A method for nitrate removal from drinking water. The method includes adapting a sludge including hydrogenotrophic denitrifiers (HTDs) by dominating the HTDs in the sludge, cultivating a microalgae biomass, forming a microalgae-HTD biomass by cultivating a mixture of the adapted sludge and the cultivated microalgae biomass, nucleating a plurality of microalgae-HTD granules by cultivating the formed microalgae-HTD biomass in a sequencing batch (SB) mode with a constant HRT, growing the plurality of microalgae-HTD granules by cultivating the nucleated plurality of microalgae-HTD granules in an up flow (UF) mode with a reducing HRT, and continuous nitrate removal from nitrate-contaminated water with a minimum HRT over the grown plurality of microalgae-HTD granules.