Filtration aid and filtration treatment method

A method for treating wastewater including an inorganic unnecessary substance comprising an inorganic ion, comprising the steps of:

• providing a wastewater including an inorganic unnecessary substance containing at least any one of nickel, fluorine, iron, copper, zinc, chromium, arsenic, cadmium, and lead, and containing an inorganic ion which is at least any one of a nickel ion, a fluorine ion, an iron ion, a copper ion, a zinc ion, a chromium ion, an arsenic ion, a cadmium ion, and a lead ion;
• insolubilizing an inorganic ion contained in the inorganic unnecessary substance included in the- wastewater to form a microfloc of suspended solid matter;
• adding a composition comprising a filtration aid consisting of a pulverized product of Corchorus olitorius and a polyacrylamide to wastewater including the microfloc, wherein a median particle diameter of the pulverized product is 200 micrometers or greater but 850 micrometers or less, and wherein the adding amount of the Corchorus olitorius in the filtration aid is 2 mg/L or greater relative to a solid content in the wastewater including the microfloc;
• and
• filtering the wastewater to which the filtration aid has been added.