Water Treatment "Part 26": Various additional filtration techniques.

Multi-layer filtration:

Water is filtered through many layers of material with varying degrees of fineness when using multi-layer filtration. The filter layers' granule sizes get smaller towards the bottom, the water is first filtered by passing through the layer with the coarse granules.
In order to accelerate the rate at which the material settles at the surface while the water flows downhill, the granules' size and density have to be selected, as well as to avoid combining the components of two distinct layers while backwashing the filter.

A layer of anthracite, which has high particle size and low density, forms part of the multilayer filter. The next layer is made up of sand, then a dense layer of garnet with small granules. Smaller solids are therefore maintained in the lower sections of the filter surface while larger solids are kept in the top layer.

Illustration of a typical drinking water treatment process.

Dry filtration:

When ammonia levels in the water are high, dry filtering is utilised, but this does not imply that this process is confined to just eliminating ammonia; it also removes iron and manganese. A continuous gaseous exchange takes place between the air and the water as it passes over a filtration surface that contains granular filtration material while air is flowing either upward or downward. Since certain bacteria might grow during dry filtering, quick filtration is frequently carried out after dry filtration to get rid of these harmful bacteria.

Upflow Filtration:

The height of the water is adjusted during this process to account for the hydrostatic water pressure required to maintain fluid balance, as well as flow and blockage resistance, which are greatest near the bottom of the filter surface.

Limestone filtration:

The material used to fill limestone filters is calcium carbonate granules or semi-fired dolomite stones. The imbalanced water being treated causes the lime stone granules to disintegrate during the filtration process, necessitating frequent replacement of the filter with new granules. Iron and manganese compounds are eliminated during this procedure.

References:

• [Introduction to Water Chemistry (Pollution- Treatment- Analysis). Dr. Nasser Al-Hayek. Publication of the Higher Institute for Applied Sciences and Technology (HIAST). Syrian Arab Republic, 2017.]
• Taparhudee, Wara (2002). "Applications of Paddle Wheel Aerators and Diffused-Air System in Closed Cycle Shrimp Farm System" (PDF). Witthayasan Kasetsart (Sakha Witthayasat). 36: 408–419. Retrieved 26 April 2020.
• Unsafe water kills more people than war, Ban says on World Day". UN News. 22 March 2010. Retrieved 10 May 2018
• Raymond Desjardins- Livre: Le traitement des eaux- 2éme edition- Ecole Polytechnique de Montréal- 1997- ISBN 2-553-00643-8
• Drinking Water Treatment- EDX- Delft University of Technology.
• Book- Drinking Water: Principles and Practices- by Hans J C Van Dijk (Author), Jasper Q J C Verberk (Author), Peter J De Moel.