Seawater Filter: Ultimate Guide

Without high-quality seawater filter, you will experience high corrosion and possible system shutdown or breakdown.

So, how do you ensure all equipment in the maritime industry continues to operate without any problems?

You need a seawater filtration system – and that’s exactly what you’re going to learn in this guide.

It focuses on various types of seawater filters, a suitable material, application, working principle, etc.

By the end of this guide, you’ll definitely be an expert in this industry.

Let’s dive right in.

What is a Sea Water Filter?

These are special types of filters that remove all possible contaminants from seawater.

More importantly, seawater filters can separate salt from water, making it safe for most applications.

Most of these filters come as a special semipermeable membrane that offers a cost-effective way of filtering sea water.

The filters require less thermal energy that distillation plants.

Seawater desalination process

Seawater desalination process – Photo courtesy: Membrane Solutions

With that in mind, let me take you a step further and explore the various types of seawater filters in the market.

Types of Sea Water Filters

There are different types of seawater filter that you can choose depending on your application.

In this section, I am going to explain to you the three types of seawater filters that are available in the market.

Keep reading.

1. Self-Cleaning Filter

As the name suggests, a self- cleaning filter refers to a kind of filter that automatically cleans itself when clogging occurs.

The advantage of this is that there is a continuous filtration of your seawater which allows your application to function continuously.

Self cleaning filter

Self-cleaning filter

With a large holding area for the contaminants, your filters can continuously filter the contaminants in the sea water.

Usually, most self- cleaning filters have two filter elements which help in the filtration of the sea water.

The availability of a clogging indicator in these filters can assist you in indicating the clogging level of the filter element.

The advantage of this is that you will be able to monitor the pressure level of your level which in turn ensures efficiency in your filtrations.

In some types of automatic filters, once the clogging indicator turns on, the cleaning process immediately kicks off.

2. Automatic Backwash Filter

The main characteristics of an automatic backwash filter are the cleaning method.

An automatic backwash filter uses the backwash method to clean its filter element.

Backwash method refers to the use of seawater to remove the contaminants from the filter elements.

What happens is that there is pumping of the sea water by pumps into the filter elements.

The pressurized water forces the contaminants on the filters to flow down the filter housing and out through the drainage valve.

The fact that it is automatic ensures that there is minimal interference during the filtration process.

3. Simplex/Duplex Filter

A simplex filter is a type of seawater filter that has one filter element for filtration of your seawater.

The main characteristics of this kind of filter are the presence of only a single filter element.

This implies that during filtration, your filter only uses this filter till when it reaches the clogging point.

At this point, you have to shut down your application to unclog the filter element.

As you will observe, a simplex filter is only suitable for applications that are not continuous due to the shutting down time.

In continuous applications, you can conveniently use a duplex filter.

The main characteristics of this filter are the presence of two filter elements which assists in the filtration of your seawater.

What happens is that there is an alteration between the two filter elements during the filtration process.

That is, when one filter element is working, the other remains completely shut.

This is possible by the presence of airtight valves.

During filtration, one of the filtration element functions till clogging happens.

At this point, the valve shuts the clogged filter elements and directs the seater into the other filter element for filtration to continue.

At that moment, you need to unclog the clogged filter element.

In modern duplex filters, the unclogging is automatic.

There are various ways that this happens including backwashing.

Backwashing refers to the removal of the contaminants from the filter element by the use of pressure.

What happens is that pumping of water by pumps takes place from the source into the filter element.

As this happens, the pressure forces the contaminants out of the filter elements and down to the filter housing.

From there, it is discharged out through the discharging valve.

Sea Water Filter Material

You can have different materials making up your seawater filter.

The choice of which material is best for your filter material will depend on various conditions such as the temperature and pH level of your seawater.

Seawater filter

 Seawater filter

However, the primary materials include stainless steel material and super duplex stainless steel.

This is particularly important when you are choosing a particular seawater filter for your application.

The reason for this is that you can have different filter materials for different applications.

To be able to understand this, let’s have a look at the characteristics of these materials.

There is high regard for the use of stainless-steel filter.

This is because of the numerous advantages it has over other types of materials.

a) Corrosion Resistant Material for Seawater Filter

You can use stainless steel seawater filters in seawater filtration since it is corrosion free.

This is particularly important since sea water is salty hence can quickly corrode the filter.

Section of seawater filter

 Section of seawater filter – Photo courtesy: Filter Safe

You can, therefore, use such filters indefinitely without the need of worrying about the corrosion element on your filters.

That brings us to the second advantage of using a stainless-steel seawater filter.

b) Low maintenance cost of sweater filter

As a result, the main cost of your filters is the purchasing and installation process.

With other types of seawater filters, you have to consider the cost of regularly maintaining the filters.

Such costs include the replacement cost of the filter element after corrosion.

