Treating water for reuse is on the rise in the food & beverage industry
Demand for water reuse technologies is growing within the food and beverage industry as more companies seek ways to streamline operations and enhance sustainability practices.
The field of reuse has expanded considerably during the last decade, thanks to advances in technology and growing demand from industry. Many corporations have made public commitments to reduce their freshwater intake by becoming more water efficient and through recycling water. Their successes are bolstering confidence in the rapidly growing field of water reuse.
Researchers predict that, by 2020, food and beverage companies will spend $6 billion per year on water technology, up from $3.3 billion in 2011.
Historically, the capital cost of treatment equipment has been a deterrent to its widespread adoption. Growing awareness of the true costs of wastewater disposal, however, coupled with advances in treatment technology, have fueled growth.
As one of the largest users of water, the food and beverage industry also is mindful of external issues that affect operations, among them, global water scarcity, prolonged drought and public pressure to be better stewards of the environment. Businesses that are focusing on sustainability plans also are realizing the viability of water reuse from stewardship and profitability perspectives.
Many companies are using recovered water in secondary applications, such as in washing applications and equipment cooling. With more advanced treatment technologies being developed, reused water can be used for even more applications. Reuse measures, coupled with operational efficiencies, are resulting in significant reductions in water use—as much as 40% in some operations, according to a 2013 report by the International Life Sciences Institute Research Foundation.
Before businesses can determine how to optimize their water footprint, they must define their objectives in water reuse. A water technology expert can help businesses identify their goals, evaluate system requirements and implement the best solution.
A conventional treatment process removes solid waste found in water and also can adjust levels such as pH and chlorine. These technologies include the use of screens, dissolved air flotation and primary clarifiers, filters, biological treatment via conventionally activated sludge, chlorination and pH adjustment. For some reuse applications, conventional treatment is all that is needed.
When a conventional treatment process is not adequate for meeting the required treatment standards, however, advanced treatment technologies can achieve a higher quality product. Advanced methods give the plant more flexibility with how and where the recycled water is used. These advanced technologies generally fall into two categories: biological and disinfection.
Biological treatment can be done through a sequencing batch reactor (SBR) or a membrane bioreactor (MBR). SBR generally has lower capital requirements than MBR, but MBR systems have lower operating costs. MBR combines biological treatment with membrane filtration to provide a high-quality effluent, meets stringent nutrient limits for phosphorus and nitrogen, and has a smaller footprint then SBR technology.
Disinfection treatment can be applied in three ways: chlorine, ultraviolet (UV) and ozone.
In chlorine disinfection, water is filtered with hypochlorite to generate chlorine residual that inactivates pathogens such as bacteria.
UV technologies are chemical free and require less contact time than chlorine disinfection. In these systems, water is channeled through a reactor that emits UV light at low wavelengths to destroy the DNA structures of microorganisms, including bacteria, viruses, yeast and mold. Virtually any liquid can be used with this technology, so it often is found in beverage processing plants. However, UV is sensitive to the clarity of the water. Higher clarity water requires less energy to treat, and, as a result, pretreatment of wastewater is common in systems where UV disinfection is used.
Ozone and advanced oxidation processes (AOP) are powerful oxidation treatment technologies that generate hydroxyl radicals, the strongest oxidant used in water treatment. AOP is an ideal disinfection approach to treat recalcitrant contaminants that are not removed by other technologies. AOP and ozone technologies are commonly coupled with other filtration technologies.
In addition to these biological and disinfection techniques, there are other advanced treatment technologies that can be used either separately or in conjunction to fulfill wastewater discharge requirements.
Membrane filtration—using technologies such as microfiltration and ultrafiltration—provides suspended solids removal found in the processing of foods and beverages. These technologies can remove some pathogens, viruses and bacteria.
In reverse osmosis (RO), salts and many dissolved organics are removed through a semi-permeable membrane. RO is used when the highest quality reuse water is needed, such as high-pressure boiler feed water or any use where low salt and contaminant levels are required. RO can be expensive and generate a concentrate brine waste stream that must be managed via proper disposal.
Treating water is only the first step in ensuring wastewater is recycled and reused efficiently and effectively within a plant. Pumps serve two purposes in a reuse system: transporting and pressure boosting. Water needs to be moved from one location to another for treatment, storage or use.
Treatment and pumping systems are primary energy consumers within a water or wastewater loop. Sizing the system and selecting the right equipment to meet specific reuse requirements are critical to maximizing energy savings over the life of the equipment.
Pressure boosting is required for some treatment technologies, including RO, where specific pressures are required to move water through a membrane. Many reuse applications, such as irrigation and equipment washing, also require boosting capabilities.
The pump and piping selection can have a considerable impact on the energy consumed during the course of the system’s life. Global water technology company Xylem Inc. estimates that a water reuse system using improperly sized piping and pumps can increase energy consumption by 200% to 300%.
There are a number of steps to ensure the right equipment is in place, including determining the flow rate, static head and friction loss. Static head is the height of a column of water that would be produced at a given pressure. Friction loss is the loss of energy—or reduction of static head—that occurs in the pipe due to viscous effects generated by its size and surface. Narrow piping, corners and valves that impede flow create friction loss.
For a boosting application, pressure and friction loss are critical factors to consider, as are the density of the water and the chemical compatibility of the water makeup.
In selecting the right pump for the application, concepts such as flow curves and best efficiency point (BEP) become important. BEP is the operating point at which the pump runs at maximum hydraulic efficiency. Also to be considered is the net positive suction head, which is important to keep the pump out of cavitation, which can degrade pump performance.
Other factors to consider in choosing a pump include the voltage requirements of the system, the environmental conditions under which the pump will operate to determine the correct motor enclosure, and whether variable speed options and controllers will enhance pump performance.
With the wide variety of food and beverage facilities in operation and the unique water needs of each facility, there is no one-size-fits-all technology for water reuse. By first determining how water reuse can benefit their operations, they can then determine which technology will meet their needs. As more companies recognize the value of water reuse on myriad levels, it will play an increasingly greater role throughout the industry.