In commercial and industrial potable water treatment, it’s not hard to quickly be overwhelmed by all of the technologies, equipment, science, and regulatory requirements involved. Seemingly simple applications can easily become overcomplicated by having too many treatment options, which tend to all blur together at a certain point. To help readers see a bit deeper into the water treatment landscape, we’ve prepared this article to outline common treatment systems as well as provide an outline on how treatment systems are selected to begin with.
Determining Water Treatment Specifications - A Practical Approach
How do most readers find themselves needing water treatment solutions to begin with? Usually by one of two ways: either a specific technical deficiency was identified in an existing water supply stream and now needs to be addressed (such as treating hardness or bacterial blooms), or when installing a new water supply that will serve a specific function. In both cases, we're already halfway to arriving at a water treatment solution, as we know the intended end water quality's parameters. This provides us with our end goal water specification.
If a specific pre-determined end water quality spec is not available, baseline should always be the governing regulatory requirements in one’s region. Namely, start with the EPA's national primary drinking water specifications, and then check your local authorities for their versions (if any).
The other half of the equation would be the quality of the water we're starting with, that we must 'treat up' to the end goal spec mentioned above. To find our starting point, we simply need to take water samples of existing water streams and have those samples evaluated by a certified laboratory. The lab will issue a water sample analysis, which now serves as our starting point.
Readers should note that for any major or process-driven new water services, water samples should be backed up by historic data pulled from qualified civil engineering firms, local water consultants, public water agencies, or by directly taking samples over long periods of time. A single sample only provides parameters at that one point in time, but for most water services, water quality will change over the year due to environmental, ecological, and other natural influences. Treatment solutions should be selected for the 'worst case' conditions reasonably expected across the appropriate time period - often this is one year, but for some situations such as groundwater wells influenced by sporadic nearby snowpack, multiple years of data may be called for.
At this point, an existing water analysis and an end-goal target requirement are in hand. Comparing these two technical documents together will render the necessary water treatment specifications moving forward. For example, if incoming fresh water is slightly hard at 55 ppm mineral contents, and the new specification is to achieve water at <20 ppm mineral contents, then the required treatment specification is to remove >35 ppm hardness. With this treatment spec determined, the next step is to compare treatment technologies suitable to the treatment profile.
Common Water Treatment Technologies
In this section we'll take a quick run through the most common potable water treatment technologies available for commercial and industrial applications. There are of course additional treatment solutions out there, some hyper-specific to certain applications, and others proprietary to commercial technology entities - we'll leave those out of the discussion as the below cover the vast majority of use-cases with mature, known solutions.
- Sediment Removal - large-scale potable water treatment typically begins with steps that remove suspended solids from the water stream known collectively as sedimentation. Water volumes are held in large vessels where gravity works to pull down solids to the vessel floor, where they can be mechanically removed later. Sedimentation is often supported by coagulation and flocculation steps, which employ chemicals to react with and bind to specific particulates, making these molecules larger and easier to settle out.
- Mechanical Filtration - using solid screens, bags, and other porous surfaces, mechanical filters provide a physical barrier that will catch particulates over a certain size as filtered water continues to flow forward. Mechanical filters can be static (unmoving) or motorized (moving), helping to physically extract particulates out of a water stream as well as capture and remove the caught solids so that the filter surface does not plug up.
- Mechanical Separation - different than filtration, mechanical separation uses mechanical and hydraulic principles to forcefully extract contaminants out of a water stream. A good example is a centrifugal separator, which spins at high RPM to force non-water contaminant molecules out of suspension in the water stream based on their difference in densities. While mechanical filtration catches solid particulates (such as sand), mechanical separation works on finer solids that would pass through the mechanical filter, as well as suspended non-water liquids and gases (such as oils).
- Membrane Filtration - combining principles from mechanical filtration and separation, membrane filtration uses hydraulic pressure gradients created across extremely small porous surfaces known as membrane filters to extract contaminants from water streams. Membrane filters can withstand hundreds or thousands of pounds of pressure, with surface porosity sizes down to 0.001 micron, together filtering out particles in the realm of microorganisms, viruses, bacteria, and even individual organic ions. Membrane filtration is often described as the method to obtain 'pure water'.
- Disinfection - disinfecting water serves to inactivate common biological activity present in a water stream, including viruses, bacteria, and other pathogens. On a public water supply scale, chlorine injection is the most common method of disinfecting water, which causes a chemical reaction that breaks down organic contaminants. Disinfection may inactivate but does not physically remove the inactivated organic material from the water stream.
- Sterilization - while disinfection treats 'most' common biological activity in a water stream, sterilization is a step higher, intended to inactivate and remove 'all possible' biological activity. Sterilization is typically used for advanced processes such as in the pharmaceutical and semiconductor industries, where any foreign materials can cause adulteration of end products down to near atomic particle scales. Ultraviolet radiation treatment is a good example of water sterilization.
- Equalization - on the more simplistic end of the water treatment spectrum we find equalization. Treatment of mild parameter disparities is often addressed by equalization, which is to mix water volumes of different properties together until they 'equalize' at the intended desired parameter. For example, hard water from a ground well can be captured in a storage tank, where a smaller volume of soft water is added from a separate source. The tank is agitated until the two water volumes are sufficiently intermixed, bringing the net hardness parameter within the desired range by mere dilution. Equalization is rarely used on large-scale potable water streams, but is a smaller scale option where cost and volumes make other options prohibitive.
- Ion Exchange - mineral contents in water streams impact taste, texture, smell, and scaling, and as such are often treated using ion exchange methods. Ion exchange is a chemical treatment process that targets removal of unwanted dissolved ions in a water stream by presenting a resin media containing similarly charged ions that will 'swap positions' with the undesired ions. Water softening, deionization, demineralization, and dealkalization are all variants of ion exchanges. Sodium, calcium, magnesium, and inorganic salts are common applications.
- Advanced Process Treatment - for very specialized use cases, advanced process water treatment technologies are required to meet very demanding specifications. In such applications, typically water treatment is solving for manufacturing, scientific, chemical reaction, or other industrial functions, well above and beyond the needs of potable water services. Pasteurization, distillation, ozone injection, thermal treatment, evaporation, and degasification are a few examples used in pharmaceutical, medical, laboratory, and semiconductor applications.
Water Treatment – No Guessing Matter
With the above description of common treatment systems, we hope that readers now have a better understanding of their options. This list focuses on potable water treatment, and leaves out many more options available for wastewater, gray water, black water, irrigation water, and other non-potable applications. We point this out in order to make a suggestion: because of the vast variety of water treatment solutions on the market today, as well as due to the high potential for accidentally mistaking solutions between applications, it is highly suggested that readers engage with a qualified water treatment system provider when selecting systems. This way, readers will have professional guidance and support during their selection and installation process, making sure that they end up with only the right components to protect their health and infrastructure.