Types of Industrial Water Filter And Their Uses
In order to remove solid contaminants from industrial process water, a number of different filters and technologies are available. Of these, the most basic is also one of the oldest. Despite being somewhat bulky, sand beds tend to be favoured by many users because of their capacity to retain a much higher volume of solids than other filtration systems. This means they take longer to become clogged and so need to be cleaned far less frequently – and this can be achieved simply by backwashing.
Compared with other filtration systems in which the contaminants are retained on the surface of thin media, a sand bed relies on its depth to trap unwanted particulate matter on the surfaces of individual grains of sand as liquid trickles slowly between them. A sand bed, however, is not the only type of industrial water filter to utilise the principle known as depth filtration. Cartridges may contain fabric bags that function in this manner although some types are restricted to surface filtration and owe their efficiency to pleats in the relatively thin filtration medium that act to increase its surface area. In addition, there are a number of alternative systems and which of these to select depends both on the nature of the contaminants present and the goal of the filtration operation.
Whether dependent on depth or surface properties, cartridges and most other industrial water filters employ porous media whose ability to remove solids from a liquid is determined by the diameter of their pores. While the pores remain fairly large, filtration is able to proceed under the action of gravity alone. However, as the pore size decreases, it becomes increasingly necessary to apply pressure in order to ensure the continued movement of liquid through the filtration medium.
South Africa, like most industrialised nations, is faced with dwindling natural resources and conservation measures are becoming more important by the day. Today, industrial water filters are frequently used for reclamation purposes. Rather than simply rendering it clean to be safely discharged back into the water table, many companies are extending their wastewater treatment in order to reuse it. In this way, each litre of water purchased can then be used three or four times rather than just once. Not only does wastewater recycling serve to reduce the pressure on the country’s dwindling reserves of this vital natural resource but, in a large chemical plant, for example, it could also save millions of rand in production costs over the course of a year.
Sometimes, industrial water filters are used not to clarify the liquid but to collect its solid contents when it may be possible to reuse them or if they should happen to have a significant market value. An example of this is the gypsum often present in mine water. Once it is recovered, it can be sold and used for the manufacture of wallboard and plaster of Paris, as an additive to retard the hardening of cement, and even as a thickening agent for use in toothpaste and shampoo. When transferred by means of a pipeline, there is often a need to remove relatively large particles from industrial water for which a coarser type of filter known as a strainer is used. These consist of perforated metal or wire-mesh-, basket-like structures and are intended to retain any large particles that could cause damage to any valves, pressure gauges, pumps, or similar devices located further downstream. Strainers are also used for the pretreatment of liquids before feeding them to a finer filtration system that might otherwise become prematurely clogged.
Undoubtedly one of the most significant advances in filtration technology has been the introduction of reverse osmosis (RO). Its purpose is not to remove suspended solids from a liquid, for which other industrial water filters are more than adequate, but rather to separate dissolved solids from a solvent. In plants, water moves freely across cell walls in order to ensure that the concentration of solutes within a cell is the same as that in the surrounding fluid. In an RO system, a synthetic polymer membrane acts like a plant’s cell wall but, by applying positive pressure to the liquid, all of it is forced through the membrane, leaving the previously dissolved solids behind. RO has gained a role in numerous industries from electronics and pharmaceuticals to food and beverages. RO membranes are widely accepted as the best industrial water filters for desalination plants.