Last Updated: September 9, 2015
This page was created by the Niche Meat Processor Assistance Network: www.nichemeatprocessing.org.
You'll need to know some basic information about your needs before you decide what system is right for your plant. Start with these questions:
Your answers to these questions are important to your planning process. Decisions made here will aid in site selection for a new facility, influence construction estimates, and be a critical component of your design and permitting processes. In general, before you can move forward with determining the right wastewater system for your facility, you need to know what you are doing (slaughter, cut and wrap, etc.), how much wastewater those activities generate (total volume) and what will be in that wastewater (pH, BOD, TSS, etc.).
For example, a small facility in Indiana that slaughters and processes poultry and red meat typically uses about 1,600 gallons/day, with a wastewater BOD level of 1,000-1,200 mg/L going into their treatment system. This is just one example: wastewater volume and strength will vary from plant to plant.
This downloadable pair of tables (pdf) offers real water quantity and quality data from real processors of varying sizes and processing activities.
Read on for wastewater treatment options and to learn more about the different systems available.
In general, if it is possible to connect to municipal wastewater treatment, this is often your best bet. If your plant is located within reach of these services, in the long run it will probably be worth it to pay the initial connection fees and monthly sewer costs rather than build and manage your own wastewater treatment system.
Once you have a sense of how much wastewater your plant will be discharging each day and the strength of that wastewater, measured in pH, TSS (Total Suspended Solids), BOD (Biological Oxygen Demand), and FOG (Fats, Oils and Greases), contact your local Public Works or Municipal Wastewater Treatment facility to find out about connection fees and estimated monthly charges.
A typical septic system will probably not work for most meat processing plants because of the high levels of BOD, TSS, and FOG in the wastewater. You’ll need to pursue other options like connecting to municipal wastewater services, building a pond or lagoon system, building a constructed wetland, or another solution.
Constructed wetlands are an option that some processors on our NMPAN listserve recommend highly.
Brushy Prairie Packing, a very small, red meat and poultry slaughter facility at Gunthrop Farms in Indiana, is quite pleased with their constructed wetland, saying “for places that have the space a constructed wetland is a relatively low maintenance natural waste treatment system that uses very little electricity and no chemicals. We love ours.”
Purdue University wrote a publication, “Recirculating Vertical Flow Constructed Wetlands for Treating Residential Wastewater,” with a lot of good pictures, including Gunthorp Farms (Brushy Prairie Packing: see chart p. 7, figure 15). Here's what Greg Gunthorp of Gunthrop Farms told NMPAN:
“When the publication was made we were slaughtering our poultry but were sending our pigs out for de-hairing and evisceration. Our system consists of six 1,000-gallon tanks for separation prior to the wetland. The first tank draws off the bottom as a grease trap. The remainder are set up as normal septic tanks pulling out of the middle. There is an effluent filter at the end of the septic tanks. The rest rooms go into a separate 1,000-gallon septic tank and enter the system just ahead of the constructed wetland.
"Blood, fat, hair, and feathers are rough on waste treatment systems and systems need to be designed accordingly. If a facility is not going to catch the blood, fat, hair, or feathers or have some means to separate them out, the waste water stream is going to be significantly stronger and take a much, much larger system.
"The water quality exiting a constructed wetland is amazing. Today there are lots of advanced waste treatment system options.”
Septic tank (left) vs. wetland (right) effluent. (photo credit: Purdue University, "Recirculating Vertical Flow Constructed Wetlands for Treating Residential Wastewater")
Anaerobic digesters are an attractive technology for small meat processing facilities. You can treat your plant’s wastewater and solid waste and generate electricity in the process!
That said, we haven’t found an anaerobic digester system that is cost-effective for a small processing facility. The systems are expensive and meat processing waste isn’t a very good substrate for anaerobic digesters. If you know of a small plant that is using an anaerobic digester, please contact us!
Pond or lagoon systems come in two types: aerated (aerobic, occurring in the presence of oxygen) and anaerobic (occurring in the absence of oxygen).
A meat processing facility that uses a pond or lagoon system will first run any processing wastewater through a pre-treatment system (more on that below). After the pre-treatment system, the wastewater will flow into the pond or lagoon system:
Aerated Ponds or Lagoons:
Aerated ponds or lagoons are relatively shallow, wide structures in which wastewater is added at one point and the effluent is removed from another point. The wastewater is retained in the pond for a certain number of days, depending on the desired strength of the effluent.
To reach the desired effluent strength, often a series of ponds is utilized with wastewater being transferred from one pond to the next, each subsequent stage lowering the BOD of the final product. Surface aerators are used to provide oxygen. The aerators also churn the wastewater, keeping any solids in the pond in suspension.
These systems generally emit odors and are usually only suitable for rural, isolated areas.
Anaerobic Ponds or Lagoons:
Anaerobic ponds or lagoons are built and operated much like aerated ponds: relatively shallow, wide structures in which wastewater is added at one point and the effluent is removed from another point. The wastewater is retained in the pond for a certain number of days, depending on the desired strength of the effluent.
To reach the desired effluent strength, sometimes a series of ponds is installed, with wastewater transferred from one pond to the next. Each stage lowers the BOD of the final product.
The key difference with anaerobic ponds is that there are no aerators to introduce oxygen to the system. Solids settle to the bottom of the lagoon. As they build up, these solids undergo anaerobic decomposition. A surface layer traps heat and some odors. However, these ponds still emit odors, on warm days in particular.
Anaerobic Lagoon at California Polytechnic State University (photo credit: Wikipedia)
You'll need to consider a number of factors before constructing any type of pond or lagoon system:
These are just a few questions to consider in building a pond or lagoon system. Talk to a qualified environmental engineer to determine which system is best for your situation, and consult with your local authorities to see what is permissible in your area.
All of the systems above, even connecting to a municipal system, require some form of pre-treatment. Pre-treatment can range from management practices (sweeping up the kill floor and processing floor before wash down to capture any solids, capturing blood on the kill floor so it doesn’t go down the drain, and similar practices), to simple filter systems, to more advanced pre-treatment options.
The main goal of pre-treatment is to limit what you “send down the line." Blood, fat and tissue are all nutrient rich materials. You or your municipal wastewater treatment facility will have to remove these nutrients before that wastewater can be discharged. Removal = cost.
"Where does the wastewater come from?" FRC Systems, a company that sells wastewater treatment systems, has a good overview of where the wastewater comes from in meat processing here on their website.
One more piece of advice from a seasoned operator:
“I know from personal experience that I would highly recommend whatever system a person installs that they overbuild the retention time and thus the settling and filter portion of the system. Chillers, scalders, etc. dumping cause huge surges on systems that need to be dealt with. Blood, feather, and animal hair cause issues that need dealt with.
"Our system works great but we've had to make some changes to deal with increased production, blood, feathers, and pig hair.”
The options presented here are by no means the only forms of wastewater treatment, just those most commonly used by small meat processors. Wikipedia, for example, has a long list of wastewater treatment technologies that you might find helpful in determining which system is best for your plant and your location.