Application of Hollow Fiber PVDF Membrane for Wastewater Recovery in Food Processing

Food manufacturing generates large volumes of wastewater every day from cleaning raw materials, equipment flushing and workshop floor washing. The wastewater features high COD, suspended solids and organic matter. Traditional treatment processes such as sediment tanks, air flotation and quartz sand filtration can remove part of the pollutants, yet the outlet water quality fluctuates greatly. The recovered water often fails to meet the standard for workshop reuse, and the occupied area of the whole system is relatively large.

Hollow fiber PVDF membrane is a pressure-driven membrane separation medium. Its asymmetric pore structure can intercept suspended particles, colloids and macromolecular organics under certain transmembrane pressure. The treated clear permeate can be reused for equipment cleaning, raw material washing and greening irrigation after simple disinfection. The concentrate with high organic content can be further sent to biochemical tank for degradation. The whole set of recovery system generally includes raw water tank, self-priming pump, bag filter, PVDF membrane module, backwash tank, chemical cleaning tank and automatic control cabinet.

The operation mode of the system adopts intermittent filtration combined with online backwashing. During normal filtration, the wastewater penetrates from outside the fiber to the inner cavity, and the clean water flows out through the collecting pipe. After running for a fixed period, the system automatically stops filtration and starts backwashing with permeate water to flush the sludge layer attached to the membrane surface. When the flux declines obviously, combined chemical cleaning is carried out, including sodium hypochlorite cleaning for organic pollution and citric acid cleaning for inorganic scaling. Reasonable TMP control and regular cleaning are the core to extend the service life of PVDF hollow fiber membrane.

Compared with conventional treatment technologies, the PVDF hollow fiber membrane recovery system has obvious advantages. It occupies less space, runs automatically, and the effluent quality is stable and not easily affected by the fluctuation of inlet water. Factories can reduce tap water consumption and total wastewater discharge, so as to lower water cost and environmental compliance pressure. In practical projects, this technology has been successfully applied in fruit juice factories, dairy workshops and starch processing plants.

However, there are still challenges in actual operation. High concentration of protein and viscous polysaccharide substances are easy to form compact fouling layers on the membrane surface, which leads to flux attenuation. Therefore, pre-treatment is essential. A pre-filter or air flotation unit should be installed before the membrane system to remove most large suspended solids and oil substances. Operators also need to record the flux and pressure data daily, formulate scientific cleaning cycles and avoid overloading the membrane.

With the stricter industrial water-saving and emission-reduction requirements, the reuse of food wastewater has become an important part of factory sustainable production. PVDF hollow fiber membrane water recovery technology provides a reliable solution for food enterprises to realize water recycling. With optimized pre-treatment and standardized operation management, the membrane system can maintain stable performance for a long time and bring continuous economic and environmental benefits to customers.