Vinasse Wastewater Treatment through Azolla microphylla-Mediated Phytoremediation and Biomass Valorization

Abstract

This study investigated an integrated resource-recovery approach for vinasse treatment, using Azolla microphylla phytoremediation followed by the production of organic fertilizer from the harvested biomass. Pre-treated vinasse obtained from a molasses-based bioethanol plant in Sukoharjo, Central Java, Indonesia, was subjected to phytoremediation for 7 days using 100 g of A. microphylla in 3 L of wastewater. The process markedly improved wastewater quality, as reflected by reductions in COD from 676 to 59 mg/L (91.27%), BOD from 94 to <2 mg/L (98.49%), sulfide from 203 to 146 mg/L (28.08%), TSS from 150 to 138 mg/L (8.00%), and turbidity from 120 to 23 NTU (80.83%), while pH increased from 7.7 to 8.3. The harvested biomass was then mixed with vinasse sludge, goat manure, rice bran, and sawdust at a 1:1:1:1:3 ratio and fermented for 30 days using EM4. The resulting organic fertilizer met national technical requirements, with pH of 8.29, total nutrient content of 3.97%, moisture content of 8.71%, organic carbon of 31.21%, and a C/N ratio of 18.57. These findings demonstrate that A. microphylla can simultaneously remediate vinasse wastewater and produce value-added compost, supporting circular-economy-based waste management in the bioethanol industry.