Why pre-filtration matters in water treatment

Industrial water treatment traditionally involves multiple stages. Each is designed to remove different contaminants and achieve a required water quality. At one end of the process, relatively coarse filtration can capture larger solids. At the other end, technologies such as ultrafiltration, nanofiltration and reverse osmosis can target extremely small particles and other contaminants.

Between these stages is an important area of mechanical filtration where suspended solids must be removed before they can travel further through the treatment system. This is where pre-filtration can play a valuable role.

At ActionLaser, we manufacture precision laser-drilled screens for industrial filtration applications. Our capabilities provide a mechanical filtration option for applications involving silt, sludge, sandy soils and other suspended solids.

Pre-filtration is an initial or intermediate stage of filtration. Its purpose is designed to remove contaminants before water reaches downstream equipment or finer treatment technologies.

Rather than asking a single filter to handle everything in the water, a multi-stage system progressively removes different contaminants. Consider industrial wastewater containing a mixture of suspended material. Removing larger and intermediate-sized solids mechanically reduces the amount of material reaching the next filtration stage.

The principle is relatively simple: remove the right contaminants at the right stage of the process.

While the concept makes sense and, on the surface, sounds relatively straightforward, water treatment is rarely simple.

A fine membrane designed for a specific filtration task still has to deal with everything delivered to its surface. Where water contains significant suspended solids, appropriate upstream treatment is an important consideration in the overall system design. Industrial filtration also needs to accommodate flow rates, operating pressures, contaminant loading and cleaning requirements.

The objective is not necessarily to achieve the finest possible filtration at every stage. It is to design a sequence of processes that achieves the required result efficiently and reliably.

ActionLaser operates within a specific part of this filtration spectrum. Our precision laser-drilled screens are not intended to replace technologies such as reverse osmosis, nanofiltration or other membrane processes. Instead, mechanical screening can perform a different function.

A precisely controlled aperture creates a physical barrier. Water can pass through the screen while particles larger than the specified aperture are captured.

Within ActionLaser’s approximate 25-to-400-micron capability, this can include contaminants such as fine sand, silt, sludge, and other suspended material commonly encountered in industrial water, wastewater and mining applications.

Depending on the required water quality, mechanical filtration may be the primary process or a single stage within a broader treatment system.

Removing suspended solids earlier will further reduce the contaminant load on equipment downstream in the system. Water-treatment infrastructure can include pumps, valves, nozzles and finer filtration technologies. Allowing excessive amounts of suspended material to pass through the process increases the burden on these components.

Effective pre-filtration provides an opportunity to capture appropriate contaminants before they reach more sensitive downstream stages. This does not mean simply choosing the smallest available aperture. The screen still needs to accommodate the required water flow and contaminant loading while integrating with the rest of the filtration system.

Two screens carrying the same micron specification will not necessarily perform identically. ActionLaser uses precision laser drilling to produce highly controlled and repeatable apertures. Screens can incorporate tapered holes, with the specified opening on the working face becoming larger towards the non-working face.

Once appropriately sized material passes through the controlled opening, the expanding geometry helps it exit through the screen rather than become lodged in the aperture. Open area, screen strength, material selection and overall geometry need to be considered when balancing filtration accuracy with required flow.

Pre-filtration captures material by design, so the accumulated solids must be managed.
Depending on the application, screens can be incorporated into systems using backflushing, wiper arms, washing or clean-in-place processes.

Other systems may maintain material in suspension for removal through suction or positive-pressure discharge. Considering the cleaning method during screen design helps maintain flow and reduce unnecessary interruptions to the filtration process.

There is no universal filtration sequence for industrial water. Mining water containing abrasive silt and sand presents different challenges from wastewater containing sludge or closed-circuit process water containing fine contaminants.

The appropriate solution begins with understanding what is in the water, what needs to be removed and the quality required at the next stage. By engineering aperture size, geometry, open area and cleanability around the application, ActionLaser helps equipment manufacturers and filtration specialists develop effective mechanical filtration and pre-filtration solutions.

When different filtration technologies are designed to perform their best, each stage can contribute to a more reliable overall water-treatment system.

ActionLaser is ideally positioned to design and manufacture a mechanical pre-water filtration solution for your water treatment specifications. Talk to the team for experienced and proven results.