On the contrast, with stainless steel sea filters, you won’t include this cost.

The fact that you can use stainless steel for high-temperature filtration is the other reason that these filters are of standard application.

c) High heat resistance

Actually, stainless steel sea filters have a high heat resistant effect which ensures that you can filter your seawater at any given time.

This is due to the availability of multiple solder joints as well as the multilayer edging.

This aspect is vital since most seawater filters are near the source which usually experiences high temperature.

Modern sea filters have the backwashing option installed which ensures cleaning of your filters with minimum human interference.

Stainless steel filters can withstand the backwashing force.

Stainless steel filters can adjust to the sea water quality fluctuation as well as achieving the backwashing ability of the filter.

d) Filter is lightweight and flexible

Lastly, the advantage of using stainless steel filters is that it is lightweight and flexible.

I know it may sound untrue, but it is a fact that stainless steel is lightweight.

You can, therefore, use it at various stages of your filtration process.

The fact that it is flexible implies that you don’t need a professional to install the filter in your filtration system.

Due to advancement in technology, most industries of late are manufacturing duplex stainless-steel filters.

These filters have superior characteristics to the stainless-steel seawater filters.

These characteristics include resistant high temperature, high anti-corrosion capability as well as high holding capacity.

You can consider choosing between these two materials when you are making a consideration as to which filter to use for your application.

Application of Sea Water Filters

At the end of the day, you might want to know where to use these seawater filters.

The sure thing is that you cannot buy a product you don’t know where to apply.

To assist you in this, let’s have a look at the areas where you can use seawater filters.

There are a lot of areas where you can apply seawater filters.

However, the common application areas include the following.

· Ballast Water Treatment

One of the common areas that you can use a seawater filter is during the ballast water treatment process.

This is important in ensuring clean and safe water for drinking.

Ballast water treatment

 Ballast water treatment – Photo source: Marine Insight

One of the essential steps in water treatment is the filtration process.

Water filtration is the removal of particles and unwanted contaminants from water.

Filtration takes place in some ways including straining, flocculation, surface capture, and sedimentation.

You will find most seawater filters near the inlet of your filtration system.

You can have different sea water filter elements depending on the size of particles that you are removing from the sea water.

For instance, you can have filter elements with smaller spacing for filtering fine silt from the sea water.

You can also have filter elements with large spacing for filtering large particles from the sea water.

At the same time, you can have more than one sea filter in your filtration process depending on the outcome you want for your water.

You also need to note that you can have different mediums for your seawater filter.

The appropriate choice depends on the number of particles that you wish to filter from the sea water.

For example, you can have filters that have disposable cartridges as the medium.

Such seawater filters are suitable for small water filtration processes.

With cartridge filters, you can have precoated filters which you can clean after the filtration process.

The limitation to this is that each time you are cleaning the filter, you need to apply a certain amount of diatomaceous earth.

In large seawater filtration, you are likely to find granular media filters.

Such filtration medium consists of sand or other granular material.

In granular media filters, you can either use slow- sand filtration or pressure filtration.

The results for such filtration is to obtain clean and safe water for human consumption.

Water Ballast Flow Process

Water Ballast Flow Process – Photo courtesy: Acrobating

Ballast water management has developed various measures to prevent, minimize and ultimately eliminate the risk of introduction of the harmful marine organism within the water.

This includes water exchange at sea as well as water treatment.

Water treatment can be through mechanical, physical, chemical or through biological processes.

Ballast uses these methods individually or by combining them.

Ballast ensures compliance with the water performance standard that is regulation D-2 of the BWM Convention.

Ballast Water Treatment Systems (BWTS) is a system designed to remove and destroy any kind of biological organisms including zooplankton, algae, bacteria from the sea water.

Since Ballast water treatment is still an evolving technology, there is an increase in the number of manufacturers.

The implication of this is that there is a limited service offer of the experience for the system.

Also, there are different systems for different types of ships.

· Desalination, Reverse Osmosis

The other area of application of seawater filters is in the desalination of seawater using reverse osmosis.

Desalination by reverse osmosis

Desalination by reverse osmosis – OAS

Desalination is the process of converting sea water which is not drinkable to drinkable water by humans.

The process entails the removal of salt from the sea water.

Among the various methods that you can use for desalination include vacuum, multi-stage, multiple- effect, vapor- compression and reverse osmosis desalination.

However, the reverse osmosis is the common method of desalination.

Reverse osmosis refers to the use of semi-permeable and pressure to filter seawater making it suitable for human consumption.

What happens is that there is an applied pressure on the semi-permeable membrane which forces water to penetrate through the membrane.

As this happens, the membrane filters the salt particles.

The result of reverse osmosis is purified water for consumption.

The source of energy for reverse osmosis can either be thermal or electric.

Energy consumption during reverse osmosis will vary depending on the size of seawater filtration that you are handling.

