How Filtration Media Is Applied in Wastewater Systems
The rise in urban population has brought with it an increased demand for sanitation services. The global sanitation challenge has been addressed in several different ways across the globe. One of the methods used to keep modern cities clean is the use of large-scale wastewater management plants. The massive volumes of water that need to be treated every day have led to the development of several innovations in water treatment technology with the aim of eliminating all toxins and hazardous compounds and restoring water to acceptable levels either for domestic or industrial use. In some cases, the water simply needs to be treated to extract all harmful elements before it can be released into rivers or to groundwater sources.
Filtration is the simplest yet most effective way to extract impurities from water. In filtration, the wastewater is made to pass through a filtration screen or filtration medium which is porous enough to let the desired fluid through but block out the impurities. Filters can either use screens to separate the solids from the liquids or a filtration medium.
Types of filtration media
A filtration medium or media is a substantial layer of material that is laid in a filtration system to form a bed of material through which the wastewater will pass. The media could be made up of a single material or a combination designed to target a specific type of contaminant. The typical materials used to make filtration media include sand, crushed glass, anthracite, geo-textile fabric, ash and shredded tyres among others.
Anthracite is the big brother of the coal family because it has the highest energy density, highest carbon content and the fewest impurities of all the types of coal. Due to its robust nature and resistance to various chemicals, Anthracite is a popular filtration media for the purification of wastewater from cities and small industries and is specifically selected for the removal turbidity and suspended solids, SS, as well as iron.
- Filter Sand
Filtration sand is the standard filtration medium used for basic filters. It has fine grains that make it suitable for purifying drinking water. Due to its structure, filter sand works for both rapid physical filtration and slow biological filtration processes. It is also an indispensable component of multi-media filtration systems.
Gravel is normally applied at the bottom of the filtration system to act as support for other filtration media like Fine Sand and Anthracite. The gravel helps to maintain the structure of the filtration media keeping it from washing away with the wastewater. Laying about five different sizes of gravel rocks helps to make sure the water flows evenly through the media and maximizing the use of the filtration system.
- Manganese Sand
Manganese and Iron in wastewater can be extracted using a Manganese Sand filtration medium. This is done by dosing the raw water with chlorine and passing it through a filter media coated with manganese.
- Activated Carbon
Activated Carbon is a filtration medium that is used in chemical filtration. This media acts as a poly filter and is suitable for the elimination of a wide range of contaminants by making them stick to its numerous pores. It works well with organic or inorganic impurities such as copper and chlorine. It is also very good at extracting colour from contaminated water.
There are some cases where a standard filtration medium is not sufficient to eliminate the contaminants from your wastewater and a multi-media filter is necessary. These are filter beds that are made up of more than two materials.
Filters with two or three media materials are known and Dual and Tri-Media, anything more is a multi-media filter. Multi-media filters are used to clean wastewater that contains a wide range of contaminants that have different conditions of extraction. Technically, the multi-media filters are only necessary for systems where the Silt Density Index (SDI) value constantly goes above 3 and the turbidity is above 0.2, NTU.
The most common multi-media filtration systems consist of sand, anthracite coal and garnet as well as a layer of gravel at the bottom of the filtration column. The media is arranged such that the course material is placed at the top and reduce as you come down. This makes it possible for large impurities to be extracted easily at the beginning stages of the system.
There are as many filtration solutions as there are filtration media. What you need to keep in mind is the volume of water, the types of contaminants you wish to remove, your available budget.
You save a lot of money by doing some research into the materials available to you before you use them. A targeted approach to wastewater treatment saves you time and money.