Simultaneous water reclamation and nutrient recovery of aquaculture wastewater using membrane distillation

A large amount of aquaculture wastewater with high load of nutrients, organic matter, and microalgae will pollute receiving water body and needs to treat before discharge. In this work, membrane distillation (MD) with the ability to avoid non-volatile substances was used to purify water and simultaneously recover nutrients from aquaculture wastewater. Results showed that micro-structures have evenly distributed on the surface of polyvinylidene fluoride (PVDF) membrane using nylon taffeta substrate. Resultant membrane has surpassed superhydrophobicity benchmark. It achieved high water contact angle of 153.3° and low contact angle hysteresis of 8.4°. The continuous separation and treatment of fish farm wastewater showed a small and steady flux reduction of 1.4 kg/m²·h, indicating less fouling by the surface-printed membrane. In the batch process of feed concentration, the water recovery reached 86.3%. The retentate concentration of fish farm water is at least five times higher than initial concentration of ammonia (16.4 to 82.2 mg/L), phosphate (18.0 to 99.8 mg/L), and potassium (68.0 to 384.8 mg/L). This concentrated feed can use as primary nutrient of liquid fertilizer. In feed concentration process, except for ammonia (>86%), rejection of all selected inorganic substances is higher than 99%.