Water filtration systems are one of the most important stages of water treatment in industrial and commercial facilities, whether filtration is the main treatment step or part of a complete system with a softener, reverse osmosis (RO) or disinfection units.
No single type of filter suits every application: the filtration system is chosen according to the water, the contaminants it carries and the purpose of the treatment.
Why do facilities need water filtration?
Raw water can carry suspended solids, sand, silt, some organic matter and fine particles. These can reduce the efficiency of equipment, production lines, pumps and membranes, block pipes and fine filters, or disturb the later stages of a treatment plant.
Filtration reduces the load on the other treatment units and makes the whole system more stable.
Sand filters
Sand filters are among the most widely used filtration systems in water treatment plants. The water passes through layers of filter media selected according to the system design.
They are typically used to remove a large share of the suspended solids and reduce turbidity ahead of the later treatment stages — in industrial water plants, well-water treatment systems and some pre-treatment stages before RO.
Multimedia filters
Multimedia filters use more than one type of filter media in the same vessel. The differences in media size and density spread the captured particles through the filter bed instead of concentrating them in one zone.
This can improve filtration and extend the run time between backwashes. The media and their arrangement are chosen according to the water quality and the operating requirements.
Activated carbon filters
Activated carbon is used in many water treatment applications. Its main uses include reducing some organic substances, improving the properties of the water and, in some applications, removing free chlorine.
Chlorine removal is especially important ahead of reverse osmosis membranes that can be damaged by continuous exposure to chlorine. The design of a carbon filter depends on the flow rate, the water quality and the required contact time.
Cartridge filters
Cartridge filters are usually used as a fine filtration stage. They come in different micron ratings, chosen to suit the application.
In RO plants a cartridge filter is usually installed ahead of the membranes as the last line of protection against fine particles. Cartridges need regular replacement according to the water quality, the operating rate and the pressure drop.
What are filter media?
A filter’s performance does not depend only on the size of the vessel or the pump, but also on the filter media used — sand, activated carbon and multimedia beds in different grades and sizes. The media should be chosen for the substance to be removed, not on price alone.
Why backwashing matters
As a filter runs, suspended solids build up in the media. Many systems therefore need a backwash to remove the accumulated material and restore the filter’s efficiency.
When to backwash depends on the pressure drop, the operating conditions and the water quality. An effective backwash keeps the filter performing and extends the life of the media.
How do you choose the right filter?
The choice starts with a water analysis and the required flow rate:
- If the main problem is turbidity and suspended solids, sand or multimedia filters may be the right choice.
- If chlorine and some organic matter must be dealt with, activated carbon may be part of the solution.
- Where fine filtration is needed ahead of RO or sensitive equipment, cartridge filters are used.
Many projects combine more than one type to get the best result.
How does filtration relate to RO plants?
Some believe that an RO plant removes the need for filtration; in many applications the opposite is true, because reverse osmosis membranes need properly prepared feed water.
The better the pre-treatment, the lower the risk of fouling and the steadier the membranes run. Filtration is therefore an essential part of protecting the investment in an RO plant. See also: how to choose the right reverse osmosis system for your facility.
Spare parts and consumables
Filtration systems need regular consumables and spare parts such as cartridge filters, filter media and some valves and components. Having them on hand in the right specifications reduces downtime and keeps the plant performing. Browse our parts and consumables.
Aqua System filtration solutions
Aqua System designs, supplies and installs filtration and water treatment systems, and supplies the cartridge filters, filter media and components needed to run them. The right design is defined from the water analysis, the flow rate and the requirements of the use.
Want to choose the right filtration system for your water source? Contact Aqua System and send your water analysis for a technical proposal that suits your project.
