SMITHFIELD FOOD

Effective and low-cost treatment of hog farm waste is a significant and important challenge for our nation. Smithfield Foods, Inc., in cooperation with a major Southeastern US University and industry partners specializing in wastewater treatment, has worked aggressively to meet this national challenge.

Smithfield’s is one of the largest pork producers and processors in the world and has vital interests in protecting and efficiently utilizing water resources associated with hog farming operations.

RATIONALE FOR AMTS UPGRADE:

Like many commercial Hog Farm operations, the Smithfield Foods site in Duplin County has relied principally on anaerobic pits for treatment of a combined waste stream of solid and liquid waste from 9 hog barns each with 720 hogs. Two barns were selected for the AMTS system. The objective of the AMTS was to receive water from an existing anaerobic pit (to include recycled liquid used to flush barns) and treat that water in an aerobic lagoon to (1) reduce ammonia and VOC levels of discharge water (2) reduce nitrogen loads for land application of effluent (3) reduce concentrations of Phosphorus and other metals
in effluent and (4) reduce noxious odors.

DESCRIPTION OF AMTS UPGRADE:

Briefly, AMTS provides the quality treatment of mechanical plants in lagoons at significant savings in capital and operating costs. The AMTS process combines ADS’s proprietary diffusion aeration products, engineered surface area (“AquaMats®”) and bioaugmentation (“Bacta-Pur®”) technologies to form a very stable, and low-maintenance integrated system for natural microbial treatment of municipal wastewater. Operational costs are typically very low. Because of the efficiency of AMTS, sludge handling is not necessary for up to 10 years or longer. AMTS process was installed in a new 11-foot deep aerated lagoon with a capacity of 4.8 million gallons adjacent to the anaerobic lagoon. The design flow rate was established at 50,000 gallons/day with a hydraulic residence time, under normal conditions, of 93 days. Flow to the AMTS aerated lagoon is pumped directly from an anaerobic treatment lagoon. The waste stream at 25,000 gallons per day per barn consisted of the anaerobic lagoon liquid from 2 commercial hog barns that each rear 720 finish hogs per cycle. The flow from the anaerobic lagoon into the AMTS lagoon was limited to 50,000 by controlled pumps.

The AMTS aerated lagoon was divided into a secondary treatment cell and a tertiary treatment cell by means of a membrane baffle curtain installed by Environmental Fabrics, Inc. Approximately 65% of the pond volume is concentrated in the secondary treatment cell with 35% reserved for the tertiary treatment cell. Aeration was supplied to both AMTS cells through a 30 HP rotary lobe, positive displacement blower based on projected oxygen demand of 2 kg O2 per kg of BOD5, 1 kg O2 per kg TSS, and 4.6 kg of O2 per kg of ammonia nitrogen. Header pipes were installed around 3 sides of the lagoon and weighted fine bubble ADS diffusion pipe was laid across the secondary treatment lagoon (12 rows at 10 foot centers) and the tertiary treatment cell (8 rows at 10 foot centers). In order to supply effective surface area to support nitrifying bacteria, the tertiary cell was initially equipped with columns of PVC corrugated media cubes, located at the passage window between the cells with diffused air supplied at the bottom of each column. After approximately 1 year of operation the fix-film media cubes were replaced with AquaMats® Model 15001 biofiltration media, because clogging causing the PVC media to float and become ineffective.

AquaMats® for Biofiltration provide bioreactive surfaces designed to extend vertically through the water column supported from an integral float tube at the surface. Seven rows of AquaMats® were installed at the end of October 2001 across the width of the tertiary treatment cell. Bioaugmentation for the AMTS was addressed by installing the BACTIVATOR™ System by Bacta-Pur® to continuously supply a metered and activated quantity of Bacta-Pur® XLG (a beneficial sludge digesting liquid bacterial product) to the secondary cell and Bacta-Pur® N-3000 (a beneficial nitrifying liquid bacterial product) to the tertiary cell. Effluent from anaerobic digestion is generally low in BOD and high in ammonia and thus is amenable to aerobic treatment for nitrification to reduce ammonia gas emission and increase plant available nitrate. The system was not specifically designed to complete the nitrogen cycle with denitrification.

AMTS COSTS---CAPITAL, OPERATING AND MAINTENANCE:

Capital costs incurred for the system were approximately $250,000 for a full-scale system for a typical farm with 9 barns producing 10,800 hogs annually, average harvest size of 220 pounds and two cycles annually. Amortized over a 10-year system useful life, the capital cost per pound of annual production is estimated at 1 cent ($.01) per pound.

Operating and Maintenance costs have compared favorably with estimates and represent a daily cost of approximately $96. This represents a cost per pound of annual production of 1.5 cents ($.015). The Operating and Maintenance costs include daily electrical consumption of on average $65 daily for a (60 HP blower), daily maintenance and inspection estimated at 1.04 man-hours per day, bioaugmentation at 2 liters/day and HCL gas cleaning of tubing @ $500/year.

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