STP emptying the same as desludging?

[everdecreasingcircle]

Our STP needs emptying as it does every year.  The engineer said it needed desluding....i just want to check that when it is emptied and jet washed clean, that it is the same as desludging or is that something else?  Its a vortex 10 that we have .  Many thanks

[ProDave]

No, never totally empty it and why would you want it jet wash cleaned?  You want to leave behind some of "the good stuff" to make it work.

 

After desludging full up with water, don't leave it nearly empty.

[everdecreasingcircle]

Thank you for getting back to me.   It would seem that is what has happened in the past.   I will speak to outmr engineer. We always fill up with water after emptying.  

[Crunchynut]

I’m not sure the advice is right.

Potentially, the dead sludge at the bottom of the tank has no bacterial qualities. It may just be inorganic stuff, for example.  It’s just taking up space and potentially gumming things up.

 

 

A clean tank filled with fresh water will soon establish the necessary bacteria. In the right conditions bacteria will reproduce rapidly.  Just like it did when it was new. 

 

I agree with you both on refilling though - in this wet weather, if there is any doubt about whether the tank has been installed with enough concrete in a high water table area, fill it up with fresh water immediately (ie don’t leave it empty to fill up naturally) lest it floats out of the ground. This might be a reason not to empty it completely, depending on how quickly you can refill it. Always best to de-sludge in the summer months if possible, for this reason.

 

By the way, what makes you believe it needs emptying?

 

 

 

Edited March 29, 2023 by Crunchynut

[Kelvin]

Why does it need emptying every year. That’s unusual for a PTP. 

[everdecreasingcircle]

Thank you for your advice, It has always been completely emptied previously and re filled every year. we were advised by our engineer during its service that it could do with emptying.

[Gill]

We're STP and new to that system having only moved here last year. We requested inspection report and sesludge before moving in. The company that conducted (who seem to be well regarded) told us deslugde every two years and they check they system at the same time. I assume time frames might differ based on tank size /occupancy - the previous owner was doing every three years. 

As others have said - never empty. Takes some time to build up the right conditions for optimal operation. 

[Crunchynut]

11 minutes ago, Gill said:

 

As others have said - never empty. Takes some time to build up the right conditions for optimal operation. 

How do you know this? Science or hear say?

[Crunchynut]

53 minutes ago, everdecreasingcircle said:

Thank you for your advice, It has always been completely emptied previously and re filled every year. we were advised by our engineer during its service that it could do with emptying.

I would ask the engineer what leads them to belleve it needs emptying. 

 

Is sludge obviously passing over the outlet?

Is the effluent cloudy?

have they run a settled sludge depth core test?

Have they run a test to show that the solids ratio is above limits?

 

I’m not saying it doesn’t need emptying, but if you are concerned then a few probing questions might help.

 

Edited March 29, 2023 by Crunchynut

[Crunchynut]

I may have been a little contrary for which I apologise to all. I’m just trying to seek understanding beneath what is said.

 

Here is my logic. 
 

First, like a say, if inorganic stuff is building up in the bottom of the tank, if you perpetually leave it there then at some point there is going to be a problem.

 

Second, bacteria reproduce at an astonishing rate in the right conditions. I believe a new tank of fresh water will soon react to the food supply (poo). Bacteria don’t need an invitation.

 

Third, bacteria soon die if the conditions aren’t right. If you leave biomass in the tank, which is mostly full of fresh water and very little food, I believe they will just die, or diminish to low numbers that the low concentration of food can support. Just like if you were starting afresh.

 

So, I may be wrong, but my logic says empty completely (notwithstanding the points about tank integrity in wet ground).

 

 

 

 

[everdecreasingcircle]

Many thanks for everyones responses.  Very helpful as always.  So glad i found this site.

[Gill]

47 minutes ago, Crunchynut said:

How do you know this? Science or hear say?

Hear say. 100%.😁

As I say, we're new to this all but have taken advice of long term septic tank users and the local company that service and desludge.   I'd go with the science but I'm light on the exact workings. 

 

 

 

[Crunchynut]

8 minutes ago, Gill said:

Hear say. 100%.😁

As I say, we're new to this all but have taken advice of long term septic tank users and the local company that service and desludge.   I'd go with the science but I'm light on the exact workings. 

 

 

 

I agree - it’s so hard to get to facts and we all do the best we can. At least this forum helps us compare notes and perhaps get closer to what’s right.

[SteamyTea]

19 hours ago, Gill said:

Hear say. 100%

 

19 hours ago, Crunchynut said:

At least this forum helps us compare notes and perhaps get closer to what’s right.

Too right.

There does seem to be a lack of scientific research available.

Makes me wonder what the plant manufacturers use when they come up with a newer design.

 

Many years ago I lived in Aylesbury, one if the larger employers there was  Klargester, only knew one person that worked there. He was a nob.

Did interview someone from there, he had lost his job. I soon worked out why.

He was a nob as well.