The limitation of this application is that there are a variety of reasons that inhibit the performance of the filtration membrane.

For instance, various contaminants such as ionic contamination, and insoluble particles lead to scaling of the membrane.

This leads to frequent replacement of the membrane.

To minimize this, you can take various actions on the membrane.

This includes using anti-scaling and antifouling inhibitors.

Reverse Osmosis

Reverse Osmosis – Photo courtesy: CEYLAN

Such inhibitors include organic polymers and biocides.

There are various factors that you need to consider if you want to clean the filter membrane.

These factors include the membrane contamination level, the changing seawater conditions or when the indicator goes off.

The limitation of this method of filtering sea water is that you must shut down your application during the cleaning process.

How a Sea Water Filter Works

The frequent question most of our customers ask – How does a seawater filter work?

There are several reasons that you may want to know how a seawater filter work.

For instance, by understanding how it works, you will be in the perfect position to understand what happens in each step of the filtration process.

Also, it will help you to understand hat to do in case of a breakdown or maintenance issue.

So, with that in mind, here is how a seawater filter works.

Seawater enters the seawater filter through the inlet which is mostly on the lower side of the filter.

As the sea water flows into the filter, the filter element captures contaminants and other unwanted particles from the sea water.

Typically, in the filter element, the seawater flows in the direction from inside to outside.

This ensures maximum capturing of unwanted particles.

The filtered seawater is collected at the top of the filter and passes out through the outlet which is generally at the top of the filter.

The process continues till the filter elements get clogged.

Clogging results in increased differential pressure of the sea water.

Unless you unclog the filter elements, the flow of the sea water will be interrupted as well as the filtration process.

However, in modern seawater filters, you don’t have to be the one to unclog the filter elements necessarily.

Modern seawater filters have a clogging indicator which will indicate when the level of clogging reaches.

At this point, the outlet and inlet valve will automatically close down while the drainage and backwash valve open up.

Water pumps from the source will pump water under pressure into the backwash valve.

The water forces the contaminants on the surface of the filter elements downwards to the bottom of the filter housing.

The drainage valve then discharges the water out of the seawater filter.

In some seawater filters, there are two filter elements which ensure that there is continuity of operations of the filter.

Thus, as unclogging is taking place on one filter element, the other one continues to operate at an optimum level.

Self-Cleaning Filters vs.AutoBackwash Filters– An Ultimate Comparison

Most people tend to confuse a self- cleaning filter with an auto backwash filter.

At the time you might find people using these two terms interchangeably.

Though it is understandable, you need to know that they are different.

Sea water treatment

Sea water treatment

Perhaps the point of similarity is the function that they perform.

But that is where the similarity ends.

To be able to understand these differences, here is a comparison of these two types of filters.

A backwashing filter consists of two filter elements which have wire clothe cylinders.

It is through these cylinders that the sea water flows trapping the contaminants inside the filter element.

The process continues until the clogging of the element occurs.

Mostly at this point, there will be a differential pressure and the backwashing process begins.

What happens during backwashing period is that flush valve will open and the gear motor opens the other filter element.

By doing so, the filter surface deviates from the cleaning nozzle.

The vertical slot which is directly on the filter element allows for the filtered seawater flows at maximum speed in the opposite direction — the flush pipe aids in discharging the contaminants.

Once the filter element has opened up, the flush valve closes while the second flush valve opens.

The purpose of the second flush valve opening up is to aid in cleaning the internal filter element.

After completion, the gear motor switches off and the flush valves close.

With a backwash filter, there is no interruption of the filtration process meaning your application will continue functioning.

On the other hand, a self-cleaning filter is a type of filter that works in conjunction with a pump to keep debris and unwanted particles away during filtration.

The self- cleaning filters consist of housing that rotates and two jets.

Water flows from the inside out in the filtration screen.

From here, it flows into the main pump, where sucking of the filtered water into the impeller takes place.

The rotating jets ejects the water from the impeller and directs the water to flow backward via the filter

As this happens, the jets remove any debris, contaminants or even live organisms that are blocking the filter screen.

This usually takes place after every ½ a second thus ensures that your filter screen is always clean during the filtration process

The advantage you have with this kind of filter is that it is efficient.

Since the filter screen is always clean, it implies that there will not be any moment where your filter will experience a pressure difference.

The disadvantage of a pressure difference is that it ends up consuming much energy.

One thing you will notice with a self- cleaning filter is that you don’t have to maintain your filter regularly.

That is regarding replacing your filter element and any part that is damaged.

This ensures that you minimize the cost of your seawater filter.


See, seawater filter is not that complicated.

I agree that you may find some processes and terms a bit confusing, but with time you will get to understand them.

All that you need is a quality seawater filter that will be able to filter that seawater to the level that you want.

Contact us today for the best quality seawater filter for your application, and you will never regret purchasing from us.

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