Alto manufactures award-winning American and Italian style cheeses and whey and milk products for the food service and food processing industries. Like many manufacturers, the co-op is affected by increasingly stringent effluent requirements. If a food processor discharges to a publicly-owned treatment system, limits are assigned locally on characteristics such as Biological or Chemical Oxygen Demand (BOD/COD) or Total Suspended Solids (TSS); fats and oils, phosphorus; ammonia; and nitrogen. Processors who have onsite treatment facilities, such as Alto, typically discharge directly to a neighboring water way. In these instances, the state determine specific limits.
Organics in the Alto wastewater are removed with an anaerobic system, leaving phosphorus that must be treated prior to discharge. Since an abundance of phosphorus can contribute to algae growth which can affect aquatic life and cause odors, government and industry are working to remove more of it from waste streams.
There are many biological and chemical removal methods available. Procorp Inc., Alto's long-time engineering and design/build partner, utilizes many of these methods. Procorp introduced Alto to the Crystalactor® technology, a crystallization process designed by DHV Water BV. The system combines the four processes commonly required in conventional phosphorus treatment processes-coagulation, flocculation, separation and dewatering-into one unit, resulting in an efficient system with a comparatively small footprint.
Located after the activated sludge treatment system, the Alto Crystalactor handles about 125 m3/h of wastewater with maximum phosphorus concentration of 25 mg/L. The heart of the Crystalactor® is the pellet reactor, 10 feet in diameter, which is partially filled with a seed material such as sand or minerals. Wastewater is pumped to maintain the pellet bed in a fluidized condition. In order to crystallize the target component on the pellet bed, a driving force is created by a reagent dosage and pH adjustment. By selecting the appropriate conditions, co-crystallization of impurities is minimized and high-purity crystals are obtained.
At Alto, quartz sand is used in the pellet reactor with lime as the reagent. In Alto's case it was the best combination to allow calcium phosphate to crystallize and form "pellets". These eventually sink to the reactor bottom and are easily discharged and replaced with fresh seed with no disruption. After atmospheric drying, the need for sludge dewatering or hauling of sludge is eliminated. Due to their excellent composition, the pellets can often be recycled or reused. The resultant solids equate to approximately 1 cubic ft per 100,000 gallons of wastewater. Operation of the system is relatively automated, with the equipment linked directly to a computerized control system that can be remotely monitored.
Hans Horetzki, dir. of engineering at Alto Dairy, says "(we) realized that in order to meet the requirements for Phosphorus limits, a new approach was needed. Not only was the dairy concerned with meeting the effluent limits, but also in addressing the amount of phosphorus being applied by land spreading. Thanks to Procorp and DHV, both issues were addressed by the installation of the Crystalactor process which achieved the desired Phosphorus reduction in the effluent while reducing the Phosphorus being land spread by almost 50%."
The Crystalactor has been used for water softening, phosphorus removal and metal recovery in over 50 projects worldwide including the largest yet, Chen Chin Lake in Taiwan at 118 million gallons per day.
Procorp, Inc. is a Wauwatosa, Wisconsin based consulting, engineering, design/build, plant optimization and operations firm with specialty in water softening, wastewater treatment, and biological and chemical phosphorus removal. Procorp is the U.S. licensee for the Crystalactor® process in water softening and phosphorus removal applications. For more information visit www.procorpinc.com, www.crystalactorusa.com or contact Linda Englander at 414/258-8777 x210 or at lenglander@procorpinc.com.
