Walter Filtration: Clean Water in California
“The future is not a place we are going, but a place we are creating. The paths are not to be found, but made, and the activity of making them changes both the maker and the destination” – John Shaar
As we’ve entered our fifth decade as a company, staying on top of our industy’s cutting-edge technology is part of what keeps Caliagua growing. We track and study the advances in our industry and are developing working capabilities in many areas. Caliagua is a civil engineering firm specializing in the construction of water treatment plants, and in our industry, advanced oxidation processes (AOPs) are a cutting edge technology that a number of our customers have utilized in their facilities. In this blog, we’re sharing some of what we’ve learned in this area. Feel free to comment below, and share your thoughts and experiences in this or other areas that your company thinks is interesting!
Let’s start by defining what AOPs are. Advanced oxidation processes (AOPs) are a set of chemical treatment procedures that remove organic (carbon-based) (and sometimes inorganic) materials in water and wastewater by oxidation through reactions with highly reactive oxidizing chemicals that can oxidize a wide variety of compounds, including those that are resistant to conventional water treatment methods. AOPs are often used to treat wastewater that contains toxic or persistent organic pollutants. They can also be used to disinfect water, making it safe for drinking.
AOPs are typically more expensive than conventional treatment methods, but they can be effective in removing pollutants that are difficult to treat with other methods. Now that clean water is no longer a simple assumption, AOPs are going to become more widely used. There are a number of different techniques and technologies involved in this field. Keep reading, and I’ll tell you about some of the most important ones, as well as where they’re used in our Southern California market area.
Membrane filtration: Membrane filtration is a process that uses very powerful pumps to force water through semi-permeable membranes to remove contaminants from water. This technology is becoming increasingly popular in water treatment because it is very effective at removing a wide range of contaminants, including bacteria, viruses, and chemicals.
The LADWP’s Diamond Valley Lake Water Treatment Plant uses reverse osmosis (RO) to remove up to 99% of the salt from the Colorado River water. Besides desalination, the RO process also removes other contaminants, like bacteria, viruses, and chemicals. Another example of RO and membrane filtration is found at the City of San Diego’s Water Treatment Plant No. 2.
The Orange County Water District (OCWD) uses AOPs to treat groundwater that is contaminated with perchlorate.
What is perchlorate? There are both natural and man-made sources of perchlorates. In nature, they can be found in some minerals, like chlorate and perchlorate salts. They can also be formed naturally in the atmosphere through the breakdown of chlorine-containing compounds. Industrial sources of perchlorates include rocket propellants, fireworks, and matches, some household products, fertilizers and water treatment chemicals all contain perchlorates.
It’s important that perchlorate is removed from drinking water because of the harm it causes to human health. Ingested in high amounts, perchlorates harm the thyroid gland’s ability to produce thyroid hormone. This can lead to diseases such as goiter, hypothyroidism, and developmental delays. As a result, the EPA has set a maximum contaminant level (MCL) for perchlorate in drinking water of 1 part per million (ppm).
Back to the OCWD…. One of our customers, the OCWD’s Groundwater Replenishment System uses a combination of AOPs, including ozonation and hydrogen peroxide (explained below), to treat groundwater that is contaminated with perchlorate.
The Metropolitan Water District of Southern California (MWD) uses AOPs to treat wastewater that is used to irrigate agricultural land. The MWD’s Chino Water Reclamation Plant uses a combination of AOPs, including ozonation and UV/hydrogen peroxide, to treat wastewater that is used to irrigate agricultural land. The AOPs help to remove a variety of contaminants from the wastewater, including pathogens, nutrients, and heavy metals.
Other examples of AOP technology include:
Ozonation: Ozone is one of those oxidation agents I mentioned above. It is very effective inb removing a wide range of contaminants, including bacteria, viruses, and chemicals. In water treatment plants, ozone is generated by passing oxygen (O2) gas through an electric field. This causes the oxygen molecules to split into oxygen atoms, which then combine with other oxygen atoms to form ozone. The ozone is then dissolved in the water to be treated.
The ozonation process typically takes place in two stages. In the first stage, the ozone is mixed with the water for a short period of time (typically 10-30 minutes). This is called the contact time. During the contact time, the ozone reacts with the organic pollutants in the water, breaking them down into harmless byproducts.
In the second stage, the ozone is removed from the water. This is typically done by passing the water through a carbon filter. The carbon filter absorbs the ozone, leaving the water clean and disinfected.
In our market, the OCWD and MWD of Southern California both utilize ozonation in their water treatment processes.
The Orange County Water District (OCWD): The OCWD’s Groundwater Replenishment System uses ozonation to treat groundwater that is contaminated with perchlorate. Perchlorate is a type of rocket fuel that can be harmful to human health.
Hydrogen Peroxide is another important oxidation chemical used in water treatment. In a process similar to ozonation, it is added in a controlled manner to the water in the treatment plants and used to breakdown organic pollutants. Water, oxygen and carbon-dioxide are the byproducts of the chemical process. It can be used to treat water in multiple ways.
Improving water clarity: Tiny particles of soil, silt, algae, and bacteria can remain suspended in water but hydrogen peroxide can be used to break them down and filter them out.
