Progressive pollution abatement in raw dairy wastewater induced by the algae Poterioochromonas malhamensis with a high-value biomass yield

Abstract

This work aimed to systematically abate in batch mode organic pollutants from raw dairy wastewater (DW) with high values of chemical oxygen demand (COD, ∼10.3 g L−1), total organic carbon (TOC, ∼2.4 g L−1), and total nitrogen (TN, ∼0.28 g L−1) by using the Poterioochromonas malhamensis algae strains. In this regard, variables such as fractions of DW (40–100%, v/v), mineral nutritional inoculum addition (0–100%, w/v) and CO2-enriched air (2–8%) were proposed to address a study in optimizing conditions with new insights on algae production. As controlled photobioreactors (PBR), a set of tubular PBRs and a pair of flat-plate PBRs (FP-PBR) surrounded by fluorescent lamps and pumped by CO2-enriched air at a flow rate of 1.4 L min− 1 per litre were used. A Box-Behnken design (BBD) for algal growing was applied using the set of tubular PBRs to get a better reduction in TOC, TN and COD, defining an optimized condition. On the best tubular PBRs-based outcome and including a holed baffles system for hydrodynamically providing a flashing light state, 9-day kinetic experiments based on a pair of FP-PBRs were performed to provide more insights on how to enhance the algal yield and COD, TN and TOC reduction. A biomass yield rate of 1.1 g L−1 per day was attained using FP-PBRs, being comparatively 10% better than tubular PBRs. Additionally, the organic pollution abatement in DW was highly significant, with a decrease of about 98%, 95%, and 92% in COD, TN and TOC, respectively, besides changing the initial bacteria diversity to another less harmful one.