Preparation of ceramic filters using waste foundry sand and its application in algae separation from open ponds

ABSTRACT The graphical abstract shows an algal bioreactor using a ceramic filter made from waste foundry sand enables water reuse, while separated algae can be utilized for sustainable biofuel production. Waste foundry sand (WFS) is generated in metal foundry industries. It is used in landfills and construction. In this study, WFS was used to prepare a porous ceramic filter by pressing and sintering techniques. The properties (e.g., specific gravity, bulk density, water absorption, etc.) of WFS were studied. Groundnut shells were added to the WFS to increase the filter pores. The porosity and pore size of the filters improved, while the compressive strength decreased. In an open pond, suspended algae grow in large volumes at relatively low concentrations. Filtration becomes the preferred option over sedimentation, as it retains a significant number of algae cells. Algae water collected from an open pond was used in the algal bioreactor. The filter module was submerged in the reactor. The filters separated 95% of the algae, and this separation rate remained constant throughout the study period, maintaining a water flux of 14 Lm−2 h−1 at a crossflow velocity of 5 m/s. Hydraulic cleaning was sufficient to recover the water flux, and the filter was reused for six cycles of operation. These data show the potential applications of WFS filters for algae harvesting and recovering fresh water for reuse.