A method for treating wastewater or sludge comprises the steps of adding the wastewater or sludge to a reactor and mixing the wastewater or sludge with a stream to thereby decrease a ratio of alkalinity to ammonium in the reactor, the reactor containing ammonium oxidising bacteria that oxidise ammonium to produce nitrite and decrease pH.

An ion removal system includes: an electrolysis device configured to generate alkaline water and acid water by electrolysis; a hard water flow path to supply the electrolysis device with hard water; a first flow path and a second flow path through which the alkaline water and the acid water generated by the electrolysis device can alternately flow; a fine bubble generation device configured to generate and supply fine bubbles to the hard water flow path, the first flow path, or the second flow path so as to adsorb and remove metal ions in water by the fine bubbles generated; and a controller, wherein the controller controls the electrolysis device to perform a first mode in which the alkaline water is allowed to flow through the first flow path and the acid water is allowed to flow through the second flow path and a second mode in which the acid water is allowed to flow through the first flow path and the alkaline water is allowed to flow through the second flow path.

An ion removal system includes: an electrolysis device configured to generate alkaline water and acid water by electrolysis; a hard water flow path to supply the electrolysis device with hard water; a first flow path and a second flow path through which the alkaline water and the acid water generated by the electrolysis device can alternately flow; a fine bubble generation device configured to generate and supply fine bubbles to the hard water flow path, the first flow path, or the second flow path so as to adsorb and remove metal ions in water by the fine bubbles generated; and a controller, wherein the controller controls the electrolysis device to perform a first mode in which the alkaline water is allowed to flow through the first flow path and the acid water is allowed to flow through the second flow path and a second mode in which the acid water is allowed to flow through the first flow path and the alkaline water is allowed to flow through the second flow path.

A hydroponic system (1) using seawater, wherein seawater (W1) is used for hydroponic cultivation of salt-tolerant plants, including a water supply pump (21) that pumps up, from the sea (S), seawater (W1) having a salinity, a bacteria content and an unwanted matter content are less than or equal to predetermined threshold values; a water tub (30) that stores seawater (W1) pumped up by the water supply pump (21) and accommodates salt-tolerant plants (P) to be cultivated; and a filter (27) that removes bacteria and unwanted matter from the seawater (W1) obtained from the sea (S); wherein the seawater (W1) from which the bacteria and the unwanted matter have been removed by the filter (27) is fed to the water tub (30).

A hydroponic system (1) using seawater, wherein seawater (W1) is used for hydroponic cultivation of salt-tolerant plants, including a water supply pump (21) that pumps up, from the sea (S), seawater (W1) having a salinity, a bacteria content and an unwanted matter content are less than or equal to predetermined threshold values; a water tub (30) that stores seawater (W1) pumped up by the water supply pump (21) and accommodates salt-tolerant plants (P) to be cultivated; and a filter (27) that removes bacteria and unwanted matter from the seawater (W1) obtained from the sea (S); wherein the seawater (W1) from which the bacteria and the unwanted matter have been removed by the filter (27) is fed to the water tub (30).

To provide a material capable of adsorbing lead from water with a pH of 8 or more. A porous body of a titanium-containing compound, which has a bulk specific gravity of 0.4 g/cm.sup.3 or less, is used as an adsorbent.

To provide a material capable of adsorbing lead from water with a pH of 8 or more. A porous body of a titanium-containing compound, which has a bulk specific gravity of 0.4 g/cm.sup.3 or less, is used as an adsorbent.

To provide a heavy metal adsorbent in which elution of aluminum from a zeolite is suppressed. A compound, which is a hydrous oxide or a hydroxide of Si, Ti, Zr, Ce or La, is mixed with the zeolite.

To provide a heavy metal adsorbent in which elution of aluminum from a zeolite is suppressed. A compound, which is a hydrous oxide or a hydroxide of Si, Ti, Zr, Ce or La, is mixed with the zeolite.

The present invention relates to a water purifier filter, and a water purifier including the same. The water purifier filter and the water purifier including the same according to the present invention include a filter housing including an inlet and an outlet, and a filter module provided in the filter housing to purify water introduced through the inlet and to supply the water to the outlet, and a material of the filter module includes sodium orthotitanate (Na.sub.4TiO.sub.4) to remove a heavy metal under water, thereby effectively removing a heavy metal including cadmium under water.