Sue Water Purification Plant No. 5 Slow Sand Filter

Westernmost of the South Row

The Sue Water Purification Plant No. 5 Slow Sand Filter (末浄水場五号緩速ろ過池, Sue Jōsuijō Gogō 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. 3 filter, at the western end of the south 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. 5 Slow Sand Filter faces No. 6 across the walkway, with the collecting well beyond. 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 Well House with a Dome

Registered for its contribution to the historic landscape, the Sue Water Purification Plant No. 5 Slow Sand Filter is described by the Agency for Cultural Affairs chiefly through the house over its clear-water well.

The front opening is framed by convex curves that rise on either side like gateposts. The corners of the body are rounded rather than sharp, and on each side except the front two tall, narrow windows stand side by side.

The roof steps up in tiers and carries a small dome at the centre, which the Agency says gives the exterior its accent. The well house covers only about 14 square metres, but the stepped roof and dome give it enough height to register as a landmark among the low beds.

The Kanazawa City Public Enterprise Bureau presents this as the common design of all six well houses. The entry for No. 4 describes the plinth and steps, this one the opening and roof. Three identical houses on each side of the walkway also mark out the supply axis in three dimensions.

Seeing It

The Sue Water Purification Plant No. 5 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. On a tour, count the tiers of the roof and look at the shape of the dome; looking west along the walkway, the domed houses line up toward the collecting well.

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