In fruit and vegetable processing, water is used extensively during the packaging process. Packhouse operations use process-water to cool, clean and to transport produce throughout the packing operation. Packhouses can incur high costs for both water usage and wastewater discharge tariffs. This can limit pack-house operations due to shortages of fresh water, as well as land for wastewater discharge.
Many packhouses are looking to decrease their water usage and reduce their wastewater tariff costs through the reuse of their process water. Wastewater generated in pack-houses is characterized by a high presence of solids creating high turbidity and total suspended solids (TSS) level and thus solids separation is the main focus in their water treatment.
Traditionally, solids separation processes are dependent on the density difference between the water and the particles. Particles either have a higher density than water and will settle, or will have a lower density and float. In packhouse wastewater, many particles have a density that is very close to that of water. In this case, in order to achieve a highly efficient process of solids separation, separation by density difference is very challenging.
While processes that remove particles using centrifugal force do exist in the market as an alternative to the separation density difference process (e.g. Hydrocyclone), they are extremely limited in the size of particles they can separate (larger than 70 um) and also the density (larger than 1.9 g/cc), and are mainly used for sand separation. The high shear forces created in the Hydroclyclone will prevent the use of coagulation and flocculation processes since the flocs will be broken and thus the operation will be ineffective.
The recently developed innovative hydrodynamic separator called Natica, developed by AquaHD, is free from the limitations of the conventional solid separation processes. The Natica works by creating centripetal forces to separate particles under low pressure (1bar).
In the Natica, the water flows through a dedicated circular structure. The pass of the water in the circular structure allows the creation of high centrifugal forces (6-8 G) under low pressure. Due to the high centrifugal forces, particles become concentrated in the outer perimeter of the separator. Owing to the laminar flow, particles stay in the outer perimeter layer and do not mix with the clean water in the inside of the separator. A specially designed outlet structure separates the stream rich in particles (near the outer perimeter) and that of the clean water. Particles that have been removed from the water will go through a further sludge thickening and dewatering treatment where the water will be sent to the head of the process to allow for 90-98% water recycling. The Natica removes a wide range of organic and inorganic particles as small as 1 microns from water with dirt load of up to 12,000 PPM of TSS.
