Microalgae cultivation and nutrients removal from sewage sludge after ozonizing in algal-bacteria system

The feasibility of growing algae in concentrated wastewater generated from sludge ozonation for simultaneous nutrients removal and biomass production was studied. The effects of bacteria addition into microalgae on nutrients removal, biomass yield and settleability, the growth rate of algae and concentrations of extracellular polymeric substances (EPS) and soluble microbial products (SMP) were investigated. The results showed that the growth rate of algae in algal-bacteria system (0.2182) was improved than in algae-only system (0.1852), while both of them are comparable with others reported previously. And the addition of bacteria enhanced COD, NH4+-N, TN and TP removal rate by 23.9 +/- 3.3%, 27.7 +/- 3.6%, 16.6 +/- 1.8% and 14.9 +/- 2.2%, respectively. And 32.8 +/- 0.7% of the TN and 50.3 +/- 1.8% of the TP were recycled from ozonated sludge-supernatant (OSS) being absorbed into algal-bacterial biomass. The algal-bacteria system also demonstrated advantages on biomass settleability and heavy metals removal. Finally, the mechanism involving matter exchange and algal bacteria system on OSS treatment in this study were discussed through evaluation of nutrients, SMP and EPS contents, nitrogen and phosphorus balance.