Synthesis and application of hydrogels with microalgae-bacteria for nutrient and PFDA removal from wastewater

Abstract

The aim of this study was to evaluate the performance of hydrogels with a consortium of microalgae bacteria and activated carbon (AC) as function of nutrient removal in wastewater containing PFDA. Hydrogels were synthetized from polyvinyl alcohol (PVA), sodium alginate (SA), and included biomass (microalgae-nitrifying bacteria), AC or both exposed to different aqueous conditions, namely raw wastewater, synthetic wastewater (SWW) with and without PFDA and PFDA solution. The performance of hydrogels was evaluated based on the change in ammonium (NH4) and nitrate (NO3) concentrations, chemical oxygen demand (COD), nitrification rate and other parameters during 72 h. Ammonium removal was possible by all hydrogels. The nitrification process was carried out by all hydrogels. Activated carbon was found to be effective as a nutrient adsorption medium in the presence of perfluorodecanoic acid (PFDA). Regarding COD, this increased in all hydrogels could be due to the leaching the components of hydrogel. The best performance was observed for the hydrogel with 5 % of biomass without AC with a nitrification rate of 0.43 mg N/g TSS·h. Hydrogel with AC (HC) was the most effective for removing PFDA (38.5%) and the hydrogel that presented that highest resistance to PFDA during nutrient removal. HBC was the most efficient hydrogel for removing nutrients in presence of PFDA. Results indicated that the presence of PFDA did affect the processes of nutrient elimination in hydrogels with biomass due to the toxicity of the emerging pollutant.