by Brodie Guy
• Biological System Aids with Wastewater, Sludge Processing at Tennessee Condiment Maker
Mizkan Americas, formerly Nakano Foods, is a subsidiary of Mizkan Group and has a heritage in the condiment business that spans 200 years. The company is a leading manufacturer of condiments in the United States with nine manufacturing plants that serve the retail foodservice, specialty, Asian and industrial trade channels. Mizkan Americas produces a wide variety of vinegars, mustards, cooking wines, sushi seasoning, jellies, salad dressings, Asian sauces and other liquid condiments. Its brands include Nakano, Four Monks, Holland House, Barengo and Mitsukan.
In the fall of 2004, the company’s production facility in Crossville, TN, was mandated by local authorities to pre-treat its wastewater for reduction of biological oxygen demand (BOD) and total suspended solids (TSS) to less than 1,000 mg/L. As a result, John Prahler, corporate engineering director for Mizkan Americas, conducted an in-depth research study of available industrial wastewater treatment technology for a compact biological wastewater treatment system that was easy to operate, requiring only minimal maintenance, and capable of handling fluctuating load conditions. That’s when Hydroxyl Systems was approached to provide an ActiveCellTM biological wastewater treatment system custom designed to treat Mizkan’s variable high-strength wastewater stream.
Mizkan Americas produces a variety of mustard and vinegar products generating a wastewater stream that’s highly loaded with organics from multiple production campaigns ranging in flow from 10,000 to 20,000 gpd. The varying organic load ranges from 1,000 mg/L to 10,000 mg/L total BOD (tBOD) and the wastewater is very acidic with a nominal pH range of 3.0-5.0 Rainwater runoff is retained and collected from the secondarily contained production tank farm. During low rainfall events, this wastewater can be highly loaded with organics from spills within the containment area. This runoff water also could account for large volumes of wastewater over the course of an extended rainfall event. Based on Mizkan’s permit, this runoff water must also be collected and treated within the wastewater pretreatment system. The Mizkan wastewater also has TSS ranging from 100 mg/L to 3,000 mg/L and is loaded with mustard seeds and bottle caps from the production floor wash down operations.
The Hydroxyl biological wastewater treatment system was designed using Hydroxyl MediaProTM software with data collected from the Mizkan facility over a three-month period to account for all of the mustard and vinegar product campaigns. This also allowed the design to factor peak flow data during extensive rainfall events. Since the wastewater treatment facility was to include a properly sized and designed equalization (EQ) tank, the fluctuating loads and flows would be dampened and buffered by collection and homogenization of incoming wastewater with the wastewater retained in the EQ tank. The EQ tank would always retain a wastewater that accounts for a tank volume of 25-30% for buffering purposes.
The pH of the wastewater collected in the EQ tank would be adjusted using caustic soda and mechanical agitation to an average pH of 7.0 to 7.5 prior to biological treatment. Therefore, Hydroxyl was able to design the biological wastewater treatment system for average load conditions rather than peak load conditions, reducing the size of the bioreactors, minimizing system footprint and lowering the overall cost of the turnkey facility.
Biofilm Carrier Solution
The wastewater generated by the production facility is collected in screened troughs and flows by gravity onto a below-grade lift station and then pumped to the biological wastewater treatment system via a set of vertical centrifugal pumps operating on a lead-lag basis. The wastewater is then fine-screened to less than 1 mm by a self cleaning rotary screen for the removal of mustard seeds, bottle caps and other solid waste.
The equalization (EQ) tank, sized for 100,000 gallons, is capable of collecting and buffering the wastewater stream along with additional storage capacity for rainfall events. The wastewater acidic pH is adjusted by controlled injection of caustic soda into a continuously operating circulation loop for raising pH up to 7.0-7.5. for the biological treatment process. The wastewater within the EQ tank is agitated by means of a submerged mechanical mixer. Once the target pH value has been satisfied, a control valve opens to direct wastewater from the circulation loop to the two-stage bioreactor system at a controlled rate of 14 gpm. A magnetic flow meter controls the adjustment of the valve and provides a signal to a nutrient dosing system where ammonia and phosphorous are dosed into the feed stream along with a defoaming agent.
The process operates within two 15,000-gallon bioreactor tanks, biodegrading wastewater using thousands of suspended biofilm carriers that are continuously mixed within the tanks. Each biofilm carrier provides an active surface area sustaining heterotrophic and autotrophic bacteria within protected cells. This dynamic population of bacteria achieves high-rate biodegradation productivity within the system, while also offering process resiliency and automated operation.
The first-stage bioreactor provides a BOD roughing process removing 50-70% of the BOD. A DO sensor mounted within the effluent discharge screen provides a monitoring and control function of the variable frequency drive (VFD) controlled positive displacement blowers to maintain the DO at a predetermined set point of ~3 mg/L.
The second-stage bioreactor biodegrades remaining organics to less than the target effluent parameters of <1,000 mg/L soluble BOD (sBOD). Dead bacteria are continuously sloughed from the biofilm carriers and exit the bioreactors via a wedge wire retaining screen as TSS with the treated effluent. This continuous sloughing action exposes the biofilm to the organic load in the wastewater and provides a self-regulated high-rate biological treatment process that is responsive to load fluctuations.
Key benefits of the biofilm carrier process include:
- Compact Design - A fraction of the size of conventional systems
- Expandable - Capacity can be easily upgraded by increasing the fill fraction of biofilm carriers
- Single Pass Process - No return activated sludge stream required
- Resilient and Responsive - Automatically responds to load fluctuations
- Minimal Maintenance - No F/M ratios or MLSS levels to maintain
The treated wastewater then flows by gravity to a dissolved air flotation (DAF) system located in a climate controlled process control building where TSS are removed from the process stream. The solids accumulate on the surface of the water within the DAF, and a mechanical flight and chain assembly slowly skims the surface of the water to a sludge holding chamber. The treated and clarified wastewater is then collected in a lift station and pumped to the sewer drain for effluent discharge to the city of Crossville Wastewater Treatment Plant, meeting the target effluent quality standards of <1,000 mg/L BOD and <1,000 mg/L TSS.
A recirculation loop was provided to allow Mizkan the capability of multi-pass processing if a highly loaded slug of wastewater is received that requires additional retention and treatment to meet target effluent requirements, or to multi-pass the wastewater stream during low organic loading conditions during weekends and facility shutdown events.
The sludge removed by the dissolved air flotation equipment is then transferred and stored in an aerated sludge tank within a climate controlled sludge process building and dewatered in a screw press to produce 17-20% solids that meets the paint filter test for dryness and landfill application. Dewatered sludge is directed to roll-on/roll-off containers for transportation to the local landfill.
About the Author: Brodie Guy is marketing manager for Hydroxyl Systems Inc., based in Victoria, British Columbia, Canada. Founded in 1993, the privately held company is an integrated systems provider of environmental technology for wastewater treatment. It’s recognized for development and marketing of ActiveCellTM biofilm carrier wastewater treatment systems, CleanSea® shipboard wastewater treatment systems, and PhotoStackTM advanced oxidation process technology. Contact: 250-381-8850 or www.hydroxyl.com