Benefits of Using Liquid-Solid Separation with Dairy Manure Lagoons

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Benefits of Using Liquid-Solid Separation with
Dairy Manure Lagoons

• John P. Chastain, Ph.D.
• Professor and Extension Agricultural Engineer
• School of Agricultural, Forest, and Environmental
  Sciences
• April 2013 CAMM Recertification Class

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Purpose

• Provide a summary of liquid-solid separation
  options
• Discuss the benefits for dairy farms
• Share some system layouts for dairy farms

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Liquid-Solid Separation Options for Swine Farms

1. Separation based on particle size screens
   presses.
2. Separation based on density of the manure
   gravity cyclones

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Mechanical Separation Screens

• Liquid manure flows through a screen.
• Particles that are captured by the screen are
  removed from the liquid manure stream.
• The liquids that flow through the screen go on to
  a lagoon or other treatment method.
• Only pressure to drive separation comes from
  gravity or the flow of the manure.

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Large particles in dairy can be easily removed by
simple screens as compared with other species.
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Some simple screen type separators
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These are mostly used for dairy manure, but not
swine manure because they use relatively large
openings.
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Issues with using simple screen separators with
dairy manure

• Large screen sizes needed to keep up with manure
  flow from barns. Flow matching is needed.
• Fine screens turn liquid manure into slurry and
  liquid manure.
• Separated solids are often too wet for optimal
  storage and handling as a solid. (Odor, flies)

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Removal of solids, N, P from dairy manure using
a 0.059 (1.5 mm) stationary screen.
Influent TS Total Solids Removed Volatile Solids Removed Nitrogen Removed P Removed
1.5 19 24 13 18
-- 46 50 17 11
3.8 60 63 49 53
Dairy solids removed by the screen had a solids
content of 19 to 23. Solids removed ranged
from 23 to 51 lb /1000 lb/day.
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Removal of solids, N, P from dairy manure using
a 0.030 (0.75 mm) rotating screen.
Influent TS Total Solids Removed Volatile Solids Removed Nitrogen Removed P Removed
0.5 0 3 --- ---
3 14 4 --- ---
Manure solids removed by rotating screen had a
solids content of 6 to 11. Too wet to handle as
a solid. (Hegg et al.,1981)
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Mechanical Separation Presses

• Applies pressure to force more liquids through a
  small screen.
• Pressing can be provided by a screw, perforated
  belts, or filter plates.
• Can be used with smaller screens than stationary
  screens.
• Separated solids can be piled and handled as a
  solid. (Less odor and flies)

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Some types of press separators
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Issues with using press separators with swine
manure

• High pressure provides dry solids, but forces
  some large particles through screen.
• Trade-off between particle capture and dryness of
  pressed cake.
• Low process flow rate.
• Tight tolerances can lead to screen replacement
  higher maintenance costs.

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Removal of solids, N, P from dairy manure using
a screw press.
Influent TS Total Solids Removed Volatile Solids Removed Nitrogen Removed P Removed
0.5 mm
2.6 25 --- 8 6
0.75 mm
10 70 77 24 24
2.38mm
10 47 --- --- 29
Separated solids ranged from 25 to 34
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Removal of solids, N, P from dairy manure using
a belt press with a 0.039 (1.0 mm) mesh belt.
Influent TS Total Solids Removed Volatile Solids Removed Nitrogen Removed P Removed
7.1 32.4 --- 10 15

Separated solids 15 (Moller et al., 2000).
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Trade offs that make use of mechanical separators
difficult

• Presses can remove more total and volatile
  solids, N and P than simple screens, but need to
  process slurry not liquid manure.
• Presses can yield drier solids than simple
  screens.
• Presses are slower than simple screens.
• Screens with small openings can remove a
  significant amount of solids plant nutrients
  but yield wet solids (slurry) at high flow rates.
  

