PURPOSE: To efficiently adsorb and treat the soluble components such as humus in water at extremely low cost at large amounts by mixing organic substance with incineration ash of sludge and granulating this mixture and thereafter sintering the granulated bodies and bringing waste water or potable water into contact with the porous sintered adsorbent.

CONSTITUTION: Organic substance (e.g. polyacrylic acid and PVA, etc.), having thickening effect is sufficiently mixed with incineration ash of sludge. This mixture is granulated at about 0.5-10mm diameter by the binder effect of the organic substance. These granulated bodies are sintered at about 800-1000°C to make organic substance into ashes. Then a porous sintered adsorbent having many holes in the inside is obtained. Thereby both the area in which the adsorbent is brought into contact with waste water and potable water and the area for adsorbing the soluble components are increased and also adsorbing performance can be remarkably improved. The soluble components such as humus in water are adsorbed to this porous sintered adsorbent and efficiently removed from waste water or potable water at extremely low cost at large amounts.