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05/26/2009 13:18 9518273 DOUGLAS KUNEY PAGE 09/10 Table 5. North Carolina Poultr7 Aerobic Lagoon Design Criteria Rird typo, Unit* Average Natumlly Moohanically Aoratcd Lagoon Live Aerobic ------J----------------- Bird -----J-----------------Bird Lagoon Surface_ Aeration Weight Surface Area Area Horsepower lbs ft2** ft2*** hp**** --------------------------------------------------------- -------------------- Layer per bird 4.0 11.6 0.30 0.00030 Pullet per bird 1.5 4.3 0.11 0.00011 One-time bird capacity. Loading rate - 50 lbs BOD5/surface acre/day: mean liquid depth - 4 ft 1000 ft2/hp of aeration and a minim= liquid depih — 10 ft. 50% satisfaction of waste COD and oxygen transfei rate of 3 lbs/hp-hr Vast amounts of land are required for naturally aerobic iagoons - as much as 23 times more surface area and 10 times more volume than! an anaerobic lagoon 10 feet deep. Thus, naturally aerobic lagoons are imptactical for primary treatmout and arc generally not recd ed for livestockland poultry manurcza. Mechanically Aeratqd Mechanically aerated lagoons combine the odor control advantages of aerobic digamrion wir-b ralativ*.ly smoll stirfece requir. mentsg. Aerators are used mainly to control odors in sensitive areas and for nitrogen removal at limited land disposal sites. Aerated lagoons have successfully met these objectives by providing enough oxygen to satisfy 50% of the waste chemical oxygen demand (COD) assuming an aerator oxygen transfer late of 3 pounds per horsepower-bout. The lagoon liquid surface should not ex, eed 1000 square feet per horsepower of aeration for floating surface aeratori to insure complete surface influence. Liquid depths should be at least 10 keet. , Table 5 gives mechanically aerated lagoon design criteria for poultry. A major disadvantage of mechanically-aerated lagoons is the expense of continually operating electrically-p'owere d aerators. Larier anaerobic lagoons may provide similar performance with less expense. Aerat4d lagoons also yield more sludge then anaerobic units because more input organics are converted to biomass. Suspension of bottom sludge by the aeratorscan cause increased lagoon liquid concentrations and stimulate foaming. Solids traps such as a septic tank type settling chamber between primary aerated and secondary lagoons can provide a convenient mechanism for solids collection and removal. Mechanically-aerated lagoon liquid nitrogen levels are significantly reduced. M-STAGE WOOS Two-stage lagoons provide certain advantages over single primary lagoons. More than two lagoons in series is rarely boneficial.1 Secondary lagoons provide temporary storage prior to land application. Aekobic systems need a second lagoon to provide storage and all the primary lagoon to function solely for biological treatment. A second lagoon also al owe a maximum liquid volume to be maintained in primary anaerobic lagoons for stabilizing incoming 32