Selecting Your Water Source: Surface Water vs. Well Water
When building a new plant, expanding, or moving operations, identifying a suitable water source is an important aspect of project planning. When municipal water isn’t available or is too expensive, facilities will need to source and treat their own raw water. For companies considering a choice between surface water and well water, it’s important to know the differences between the two, and how these differences determine appropriateness for a given application, and what kinds of water treatment might be needed.
Pros and cons of surface water
Surface water is any body of water that collects naturally on earth’s surface, such as lakes, rivers, ponds, wetlands, or seawater. These bodies of water are open to the atmosphere and primarily fed by precipitation and snowmelt. The advantages of using surface water for industrial processes include relative ease of access, as well as ample availability. These benefits can make surface water a good fit for thirsty applications, like cooling towers, power generation, mining, or large-scale manufacturing.
On the other hand, the main drawback of using surface water is quality. Since bodies of surface water are open to surrounding land, air, and connected waterways, they contain a complex mix of naturally occurring organic material as well as contaminants that can be carried into the body of water in the form of stormwater runoff and wastewater discharges from nearby municipalities, farms, or industrial facilities. To compound the quality issues associated with surface water is that it will vary due to weather and seasonal events. For instance, heavy rain in the spring can lead to additional contaminants to be accumulated in the body of water.
What contaminants are present in surface water and how do they get there?
Surface water may contain a complex range of contaminants, including any of the following materials:
- Biological material: Bodies of surface water are naturally home to various aquatic plants and animals, ranging from algae to fish. Facilities will generally need to fit water intake equipment with screens to protect wildlife in accordance with environmental regulations, and will often employ coarse filtration to remove larger particles and simplify downstream treatment needs.
- Minerals: As rocks naturally weather and break down, they release dissolved minerals into surface water. The exact makeup will vary depending upon the geology of the area, but surface water may include calcium, magnesium, bicarbonate, silica, potassium, chloride, and various other minerals. Any of these can lead to problematic scale buildup, inefficient heating, corrosion, and other issues. To deal with high mineral content, facilities may adopt any of several water treatment methods, including lime softening, ion exchange (IX), nanofiltration (NF), or reverse osmosis (RO).
- Agricultural chemicals: Stormwater runoff can carry pesticides and fertilizers from farm fields into nearby bodies of water, where they can disrupt the ecosystem and otherwise create various water treatment challenges. This is because nitrogen and phosphorus from fertilizers can fuel algae growth, which can lead to clogs, excess sludge production, toxins, odors, and other problems with the source water. Additionally, any pesticides that make their way into process streams and/or wastewater pose health hazards to humans and animals. Often, facilities will need to employ RO and/or granular activated carbon filtration (GAC) to treat water that has been contaminated with agricultural chemicals.
- Pathogens: Bacteria, viruses, and other kinds of microorganisms can proliferate in surface water due to sewage overflows, agricultural runoff, and urban stormwater runoff. Any water intended for human consumption will need to be disinfected through some means; commonly this is achieved through chemical (e.g. chlorine/chloramine addition), heat, UV disinfection, or by RO.
- Waste residues: There is a long list of potential pollutants that make their way into surface water due to human activity. Pollutants may be discharged directly to waterways in the form of industrial and municipal wastewater, while contaminants present in the air or on land can be washed into bodies of surface water by storm runoff. Of particular concern are materials that are reactive and/or toxic to humans, such as heavy metals (e.g. arsenic, zinc, lead, and cadmium); ammonia compounds; organic chemicals (e.g. acetic acid, methanol, and acetone); oil and gas from roadways; and sulfides, among many other examples.
Taken individually, no single contaminant is necessarily difficult to treat. But because surface water can have so wide a range of contaminants present, a raw water treatment system can be quite complex, with multiple treatment stages and technologies required to achieve the level of quality needed for a given application.
Pros and cons of well water
Well water is sourced from underground aquifers that are housed below the earth’s surface. These pools of groundwater form as water from the surface percolates through soil layers and collects into voids in the underlying rock or sediment. Since groundwater undergoes a sort of natural filtration as it makes its way through soil, a key benefit of using well water is that it tends to have less microbial and chemical contamination compared to surface water. Another benefit is that groundwater can be less susceptible to drought than surface water, which can make it a good choice for remote facilities that need a reliable supply of water. Additionally, well water supplies are shielded from atmospheric weather conditions such as seasonal rains and generally have more consistent levels of contaminants to be dealt with relative to surface water supplies.
