Integrated route of fast hydrothermal liquefaction of microalgae and sludge by recycling the waste aqueous phase for microalgal growth

•SAP after hydrothermal of sludge was used to cultivate the green microalga Chlorella sp.•Chlorella sp can effectively remove N and P in SAP.•The addition of CO2 was beneficial to increase the unit biomass of Chlorella sp and promote the accumulation of lipids.•F-HTL can obtain bio-oil with higher quality in a shorter reaction time.