Raw water (untreated water found naturally in the environment) can come from many sources, including rivers, lakes, oceans, or groundwater. But when you are using this water for either domestic and/or industrial use, many times it needs to be treated first, depending on what you need it for.
Since what is present in the water can cause a myriad of issues (contamination in drinking water can make people sick, solids in industrial water feed can foul equipment and cause costly system downtime, etc.), it’s important to know what might be present in your raw water source, what the potential problems might be if they’re left untreated, and ways to avoid these issues moving forward.
So here we break down “Five Common Problems with Raw Water and How You Can Treat Them”:
1. Suspended and colloidal solids in your raw water feed
One of the most predominant complaints we get here at SAMCO is that there are suspended and/or colloidal solids in our clients’ raw water source. Typically these solids are found in surface waters (rivers, lakes, and oceans as opposed to groundwater) and are present in the form of dirt, dust, or decayed vegetation, to name a few.
If you allow these suspended and colloidal solids to remain in your raw water process feed, you might end up with the following issues depending on if you’re using the raw water for domestic or industrial purposes:
- Unpleasant odors in food and beverage products
- Fouled process equipment and downtime
- Energy losses for your plant
Municipalities will generally do a good job of removing many of these solids, as they need to maintain compliance with state and federal regulations, but many times industrial processes need to go far beyond what the standards are for drinking water. So even if your plant is drawing its feed water from a municipality, it might need to be treated for suspended and/or colloidal solids anyway. Be sure to check with your water treatment experts to see what they recommend.
The biggest problem in raw water, with suspended solids in particular, is variation in the suspensions—suspended solids increase and decrease as the seasons change, wreaking havoc on water treatment plants that might be constantly changing their chemistry to maintain water clarity for their process.
Colloidal solids can be more difficult to treat than suspended since they are very fine particles that don’t settle well on their own and can get down into the sub-micron range, but there are methods that can help coagulate these solids for settling, among other methods for removal.
How to treat them
When you’re designing your raw water treatment system, you are most likely going to be using some kind of clarification/gravity settling system, which are typically large circular clarifiers or modified clarifiers with internal inclined plates. To minimize the impact of varying suspended solids, allow for a slight overdesign in the clarifier and couple that with a robust chemical addition system that allows you to vary the dosages and types of chemicals you’re feeding the system to allow for these seasonal variations in suspended solids.
If you have colloidal material in your raw water process feed, you need to look into chemistry that allows you to coagulate these particles, bringing them together so they can settle out. Again, having pumping and chemical feed systems that allow for various types and concentrations of chemicals will go a long way to minimizing the amount of colloidal material in the feed water.
The most effective way to remove suspended and colloidal solids from your raw water feed is to use ultrafiltration (UF) for polishing after the clarification stage or replace the clarifier completely with UF. As long as you don’t have an unbelievably high amount of suspended solids, UF can be used to directly filter the raw water feed for suspended and colloidal solids, and since it’s an absolute barrier, it handles the seasonal variations effectively.
2. Silica and colloidal silica in your raw water feed
The presence of silica and colloidal silica in your water feed is a problem that occurs in both surface water and groundwater streams. One of the most abundant minerals on the planet, silica (generally found in nature as quartz) is a common problem, especially in dry areas such as Mexico where it occurs naturally due to rock formations.
When you have high silica in your feed water, it affects the performance of various industrial operations, including:
- Fouling and scaling of boiler equipment
- Reduced efficiency of plant equipment
- Product contamination
How to treat them
On a raw water treatment system, usually the removal methods for silica and colloidal silica will be using a coprecipitant with aluminum-based coagulants, which are really effective for getting down into the lower ppm levels of silica. Sometimes you will need to treat the raw water feed further, if required, to get down to a purer quality of feed water for use in boilers and other processes.
3. Iron in your raw water feed
Typically not a problem in surface waters (as the oxygen in the air will oxidize it and form it into particles), iron becomes a problem in raw water, where it is generally dissolved. When the iron-contaminated water is drawn to the surface and used, it will oxidize and turn the water red.
If the iron isn’t removed, it could get into all kinds of equipment and:
- Coat fixtures (such as hot water tanks)
- Foul industrial processes
- Cause foul tastes and odors in products
How to treat them
To remove iron from your raw water stream, it needs to be oxidized, which will then take the dissolved iron and form a particles that can be settled out in a clarifier like any other suspended particles. Another way is to exchange it out of the water via green sand media or resin such as ion exchange.
4. Bacteria in your raw water feed
Bacteria or living organisms are more prevalent in surface water and can cause many types of health problems, especially in developing nations. In developed nations, such as the United States, municipal water treatment systems are set up to remove these living organisms, which include bacteria, cryptosporidium, giardia cysts, and viruses such as hepatitis.
In industrial processes, living organisms can cause all sorts of costly issues to products and industrial processes, especially in the food and beverage industry.
If harmful bacteria, viruses, or cysts are not removed from potable water or water used industrially for rinsing soda cans, for example, someone who might come into contact with the living organisms can experience all kinds of health issues, including acute sickness, severe digestive problems, or death. Some of the health threats include:
- Giardia and Cryptosporidium
- E. coli
- Hepatitis A and E
How to treat them
Gravity clarification can reduce many of these living organisms as possible through settling of suspended solids, which should be followed by an oxidizing agent such as ozone, peroxide, or chlorine. Newer technologies are also being used, more specifically UF membranes, which are extremely effective in removing the live organisms from the water.
5. Hardness in your raw water feed
Last but certainly not least, many of our clients come to us for solutions in removing hardness from their raw water streams, which can cause all sorts of problems for both industrial and domestic uses.
In industrial and domestic processes, when you heat raw water streams in your plant’s processes, if left untreated, the hardness starts plating out and:
- Coating equipment fixtures
- Plugging pipes/scaling equipment
- Coates boiler tubes causing severe energy loss and failure in boilers
- Causes sludge in the washing machine and coats clothes
How to treat them
When you have high hardness in your raw water feed, you can remove most of it along with the clarification process by using a cold or warm lime process addition to precipitate and reduce the hardness. Another commonly used technology for hardness reduction is ion exchange, better known as water softener. Water Softeners are used extensively in homes and industry.
How SAMCO can help
SAMCO has over 40 years’ experience helping solve some of the most complex problems for both domestic and industrial raw water treatment. If you’d like to contact one of our engineers to see how we might be able to help you, contact us here or visit our website/raw water treatment page for more information about some of the cutting-edge technologies we can offer to help improve the quality of your process.
Some other articles about raw water treatment systems you might be interested in include:
- Do You Need a Raw Water Treatment System for Your Plant?
- How to Choose the Best Raw Water Treatment System for Your Plant
- What is a Raw Water Treatment System and How Does it Work?
- Five Common Problems with Raw Water Treatment and How to Avoid Them
- Treated vs. Untreated Raw Water for Your Plant
- 12 of the Best Raw Water Treatment Equipment Supply and Technology Companies
- How Much Does a Raw Water Treatment System Cost? (Pricing, Factors, Etc.)