Canned fruits and vegetables are easy to carry, transport and store, and can meet special demands for scenarios such as mountain climbing and ocean voyages. Wastewater is generated during the processing of canned fruits and vegetables. How should such wastewater be treated? This article, together with a manufacturer of Online Water Quality Monitors, briefly discusses this topic.
A certain volume of wastewater is produced during canning processes, and the water quality and volume vary significantly depending on raw materials, finished products and production processes. The sources and characteristics of the wastewater are specified as follows:
- Wastewater Sources
Wastewater from fruit canning mainly comes from sterilization, can filling, peeling, and cleaning of equipment and utensils. Wastewater from vegetable canning is mostly generated during blanching and washing procedures. Copper sulfate may be added in the blanching stage, resulting in copper ions contained in the discharged wastewater.
- Characteristics of the Wastewater
Wastewater from both fruit and vegetable canning contains high concentrations of organic matter and suspended solids. Wastewater from vegetable processing holds relatively high nitrogen content and low phosphorus content, while fruit processing wastewater features higher phosphorus and lower nitrogen levels. The pH value of the wastewater ranges from 5 to 10, and it can be degraded by microorganisms with relative ease.
Treatment Methods for Wastewater from Fruit and Vegetable Canning
This type of wastewater features favorable biodegradability, so anaerobic and aerobic treatment technologies can be adopted. Small-scale canning factories with low wastewater discharge volume may adopt coagulation and sedimentation treatment. Multiple treatment options are available, several common ones are introduced below:
- Biofilm Process
High-rate biofilters and conventional biofilters are widely applied to treat canning wastewater with this process. This process is more suitable for regions with warm climates and less applicable in cold areas.
- Sequencing Batch Reactor (SBR) Process
The SBR process integrates an aeration tank and sedimentation tank. Biochemical reactions proceed in a single tank by stages, with intermittent inflow and outflow. It delivers stable treatment performance, strong resistance to load fluctuations, low sludge yield and short sludge age, which inhibits the growth of filamentous bacteria. Its operation covers five phases: filling, reaction, sedimentation, decanting and idle. It is recommended to equip the SBR tank with a regulating tank or deploy two or more sets of reactors.
After disinfection and mold removal treatment of wastewater, operators shall conduct Online Water Quality Monitoring to test various harmful substance indicators in the wastewater. The wastewater can only be discharged after testing results meet relevant discharge standards.
