibiotic removal efficiencies for manure and biosolids waste management practices and to identify conditions that enhance antibiotic degradation.
Loss of the antibiotics florfenicol, sulfadimethoxine, sulfamethazine, and tylosin was studied during pilot-scale static pile thermophilic composting and the effects of temperature and feedstock particles on antibiotic removal rates were tested. The antibiotics were spiked into dairy manure solids and wastewater biosolids, and treatments included aerated and non-aerated manure and biosolids/wood-product (1:3 v/v) composting.
1. Antibiotic
Degradation during
Dairy Manure Solids
and Biosolids
Composting
A. I. Bary*, S.M. Mitchell*, J.L.
Ullman, C.G. Cogger*, A.L. Teel*,
R.J. Watts*
*Washington State University
University of Florida
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2. Introduction
• 5-90% of human
and animal
administered
antibiotics are
excreted
unchanged.
• 0.1 – 240 mg/kg
(ppm) in manure
3. • 250 different antibiotics available
• 17 different classes
• Antibiotics within a class have similar core
chemical structures, antibacterial properties, and
environmental fate and transport behaviors
• Three antibiotic classes were investigated in this
research
• amphenicol, macrolide, and sulfonamide
3
Introduction
4. 4
Chemical properties Structures
Amphenicol – Florfenicol
Water sol. = 5,900 mg/L
Log Kow = -0.12
Macrolide – Tylosin
Water sol. = 100,000 mg/L
Log Kow = 1.6
Sulfonamide – Sulfadimethoxine
Water sol. = 343 mg/L
Log Kow = 1.63
Sulfonamide – Sulfamethazine
Water sol. = 1,500 mg/L
Log Kow = 0.89
• Antibiotic chemical structures and
properties affect how the antibiotics
degrade and move in the environment.
Introduction
5. • Degradation half-lives in water are higher
compared to degradation half-lives in waste.
5
Antibiotic degradation half-lives (days) reported in current publications
Water Soil Manure Composting
Florfenicol No degradation 2-30 d 4 d No data
Tylosin No degradation 30 d 6 d 19 d – Turkey litter
20-44 d – Cattle manure (windrow)
4-10 – Horse manure
Sulfadimethoxine No degradation 40 d 2 d No data
Sulfamethazine No degradation 60 d 5 d No degradation – Turkey litter
27-237 d – Cattle manure (windrow)
Introduction
6. 6
Feedstocks
1. Fresh, de-watered dairy manure solids
2. Fresh, anaerobically digested and de-watered
biosolids
3. Ground Douglas fir was used in a 3 to 1 ratio (by
volume) with biosolids
Methods
7. • Four composting treatments were tested:
• aerated manure
• non-aerated manure
• aerated biosolids/wood-product (1:3 by vol.)
• non-aerated biosolids/wood-product (1:3 by vol.)
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aerated
manure
non-aerated
manure
aerated
biosolids/wood
(1:3 by vol.)
non-aerated
biosolids/wood
(1:3 by vol.)
aerated
manure
non-aerated
manure
aerated
biosolids/wood
(1:3 by vol.)
non-aerated
biosolids/wood
(1:3 by vol.)
Methods
8. • 1/3 of the feedstock for a batch was added to a
manure spreader
• 1/3 of the antibiotic solution in water was spread
evenly on the feedstock
• Method was repeated
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Methods
9. • Manure spreader was turned on and the feedstock was
mixed.
• Mixing with the manure spreader was repeated, and
time zero samples were collected.
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Methods
10. • Aeration pipes were placed into the bins
• Plenum chamber material (coarse wood) was added
• Bins were filled with the antibiotic-fortified feedstock
• Temperature probes were placed at two depths
• Air was turned on (30 s on, 1 hr off)
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Methods
16. Composting
Temperatures reached 65-75°C
Manure remained 75% water
Biosolids dropped from 65% to 50%
water
pH values were 8.6 for manure and 6.2
for biosolids compost
Finished compost had C:N ratios of 23
for dairy manure and 14 for biosolids
compost
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19. Conclusion
The dairy manure solids and biosolids/wood
feedstock facilitated rapid antibiotic
degradation during pilot-scale static pile
composting.
90-95% of the antibiotics were removed after
4 weeks.
Final compost material obtained under these
conditions may present minimal human and
ecological health risk when applied to the
environment.
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The percent oxygen was 5% or greater from 10-25 days, so all the bins were operating under aerobic conditions.
The type of feedstock material had a large effect on the temperature. The less dense biosolids and wood mixture compost had higher oxygen concentrations compared to the less dense manure compost. The forced aeration treatments were only slightly higher than the passive aeration treatments. This may be due to the low volume pilot-scale bins that were used.
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The moisture content remained at 73% in the manure compost. The biosolids and wood mixture compost started out at about 65% water and then decreased to about 50%. Again, there was no difference between the aerated vs. non-aerated treatments.
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The pH of the manure started out at 8.2 and the pH increased to about 8.6 after the 28 d composting period.
The pH of the biosolids and wood mixture started out at about 7.8 and it decreased to about 6.3.
81
The carbon to nitrogen ratio in the manure was 37 and it dropped to about 22.
The C:N in the biosolids and wood mixture was 10 and it increased to about 14.
91
That concludes my dissertation presentation.
I would like to acknowledge the EPA STAR fellowship program for 3 years of funding, and I want to thank my committee members and lab group as well.
Thank you for your attention. Are there any questions?