| 21. | This replaced the sand filters traditionally used.
|
| 22. | The Horizon's problem was traced to spray from the whirlpool tubs, a result of contaminated sand filters.
|
| 23. | The works were built in 1908 and by 1924 there were five reservoirs and eight sand filters.
|
| 24. | Slow sand filters now are also being tested for pathogen control of nutrient solutions in hydroponic systems.
|
| 25. | The purification system was a slow sand filter design that became obsolete by the late 20th century.
|
| 26. | Legionella was traced in the tubs'sand filter.
|
| 27. | The rapid filters and the slow sand filters engaged in competition as to which technology was superior.
|
| 28. | Most sand filters have high-rate elements that use the entire depth of the sand to remove particles.
|
| 29. | Ash can enter filtration systems such as open sand filters both by direct fallout and via intake waters.
|
| 30. | "' Slow sand filters "'are used in water purification for treating raw water to produce a potable product.
|
