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These trends toward more and larger broiler chickens greatly affect slaughter and processing plants and leads to much greater concentration of contaminants in poultry plant wastewater. Among these contaminants, nutrients (phosphorus and nitrogen) are becoming an increasing concern to environmental regulators. High nutrient concentrations (eutrophication) in natural water bodies can result in harmful algal blooms (HAB) and hypoxia (reduction in oxygen available to aquatic life). Regulators are thus focused on mitigating these effects, and producers are increasingly facing more stringent total phosphorus (TP) limits.
Secondary Protein Nutrients (SPN) are the DAF skimmings that result from the poultry wastewater treatment process. These skimmings are high in valuable fats, oils and grease from poultry processing. Like other processing by-products (such as trimmings, blood, bones and feathers), SPN can be recycled by rendering plants, and used for animal feed, biofuels, lubricants and other products. When processing plants sell DAF skimmings as SPN to renderers, not only do they realize some revenue, but they avoid the alternative very expensive disposal cost. DAF sludge that cannot be rendered is usually disposed of through land application or, increasingly, landfill disposal. As with other biosolids and sewage waste, sludge disposal is very costly and suitable land for application is becoming more scarce. Consequently, poultry processors are much better off selling SPN to renderers rather than paying for disposal through land application.
However, plants that use FeCl or other metal salts in their wastewater treatment often are unable to sell DAF skimmings to renderers as SPN. This is due to potential toxicity and the increased risk of combustion in the heat processing in the rendering operation. Plants using FeCl thus are forced to use land application for disposal of DAF sludge. Often multiple DAFs are used so that some skimmings can be generated and sold as SPN prior to the application of FeCl in a secondary DAF.
NClear’s patented TPXTM nanocrystal technology was designed as a non-toxic, effective and efficient means to remove certain contaminants, especially phosphorus, from water and wastewater. Because TPXTM is a calcium-silicate synthetic mineral, it does not contain any toxic metals. Unlike FeCl treatment systems, TPXTM-treated DAF skimmings can be sold to rendering plants as SPN, providing a revenue source. More importantly, these solids no longer need to be land applied or sent to a landfill. The ability to recycle solid waste can help poultry processors meet their sustainability goals in addition to improving their bottom line. In addition to enhancing phosphorus removal, TPXTM has coagulative properties that, used in conjunction with certain polymers or other coagulants, can help meet stringent discharge levels for TSS, COD and BOD. TPXTM can also help reduce operating costs by eliminating secondary DAF treatments, and reducing transport costs as a result of improved dewatering.
NClear has tested TPXTM at a poultry kill plant in Georgia in a series of 72-hour sidestream tests. NClear’s mobile pilot system included a custom-built 10 gallon per minute (gpm) DAF with multiple chemical injection points and floc tubes, polymer and coagulant feed tanks, acidulation system, equalization (EQ) tanks and the TPXTM slurry system.
The pilot system allows NClear to effectively simulate the plant’s entire wastewater processing plant. EQ tanks are sized to simulate the retention time and aeration characteristics of the plant’s flow equalization basin(s), as well as any equalization tanks or ponds at the effluent end of the wastewater process.
Pilot Evaluations were conducted around the clock for 72-96 hours, with daily composite testing of both direct DAF effluent and aerated EQ tank effluent. NClear’s portable lab provided real-time analysis of pH, TP, Ortho P (OP), and COD. Composite samples were also sent to a third-party lab for independent verification of results and additional analyses of BOD, TKN and TSS. Results were compared with the facilities own wastewater effluent and were used to evaluate full scale treatment costs.
Representative results from the facilities lab are shown in Table 1, and demonstrate that NClear’s TPXTM solution achieved better results for all analytes than the current FeCl treatment system. In addition, DAF skimmings were tested and processed by American Protein’s (now Tyson) rendering facility in Gainesville GA, and were confirmed to be a drier sludge that contained no metals or toxicity and was acceptable for rendering. In addition, plant personnel estimated that the total wet volume of skimmings produced was reduced by approximately 30%, which translates to significant savings due to less water transport and more efficient cake production.
Table 1. Pilot results from the processing plant, as reported by the facilities corporate lab. Results are from a representative 24-hour composite sample. Similar results were replicated over 11 separate 24-hour test periods at this location.
Together with facility personnel, NClear analyzed current total wastewater costs at the facility. The plant currently operates two EQ basins and two DAFs. The DAFs are sometimes run in sequence with FeCl addition in the second DAF, and sometimes run concurrently with FeCl in both DAFS. When they are run in sequence, some of the solids from DAF1 can be sold as SPN; when run concurrently all DAF solids are land-applied. Current costs evaluated include: Chemicals (anionic and cationic polymers, FeCl, quicklime, and an organic coagulant); transport costs for DAF solids (both to land application and, when DAFs are run in sequence, to rendering); and land application fees. As an offset to current costs, there is some SPN revenue when DAF’s are run in sequence. The total of these current costs is approximately $7,800 per day, or $4.60 per 1,000 gallons treated (based on average flow of 1.7 MGD).
As shown in Table 2, the TPXTM solution results in a savings of 27% in total wastewater treatment costs, reflecting a savings of over $2,000 per day, which adds up to more than $550,000 per year.
Table 2. Current and estimated future wastewater processing costs at the processing plant, per day based on approximately 1.7 MGD flow rate. Future Cost reflects the full scale costs associated with NClear’s TPXTM solution.
The data above shows that while there is a significant increase in chemical costs, as TPXTM (an engineered synthetic mineral) is substituted for commodity chemicals (FeCl and quicklime), this cost is more than offset by the savings in land application, the SPN revenue increase, and the total reduction in transport costs due to less total DAF solids. But the significant savings is only part of the benefit. TPXTM is more environmentally friendly than metal salts, as it maximizes the plant’s ability to recycle biproducts and eliminate land application practices (or even landfill disposal). It also provides operating benefits by eliminating the need to operate multiple DAF’s in sequence, reducing total solids production, and eliminating manual tasks such as lime mixing.
The substantial cost savings, operational benefits and, most importantly, the advancement of sustainability objectives make this an ideal solution for the facilities wastewater processing.
Electrichlor, founded in 2001 and based in Laramie, Wyoming, is a leading manufacturer of hypochlorite generators serving the marine, maritime, power generation, petroleum, and water treatment industries. NClear acquired Electrichlor in February 2021.
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