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Combination of an in-channel flighted conveyor
screen and a small screw press to treat liquid
manure
Screw Press
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Liquid-solid separator that employs three
techniques fine stationary incline screen (0.020
in), screw press, and an inclined flighted
conveyor screen (courtesy of US FARM Systems,
Tulare, CA).
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Removal of solids, N, P from dairy manure using
the combination machine (US FARM Systems).
Influent TS Total Solids Removed Volatile Solids Removed Nitrogen Removed P Removed
lt 1.5 50 56 23 20

Flushed manure, stalls bedded with composted
dairy solids, separated solids TS 23
(Chastain, 2009).
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Presses have also been used to remove solids from
anaerobically treated manure lagoon sludge and
digester solids.
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Treatment of anaerobically digested manure using
a screw press with a 0.020 (0.50 mm) screen
(dairy).
Influent TS Total Solids Removed Volatile Solids Removed Nitrogen Removed P Removed
7.5 50 56 16 24
8.3 47 53 17 20
Separated solids ranged from 24 to 25 TS and
could be stacked (Gooch et al., 2005).
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Liquid-Solid Separation by Settling
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During gravity settling the fluid mixture
separates into liquid and settled material layers.
Cliquid Vliquid
Liquid Layer
CI VI
Settled Material
CSM VSM
Before Settling
After Settling
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Factors that determine the effectiveness settling

1. Particles must be heavier than water.
2. There must be enough water in the mixture for the
   solids to separate and form a large liquid layer
   to form.
3. Want to provide sufficient settling conditions
   very low flow velocity

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Gravity settling can be used for

• Removing solids nutrients from runoff from
  outdoor lots.
• Flushed manure from freestall buildings and
  milking centers.

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Gravity settling cannot be used to treat dairy
manure with a TS greater than 3.
Gravity settling cannot be used to treat slurry
manure.
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Gravity settling can work for dilute dairy lagoon
water and sludge mixtures.
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Removal of solids, N, and P from liquid dairy
manure by gravity settling. (Inflow TS 1.7)
Total Solids Removed Volatile Solids Removed Nitrogen Removed P2O5 Removed K2O Removed
61 66 41 45 25
Gravity settling can greatly reduce the loading
of solids and phosphorus on a lagoon. Volume of
settled solids was 25 of flush volume (SVF
0.25)
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Solids and Nutrient Content of Liquid Dairy
Manure Before After Settling for 1 hour.
Flushed Manure Liquid From Settling Settled Solids
TS 1.7 0.9 4.1
Pounds / 1000 gallons Pounds / 1000 gallons Pounds / 1000 gallons
VS 111.6 50.5 290.7
Org-N 3.8 1.4 10.7
TAN 6.3 6.5 6.4
P2O5 3.4 2.5 6.0
K2O 7.6 8.0 7.8
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Change in ratio of PAN and P2O5
Flushed Manure Liquid From Settling Settled Solids
Pounds / 1000 gallons Pounds / 1000 gallons Pounds / 1000 gallons
Org-N 3.8 1.4 10.7
TAN 6.3 6.5 6.4
PAN- incorp 7.3 6.0 11.5
P2O5 3.4 2.5 6.0
PANP2O5 2.1 2.4 1.9
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Gravity settling improves the balance of N to
P2O5 for many crops for the liquid part while
increasing the relative P2O5 content in the
separated solids.
Most grain crops want PANP2O5 2.2 to 2.5.
Flushed Manure Liquid From Settling Settled Solids
PANP2O5 2.1 2.4 1.9
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Main issues with gravity settling to take into
account are

• Cost and permitting of settling basin or pond
• Potential for increase in odor.
• Cost of permeable cover that can greatly reduce
  odor.
• Purchase and maintenance cost of agitation and
  pumping equipment.
• Requires transport to fields.

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Since the settled solids are slurry they can be
used to load a press if dry solids are needed.
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Addition of Polymers (PAM) and Metal Salts

• These chemicals can be used to improve the
  performance of any method of liquid-solid
  separation.
• Requires TS less than 6
• PAM, Alum, Iron Chloride, and others can be used
  alone or in combination at proper dose.

