An investigation into the efficiency of microalgal dynamic membrane photobioreactor in nickel removal from synthesized vegetable oil industry wastewater: A water energy nexus case study

Abstract

With growing concerns toward heavy metal pollution in wastewater due to their negative effects on human health and also the environment, a lot of effort has been put to find some novel and efficient methods in order to reduce or eliminate such hazardous elements. Chlorella vulgaris microalgae has been successful in heavy metal removal hence, the current study tries to develop an effective nickel removal technique using the combination of membrane separation along with microalgae dynamic membrane (DM) plus Chlorella vulgaris suspension in order to treat the synthetic vegetable oil wastewater. The experiments were divided into three phases. First phase was to comprehend the effect of microalgae's dry weight (DW) on nickel removal efficiency. With nickel's initial concentration being 10 mg. L−1, the results indicated that by tripling the concentration of microalgae, the removal efficiency increases by more than 66% within the first hour of treatment. There was no significance increase in treatment efficiency by increasing the treatment time from 1 h to 24 h. In phase 2, by initializing the nickel concentration to 10,12.5,17.5 and 20 mg. L−1, the experiments were done in a continuous mode inside a DM bioreactor (DMBR) after the microalgae DM was formed, which led to nickel's removal efficiency being reduced from 60% of previous phase to 22% after 1 h. In the third and last phase, fluidized microalgae inside a photobioreactor (PBR) plus micro-algae DM (DMPBR) were put in use. Comparing the results of this phase with last two phases, this phase with 72% removal compared to 63.6, 52 of previous phases, had the best results yet. To conclude, forming a dynamic membrane, not only preserves the primary membrane but also enhances the heavy metal removal efficiency.