Treatment of Slaughterhouse Wastewater

1
Treatment of Slaughterhouse Wastewater

• Mike Lawrence
• NDSU
• Fall 2006

2
Overview

• Challenges
• Wastewater Parameters
• Treatment Options
• Process Modifications
• Typical On-site Treatment Options
• Design Problem

3
Challenges of Slaughterhouse Wastewater

• Wastewater contains large amounts of blood, fat,
  and hair
• Wastewater is above municipal standards which
  leaves two options on site treatment or pay to
  be treated elsewhere
• On site treatment with low capital and
  maintenance costs is desirable

4
Wastewater Parameters

• BOD approx. 1,000 to 4,000 mg/L
• COD approx. 2,000 to 10,000 mg/L
• SS approx. 200 to 1,500 mg/L
• High Oil and Grease content
• Possible high chloride content from salting skins

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Treatment Options

• Discharge to sewer to be treated by municipal
  treatment plant
• Land application of wastewater for irrigation
• Reduce amount of wastewater and/or concentrations
  with the wastewater by changing the processes
• On site Treatment
• Flow Equalization, Screening, Dissolved Air
  Flotation, Primary Sedimentation
• Aerobic Treatment
• Anaerobic Treatment

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In-Plant Modifications to Reduce Pollution

• Main goal should be to prevent product from
  entering the waste stream and using the least
  amount of water possible
• Reduce the amount of water used, saves money in
  two ways
• Use high pressure and just enough
• Proper detergents
• Lower volume of water helps equipment
• Reuse as much water as possible

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Line Separation

• Separating the various waste streams as much as
  possible
• Sanitary lines should be discharged directly to
  the city sewer
• Grease waste streams and non grease waste streams
  can help reduce treatment costs
• Separate Blood line

8
Blood Recovery

• Blood has ultimate BOD of 405,000 mg/L
• One head of cattle contains 49 lbs. of blood
  which equals 10 lbs. BOD, compared to 0.2 lbs.
  discharged per person per day
• All blood should be recovered in a separate line
  draining to a tank
• Blood is then dried, commonly a continuous drier
  is used
• Profitable end product

9
Stockpen Area

• Stockpen waste and other manure should be hauled
  away as a solid
• Cleaned periodically with as little water as
  possible
• Ideally this water would go to a separate tank
• From the tank it would be emptied into a truck
  and land applied

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On-Site Treatment

• Costs of treating on site or letting the
  municipality treat the waste should calculated
• Maintenance and operation should be also put into
  cost analysis
• Flow equalization is usually a very good first
  step in on-site treatment

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Hydrasieve

• BOD Removal 5-20
• TSS Removal 5-30

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Hydrasieve
Width (ft) Height (ft) Capacity (gpm) Estimated Price
2 5 75 5,200
3.5 5 150 6,400
4.5 7 300 8,000
5.5 7 400 10,000
6.5 7 500 12,000
7 7.3 1000 20,000
14 7.3 2000 40,000
21 7.3 3000 60,000
28 7.3 4000 80,000
35 7.3 5000 100,000
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SS and Grease Removal

• Grease removal could be very profitable
• Skimming operations
• 20 to 30 BOD removal
• 40 to 50 SS removal
• 50 to 60 grease removal
• Dissolved Air Flotation, DAF
• 30 to 35 BOD removal
• 60 SS removal
• 80 grease removal

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Skimming Operation (Primary Sedimentation)

• Detention time 1.5 to 2.5 hr
• Overflow Rate 800 to 1200 gal/ft2d

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Dissolved Air Flotation (DAF)

• Hydraulic Loading Rate
• 1.5 to 5.0 gpm/ sq. ft.
• Solids Removal Rate
• 1.0 to 2.0 lbs/hr/sq. ft.

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Anaerobic Lagoons

• Ideally the lagoon would be covered, odor gas
  production contained, heat retention
• Not well suited for colder climates
• Detention time 20 to 50 days
• BOD5 loading 200 to 500 lb/ac.-d

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Anaerobic Contact Reactor (ACR)

• Hydraulic Retention time 0.5-5 days
• Organic Loading rate of 1.0-8.0 kg COD/m3-d

Flocculator or
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Anaerobic Sequencing Batch Reactor (ASBR)

• HRT 6 to 24 hours
• SRT 50 to 200 days
• 98 removal with 1.2kgCOD/m3-d
• 92 removal with 2.4kgCOD/m3-d
• Possibly rates to 5 kgCOD/m3-d
• Effluent SS range between 50 100mg/L depending
  on HRT

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Upflow Anaerobic Sludge Blanket (UASB)

• Proteins and fats may cause problems in formation
  of granules.
• Loading rates of 4-12 kg sCOD/m3-d
• Retention times of 7-14 hours

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Design Problem

• Flowrate120,000 gpd, 83 gpm, Max 300 gpm
• TSS1500 mg/L
• COD5000 mg/L
• sCOD3000 mg/L
• BOD52,000 mg/L
• Reduce levels to municipal levels and discharge
  into sewer

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Screening

• Hydrasieve
• Use prior to flow equalization to save on pumps
  and buildup in the tanks
• Design for max flow of 300 gpm
• 4.5 by 7 foot model will handle flow
• Approximate cost of 8,000

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Primary

• Loading Rate of 600 gal/ft2-d
• Final Design
• 8 ft. wide, 25 ft. long, 10 ft. deep
• 8 ft. of weir w/ loading rate of 15,000 gpd/ft
• HRT 3 hours

10 ft
8 ft
25 ft
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Anaerobic Lagoon

• Covered for heat retention
• Side depth 8 feet
• Final Design 540 lb BOD5/ac-d
• HRT80 days

Plan View
400 ft
400 ft
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Anaerobic Contact Reactor

• Final Design HRT5 days
• Loading Rate 1.0 kg COD/m3-d
• Clarifier design based on 24m/d settling velocity

56 ft
16ft
10 ft
Anaerobic Contact Reactor, Completely Mixed
Clarifier
30 ft
Flocculator, Deglassifier
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Aerated Sequencing Batch Reactor

• Two reactors of same size
• Feed 8 hr, react 37.5 hr, settle 2 hr, drain .5
  hr
• Feed 8 hr, react 13.5 hr, settle 2 hr, drain .5
  hr

24 ft
46 ft
Supernatant Drain 11.5 ft above bottom
Sludge waste at bottom
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Upflow Aerated Sludge Blanket Reactor

• Loading Rate of 10 kg sCOD/m3-d
• Two tanks, operated in parallel
• Diameter 4.5 m, Height 7 m,
  2.5 m for gas storage

4.5 m
7 m
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Final Design

• Include Hydrasieve effectiveness and low
  capital, O M costs
• Upflow Anaerobic Sludge Blanket Reactor
• Tank is smaller than most of the others due to
  high organic loading rate
• Provides constant source of methane gas