1、 Project Background
Donghai Fisheries Co., Ltd., located in Peru, is a modern canned fish production enterprise with an annual production capacity of 10000 tons. The wastewater generated during its production process has typical industry characteristics: the daily discharge of wastewater is about 800 tons, the oil content is as high as 350-400mg/L, far exceeding the discharge standards, and it also contains a large amount of protein, fish scale debris, and residual processing materials. The COD concentration is in the range of 2500-3000mg/L for a long time. The traditional “grid+air flotation+biochemistry” process can remove some pollutants, but the efficiency of the pressure filtration process is low, and the moisture content of the filter cake is as high as 75%, which not only leads to a sharp increase in the cost of subsequent sludge treatment, but also the oil content in the effluent still fluctuates between 80-120mg/L, making it difficult to achieve stable standards.
2、 Core Challenges and Solutions
Difficulties in oil separation:
The oil in canned fish wastewater exists in both emulsified and suspended states, and traditional air flotation processes are difficult to completely break the emulsion. The project team introduces a program-controlled automatic hydraulic chamber filter press, paired with oil resistant polypropylene filter cloth, to achieve oil retention through three-stage filtration:
Pre treatment stage: The wastewater is first treated with an oil separator to remove floating oil, and then FeCl Ⅲ coagulant (dosage of 400mg/L) is added to disrupt colloidal stability, forming flocs with particle size>50 μ m;
Filter pressing stage: Under a feed pressure of 0.8 MPa, a dynamic filter cake layer is formed on the surface of the filter cloth, which physically intercepts oil droplets with a particle size greater than 1 μ m. At the same time, the convex structure on the surface of the filter plate strengthens the mechanical screening of emulsified oil;
Squeezing stage: Apply a pressure of 1.2MPa to the filter cake through a hydraulic system, further extrude the oil, and ultimately reduce the moisture content of the filter cake to below 55% and the oil content to less than 8%.
Improvement of solid-liquid separation efficiency:
The supporting automatic unloading conveyor belt system (with a bandwidth of 800mm and a conveying speed of 0.5m/s) realizes the full process automation of pressure filtration, unloading, and transportation:
Intelligent linkage: After the filter press completes one working cycle (about 45 minutes), the filter plate automatically opens and the filter cake slides down to the conveyor belt by gravity;
Anti sticking design: The surface of the conveyor belt is treated with a PTFE coating, combined with a high-pressure water spray device, to avoid conveying blockage caused by filter cake adhesion;
Resource utilization: Filter cake with a moisture content of 55% can be directly used as feed raw material, and it is estimated that it can generate approximately 120000 yuan in by-product income annually.
Box type filter press: equipped with a PLC control system, it can automatically adjust the feed pressure and pressing time according to the inlet water quality. Actual test data shows that the electricity consumption for treating one ton of wastewater is only 0.85 kWh, which is 40% lower than traditional plate and frame filter presses;
Conveyor belt: seamlessly connected to the discharge port of the filter press, adopting modular design, can quickly replace worn parts, and the maintenance cycle is extended to 6 months.
3、 Implementation effect and economic benefitsEnvironmental benefits:
The oil content in the effluent has decreased from 120mg/L before the renovation to 12mg/L, with a COD removal rate of 97% and an annual reduction of approximately 28 tons of oil emissions;
The moisture content of the filter cake decreased by 20%, and the amount of sludge transported outside decreased from 60 tons per month to 22 tons, reducing transportation costs by about 70%.
economic performance:
The annual revenue from the resource utilization of filter cake is 120000 yuan, offsetting 60% of the depreciation cost of filter press equipment;
The combined cost of electricity consumption and medication has decreased by 35%, resulting in an annual savings of approximately 250000 yuan in operating expenses.
social results:
After the implementation of the project, the enterprise passed the ISO 14001 environmental management system certification, becoming a benchmark for environmental protection in the local aquatic product processing industry and promoting the improvement of regional green manufacturing level.
4、 Customer reviews
By introducing a combination solution of box type filter press and conveyor belt, we have completely solved the long-standing problem of wastewater treatment. Now, not only can we achieve stable and compliant discharge, but the filter cake can also be used as feed raw material to create additional income. The intelligence level of this equipment far exceeds expectations, and the operation and maintenance costs have been reduced by nearly half
——Rene, Production Director of Donghai Fisheries Co.,
Post time: Aug-25-2025