Wastewater from the food industry often contains high concentrations of contaminants such as solids (SS), chemical oxygen demand (COD), ammonia nitrogen and total phosphorus. The sources and components of this wastewater are diverse and complex because they involve the production of a wide range of products such as alcohol, meat, and dairy products.
To sum up, the sources of contamination of food wastewater can be divided into the following categories:
1. Raw material cleaning stage: In the process of food processing, the dirt generated by the cleaning of the raw material surface enters the water, which significantly increases the content of suspended solids in the sewage.
2. Production process: Due to the presence of fats, salts, sugars and proteins in raw materials, these components that are underutilized in production are eventually discharged into water and become the main source of pollutants such as COD, ammonia nitrogen and phosphorus.
3. Chemical additives: The use of preservatives, additives and other chemicals in the molding stage further increases the difficulty of wastewater treatment.
A food company was faced with the challenge of wastewater treatment, and it was difficult to meet wastewater discharge standards due to many problems with existing facilities. The company needed to expand and renovate the wastewater treatment plant, with a design influent COD concentration range of 4000-7500mg/L and ammonia nitrogen concentration of 20-50mg/L.
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1. Pretreatment
In the face of suspended solids problems, in addition to improving existing facilities, the introduction of coagulation flotation technology is key. Suspended solids are polymerized into large flocs by coagulants and flocculants, which are then adsorbed onto air bubbles and brought to the surface of the water for removal. This process greatly improves the cleanliness of the wastewater and creates favorable conditions for subsequent biochemical treatment.
2. Biochemical treatment
Due to the high concentration of COD in the initial wastewater, the traditional aerobic biological treatment method (A2/O) is no longer sufficient to meet the treatment needs. Therefore, it is necessary to add a UASB reactor after the hydrolysis acidification tank to strengthen the removal of organic matter in the wastewater. The UASB reactor is an efficient and proven anaerobic treatment technology suitable for environments with high concentrations of organic matter, which degrades organic matter into carbon dioxide and methane through microbial action.
The structure of the UASB reactor includes a granular sludge layer, an influent distribution system, a suspended sludge layer and a three-phase separator. The A2/O process further assumes the responsibility of denitrification and phosphorus removal, and effectively reduces the concentration of ammonia nitrogen and total phosphorus through the synergistic effect of anaerobic, anoxic and aerobic environments.
3. In-depth processing
At the end of the process, MBR membrane technology is introduced as a last line of defense. The MBR membrane process not only replaces the traditional sedimentation, coagulation, filtration and other steps, simplifies the process flow, reduces the floor space, but also realizes the complete separation of hydraulic retention time and sludge age due to its efficient retention performance, and enhances the operational stability of the system.
After this series of treatments, the food company's wastewater treatment capacity has been significantly improved, and it can stably meet the discharge standards, reducing the potential impact of wastewater treatment problems on production. If you find this article helpful, please don't skimp on your likes, followers, and favorites.