Granule-forming method and waste water treatment method

A granule-forming method using a semi-batch reaction tank, the method comprising forming granules by repeatedly performing an operation cycle having an introduction step of introducing an organic matter-containing wastewater, a biological treatment step of biologically treating treatment target substances in the organic matter-containing wastewater by using a microbiological sludge, a settling step of allowing the microbiological sludge to settle, and a discharge step of discharging a biologically treated water that has been biologically treated, wherein

• the operation cycle includes a first operation cycle for performing the biological treatment step at a first sludge load, and a second operation cycle, performed after the first operation cycle, for performing the biological treatment step at a second sludge load, and
• the first sludge load is set such that a soluble BOD concentration inside the semi-batch reaction tank upon completion of the biological treatment step of the first operation cycle does not fall to a threshold value or below, and the second sludge load is set such that a soluble BOD concentration inside the semi-batch reaction tank upon completion of the biological treatment step of the second operation cycle does not exceed a threshold value.