Color: Hydrogen peroxide can be used to remove color from water by oxidizing the organic matter that causes color.
Organic pollutants: Hydrogen peroxide can be used to remove a wide variety of organic pollutants from water, including those that are resistant to conventional treatment methods.
Chlorine byproducts: Hydrogen peroxide can be used to remove chlorine byproducts from water, such as trihalomethanes (THMs). Colorless, tasteless, and smelling slightly of chlorine, these chemical compounds are formed when chlorine or other disinfectants used to control microbial contaminants in drinking water react with naturally occurring organic and inorganic matter in water.
In addition to ozonation, the Metropolitan Water District of Southern California’s Chino facility also uses hydrogen peroxide to treat water. In fact, it is one of the largest hydrogen pertoxide facilities in the world. The water treated there is used to irrigate agricultural land, and because of this facility, perchlorate is kept out of the agricultural products consumed by millions of people. The Monterey Park Water Department also uses hydrogen peroxide to treat groundwater that is contaminated with volatile organic compounds (VOCs), harmful to human health.
There are a number of great benefits that stem from using hydrogen peroxide to treat water. Its effective at removing a wide range of contaminants; bacteria, viruses, and chemicals.
It is relatively non-toxic and doesn’t produce any harmful byproducts. Finally, ot can be used to treat a variety of water sources, including groundwater, surface water, and wastewater.
Photocatalysis: Photocatalysis is a process that uses light to activate a catalyst, which then oxidizes contaminants in water. Photocatalysis is a promising AOP for removing contaminants that are difficult to remove using other methods. On the other hand, it also comes with a few challenges. It can be expensive to implement, it can be difficult to operate and maintain and the catalyst can be deactivated over time.
The Orange County Water District (OCWD): The OCWD’s Groundwater Replenishment System uses photocatalysis to treat groundwater that is contaminated with perchlorate. Perchlorate is a type of rocket fuel that can be harmful to human health.
Fenton’s reagent: Fenton’s reagent is a mixture of hydrogen peroxide and iron (II) that is used to oxidize contaminants in water. Fenton’s reagent is a very effective AOP for removing a wide range of contaminants, including organic compounds and heavy metals.
The Metropolitan Water District of Southern California (MWD): The MWD’s Chino Water Reclamation Plant uses Fenton’s reagent to treat wastewater that is used to irrigate agricultural land. The Fenton’s reagent helps to remove a variety of contaminants from the wastewater, including pathogens, nutrients, and heavy metals.
Here are some of the benefits of using Fenton’s reagent in water treatment:
- It is effective at removing a wide range of contaminants, including organic compounds and heavy metals.
- It is relatively non-toxic and does not produce any harmful byproducts.
- It can be used to treat a variety of water sources, including groundwater, surface water, and wastewater.
However, there are also some challenges associated with using Fenton’s reagent in water treatment:
- It can be expensive to implement.
- It can be difficult to operate and maintain.
- The iron (II) can precipitate out of solution, which can clog pipes and filters.
Nanotechnology: Nanotechnology is the use of materials at the nanoscale (1-100 nanometers). Nanotechnology is being used to develop new water treatment technologies that are more efficient and effective than traditional methods. For example, nanoscale filters can be used to remove very small contaminants from water.
Nanotechnology is being used in water treatment in a number of ways, including:
Adsorption: Nanoparticles can be used to adsorb, or attract and hold, contaminants on their surface. This is a promising method for removing a wide range of contaminants from water, including bacteria, viruses, chemicals, and heavy metals.
Photocatalysis: Nanoparticles can be used in photocatalysis, which is a process that uses light to activate a catalyst, which then oxidizes contaminants in water. This is a promising method for removing a variety of contaminants from water, including organic compounds and heavy metals. For instance, A company called Katalyst Water is using photocatalysis to remove organic contaminants from wastewater. The photocatalyst is a semiconductor that is activated by light. When the photocatalyst is activated, it produces free radicals that can oxidize the organic contaminants.
Membrane filtration: Nanoparticles can be used to create membranes that are highly selective for certain contaminants. This is a promising method for removing specific contaminants from water, such as arsenic or fluoride. For instance, A company called NanoSieve is using membrane filtration to remove heavy metals from water. The membrane is made of nanoparticles that are very selective for heavy metals. The heavy metals are able to pass through the membrane, but other molecules are not.
Sensors: Nanoparticles can be used to create sensors that can detect very low levels of contaminants in water. This is a promising method for monitoring water quality and ensuring that water is safe to drink.
The nanoparticles are able to bind to the arsenic molecules and remove them from the water.
Nanotechnology water treatment technology
Desalination: Desalination is the process of removing salt from seawater. Desalination is becoming increasingly important as a way to provide fresh water in areas where there is a shortage of freshwater.
Water reuse: Water reuse is the process of treating wastewater so that it can be used for other purposes, such as irrigation or industrial processes. Water reuse is an important way to conserve water and reduce the amount of wastewater that is discharged into the environment.
Water reuse water treatment technology
These are just a few of the leading edge technologies that are being developed for water treatment. As the water crisis worsens, it is likely that we will see even more innovative technologies being developed in the coming years.