Co-culture of Chlorella and wastewater-borne bacteria in vinegar production wastewater: Enhancement of nutrients removal and influence of algal biomass generation

Vinegar is an important seasoning and its annual output continues to increase in China. Vinegar production is accompanied by a large amount of wastewater which contains many nutrients, including acetic acid, nitrogen and phosphorus. In this study nutrients removal during the co-culture of Chlorella and wastewater-borne bacteria (Bacillus firmus and Beijerinckia fluminensis), as well as Chlorella biomass accumulation, pigment and lipid production in vinegar production wastewater were investigated. The removal rates for chemical oxygen demand (COD), total nitrogen (TN) and total phosphorus (TP) were significantly improved after the addition of the bacteria. At the end of the cultivation, the highest COD, TN and TP removal rates were improved by 22.1%, 20.0%, and 18.1%, respectively, compared with the control group without adding bacteria. The mean growth rates of the algae in most goups decreased slightly during the co-culture with the bacteria. The wastewater-borne bacteria Beijerinckia fluminensis effectively enhanced the pigment content of Chlorella sp. The chlorophyll a, b, and carotenoids concentrations were increased by >35.7%, 20.9% and 11.2%, respectively. This study demonstrated an efficient microalgae and wastewater-borne bacteria co-culture system that can be potentially used for vinegar production wastewater treatment and also the recovery of high-value byproducts of algal pigment may offset the decrease in algal biomass.