Treatment of Slaughterhouse Wastewater Mike Lawrence NDSU Fall 2006 Overview Challenges Wastewater Parameters Treatment Options Process Modifications Typical On-site Treatment Options Design Problem.
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Treatment of Slaughterhouse Wastewater Mike Lawrence NDSU Fall 2006 Overview Challenges Wastewater Parameters Treatment Options Process Modifications Typical On-site Treatment Options Design Problem 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 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 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 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 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 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 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 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 Hydrasieve BOD Removal 5-20% TSS Removal 5-30% Hydrasieve Width Height Capacity Estimated (ft) (ft) (gpm) 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 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 Skimming Operation (Primary Sedimentation) Detention time 1.5 to 2.5 hr Overflow Rate 800 to 1200 gal/ft2*d 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. 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 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 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 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 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 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 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 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 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 Anaerobic Contact Reactor, 30 ft Completely Mixed Clarifier Flocculator, Deglassifier 10 ft Aerated Sequencing Batch Reactor Two reactors of same size Feed 8 hr, react 37.5 hr, settle 2 hr, .5 hr Feed 8 hr, react 13.5 hr, settle 2 hr, .5 hr drain drain 24 ft 46 ft Supernatant Drain 11.5 ft above bottom Sludge waste at bottom 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 7m 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