The science behind sewage treatment plants

[Crunchynut]

Further to this, I’ve found out that some filamentous bacteria  can reproduce every 20 minutes. That is, they split into 2 every 20 minutes. This means that you get exponential growth of that type of bacteria - or at least initially, until the amount of bacteria starts to make conditions for reproduction suboptimal and therefore it slows down or stops. So in a 1 hour power outage you might increase the amount of filamentous bacteria in the biomass by 8 times in ideal conditions. Enough to make the level of floc look unusually high?

Maybe.

 

Next time I have a power outage I’ll pay more attention. I’m not brave enough to do it deliberately. Please let me know if you observe the same.

Edited March 29, 2023 by Crunchynut

[dpmiller]

we had a pump failure a few months back that wasn't spotted for a week or more, and the system normally only aerates for 20mins in the hour or so; I've never seen any foaming or such in three years.

[Roger440]

On 17/03/2023 at 21:29, Crunchynut said:

I have a Vortex too and have experienced the same with the SSR (settled sludge return). How do you unblock it? I either poke around the inlet to the pipe with a long stick, or dismantle the cross pipe so I can jet some water from a hose down the pipe. It has solved the problem on the couple of occasions it has happened. What do you do? 

 

What you have observed re: cloudy effluent is explainable:

For good settlement in the settlement chamber you want the bacteria to stick together in a floc (lumps of sludge). The reason they stick together is because the bacteria form a sticky coating that is partly a defence mechanism to there being limited amounts of oxygen available. These flocs are more dense than water and hence sink in the settlement chamber, allowing clear effluent above to pass over the outlet weir. If there is too much dissolved oxygen (DO) then the bacteria don’t build up that sticky coating and hence don’t stick together, so you get fragments left over in the effluent making it cloudy. So, why does a high rate of SSR make the effluent cloudy? Well, because the longer the biomass is in the settlement tank it is obviously not being oxygenated by the bubble diffuser, so the DO balance is kept low. If you increase SSR then more of the biomass gets oxygenated per minute and that might lead too much DO and cloudy effluent.
 

As you know, the good thing about the Vortex is that the big lid allows you to easily see what’s going on (the reason I chose it over others) and that the SSR and aeration rates are adjustable. The frustrating thing is that they are fed from the same blower, so if you adjust one it affects the other. I understand why they have done that - you would otherwise need 2 blowers and twice the energy consumption - though it  makes adjustment slightly more intricate and if one goes up the other goes down. If you increase SSR you may need to reduce aeration a fraction more than it will naturally do. Personally I leave the fine bubble diffuser valve fully open and ‘throttle’ it by controlling how much air goes to the coarse bubble diffuser. 

 

 

Bit late in reply, but,

 

To clear it, just disconnect the pipe to the SSR at the adjustment valve and connect to a water hose. Turn on and leave for a few minuites. You will see some bubbling once its broken through the sludge.

 

SAfter this, i normally wind the SRR to max fir a few hours to try and drag as much as possible out.

 

All that said, the frequency with which you have to do that will steadily increase. Which is the trigger to empty it.

[Roger440]

3 hours ago, Crunchynut said:

Further to this, I’ve found out that some filamentous bacteria  can reproduce every 20 minutes. That is, they split into 2 every 20 minutes. This means that you get exponential growth of that type of bacteria - or at least initially, until the amount of bacteria starts to make conditions for reproduction suboptimal and therefore it slows down or stops. So in a 1 hour power outage you might increase the amount of filamentous bacteria in the biomass by 8 times in ideal conditions. Enough to make the level of floc look unusually high?

Maybe.

 

Next time I have a power outage I’ll pay more attention. I’m not brave enough to do it deliberately. Please let me know if you observe the same.

 

Over time all sorts of stuff has occured in the settlement chamber.

 

However, ive found its very quick to recover if everything is adjusted correctly.

[Roger440]

On 17/03/2023 at 22:17, jamieled said:

Glad to have found this thread. Any tips for a vortex where we're getting really high rates of floating sludge in the settlement chamber (and outflow chamber)? I manually push it all back through the floating sludge return every couple of days now. Started about 3 months after we last got it emptied.

