Introducing a dual approach to industrial wastewater reclamation and microalgae harvesting by filamentous fungus

Abstract

Abstract

Fungal-assisted bioflocculation offers a promising and economical method for harvesting microalgae, although there is a lack of studies on fungi and microalgae co-cultivation in real/unsterilized wastewater without additional carbon sources. In this study, the capability of fungus (Aspergillus oryzae) for the simultaneous purposes of microalgae (Chlorella sorokiniana) harvesting, purification of pretreated fish processing wastewater (FPWW) (free from oils and fats) and recycling of algal/fungus pellets was investigated. A. oryzae was successfully produced in pellet form at pH 4–5 and used first in harvesting a pure C. sorokiniana suspension. The highest harvesting efficiency (98 %) within 6 h was obtained under optimised conditions of an initial pH of 9, 150 rpm, and a fungus:algal biomass ratio of 2.5:1. SEM analysis showed that successful fungus-microalgae symbiosis was established by integrating A. oryzae hyphae with C. sorokiniana cells. The formed algal/fungus pellets were further used to purify FPWW. The results showed that both microalgae monoculture and co-culture had high total nitrogen (TN) (89.6 %, 93.4 %), total phosphorus (TP) (95.4 %, 92.9 %) and chemical oxygen demand (COD) (67.9 %, 69.4 %) removal efficiency. A. oryzae pellets showed potential for use as a bioflocculant in harvesting microalgae and FPWW suspension, with harvesting efficiency of 99 %. Also, algal/fungal pellets show potential for recycling, although more investigation is needed to assess their long-term effects. These findings suggest a possible advance in microalgae harvesting and nutrient removal with algal/fungus pellets, offering a cost-effective solution to enhance sustainability and productivity in algal-based treatment systems.