The main drawbacks of using well water include costs of pumping infrastructure, limits on withdrawals, and high dissolved solids content. Unless a well already exists, a facility will need to drill and maintain a well and pump to bring groundwater to the surface. These costs can range from moderate to substantial depending on the location and depth of the aquifer, and the volume of water needed. Additionally, there are often regulatory limits on groundwater extraction, which can constrain facilities with high volume needs. Finally, groundwater often contains significant mineral content, which can lead to depositions and scale buildup if left untreated.
What contaminants are present in well water and how do they get there?
Groundwater typically has a different constituent profile than surface water owing to how it collects beneath the earth’s surface. In short, as water seeps through layers of soil and rock, organic material and larger particles are filtered out. At the same time, soluble metals and minerals from surrounding rock may dissolve into the water. As a result, groundwater may have less of the toxic chemicals and organic matter commonly found in surface water, but it still may be high in total dissolved solids (TDS). Examples of constituents most commonly found in well water include:
- Minerals: Mineral content is often present to some degree in any source of raw water, but high hardness is more likely in groundwater than in surface water. High levels of calcium and magnesium are particularly common in areas where the bedrock and soils are comprised of limestone, dolomite, chalk, gypsum, or basalt. Well water with high levels of TDS will typically need to be treated to remove scale-forming minerals in order to prevent clogs and damage to machinery, and ensure safe and effective performance in high-heat or high-pressure applications, like boilers.
- Heavy metals: Groundwater can accumulate metal ions as it travels through soil and porous rock. These metals may be naturally present in the environment, or they may be carried into the aquifer by runoff and surface water seepage. Heavy metals can easily interfere with industrial processes, and many are also very toxic to humans, like arsenic, antimony, cadmium, and lead. For these reasons, if even a low concentration of heavy metals is detected in a well water supply, the facility will need to remove them, usually by means of IX, membrane separation, adsorption, or chemical precipitation.
- Radionuclides: Radioactive material is naturally present in underground rock formations, and it can also make its way into aquifers through human activities such as mining, oil and gas extraction, and wastewater seepage. Radionuclides, like uranium, radium and radon, are strictly regulated in drinking water and wastewater because they pose significant health risks. IX can be an exceptionally effective targeted removal method for radionuclides, while RO, adsorption, and/or chemical precipitation are good for broad-spectrum contaminant removal.
- Pathogens: Underground aquifers don’t provide the light, oxygen, or food sources that most microorganisms need to thrive, so in general, you’re less likely to find bacteria and viruses in well water than in surface water. Exceptions can occur due to leakage from nearby septic systems or sewers, particularly in shallower wells. For this reason, well water should be tested and disinfected if necessary.
Compared to surface water, groundwater is somewhat protected from contamination by many industrial pollutants and microbes. However, contaminants can still make their way into well water, so it is crucial to regularly test well water and employ appropriate treatment, especially if the well water is intended for human consumption.
Water quality varies significantly by location
Bear in mind that the precise makeup of any raw water source will vary significantly depending upon factors like nearby industrial or agricultural activity, as well as the geology and climate of the area. For example, say you have two wells—one in an area where the bedrock is mostly composed of limestone, and another where it is mainly granite. Since limestone tends to leach calcium and magnesium, water drawn from the first well might be quite hard, while water from the other well is not. So even though both of our samples are taken from wells, they have a completely different chemistry because of the local geology.
That’s why it is so important to get precise data when it comes to developing a water treatment solution. This is often achieved by doing a raw water characterization study, which will provide a complete analysis of source water that engineers can use to develop a water treatment system based on the actual makeup of the groundwater or surface water at a particular location.
How SAMCO can help
When it comes to water treatment, there’s often more than one way to achieve separation or purification goals—but that doesn’t mean that every solution is equal. At SAMCO, we have over 40 years’ of experience in building custom water treatment systems that are designed around our customers’ specific goals. Whether you are looking to use less chemicals, lower energy costs, cut water use, or meet some other objective, SAMCO can help you navigate available water treatment technologies like IX or RO, and make an informed choice.
For more information or to get in touch, contact us here to set up a consultation with an engineer or request a quote. We can walk you through the steps for developing the proper solution and realistic cost for your water treatment system needs. Or, if you would like to learn more about the topics discussed in this article, here are some blog posts that might interest you: