At a fruit jam manufacturing facility in Manchester, England, cleaning hoses in the fruit room were identified as one of the highest end uses of water in the facility . The new nozzles and training cost only £100 , but resulted in savings of £3,000 to £4,000 per year . The simple payback period for this measure was less than two weeks.Similarly, Harvest FreshCuts was able to reduce the water it uses for cleaning by 10% through the installation of efficient high pressure spray nozzles on hoses, regular hose and nozzle maintenance, and operator training . Clean equipment immediately after use. Waiting too long to clean equipment can allow product residues to become dry and crusty and harder to remove, requiring more water consumption in the cleaning phase. Processing equipment should be immediately cleaned after production has stopped to minimize the water necessary for cleaning . Optimization of clean-in-place performance. Clean-in-place processes should be programmed to use only enough water and detergent to perform the desired cleaning task at a particular piece of equipment. Dry cleaning prior to clean-in-place cycles can further reduce the minimum amount of water and detergent needed . An environmental assessment at Harvest FreshCuts determined that by introducing a cleaning system that ensured accurate water and chemical usage during the cleaning cycle, blueberry grow pot the volume of internally recycled water could be increased by 40% . Pigging. A pig is a solid plug or ball that is pushed through a pipe to remove deposits adhering to pipe walls. Pigging can be performed instead of rinsing pipes with water to reduce water consumption, where the piping system is amenable to pigging .
At Nelsons of Aintree, a jam manufacturer based in the United Kingdom, a pigging system was installed to clean a long pipeline used for transporting jam. Previously, cleaning the pipeline used large volumes of water and flushed most of the jam residues into a drain. In the new system, rubber pigs made from food grade rubber are propelled through the pipe using compressed air and stopped at the other end of the pipe by a bar that stops the pig but allows jam to pass. The pig is returned by switching the direction of the compressed air via a valve. The pigging system saved the company £105,280 per year by reducing water use, effluent discharge volumes, and energy consumption and another £134,780 per year in avoided product losses . Reportedly, the system allowed the company to save 173 tons of jam per year while reducing water use by around 528,000 gallons per year. Low pressure foam cleaning. Traditionally, walls, floors, and equipment are cleaned using brushes, high pressure spray hoses, and detergents. Low pressure foam cleaning methods, in which cleaning foam is sprayed on surfaces and allowed to settle for 10 to 20 minutes before rinsing with low pressure water, can save both water and energy compared to high pressure cleaning methods . However, this method does not provide scouring ability and thus might not be a feasible replacement for all high pressure cleaning applications.Control of volume in clean-in-place processes. The control of water flows for burst rinsing and clean-in-place processes should be based on required water volume, not a pre-determined time, to reduce cleaning water quantities . Pre-soaking of floors and equipment. An effective means of reducing water consumption in cleaning is to pre-soak soiled surfaces on floors and open equipment prior to cleaning. Pre-soaking can be effective at loosening dirt and hardened food residues so that less water is required in the actual cleaning operations .In the conventional method of once-through water use , fresh water is used once for process and cleaning applications and any water not contained in the final product is then discharged into the wastewater stream.
Although once-through water use methods are increasingly less common in modern fruit and vegetable processing facilities, they represent the most inefficient methods of using water and should be avoided wherever possible. Preferably, water should be recovered and reused or recycled within the facility to reduce fresh water purchasing and treatment costs while also reducing the volume and associated costs of wastewater treatment and disposal. According to Raghupathy , at least 50% to 60% of water in typical food processing facilities can be recovered for reuse. However, the extent to which fresh water use can be reduced via water reuse and recycling measures in any fruit and vegetable processing facility will ultimately depend on product hygiene considerations.In general, recycling is feasible and practiced commonly in the U.S. food processing industry in the first two applications but generally not practiced in the third application due to hygienic concerns. Where feasible, the elimination of once-through water use can lead to significant water savings, as illustrated by the following case studies. At the Gangi Brothers Packing Company, a canned tomato product manufacturer in San Jose, California, water is used in fluming tomatoes from trucks, tomato rinsing, vacuum pump seals, boiler makeup, and process cooling. In 1989, the company implemented an aggressive water efficiency program, which included the recycling of flume water and the installation of evaporative cooling towers to recycle cooling water. Reportedly, the company reduced its water consumption by 94 million gallons per year, which led to savings of around $130,000 per year . The reported payback period on the equipment and modifications was less than one year. Stahlbush Island Farms, a grower, canner, and freezer of fruits and vegetables in Corvalis, Oregon, reduced its consumption of water by more than 50% through innovative water recovery and recycling systems. Water is pumped from wells at a temperature of about 55° F, where it is quickly used to cool hot pumpkin puree. Next, the water passes through a second heat exchanger, where it cools oil from the facility’s refrigeration system compressors. When the water leaves the second heat exchanger, it has been heated to around 100° F.
The warm water is then pumped to a surge tank, where it is used in one of four different applications: to wash pumpkins as they enter the processing plant, to clean food processing equipment, for condenser water in the facility’s refrigeration cycle, and for boiler makeup water . As an additional benefit, the recycled water is used to provide warm boiler makeup water and to preheat the washed pumpkins, saving energy. Listed below are some of the most significant opportunities for water recovery, reuse, and recycling applicable to fruit and vegetable processing facilities.Reuse of washing water. In the initial washing of fruits and vegetables, a large volume of water is often necessary and the concentration of dirt in the wastewater exiting the process is typically low. In many instances, a recirculation system can be installed to maintain an acceptable concentration of dirt in the wash water while reducing fresh water inputs. A basic recirculation system consists of a strainer or filter to remove solids and a pump for circulating water back to the washing process . For wash water with high dirt concentrations, a flotation unit or centrifugal separator can be added to help remove solids. Additionally, ultraviolet or ozone treatment modules can be added to reduce bacterial loads, where needed. Cooling towers. Once-through cooling systems can be replaced by cooling towers, which continuously recycle cooling water and lead to significant water savings. The U.S. DOE estimates that to remove the same heat load, once-through cooling systems can use as much as 40 times more water than a cooling tower . In a cooling tower, circulating warm water is put into contact with an air flow, hydroponic bucket which evaporates some of the water. The heat lost by evaporation cools the remaining water, which can then be recirculated as a cooling medium. For example, cooling towers can be used to recirculate water from evaporative can coolers in the canning process, with recycling occurring continuously until the water no longer meets cleanliness standards .Recycling of final rinse water. Final rinsing is done to remove residues of detergents from the equipment after it has been cleaned. The final rinse water, while not suitable for additional final rinsing applications, can be recovered and used for initial rinsing or intermediate rinsing purposes rather than being discharged to the wastewater stream . Recycling of evaporator condensate. Depending on the quality of condensate reclaimed from products in evaporation processes, condensate water can be reused for other low-grade facility applications such as equipment pre-rinsing and surface pre-soaking. Additionally, condensate recovery systems can be fitted with heat exchangers such that hot condensate can be used for pre-heating the evaporation process input streams, which saves energy . Segregation of wastewater systems. When all facility wastewater streams are combined into a common wastewater flow, opportunities for recovering and recycling the wastewater streams with reclaimable water are lost. Where feasible, the use of separate process wastewater systems should be considered to maximize opportunities for water recovery and recycling. For example, in 1993 a UK based snack food company performed a facility audit to determine if water savings could be realized if process wastewater streams were segregated prior to on-site treatment. The company found that by segregating its potato wash water, hot starch water, and cold starch water streams for separate recovery and treatment, its water consumption could be reduced by 19% .
The potato wash water was reused after grit removal and the cold starch water was recycled after good quality starch was recovered. The annual savings in water supply costs were estimated at £90,000 .Membrane filtration. Membrane filtration technologies have been applied in many industries to clean wastewater prior to disposal and to recover water for recycling in various facility and process applications. Membrane systems used in wastewater treatment at fruit and vegetable processing facilities have been documented to reduce freshwater intake and effluent by as much as 85% . The potential barriers to implementation include relatively high capital costs, as well as the need for specific membranes for specific applications . At the Tri Valley Growers’ Oberti Olive facility in Madera, California, reverse osmosis and ultra-filtration membrane systems were installed to treat the facility’s well water, flotation brine, oil mill slurry, yeast broth, and biotower water. The membrane systems reportedly reduced the company’s freshwater intake and effluent discharge by 80% to 85%, allowed for the recovery of salt from brine water, allowed for the recovery of solids for sale as animal feed, and reduced land use by evaporation ponds by 85% . At the Michigan Milk Producers Association facility in Ovid, Michigan, a reverse osmosis membrane filtration system was installed to concentrate organic impurities in evaporator condensate. The filtered hot condensate water is reused for clean-in-place water, tank wash down water, and boiler makeup water. The reported benefits include a reduction in well water consumption and wastewater discharges of 100,000 to 150,000 gallons per day, a reduction in boiler and wash water treatment costs of $6,000 to $8,000 per month, and a reduction in scale buildup on pipes . Hydrocyclones. For wastewater streams with significant solids content, such as heavily soiled wash water, hydrocyclones can be used to separate out solids and reclaim water for use in other facility applications. Such systems can often have three major benefits. First, a significant amount of water can be recovered and recycled within a facility, reducing the necessary purchases of fresh water. Second, because wastewater ultimately has less solids content, wastewater disposal costs are often reduced. Third, recovered solids can often be recycled as animal feed, mulch, or agricultural additives. At the Smith Snack Food Company, the largest manufacturer of potato- and corn-based snack foods in Australia, a hydrocyclone system was installed in 1997 to reduce the solids content in wastewater streams at the company’s Adelaide facility. Hydrocyclones were installed on the facility’s corn and potato washing lines, with solids being collected in a sludge tank and reclaimed water being recycled back into the initial washing processes for potatoes and corn. The system reportedly reduced water consumption in the washing processes by more than 80% while also saving the company around $130,000 per year in reduced wastewater disposal costs . The simple payback period was estimated at just five weeks. Recycling of can cooling water. When can cooling water is not recirculated, it can be recovered and used for the initial washing of incoming products, as a rinse for caustic peeling processes, in canning belt lubrication, and in miscellaneous facility cleanup operations .Recycling of blanching and cooking water.