Did you catch the recent news about how the massive draws of water by agriculture, homes, and businesses have shifted the earth’s axis a tiny amount to the east? It’s not a huge shift – only about 1.7 inches per year – but it’s enough that it could play a role in climate change and the global sea level rise.
Many districts have water treatment plants and clean water that’s drawn from rivers, lakes, or ponds. In some areas where water sources have been running water reuse is essential. That means treating wastewater, pumping that cleaned wastewater to water treatment plants, and preparing that water for people to use. For this to work, filtration systems are a key component in making sure contaminants are removed.
The basics of water treatment are:
- Coagulation – Chemicals like iron or salts are mixed into the water. They have a positive charge. Meanwhile, contaminants like dirt have a negative charge. The opposite charges attract and cause them to bind.
- Flocculation – The water is mixed so that heavier particles form. Additional chemicals may be added to get the particle clumps known as flocs to get as large as possible.
- Sedimentation – The water is now allowed to settle. The larger flocs sink and can be removed from tanks. The rest of the water goes to filtration.
- Filtration – The treated water is pumped or travels via gravity or centrifugation through some kind of filtration system to remove bacteria, chemicals, parasites, viruses, and any other particles. Contaminants like cryptosporidium E. coli, giardia, and legionella can be found in groundwater and surface water due to animal and human waste and can make humans sick if they’re not filtered and exposed to a disinfectant.
- Disinfection – Water is treated with a chemical disinfectant such as chlorine, chlorine dioxide, or chloramines to kill any remaining bacteria, parasites, or viruses. Some water treatment plants use UV lights and ozone, but chlorine is often preferred as it can also kill the germs that build up in pipes around the water treatment plant. Once the water is treated, it’s often allowed time to sit to ensure chemical disinfectant levels meet the EPA guidelines before the water goes to homes and businesses.
The Types of Filtration Systems and Their Role in Treating Water
What are the different types of filters used in water treatment? Several options are good for adsorption, meaning they capture and hold contaminants, and only clean water is allowed through the filter. Most plants use one of these filtration options:
- Activated Charcoal:
Activated carbon filters are good for removing odors from water. They also capture particles and germs. Water treatment plants tend to use granular activated carbon as it’s able to adsorb a variety of contaminants, including some pharmaceuticals. When activated carbon needs to be replaced, it’s also compostable, which makes it an environmentally-friendly option.
This is also likely to be a form of water treatment that will be familiar to you. It’s the charcoal material found in many fish filters, pet water fountains, and pitcher filter systems like Brita or Pur. If you have a refrigerator with filtered water, you likely have an activated carbon filter doing the work.
- Coconut Fiber Filters:
Some water treatment plants have tested out coconut fiber filters. Created from the fibers of a coconut shell, these filters are great for absorbing contaminants. Plus, it gives the coconut shell fibers a second use after the coconut meat is removed for the food industry.
Coconut fibers don’t break down as easily. While an activated carbon filter usually requires some time to clear out the carbon dust, you don’t run into that with coconut fibers. It’s worth a closer look if it’s an option in your area.
Microfiltration is one option that can be used in a water treatment plant. It’s good for removing bacteria and suspended solids, but it’s not as good for removing viruses and salts. If it’s used, it’s usually a pre-treatment step.
Nanofiltration is more energy-efficient than reverse osmosis and is more likely to be used when converting treated wastewater to clean water for residential and business use. The process is similar to reverse osmosis, but it uses lower pressure. It’s also not as effective as reverse osmosis and removes about 90% of salts and almost all of the bacteria, organic matter, and viruses in water. It’s better at removing contaminants than either microfiltration or ultrafiltration.
- Reverse Osmosis:
Reverse osmosis requires a filter and is one of the best ways to get contaminants out of water. Water is pushed through a semipermeable membrane to remove viruses, bacteria, organics, dissolved salts, and other particles. It’s only 99% effective, but chemical or UV treatments kill off anything that remains.
There are two types of sand filtration. Slow sand filtration has the water travel through a funnel of sand where bacteria have colonized on the surface of the sand. As the water slowly passes through the bacteria layer known as biofilm, the microbes digest any contaminants. Anything that slips by is caught in the sand. It’s a slow process and requires a lot of space.
Because slow filtration is a time-consuming process, rapid sand filtration is often preferred. The sand filters have higher flow rates and don’t require as much space, but the sand filters do have to be back-washed regularly.
We’ve talked about microfiltration and nanofiltration. Ultrafiltration falls between the two in terms of what it can and cannot remove. It’s not good for removing salts, but it’s fantastic at removing bacteria and viruses.
With ultrafiltration, water is pushed through a filter with pores as small as five nanometers at low pressure. The tiny pores capture viruses, organic material, and other contaminants. Filters are back-washed with chemicals from time to time. Typically, ultrafiltration occurs as a pre-treatment step before reverse osmosis.
Which System Is Best?
Which is best? It’s hard to answer that without having a list of the contaminants that are most prevalent in your area.
When it comes to filtration systems, the type you use will vary depending on the contaminants that affect your district’s water. If you have higher levels of E. coli due to a number of area farms, you’ll likely need a different filtration system than a water treatment plant in a city where there are many industrial plants. Working with an expert in water treatment filtration ensures you have the right system.
Continuing research will help make water treatment processes even better. As water treatment plants look for better ways to filter newer contaminants like PCBs and forever chemicals, hopes are to make water cleaner, faster.
Stay up to date on the latest water treatment advancements by working with an expert in clean water. Lakeside Equipment is nearing a century in water treatment equipment and technologies for your water treatment and wastewater treatment plant. Give us a call or reach us online to learn more about the best water treatment filtration options.