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Chemicals can be used to remove 70 to 90 of the
solids and P for most methods of liquid-solid
separation

• Need proper dose
• Need proper mixing
• Need proper dilution
• Need

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Best Liquid-Solid Separation Options for Dairy
Facilities

• Presses Slurry Systems
• Combo Systems Liquid Systems
• Gravity Settling Liquid Systems
• Use chemicals? If more TS, VS, P removal needed.
• Separation of lagoon sludge?
• Yes with right equipment and
• TS content.

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Benefits of Liquid-Solid Separation for Manure
Storages not for recycle systems
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Benefits of Liquid-Solid Separation for Storages

• Remove large particles to reduce energy and time
  needed for agitation and pumping
• Reduce storage volume by up to 20 if TS removal
  is on the order of 40.
• Remove large particles that could cause clogging
  of pipes and nozzles.

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Benefits of Liquid-Solid Separation for Treatment
Lagoons best for recycle systems
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Lagoon Sizing

• Lagoon Volume (Manure Volume Treatment Volume
  Sludge Storage Volume)
• On top of these volumes add DEPTHS for Net Rain
  (PR), 25 year 24 hr storm minimum of 12 of
  freeboard.
• These depths are required for any manure storage.

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Typical Lagoon System
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Well treated recycled lagoon water needed for
manure removal.

• High loading rates strong recycle water for
  flush freestall buildings.
• Need well treated lagoon water to make recycle
  flush buildings function properly.
• Maximum loading for recycle should be based on
  ASABE Standard.

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Manure Storage Volume

• Will include all manure, wasted water, and other
  solids added to manure per day (bedding and
  wasted feed)
• Typically use a storage period ranging from 180
  days in warm southern climates to 365 days in
  cold climates (e.g. Midwest)
• Liquid-solid separation can reduce this volume by
  10 to 25. Best to be conservative.

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Treatment Volume

• Depends on VS loading rate , LR lb
  VS/1000ft3/day.
• TV (ft3) 1000 (lb VS/day / LR)
• Design loading rate depends on the climate.
• Larger loading rates can be used in warm climates
  than in cold climates (ANSI/ASAE EP403.4, ASABE,
  2011)

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Variation of LR With Climate(ANSI/ASAE EP403.4,
ASABE, 2011)
Location Loading Rate, lb VS/1000ft3/day
Southern Minnesota (Cold) 3.0
Iowa 3.5
Kansas 4.0
North Carolina 4.5
South Carolina Georgia 5.0
Central Texas 5.5
Central Florida (Hot) 6.0
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VS Removal Reduces TV, ft3 / 1000 lb of live
animal weight, Dairy Cows (11.8 lb VS/1000 lb)
Loading Rate VS Removed by Liquid-Solid Separation VS Removed by Liquid-Solid Separation VS Removed by Liquid-Solid Separation VS Removed by Liquid-Solid Separation VS Removed by Liquid-Solid Separation
lb VS/1000 ft3-d 0 20 40 60 80
3.0, MN 3936 3149 2362 1574 787.2
3.5, IA 3374 2699 2024 1349 674.7
4.0, KS 2952 2362 1771 1181 590.4
4.5, NC 2624 2099 1574 1050 524.8
5.0, SC 2362 1889 1417 944.6 472.3
5.5, TX 2147 1718 1288 858.8 429.4
6.0, FL 1968 1574 1181 787.2 393.6
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VS Removal Reduces TV, ft3 / 1000 lb of live
animal weight, Finishing Swine (5.01 lb VS/1000
lb)
Loading Rate VS Removed by Liquid-Solid Separation VS Removed by Liquid-Solid Separation VS Removed by Liquid-Solid Separation VS Removed by Liquid-Solid Separation VS Removed by Liquid-Solid Separation
lb VS/1000 ft3-d 0 20 40 60 80
3.0, MN 1668 1335 1001 667.3 333.7
3.5, IA 1430 1144 858.0 572.0 286.0
4.0, KS 1251 1001 750.8 500.5 250.3
4.5, NC 1112 889.8 667.3 444.9 222.4
5.0, SC 1001 800.8 600.6 400.4 200.2
5.5, TX 910.0 728.0 546.0 364.0 182.0
6.0, FL 834.2 667.3 500.5 333.7 166.8
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Sludge Storage Volume, ft3/1000lb /year
(ANSI/ASAE EP403.4, ASABE, 2011)

