Ceramic membranes are the most crucial part of a water filtration system, where the membranes are stored in a housing. Within this housing, liquid is filtered as the ceramic membranes filter fluids by removing, e.g., suspended solids, oil droplets, oil emulsions, particles, and bacteria. Ceramic membranes can purify liquids at different levels depending on the specific needs and requirements, which make ceramic membranes relevant for several tasks in various industries. Membranes can be used for harsh environments such as for filtration of marine scrubber washwater, produced water, flue gas condensate, and heavy metal removal. Still, they are also applicable in environments, demanding high sanitation standards, such as for drinking water treatment, pool and spa filtration, aquaculture purification, and algae filtration. Ceramic membranes can both be utilized for pre- and post-treatment depending on various processes and filtration requirements.

Ceramic silicon carbide membranes from Liqtech in a housing for liquid filtration


Dimensions & Filtration Principles

A ceramic membrane can be developed on supports that are in various forms and dimensions. Based on more than 20 years of experience, we have thoroughly constructed unique membranes on various supports in different geometries such as tubular, flat sheet, disc, aqua solution®, etc

Tubular membranes, flat sheet membranes, disc membranes, and aqua solution membranes from Liqtech

These various designs enable two different filtration principles, meaning that regardless of the respective liquid to be filtered, there is an ideal method. The two filtration principles are called the inside-out principle and the outside-in principle, respectively. The inside-out principle comprises cross-flow filtration, semi-dead-end filtration, and dead-end filtration, while the outside-in filtration principle comprises submerged modules for vacuum-driven filtration. Read more about the inside-out and the outside-in filtration principles here.


Materials

Regardless of a ceramic membrane’s form and dimensions, it is made of inorganic materials, such as silicon carbide, zirconia oxide, alumina, or titania. With more than 20 years of research and development experience within ceramic membranes, we have based our patented ceramic membranes on silicon carbide, also abbreviated SiC. Silicon carbide is the second hardest material in the world only beaten by diamonds. Utilizing a solid material secures a high-quality and robust membrane with a long working lifespan. Silicon carbide is a semiconductor, which contains silicon and carbon. SiC is linked to unique advantages such as providing a porous support structure, which only filtered water can permeate while impurities are rejected. Besides that, SiC provides high flux, chemical resistance in all pH-values from 0-14, and thermal resistance up to 800°C. Read more about the advantages of the strong material silicon carbide here.

A membrane can have one or several parallel flow channels, which extend through the whole element in the porous support structure. 

Membrane Filtration Microtechnology - LiqTech

In order to obtain all the desired effects of a ceramic membrane, a specific coating material is put on the walls of all flow channels of the membrane. This particular coating material contains silicon carbide and is first dried and then sintered at a high temperature in an inactive atmosphere. Not only does this layer of coating provide the membranes ruggedness and durability, but it also determines the membranes’ flow channel pore size and water flux. Read more about the membrane production process here and the membrane coating here.


Liquid Filtration

Liquid filtration consists of various processes. A pump ensures that the feed stream is exposed to pressure from one end of the membrane, which will make the liquid flow through the flow channels of the membrane. The liquid that flows through the membrane barrier is called permeate. The permeate flows towards the membrane's outer carrier and is removed continuously as a filtered liquid. Suspended solids, oil droplets, oil emulsions, particles, and bacteria cannot permeate the barrier and are thus rejected. All rejected elements are called concentrate. The concentrate flows through the membrane flow channels and ends up at the other end of the membrane. Read more about the liquid filtration process here.

 


Membrane Cleaning

As the liquid is filtered, visible and invisible objects such as particles, oil, and biomass from the feedwater will eventually start to foul the membranes. But with a three-process cleaning procedure, complete fouling is avoided. This cleaning procedure can occur either manually, semi-automatically, or automatically.

The first process is a crossflow, which cleans the membranes with feedwater due to the shear force on the membrane surface. This process is what happens most frequently.

The second process is a traditional backwash. A backwash is generated by a backwash pump, flushing water back through the membrane pores from the opposite direction.

The third process is a chemical cleaning-in-place, also abbreviated CIP. Cleaning-in-place involves chemicals, heat, and water to clean all the membranes without dismantling the water treatment unit. CIP is an effective method to quickly and efficiently clean the membranes, which is critical in liquid filtration processes. An effective cleaning process ensures low downtime of the whole water filtration system, which provides a more efficient and cost-effective operation. Read more about how a ceramic membrane is cleaned here.

ceramic membrane solutions


Sustainable Standards of the Future

Besides the abovementioned advantages and features, ceramic membranes can reduce energy consumption, reduce water consumption for backwash, increase capacity, and fit into a small footprint. This secures compliance with current and future environmental regulations and more sustainable, efficient, and cost-effective operations. Thereby, ceramic membranes enable other industries to grow while meeting the sustainable standards of the future.

Clean water filtration ceramic membranes - LiqTech


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