Removal of phosphorus from aquaculture tailwater by different biochars

Abstract

Aquaculture tailwater with excessive phosphorous can easily lead to eutrophication of receiving water body. The existing treatment methods have disadvantages such as secondary pollution, high cost, and poor stability. Biochar as a low-cost adsorbent for phosphorus removal has been extensively studied, while basic data on the treatment of actual aquaculture tailwaters using biochar are lacking. Herein, four biochars, i.e., wood biochar(WBC), vancomycin fermentation residue biochar(VBC), eel manure biochar(MBC), and seawater-modified wood biochar(SBC), were prepared. Meanwhile, the phosphorus removal effects on three actual aquaculture tailwaters (freshwater, concentrated and marine tailwaters) were investigated. The results showed that the removal efficiency of total phosphorus by the biochars increased with the increase of dosage. Among them, SBC exhibited the best adsorption performance, followed by VBC. WBC was less capable of removing phosphorus, while MBC could not adsorb but even release phosphorus. The adsorption of phosphate in three tailwaters by SBC reached equilibrium at 30-60 min with the removal rate of 76.78%-93.07%, while the removal rate of organic phosphorus was as low as 14%-17%. The kinetic data for different forms of phosphorus could be well fitted by the pseudo-second-order. The adsorption mechanism of phosphate by SBC primarily included ligand exchange and chemical precipitation. This study is expected to provide guidance for the treatment of actual phosphorus-containing wastewater by biochars and promotes biochars and modified biochars from basic research to practical application.

Keywords

• biochar
• modification
• aquaculture tailwater
• adsorption
• phosphorus