• Depends on TS loading rate , MTS lb TS added
  per year.
• Sludge accumulation rates
• Swine 0.0219 ft3/lb TS Added
• Dairy 0.0729 ft3/lb TS Added

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Liquid-solid separation will reduce sludge build
up in a treatment lagoon Critical for dairy!
TS Removed By Separator Swine Sludge Volume Per Year Dairy Sludge Volume Per Year
0 52.0 ft3/AU 383.2 ft3/AU
20 41.6 306.5
40 31.2 229.9
60 20.8 153.3
80 10.4 76.63
Solids Production Swine 6.5 lb TS/AU/day,
Dairy 14.4lb/AU/day
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Odor Reduction?

• Research has shown that most of the odor comes
  from particles that are smaller than 0.0098
  (0.25mm).
• Must have high-rate separation to greatly reduce
  odor production from liquid manure.
• However lower VS loading rates have been shown to
  reduce frequency of odor from a lagoon.

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Effect of VS Loading Rate on Odor Frequency
(adapted from Humenik, et al. 1981)
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Well treated recycled lagoon water needed for
manure removal.

• High loading rates strong recycle water for
  flushing.
• Increases odor and ammonia problems in and around
  buildings.
• Need well treated lagoon water to make our
  recycle flush buildings function properly.
• Maximum loading for recycle in SC
• 5 lb VS/1000
  ft3-day.

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Use of a mechanical separator (MS) to reduce
loading on lagoon
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Enhancing solids and nutrient removal by using
chemicals slows the system down in this
configuration.
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Use of a mechanical separator (MS) to reduce
loading on lagoon - Advantages

• Small amount of space needed as compared to
  settling.
• Can be added to existing systems in many cases.
• Solids can be dry enough to stack or store in a
  small volume.
• Need separator throughput rates of 150 to 200
  gpm.

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Use of a mechanical separator (MS) to reduce
loading on lagoon - Disadvantages

• Energy to operate system.
• Screens, drives, motors, belts, augers require
  maintenance
• High solids removal requires small screens and
  low throughput rates often main problem.
• High removal systems often generate wet solids.

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Gravity settling can be used to make high-rate
mechanical separation easier also reduces
chemical costs.
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Add a settling basin or pond before the lagoon
basins drain dry, ponds do not.
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Can use chemicals to enhance removal of solids
and plant nutrients for a settling basin or pond.
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Drain-dry basinsnot many used in SC but could be.
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Add a settling basin or pond before the lagoon
Advantages

• Greatly reduces VS loading
• Greatly reduces or eliminates sludge build up
• Solids are in a semi-solid or slurry and plant
  nutrients are more accessible than sludge on the
  bottom of a lagoon.
• Size based on desired storage volume and period.
• Reduces organic-N mineralization in lagoon and
  conserves N by reducing ammonia generation and
  loss.
• Less maintenance than a mechanical separator

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Add a settling basin or pond before the lagoon
Disadvantages

• If solids are too dry the fly population could
  increase. A layer of water is needed to control
  flies.
• May cause an increase in odor near settling
  pond/basin. Permeable cover could help.
• Takes up more space than mechanical separation.

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A reception pit/settling basin used with a
mechanical separator to dewater lagoon sludge.
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Summary

• Liquid-solid separation can be used to
  significantly reduce treatment and sludge storage
  volumes.
• Allows use of smaller structures to save money.
• Allows more economical use of lower loading rates
  to improve recycle water quality.
• Can help reduce ammonia and odor production

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Summary (2)

• Can allow use of anaerobic treatment lagoons in
  colder climates.
• Can be used to remove a portion of VS and
  Organic-N that would breakdown in the lagoon to
  yield methane, ammonia, and carbon dioxide.
• Reduces cost of sludge management to maintain
  lagoon function.

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Agricultural Mechanization Business School of
Agricultural, Forest, and Environmental
Sciences ContactChristi Leard 864.656.3250 ccam
pb3_at_clemson.edu http//www.clemson.edu/cafls/safe
s/agmec/