Harvested root vegetables are washed prior to packaging for sale. It is a multi-step process to clean the produce. Before the vegetables come into contact with water, the dry soil can be removed which will reduce the amount that must be washed off. Not every packing process uses this step, which is a valuable tool both for removing soil and for reducing the amount of work required to treat the washwater prior to discharge.
| Goal: Decrease the amount of soil entering a washwater treatment system. Solution: Install a dry soil removal system prior to vegetables entering the washing process. The vegetables are sent over a finger table (Figure 1) that jostles dried soil off. This system is also able to be used in the field on a harvester. Then they travel on a belt towards an angled belt where the vegetables roll down due to gravity and the angled belt, travelling in the opposite direction to the vegetables, carries soil or dried leaves away (Figure 2). The majority of the soil is removed by the finger table. |  Figure 1: Finger table; this system can be used in place of a conveyor belt or to turn the direction of vegetable flow |
Figure 2: A generalized version of a soil removal belt (A & B) and one integrated into a wash line (C)
Results: Under typical processing conditions this system is able to remove 1 cubic foot of soil from every 2750 pounds of carrots washed for a total of 64.9 cubic feet over one day of washing. This soil removal lessens the solid load in the washwater treatment system. Dry soil is also easier to handle and dispose as compared to wet soil mixed in with water. Over one day of washing, this pre-wash system intercepts 39.3 grams of phosphorus and prevents it from entering the washing system’s wastewater. This is less phosphorus that would need to be removed by treatment prior to discharge.
Conclusion: The addition of a dry soil removal system diminishes the pressure on solids removal treatments and nutrient removal prior to discharge. They can be installed into an existing wash line with minimal modifications as they also act as conveyors or turning mechanisms.
Next Steps: The implementation of this type of system would have a great impact based on the collected data. If all the carrots grown in the Holland Marsh area including surrounding growing vicinities, an average of 44.6 kg of phosphorus would be prevented from entering the watershed.
Conclusion: The addition of a dry soil removal system diminishes the pressure on solids removal treatments and nutrient removal prior to discharge. They can be installed into an existing wash line with minimal modifications as they also act as conveyors or turning mechanisms.
Next Steps: The implementation of this type of system would have a great impact based on the collected data. If all the carrots grown in the Holland Marsh area including surrounding growing vicinities, an average of 44.6 kg of phosphorus would be prevented from entering the watershed.
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