Membrane Filtration Pretreatment and Phytoremediation of Fish Farm Wastewater

Abstract

Phytoremediation is an effective and environmentally friendly method for the treatment and recycling of the wastewater generated by the aquaculture industry. This study investigated the phytoremediation performance of Spirodela polyrhiza on fish farm wastewater following filtration by three different microfiltration membranes. The overall goals of this study were to determine the effects of physical membrane filtration pre-treatment on the subsequent phytoremediation process. The nutrient uptake by S. polyrhiza and water quality after phytoremediation were monitored under a controlled environment for a duration of 14 days. The results showed that the smallest membrane pore size (0.2 µm) was the most effective in removal of suspended solids. However, it was also the fastest to foul. Therefore, a 20 µm pore membrane was chosen that had 3.1 times the filtration capacity by volume of the 0.2 µm membrane before fouling. The subsequent phytoremediation study showed that filtered wastewater has a significantly lower initial reading of water quality with 33%, 53%, 36% and 30% reduction of chemical oxygen demand (COD), turbidity, mixed liquor suspended solids (MLSS), as well as mixed liquor volatile suspended solids (MLVSS), respectively. The final reading for the nitrate, phosphate and ammonia level were 9.4 mg/L, 0.27 mg/L and 1.4 mg/L, respectively. This study indicates that combining phytoremediation with membrane filtration improves the overall performance of the remediation process when treating fish farm wastewater.