Most poultry processing plants that employ water reuse systems utilize mid-plant treatment systems. In a mid-plant system, specific wastewater streams, such as from immersion chillers or bird washers, are collected for treatment and reuse. USDA regulations allow for the use of advanced biological treatments in water reuse systems. Water reuse after a plant's advanced biological treatment system can, theoretically, allow the processor to treat and reuse all of the plant's wastewater.
The implementation of water reuse systems is driven by the cost of water and wastewater treatment and the availability of water. Tightening effluent limits and local water shortages are making water reuse more attractive. New permit standards for effluent quality, in many cases, require bringing treated wastewater back to nearly the same quality level as drinking water. In some cases, this means that effluent is of higher quality than water from on-site wells. For some plants, it will be less expensive to treat high quality effluent for reuse than to purchase additional city water or treat well water.
An advanced biological treatment water reuse system, designed and operated by Environmental Management Corporation (EMC), a subsidiary of the Linde Group, is now employed at a U.S. poultry plant. The plant slaughters, cuts up and debones over 200,000 broilers a day. Over 700,000 gallons of water per day are reused in the plant. City water usage at the facility has been reduced to 4.5 gallons per bird with the implementation of water reuse.
Advanced biological water reuse systems are required to treat water to a higher standard of quality than mid-plant reuse systems, and this allows for the reuse water to be employed in more places in the plant. (Sanitary waste from the plant must be segregated from any water that will be treated for reuse.) Treatment of water for reuse can be as simple as ozone application, filtering and addition of chlorine. Ozone sanitizes the water, and chlorination provides a residual sanitizer. Filtering the water reduces turbidity. Treated reuse water can be nearly equivalent to potable water and can be treated to a point where it creates no food safety or food quality problems.
Reuse water can be used in hanging, picking and evisceration operations, in the chiller and in the sanitation process. Reuse water cannot be used in product formulations or as a final product rinse.
Water reuse systems can cause a rise of normally harmless compounds in the water to detrimental levels. Cycling up of contaminates like iron or nitrates can cause meat quality problems in some systems. Technology exists to remove all potential contaminates from reuse water to allow 100 percent of a plant's water to be reused, but such a system would be cost prohibitive. Given current costs and technology, the maximum practical level of water reuse for a poultry plant, which will vary somewhat by location of the plant, is around 60 percent to 70 percent, according to water treatment experts.