Technical Sharing | Eight Different Methods for Pure Water Equipment Treatment Processes

Part 3: Membrane Microfiltration (MF) Pure Water Treatment Process

The membrane microfiltration method includes three forms: deep filtration, screen filtration, and surface filtration.

• Deep Filtration uses a matrix made of woven fibers or compressed materials to retain particles through inert adsorption or capture, such as commonly used multi-media filtration or sand filtration. It is a cost-effective method that can remove over 98% of suspended solids while protecting downstream purification units from clogging, thus often serving as pre-treatment.

• Surface Filtration has a multi-layer structure. When a solution passes through the filter membrane, particles larger than the membrane's internal pores are retained and primarily accumulate on the membrane surface, as seen in commonly used PP fiber filtration. Surface filtration can remove over 99.9% of suspended solids and can also be used for pre-treatment or clarification.

• Screen Filtration Membranes have a essentially uniform structure, like a sieve, retaining all particles larger than the pore size on the surface (the pore size measurement of these membranes is very precise), such as the point-of-use final safeguard filter in ultrapure water systems. Screen microfiltration is typically placed at the final point of use in a purification system to remove residual trace resin fragments, carbon fines, colloids, and microorganisms.

Part 4: Ion Exchange Pure Water Treatment Process

The principle of the ion exchange method is to purify water by exchanging inorganic salt ions in water, such as calcium ions (Ca²⁺), magnesium ions (Mg²⁺), sulfate (SO₄²⁻), nitrate (NO₃⁻), etc., with ions in the ion exchange resin. This process allows the anions and cations in the water to be exchanged with those in the resin, thereby purifying the water.

Part 5: Reverse Osmosis (RO) Pure Water Treatment Process

This process uses pressure as the driving force and utilizes the selectivity of the reverse osmosis membrane, which allows water to pass through but not solutes. It is a substance separation process that extracts pure water from water bodies containing various inorganic substances, organic substances, and microorganisms. The pore size of a reverse osmosis membrane is less than 10 Å (1 Å equals 10⁻¹⁰ meters), giving it a strong sieving effect, with a desalination rate of up to 99% and a bacteria removal rate greater than 99.5%. It can remove impurities such as inorganic salts, sugars, amino acids, bacteria, and viruses from water. Based on raw water quality and product water quality requirements, with proper design, RO is the most economical and effective method for purifying tap water and is also the best pre-treatment method for ultrapure water systems.

Part 6: Ultrafiltration (UF) Pure Water Treatment Process

Microporous membranes remove particles based on their pore size, while ultrafiltration (UF) membranes function like molecular sieves, separating molecules in a solution based on size by allowing the solution to pass through extremely fine pores.

Ultrafiltration membranes are tough, thin, selective permeable membranes, typically considered to have a filtration pore size of about 0.01 μm. They can retain molecules larger than a specific size, including colloids, microorganisms, and pyrogens. Smaller molecules, such as water and ions, can pass through the membrane.

Part 7: Ultraviolet (UV) & Ozone Sterilization Ultrapure Water Treatment Process

Ultraviolet light emitted at 254nm/185nm by UV lamps can effectively kill bacteria and degrade organic matter.

Part 8: EDI Pure Water Treatment Process

This is a new method for producing deionized water, also known as Continuous Electrodeionization technology. In an EDI device, ion exchange resin is packed between anion/cation exchange membranes to form EDI units. This method does not require the use of acids and alkalis for resin regeneration, making it environmentally friendly.