Sue Water Purification Plant No. 4 Slow Sand Filter

The Middle of the North Row

The Sue Water Purification Plant No. 4 Slow Sand Filter (末浄水場四号緩速ろ過池, Sue Jōsuijō Yongō Kansoku Rokachi) is a reinforced concrete filter bed built in 1931 at the Sue Water Purification Plant in Suemachi, Kanazawa City, Ishikawa Prefecture, and was registered as a national Registered Tangible Cultural Property on 28 August 2001. It lies west of the No. 2 filter, in the middle of the north row. It covers 1,375 square metres and has its own clear-water well to collect the filtered water.

The Sue Water Purification Plant No. 4 Slow Sand Filter faces No. 3 across the walkway. Slow sand filtration passes water gently down through a bed of sand. A living film forms on the surface of the sand and does much of the cleaning, so the method relies little on chemicals but needs a great deal of space. At Sue the answer was six filters, three on each side of the walkway that carries the supply axis west.

The Kanazawa City Public Enterprise Bureau dates the completion of all six slow sand filters to June 1931 and gives each clear-water well an area of 14 square metres. The original filters still carry the slow-filtration line today.

A Plinth and Three Steps

The filter was registered for its contribution to the historic landscape. In its entry for the Sue Water Purification Plant No. 4 Slow Sand Filter, the Agency for Cultural Affairs looks closely at the base of the well house.

On the south side, facing the walkway, stands a reinforced concrete house over the clear-water well, almost square in plan with a building area of 14 square metres. Its front faces the walkway, toward anyone walking by.

It sits on a plinth capped with granite that runs right round the building. At the front are three steps, flanked by wing walls that curve outward. A service building that almost nobody enters was given the bearing of an entrance porch.

The Kanazawa City Public Enterprise Bureau describes the six well houses as having front openings framed by convex curves like gateposts, rounded corners, and a stepped roof topped by a small dome. The entry for No. 4 describes the base; the entry for No. 5 describes the top. Together they give the whole building.

Seeing It

The Sue Water Purification Plant No. 4 Slow Sand Filter can be seen up close only on the plant's pre-booked group tours, which the bureau says cover the sedimentation basins and filters and last about 40 minutes. Tours are for groups such as local governments and community associations, and applications are due two weeks ahead.

The filter field lies well west of the front garden and cannot be approached from the area open without booking. From the walkway, stand in front of the well house and look for the granite-capped plinth and the three steps between curved wing walls.

Nothing is published on photography, so ask the guide. Directions and garden hours are on the Sue Water Purification Plant page.