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

5. 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

6. 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

7. 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

10. 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

11. Hydrasieve • BOD Removal 5-20% • TSS Removal 5-30%

12. Hydrasieve

13. 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

14. Skimming Operation (Primary Sedimentation) • Detention time 1.5 to 2.5 hr • Overflow Rate 800 to 1200 gal/ft2*d

15. 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.

16. 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

17. 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

18. 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

19. 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

20. Design Problem • Flowrate:120,000 gpd, 83 gpm, Max 300 gpm • TSS=1500 mg/L • COD=5000 mg/L • sCOD=3000 mg/L • BOD5=2,000 mg/L • Reduce levels to municipal levels and discharge into sewer

21. 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

22. 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

23. Anaerobic Lagoon • Covered for heat retention • Side depth = 8 feet • Final Design 540 lb BOD5/ac-d • HRT=80 days Plan View 400 ft 400 ft

24. Anaerobic Contact Reactor • Final Design HRT=5 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

25. 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

26. 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

27. 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