Water is a crucial resource for any industry. Maximal re-use of water reduces the company’s costs greatly. But industrial wastewater contains high levels of toxic substances and cannot be reused as it is. Elimination or reduction in the level of these components requires a treatment process. This, again, involves some expenses. To make the whole cycle more cost-effective, one must make the right choice of membrane filters and filtration method.
Cost is not the only factor that influences the membrane element market. Industries are also expected to adhere to the water safety norms. So, if a membrane is priced low, it should be able to deliver efficient filtration too.
The properties of every membrane material differ. So, not all of them can be expected to suit every industrial process.
Membranes are considered to be semi-permeable. Their pore size and density decides what passes through it and what gets filtered. If the contaminants in the waste water are smaller in size, the pore size should be further decreased to filter them out. The pore distribution decides the energy and power input required.
Most large scale filters are synthetic polymers. These are a preference because the metallic or ceramic filters cannot be employed as multi-purpose. Filtration procedures might require vacuum or pressure which the membrane material must be able to withstand.
The pH of the wastewater might be acidic or basic depending on the product being processed. The membrane must be tolerant to that specific pH setting. It must also be able to withstand a wide range of temperatures. A bi-directional strength also aids the cleaning of the filters.
Since re-use of water is looked at as an alternative to spending on fresh water resource, the membrane material must cost low along with having the aforementioned properties.
Global market research reports suggest the following as the most commonly employed filtration processes:
Microfiltration employs filters of about 0.03-10 microns. It is capable of filtering out sand, silt, and clay. The quantity of chemicals that can be employed during the filtration process is strictly limited. Membrane-filtration is also capable of blocking the entry of micro-organisms thus reducing the severity of treatments like chlorination. While this includes a range of pathogens, it is not virus-proof.
To increase the efficiency of this process, a number of pre-treatments are required.
Pore size for ultra-filtration is about 0.002 to 0.1 microns. It is also a size-exclusion filtration process and the efficiency of filtration does not depend on the depth of the media. It employs no chemicals. Although this is not an absolute barrier to viruses, it does eliminate a few.
Since the pore size is considerably manageable, it doesn’t require a high external pressure input.
Pores of nano-filters are about 0.001 microns in diameter. To push water through these tiny pores requires a high energy input. But these filters are capable of eliminating all bacteria, cysts, viruses and other humic material too. This filtration is also capable of treating corrosive water to remove alkalinity and hardness.
Reverse osmosis is generally referred to as RO and is particularly efficient if employed as a series of units. Disinfectants might be recommended to ensure water safety. But it does appreciably filter out most contaminants even when their concentration is low.
Reverse osmosis is faced with a certain limitations like high capital and operating costs. The membrane is also more prone to fouling.
The growing level of industrial processes around the globe brigs along a requirement of better water treatment options. This stems from the increased level and diversity of the contaminants. Water scarcity is also a matter of concern in a lot of regions. Better treatment facilities will help tackle the problems that arise from this shortage as they better the usability of wastewater.
Research should be aimed at producing filters and processes with the following properties: