What About the Water After the Los Angeles Wildfires?
I am not here to talk about the lack of water for Angelenos while they were fighting the wildfires. I’ll leave that to the politicians. I am talking about potable water, or the lack thereof, after the wildfires. I never really thought about the lack of quality drinking water after the fires until last week, when we started getting calls from people whose houses were still standing but were told that the water is not safe.
The wildfires in the Los Angeles area have destroyed thousands of structures, including many homes, leaving firefighters tirelessly battling the flames. Communities like Pacific Palisades, Altadena, and Pasadena, along with others in California, have been transformed beyond recognition or totally destroyed. As evacuation orders are lifted, residents returning home should prioritize ensuring their drinking water is safe.
What many don’t realize is how severely wildfires can impact community drinking water systems, the water supply, and even the infrastructure itself. In response, several local water systems in the Los Angeles area have issued warnings against using potentially unsafe drinking water. Fires can compromise the safety of drinking water as well as the pipes and storage tanks in multiple ways.
One issue is the strain on water systems caused by the high demand for firefighting, which can deplete resources. Additionally, extreme heat can partially melt plastic pipes and meters, releasing harmful chemicals. Smoke may infiltrate water systems, and damaged infrastructure can allow contaminants to enter the supply. After wildfires, damaged water systems have been found to contain a range of hazardous, cancer-causing chemicals, such as benzene. These substances can pose immediate health risks if the water is consumed or used, with symptoms including nausea, headaches, and skin rashes.
Wow! Talk about adding insult to injury! It may take months or even years for the water to be totally safe to drink. It is also incumbent upon me to advise you that the water may never be totally safe to drink without some form of water treatment.
It is a sad fact of life that when disasters strike there are despicable people
who try and revictimize victims of the disaster. Unfortunately, there are predators popping up all over the place, from landlords who are seeking exorbitant amounts of rent, to contractors and charlatans overcharging victims and selling overpriced poorly engineered water treatment equipment. Sadly, there are companies exploiting Angelenos who have lost so much and experienced unspeakable heartbreak.
Wildfires, such as those that affected LA, can release carcinogenic contaminants like benzene into the water, making it unsafe. We have been getting calls asking us for systems that will remove benzene. When anyone calls and asks how to do this, I have a standard answer: “measure twice, cut once!” What I mean by that is you should get a good detailed water analysis from a reputable laboratory before you purchase and install any water treatment equipment in your home.
I do not mean a simple test like a salesman might do in your home, but rather a detailed water analysis such as this one. It tests for benzene and over a hundred other contaminants. It is absolutely essential when you desire to have safe, clean water for your home and family. Now, I realize that some people will have to rebuild their homes, so they presently do not have a home where they can install water purification
equipment. I would advise you to save this article for the day that you do and our hope and prayers are with you.
When considering a water treatment system, you need to understand a couple of very important things:
1. Reverse Osmosis removes the widest spectrum of contaminants of any water treatment method; and
2. “Prolonged contact” Granular Activated Carbon is the best method to remove many (even most) chemical contaminants.
Some companies are selling “whole house” filters which are designed for light duty use in smaller homes. They contain just a few pounds of carbon and if you go inside the home and test the water for chlorine at the kitchen sink, it may say "zero". However, turn on another faucet or a second shower and you will smell the chlorine, there is simply not enough carbon to give proper contact time.
Types of Carbon Filtration: Upflow vs. Downflow
The difference between upflow and downflow carbon filtration in a tank filter lies in the direction of water flow through the carbon media and its impact on filtration efficiency, contact time, and maintenance.
Here's a breakdown:
Upflow Carbon Filtration
• Flow Direction: Water enters from the bottom of the tank and flows upward through the carbon media.
• Key Characteristics:
o Reduced Channeling: Upflow systems minimize channeling (where water creates pathways that bypass much of the media) by forcing water to flow against gravity.
o Media Expansion: The upward flow typically fluidizes or lifts the carbon media, ensuring better contact with the water.
o Backwashing Not Always Necessary: Since the media remains fluidized, it can be self-cleaning to some extent, reducing the need for backwashing.
o Applications: Used when longer contact time with the carbon media is required for better adsorption of contaminants like chlorine, chloramines, or organics.
Downflow Carbon Filtration
• Flow Direction: Water enters from the top of the tank and flows downward through the carbon media.
