An increase in poultry processing has generated a steady rise in wastewater pollutant concentrations. Despite mechanical improvements in wastewater treatment, many poultry processors continue to pay unnecessarily high fees for municipal water discharges. The patented, state-of-the-art screening system, set up by the US$ 100-million-annual processor, Michigan Turkey Producers, in conjunction with Lyco Manufacturing, provides an industry showpiece for poultry wastewater treatment that helps processors better manage the quality and volume of discharges.
Like many poultry processors, Michigan Turkey Producers, a medium-sized poultry processor of live tom turkeys handling 4.5 million birds annually, keeps a tight rein on their biochemical oxygen demand (BOD) and total suspended solids (TSS) levels in their discharged wastewater.
But, where most processors are careful to limit poultry processing byproducts from entering and contaminating their wastewater stream - because of the difficulty in removing them prior to discharge - Michigan Turkey operates quite differently. The company places little limits on the volume of particulate organic matter allowed to be put through their wastewater, because of a unique double screening system they employ, built by Lyco Manufacturing that effectively removes sufficient load before discharge to leave levels of BOD and TSS well within municipal standards.
Michigan Turkey is a live turkey processor, and a boned meat company, located in Wyoming, Michigan, USA. “We process just toms, roughly 20,000 birds per day,” Mike DeVries, plant engineer for the company, explained. “Our average bird weight is about 40 pounds live, and 34 pounds dressed. Ninety percent of everything we do is boneless. We ship to industrial users who cook our products into a deli product, a log or loaf. Our brands are the Golden Legacy Brand, and Silver Legacy Brand. Sixty percent of our meat goes out fresh, 40 percent goes out frozen. The greatest part of our distribution, about 70 percent, is in the midwest US and east coast; but we also sell (the remaining 30 percent) into Russia, Japan, China, Central America, Canada and South Africa as well. Our total facility is comprised of three buildings on 42 acres, we have 375,000 square feet of operations space with 187,000 of that for live-bird processing.”
The Lyco Double Drum screen can handle up to 30,000 gallons per minute.
“We purposely set up our wastewater system to handle anything that comes down it, any volume and concentration of particulate matter,” DeVries said. “Consequently, we have a lot more load coming down our drains that we have to get out than other processors. This is different from how most poultry operations function, where usually they are trying to keep the load in their wastewater at a continually lower concentration throughout processing, but this is because their screening system can’t handle it. We are moving 700,000 to 800,000 gallons of wastewater a day through our system without any jam ups at the screening, and we are ending up with BOD and TSS ratings well within municipal standards.”
“In our picking operation we drop right to water with our feathers, and we actually move our feathers via water,” continued De Vries, “so we had to have a Lyco screen for that as well. The cost for us on the rendering side, or downstream side of processing, was the moisture content, so with the Lyco double drum screen we found that we generate an extremely dry feather and consequently avoided any surcharging for moisture. That has been an enormous benefit all the way to the point that our rendering actually had to add moisture to process our feathers. The advantages are avoiding a surcharge, and also the advantage of being able to haul more volume with less weight.”
Poultry processing is a relatively high water usage activity, as is typical of many food processing industries. For broilers, five to ten gallons are used to process one five-pound, average-sized bird. For turkey processors the volume of water used is considerably higher - the average live weight of slaughtered turkeys exceeds 27 pounds. In some cases, such as the processing of large toms, as done by Michigan Turkey, bird weights can reach up to 40 pounds, with water consumption for processing in the range of 35 to 40 gallons per bird. It is not unusual for a poultry processor to generate 750,000 to 1,500,000 gallons of wastewater daily.
This water is laden with proteins, fats and carbohydrates from meat, fat, blood, skin and feathers. The water is also polluted with a fair amount of grit and other inorganic matter. Waste load can be determined by a number of different measurements, including BOD, TSS, chemical oxygen demand (COD), and fats, oil and grease (FOG), but poultry plant wastewater is most often tested for BOD, ¬ a measure of the amount of oxygen needed to degrade the organic matter (feathers, fat and blood) in the wastewater.
Poultry processors are required to remove the majority of the soluble and particulate organic material in their wastewater prior to discharge from the plant in order to achieve compliance with local, state and federal environmental regulations. The problem is that few screening systems are really capable of continuously cleaning out all of this material to a level within the standards of municipalities, and municipalities use BOD loads to determine charges and surcharges for wastewater dischargers.
“We discharge ultimately to a city municipal system and they charge us for anything that we put into the water,” said DeVries. “We have to control our loading costs to avoid additional surcharges. With the Lyco double drum screens we are able to load up as we process, and then pull everything out of the wastewater before we discharge. It is a very efficient system.”
Lyco’s Double Drum screen uses rotary action to separate waste solids from liquids in one step, eliminating the need for two sequential, single-stage screens. Primary screening takes place when the wastewater enters the inner drum from the inside and screens out solids within the range of 0.06 in to 0.02 in. Secondary screening follows as the wastewater passes through the outer drum, screening particles as small as 0.02 in. The net result is that more solids are screened out of the wastewater.
“The Double Drum screen, which can handle up to 3,000 gallons per minute, was designed to eliminate the need for primary and secondary screening,” said Terry Brady with Lyco. “Our research shows that in the majority of screening applications processors used a perforated primary screen then pumped the water to a secondary screen. Lyco designed a way to do the primary screening with the inner drum screen first, and then the secondary screening done with the outer screen, which is the finer screen.”
There is also the issue of blinding - poultry is laden with fats and other slimy-type particulates that clog the screen openings. This is a common problem with traditional screening equipment - limiting the volume of wastewater and load that can be moved through a screen, which causes water and particulate to “spill” over the end of it. The Lyco double-drum uses a self-cleaning wedge-wire screen material, and a patented traveling spray system - which can use as little as 10 gallons per minute (gpm) of fresh water to keep the screen open, compared to typical rotary screens that consume 36 gpm. These features drastically minimize, if not entirely eliminate, screen blinding.
The Lyco Double Drum screen uses rotary action to separate waste solids from liquids in one step.
“A lot of other screen designs let material go through because they don’t have the ability to manage it,” said De Vries. “Particularly when it gets into high volume quantities of material going through. This is not the case with the Lyco double drum. It can handle anything we put through it, regardless of the gallons per minute or particulate load.”
“I have been around a lot of screens used in the poultry industry, and have experienced their external and internal problems firsthand,” continued De Vries. “I look for screening equipment that is heavy duty, durable, engineered to be user friendly, tool friendly and mechanic friendly. I want to be able to set it up and have it run with minimal maintenance. We have literally loaded the Lyco double drum with thousands of pounds of product at different times and it has performed without any problems. Our need has been to get our heavily laden particulate out of the wastewater before we discharge it to the municipal system. The Lyco screen manages that for us, particularly with TSS, which ultimately returns thousands of dollars back to us each month.”
Poultry processors can have their rates reduced by a large portion using the double drum - such as a 40 percent charge reduction from municipalities, which could equal $50,000 to well over $100,000 in saving a year.
Approximately 84 percent of poultry processors in the US are using some form of screening application to reduce wastewater particulates - including internally-fed rotary screens, externally-fed rotary screens, and shaker-and-bar type screens. The vast majority of these are single-screen applications. With the advent of double-screen technology, processors can now capitalize on a much more efficient and cost-effective system for their wastewater treatment.
Author’s Note
Jim McMahon is a freelance journalist who specializes on manufacturing equipment and process technology. Contact Jon Butt, division manager of Liquid & Solid Separation of Lyco Manufacturing, Inc., for more information by email: [email protected].