 

There's no particular nasty smell, but I've tried a few combinations of settings with the blower valves and haven't had much luck. It looks like when water inflows into the tank this pushes some sediment dense water into the settlement chamber which the floating sludge return then can't cope with. I might be wrong on this of course.

 

Thats not right.

 

Vortex seem to change design details on every other tank they sell, but how often and for how long does the floating sludge run?

 

Mine does 3 mins every hour. Generally more than enough.

 

I had rhe same issue as you early on. I just twiddled the various adjustments, so both bubblers, SSR and floating sludge settings.

 

The SSR seems mosrt crtiical. I can now tell by the way it comes out of the overspill hole if its right.

 

[Crunchynut]

1 minute ago, Roger440 said:

 

 

However, ive found its very quick to recover if everything is adjusted correctly.

I agree. That is what I am learning - symptoms can change overnight. Clever things these bacteria.
 

Brings us back to the whole essence to this post - they are hardly ‘install and forget’ if they are to be kept working consistently within their design spec.

[Crunchynut]

2 minutes ago, Roger440 said:

 

 

The SSR seems mosrt crtiical. I can now tell by the way it comes out of the overspill hole if its right.

 

Same here. I like it to be just spilling over occasionally.

[Roger440]

4 minutes ago, Crunchynut said:

I agree. That is what I am learning - symptoms can change overnight. Clever things these bacteria.
 

Brings us back to the whole essence to this post - they are hardly ‘install and forget’ if they are to be kept working consistently within their design spec.

 

I have a few collegues in Oz.

 

One of them had a rural property with a septic tank or STP.

 

Government type comes round twice a year to test the outfall. Woebetide you if it fails.

 

They are super hot on stuff like that over there. They love reules.

[Roger440]

5 minutes ago, Crunchynut said:

Same here. I like it to be just spilling over occasionally.

 

Mine spills over continuously.

[Crunchynut]

1 minute ago, Roger440 said:

 

Mine spills over continuously.

Do you have to throttle back the coarse bubble rate to get that much SSR flow? 

 

I have a pumped inlet so by the time the stuff has been pumped there aren’t any  lumps (urgh) so coarse bubbles don’t really have a job to do. But even then, if SSR is full chat then I think that would break up any new arrivals. That’s on the newish tanks - I notice on older tanks the SSR just dumps back into the aeration chamber, not the inlet chamber.

[dpmiller]

does everyone with one of these Vortex plants have to do all this dicking around?

[Crunchynut]

1 hour ago, dpmiller said:

does everyone with one of these Vortex plants have to do all this dicking around?

They don’t have to,  no. They could just set up once at installation and forget about it, just like other systems.

 

But do you really believe any system works perfectly for their life after initial installation?

 

I doubt it, and that is the whole point of this thread - that, probably, most people are unaware whether their system is working to spec or not, and there is very little information around to help. And 12 months between ‘service’ is a long time for things to be going wrong.

[joe90]

1 hour ago, dpmiller said:

does everyone with one of these Vortex plants have to do all this dicking around?

No, I installed mine, got a chap to set it up for me from a local company (he had his own Vottex at home) and not touched it since, yes sludge levels change occasionally but nothing that required “dicking around “.

[jamieled]

14 hours ago, Roger440 said:

 

Thats not right.

 

Vortex seem to change design details on every other tank they sell, but how often and for how long does the floating sludge run?

 

Mine does 3 mins every hour. Generally more than enough.

 

I had rhe same issue as you early on. I just twiddled the various adjustments, so both bubblers, SSR and floating sludge settings.

 

The SSR seems mosrt crtiical. I can now tell by the way it comes out of the overspill hole if its right.

 

I have it set to run for about 5 minutes every hour. Could you describe what your SSR looks like when it's working well (accepting what works well for you may not necessarily work for me)? Is there a lot of overspill?

[Roger440]

7 minutes ago, jamieled said:

I have it set to run for about 5 minutes every hour. Could you describe what your SSR looks like when it's working well (accepting what works well for you may not necessarily work for me)? Is there a lot of overspill?