Key Characteristics:
o Compact Media Bed: Gravity helps pack the carbon media tightly, ensuring consistent filtration.
o Risk of Channeling: Without proper design or backwashing, water may create channels, reducing the effective use of the carbon media.
o Backwashing Required: Regular backwashing is necessary to prevent compaction, remove trapped debris, and maintain efficiency.
o Applications: Commonly used for sediment removal, taste and odor correction, and basic filtration tasks.
The choice between upflow and downflow carbon filtration depends on the specific application, water quality, and maintenance preferences. Upflow is often favored for applications requiring efficient contaminant adsorption and minimal maintenance, while downflow is suitable for simpler filtration tasks. The problem, however, is you cannot put nearly as much carbon in an upflow tank as you can in a downflow tank. For example, in a 10” x 54” media tank, you can have 1.5 cu/ft of carbon in the tank if you are utilizing it in the downflow position. This means that you must use a backwashing control valve and while maybe you only have to backwash for a few minutes every 10 days to two weeks, that is something that you have to do. In that same upflow tank, you can only have about 1.0 cu/ft of carbon because if you have too much carbon under high flows, it packs and obstructs the upper distributor, limiting the flow. In my opinion, for the absolute best carbon filtration, it is best to utilize downflow filtration with a
backwashing valve that occasionally reclassifies the media bed and prevents
channeling.
If you would like to dig a little deeper and gain more understanding of filtration,
particularly carbon filtration, let’s talk about Empty Bed Contact Time (EBCT). EBCT is a key concept in water treatment, especially for filtration systems like carbon filters. It refers to the amount of time water spends in contact with the filter media within the filter bed (e.g., activated carbon, resin). EBCT is a critical parameter for ensuring adequate removal of contaminants.
How EBCT is Calculated
EBCT is expressed in minutes and is calculated using the formula:
EBCT=Volume of Filter Media (in cubic feet or liters)/Flow Rate (in cubic feet per minute or liters per minute)
Key Components of the Formula:
1. Volume of Filter Media: The empty space that the media occupies in the filter tank, excluding water.
2. Flow Rate: The rate at which water flows through the filter.
Why EBCT is Important
Adequate Contaminant Removal:
o Longer EBCT allows for more interaction between the water and the filter media.
o Essential for processes like adsorption (e.g., activated carbon) or ion exchange (e.g., softeners).
2. Media Efficiency:
o Optimized EBCT ensures the media works effectively without premature exhaustion. For example, carbon filters need sufficient time to adsorb chlorine, volatile organic compounds (VOCs), or taste and odor compounds.
3. System Design:
o EBCT guides the sizing of the filter tank and media volume for specific treatment needs.
o Short EBCT might lead to incomplete treatment, while excessively long EBCT could be unnecessarily costly.
Typical EBCT Ranges
• Activated Carbon:
o For chlorine removal: 5–10 minutes.
o For organic contaminant removal: 10–20 minutes.
• Ion Exchange Resins:
o Typically 2–5 minutes, depending on the resin and application.
• Biological Filtration:
o Often requires 10–15 minutes to allow microbes enough time to process contaminants.
Example
If you have a carbon filter with:
• Media volume: 2 cubic feet.
• Flow rate: 5 gallons per minute (GPM) (0.67 cubic feet per minute).
- Volume of Filter Media = 2 cubic feet
- Flow Rate = 0.67 cubic feet per minute
In this case, the EBCT is 3 minutes, which might be insufficient for certain applications like removing organics but adequate for basic chlorine removal.
Optimizing EBCT
• Increase Media Volume: Provides more contact area and longer EBCT.
• Reduce Flow Rate: Slower flow allows water to spend more time in contact with the media.
• Series Filtration: Using multiple filters in series can increase total EBCT.
Proper EBCT is vital for achieving effective water treatment tailored to the contaminants and performance goals of the system.
I realize that this is highly technical, but it is important that you understand
that prolonged contact and adequate empty bed contact time is what will deliver you clean, great-tasting water that is safe to drink. There are no shortcuts, which is why you need a water treatment company with nearly three centuries of combined experience in treating the worst water, rather than a slick marketing company that happened to pick water treatment as a hot product to sell. At US Water Systems, we are water treatment experts not slick marketers. We don’t have a “one size fits all.” Every application is different and a water test is absolutely essential.
At US Water Systems we design systems to solve your water problems, address health issues and suit your lifestyle. Here are some typical systems we have recently designed. If you don’t have a “cookie cutter” house, why would you want a “cookie cutter water treatment system.
