Sewage treatment plant intermittent use

[jfb]

So i set aside last friday to order a sewage treatment plant(STP), book in my digger driver, hire digger buy shingle etc but then spent the whole day down the rabbit hole of different STPs.

I have done a fair bit of reading/research and was all set to get a Vortex but by the end of the day and talking to many different people am no closer to a decision so if anyone has any advice/experience it would be greatly appreciated.

I am making a small barn next to my house into a small 2 bed dwelling so was looking for a 4/6 person STP. Vortex seemed to tick all the boxes because it can be turned down as appropriate. But the problem is that there is a chance we will use it as a holiday let rather than constant occupancy. There seem to be many claims about how well different STPs can cope with intermittent use and on speaking to the Vortex manufacturers they recommended their Falcon as it is a three stage process which copes better with times of no use. But then on speaking to a Marsh rep (their STP seem to be a three stage design as well) he was very sceptical of any claims that they will continue to function if there is no use for as little as 10 days. Went back to Vortex/Falcon and they then recommended their Filterpod but I haven't really got my head round the pros/cons of it and it is expensive. I don't have the option of joining my existing septic tank for the house or making a new combined one for both so am a little stumped how to proceed. I suppose I could always pop into the barn when it isn't inhabited to feed the STP myself but that doesn't seem like the ideal solution!

Anyone had actual experience of STPs and times of less use and how well they cope?

Also - anyone had any experience of the Matrix STP - seems similar to the vortex but it has a three stage system and is cheaper than the falcon?

[ProDave]

A word of warning. Don't plant it in shingle unless you are VERY sure the water table will never come up high where you are.

[jfb]

thanks I have already got cement and ballast on my order list as I am in a high water table area!

[Mr Punter]

36 minutes ago, ProDave said:

A word of warning. Don't plant it in shingle unless you are VERY sure the water table will never come up high where you are.

 

Agreed as I have done this with a pump station.  The ground water pressure began to crush the chamber.  It was too late to dig out, so we just concrete inside the bottom 2 feet of the chamber.  Luckily the chamber was oversized and it seems to have stopped deforming but in hindsight it would have been better to concrete base, install chamber, fill with water and concrete surround.

[Jeremy Harris]

Some treatment plants need a ground anchor kit in order to be able to concrete them in, I believe, and some don't.  Ours (a Biopure) had two options for installation in a high water table position; one was to use their ground anchor kit (essentially some galvanised chains and angle iron) the other was to cast a concrete ring around the base.  The tank had moulded lugs around the lower part that could be embedded in concrete to make sure it stayed down.

 

Unlike a pumped system, a treatment plant will usually sit full of effluent, so having them float up is only a problem when they are empty, when being initially lowered into the hole and when having the sludge pumped out every two or three years.

[ProDave]

We made that mistake (were advised badly) at our last house, so we make sure we only ever get it desludged in a very dry spell when we know the water table is down, e.g. it was done just a couple of weeks ago after our long dry spring / early summer.

[jfb]

good to know about sensible pumping strategies.

 

anyone with any advice/knowledge on the pitfalls of intermittent use for sewage treatment plants?

[Ian]

On 16/06/2018 at 11:42, jfb said:

 

Anyone had actual experience of STPs and times of less use and how well they cope?

 

I'm using a Bio-pure 1 for a small holiday home with just 2 of us using the building at weekends only. The manufacturer advised me to install the air pump on a simple time switch 2 hours on & 2 hours off. 

It's been running now and in use without any problems since about January 2017. Since I installed mine they have altered the design slightly to further improve its performance during intermittent use.

[jfb]

good to know Ian - do you know what they did to alter the design to further improve use for intermittent use?

 

[Ian]

7 minutes ago, jfb said:

good to know Ian - do you know what they did to alter the design to further improve use for intermittent use?

 

its a system to automatically return sludge from the outer ring back to the inner one

[joe90]

I have just installed a vortex because it can be turned down to match the occupancy, we are in very wet ground and concrete up to within 400mm of ground level, no ground ancour needed as ridges around it are held by the concrete. I have not heard of a plant for intermittent use.