 

Ill do a video for you.

[Roger440]

5 hours ago, dpmiller said:

does everyone with one of these Vortex plants have to do all this dicking around?

 

I think they take a lot of getting right.

 

Once thats done, it works fine until the SSR can no longer cope.

 

As ive said before, its the systems weakness.

 

When it becomes a problem will vary massively between users.

 

Id probably buy something else if i had my time again. In fact, id fit a septic tank! No power consumption and no noise.

 

[Alan Ambrose]

>>> Ill do a video for you.

 

The kind of thing the 9 o'clock News warns its viewers about in advance? 

[saveasteading]

I have an innate preference for 3 chamber systems. They continue to work whether aerated or agitated or not. The wiers between sections prevent solids getting right through. Occasionally they might be overworked, but a decent drainage field will complete the process.

 

In this old house we have, and are entitled to keep, a single brick chamber that discharges to soakaway. It is far from fully treated, but by inspection a 2nd and 3rd chamber would do the job.

[saveasteading]

3 hours ago, Alan Ambrose said:

The kind of thing the 9 o'clock News warns its viewers about in advance? 

I always decribed drain survey recordings as dirty videos, despite nobody ever laughing.

[Crunchynut]

8 hours ago, jamieled said:

I have it set to run for about 5 minutes every hour. Could you describe what your SSR looks like when it's working well (accepting what works well for you may not necessarily work for me)? Is there a lot of overspill?

This  may help.  Give it a miss if you are squeamish!
 

https://youtu.be/QHaRbszsSC4

 

[ToughButterCup]

On 15/03/2023 at 20:24, Crunchynut said:

Some people will want to install and forget, which is fine. Read no further.

...

Finding information in the U.K. is difficult. It’s as if regulations for home sewage treatment  plants have been brought in but not really understood, and the real world running of plant to achieve these goals ignored. Some of the literature I have found - largely on manufacturer sites - is laughable. Clearly they don’t really understand, or they thing we are too unintelligent to understand, or both. That’s my opinion anyway.

...

 

Exactly correct ( === ) .

 

Here's a memorably informative post from a few years ago: it might help ....?  Two authors ( @Jeremy Harris and @Stones ) provide really good summaries of the issues.

 

The soft and smelly is as hidden as it can be in the UK. Vee Tschermans are not so skveemish.

[saveasteading]

1 hour ago, ToughButterCup said:

really good summaries of the issues.

Yes they are.

I would add this.

The need for desludging is generally overstated. If the plant is working well there isn't much sludge, just stuff that shouldn't be flushed, and that floats or sinks out of harms way.

If the pump fails, a 3 chamber keeps working but not so well. The pump is just like a fish tank one. Cheap and easy to replace.

The soakaways for treated outfall as mentioned are many times smaller than the regulations require. The regulations are wrong in my opinion, but beware of an earnest bco if you don't have enough land.

[joe90]

37 minutes ago, saveasteading said:

If the pump fails,

Usually the diaphrams fail and they can be replaced cheaply.

[SteamyTea]

31 minutes ago, joe90 said:

Usually the diaphrams fail and they can be replaced cheaply.

Aren't diaphragms one of the things 

1 hour ago, saveasteading said:

just stuff that shouldn't be flushed

 

[ToughButterCup]

We recently had a large rain 'event' ( as the Met Office are wont to call them) . It rained hard all day - no wind just hard dense rain. All day long.

 

A couple of years earlier, our BCO at the time - never had a visit from the same BCO twice - suggested we  connect the guttering from one side of the Piggery (roof area 10sq m) to the foul drainage. 

 

"It'll just keep the foul drain wet and help flush stuff through" was her memorable advice. Good idea I thought. The tank has been ticking along nicely for the last three years.

 

24 hours after the deluge, the poo tank started smelling . I don't think her advice was a good idea now. 

 

I have no proof that the rain caused the change in the processes going on in the tank.  But a few hundred gallons of fresh clean water must have changed something. 

 

Local advice "Yer wanna foind a good-n dead fezzunt and stick'n in lad... tharal sort it"

(On reflection, I think that guy might have come from Somerset)