When I started working at Ovivo back in 2011
they had an installed base of about 200+ MBR (membrane bio-reactor) plants at the time.
Most of them were very small plants and the plant operators might even be part time. One city in Ohio even had its police chief doing double duty as the wastewater plant operator. The plant operators would call me for tech support and the most common question I got was how much bleach and water do I need to use to do a CIP (clean in place)?
Quick explanation for non-wastewater people: in an MBR you have these filters (membranes) that are submerged in a tank full of (dirty) water. The membranes filter clean water out of the tank, but over time they get clogged (fouling), and they have to be cleaned. The way you do it is to back-fill them with a very mild bleach solution. In other words, the membranes stay in the tank, the tank stays full of wastewater, but the bleach goes on the inside of the membranes and you let it sit there soaking for a few hours.
C1V1 = C2V2
Basically it all comes down to the dilution equation, concentration times volume (initial) equals concentration times volume (final). In plain english, if you start with a bottle of bleach it'll say 6% on the label, that's C1. The bottle is probably 1.5 gallons, and that's V1. Now you dump the bleach into a big tub and add a whole bunch of water, say 13.5 gallons: you just wound up with 15 gallons total: that's V2. But now that you added all that water it's not 6% bleach anymore. In fact, you increased the total volume by 10 times, so guess what: the same thing happens to the strength of the bleach. It's 10 times less. So C2 is going to be 0.6%.
Sounds simple, but it gets a little hairy in an MBR plant because you have to have a lot of information. What kind of membranes do I have? How much volume do they hold? What's the bleach concentration for a normal clean? How about for an emergency clean? And so on. Don't forget that sometimes you might use acid instead of bleach.
One of my coworkers came up with the idea that there should be a smart phone app so that operators could just hit a few buttons and let it do the math for them. So in 2019 I built an iPhone app. The code is here. It's no longer on the app store because I didn't have time to update as Apple came out with new verions of the iPhone, so I've built a web version here on this page as well.
Most of them were very small plants and the plant operators might even be part time. One city in Ohio even had its police chief doing double duty as the wastewater plant operator. The plant operators would call me for tech support and the most common question I got was how much bleach and water do I need to use to do a CIP (clean in place)?
Quick explanation for non-wastewater people: in an MBR you have these filters (membranes) that are submerged in a tank full of (dirty) water. The membranes filter clean water out of the tank, but over time they get clogged (fouling), and they have to be cleaned. The way you do it is to back-fill them with a very mild bleach solution. In other words, the membranes stay in the tank, the tank stays full of wastewater, but the bleach goes on the inside of the membranes and you let it sit there soaking for a few hours.
C1V1 = C2V2
Basically it all comes down to the dilution equation, concentration times volume (initial) equals concentration times volume (final). In plain english, if you start with a bottle of bleach it'll say 6% on the label, that's C1. The bottle is probably 1.5 gallons, and that's V1. Now you dump the bleach into a big tub and add a whole bunch of water, say 13.5 gallons: you just wound up with 15 gallons total: that's V2. But now that you added all that water it's not 6% bleach anymore. In fact, you increased the total volume by 10 times, so guess what: the same thing happens to the strength of the bleach. It's 10 times less. So C2 is going to be 0.6%.
Sounds simple, but it gets a little hairy in an MBR plant because you have to have a lot of information. What kind of membranes do I have? How much volume do they hold? What's the bleach concentration for a normal clean? How about for an emergency clean? And so on. Don't forget that sometimes you might use acid instead of bleach.
One of my coworkers came up with the idea that there should be a smart phone app so that operators could just hit a few buttons and let it do the math for them. So in 2019 I built an iPhone app. The code is here. It's no longer on the app store because I didn't have time to update as Apple came out with new verions of the iPhone, so I've built a web version here on this page as well.
Membrane Cleaning Calculator
Select chemical:
Select membranes:
Select no. of membranes:
Cleaning solution strength:
You will need 120gal of water and 12 gal of 6% bleach for your CIP soak