This former Samsen Water Treatment Plant, now the Thai Waterworks Museum in Bangkok (fig.), used a variety of water purification systems.

One such system is known as the slow sand filter, in which not the sand itself, but a complex biological film that grows naturally on the surface of the sand, is used to filter the water.

Whereas the sand used in filtering process was dredged from the Kwae River in Kanchanaburi (fig.), the water itself was pumped into the plant from the upstream Chao Phraya River nearby.