Occasional Use Sewage Treatment

[RossMcO]

We are building in a National Park in Scotland (site plan allatched), and have approved plans to install a Klargester Biodosc system to treat our waste water before discharging to a water course on site.  We were not involved at the point that the Klargester system was specified.  

From reading the forum, I've been convinced that the air bubbler systems make more sense than the Klargester mechanical agitation system,  so thanks to everyone for the education so far.  

My next task is to select an alternative system and convince my architect & groundwork contractor (and SEPA?) to alter the intended plan.   But before then, I have a question for the forum.  This house will hopefully serve as out retirement home, but until then will only see occasional use.  We live in Germany full time, and it is likely that the house will be unoccupied for up to three months at a time.  

Reading the different threads, there is a lot of discussion about cycling the pumps to best manage electricity consumption and treatment efficiency, but what happens if there is no new foul or grey water input for two three months?

Does anyone have experience of an intermittently used system, or strategies for managing the unoccupied periods?

Any advice on one system or supplier over another in this use case?

 

Thanks in advance,

Ross.

 

Site Plan.pdf

[Russell griffiths]

We have a Graf tank, it has a computer thingy in a shed that runs the compressor. 
it is set to run the pump for 6minutes it then turns off for 4 minutes( these times could be reversed im going senile ) 

the idea is that it blows enough to agitate the poo, then when it is off it’s not long enough for it to settle over the diffuse holes before it fires back up again. 
 

if you are worried about lack of input into the system I believe there is a thing that sits in the tank and it will deliver a measured dose of good bacteria stuff if you are away for any length of time. 

[RossMcO]

Thanks Russel,

I’ve been in touch with Graf by email, and hope to have a call with them this week.  I’ll ask about their options for additional bacteria dosing.

[Kelvin]

The professionals  seem to specify a Klargester by default. Ours did the same. I changed it to the Graf One2Clean system. You do need to get approval from SEPA which is as easy as filling in a form and sending them the technical details of the treatment plant you intend using. 

[saveasteading]

1 hour ago, Kelvin said:

The professionals  seem to specify a Klargester

It was once the default and became the term for a digester. like having a Hoover.

Their marketing and technical advice helped a lot too. But that was a long time ago,

It is rather a bad habit to use the term generically these days. I can only assume that an professional using the term without a model number etc, isn't up to speed.

[crooksey]

Agree with the above, Graf can supply a "dosing" system and you can also set "holiday mode" which reduces energy consumption.

 

If the plant will be used in holiday mode, I strongly recommend a gravity outlet over a pumped (if possible) and adding a dual flap NRV between the water course and the pump. If you are not there in the event of extreme weather or a higher than usual water course, this will protect the plant.

[SteamyTea]

11 hours ago, Kelvin said:

Klargester

All the people I sacked for being useless either came from Klargester, or ended up there. Aylesbury's finest.

[RossMcO]

Thanks, for the comments. 
@crooksey gravity fall should be straight forward, the slight has a healthy slope.  The non-return-valve sounds like a sensible precaution, so I will talk that through with the groundworks contractor.

 @Kelvin
@saveasteading don’t want to do the architect a dis-service- it was spec’d to the model/part number and SEPA approved, I was just being a bit lazy with shorthand.  

[RossMcO]

@SteamyTea I guess it’s good they had somewhere to go somewhere.  Bad news is if they all stayed there together and fostered their collective incompetence. 🥴

[Kelvin]

So was ours. My point is more that there are better alternatives. At the very least they ought to discuss these decisions with you as in why this type over that type. When I questioned it with my architect he just said they always specify Klargester and they weren’t aware of the other systems. 
 

The only reason I became aware of the options and potential issues with a Klargester type system is I visited the NSBRC in Swindon. They have a section on treatment plants and a cut away Biodisc so you can see how it works. As soon as I saw that I immediately thought what happens if that fails, someone is in there trying to fix it and that someone was going to be me! 

Edited February 4 by Kelvin

[JohnMo]

19 hours ago, RossMcO said:

approved plans to install a Klargester Biodosc

It may show on your planning or building warrant, but it's not set in stone. The sewage system is only approved when when you have been through the full approval process with SEPA and have a duly approved certificate for that exact make and model. So up to that point are free to change things, after certificate issue you are not, without reapproval of the full system and new certificate.

[RossMcO]

Thanks John,

 

We have SEPA approval, so if I chose to change horses at this stage it will require resubmission.  

 

Since my last note, and guided by the above discussion, I've had some more conversations with architect and Graf, and the plot thickens.

 

Given the intermittent use, Graf UK recommended that I consider a third system: Biorock https://biorock.com/products/small-sized-systems/ecorock, which if we can manage gravity outflow, can be an unpowered system, and would not need regular dosing as per the Graf One2Pure tank.  

 

This approach on one hand is attractive as there are no ongoing running costs, but on the other hand, is it a bit of a retrograde step - it looks like a traditional septic tank with an added aerobic filtration system (filtration media lifetime claimed as <10 years)?

 

Does anyone have experience of the BioRock system?

 

Ross.

 

 

[saveasteading]

55 minutes ago, RossMcO said:

is it a bit of a retrograde step

I don't know the product but am interested enough that i will look into it for future reference.

Have they explained their logic?

 

I wouldn't  (ahem) poh-pooh it until checked out.

It is all using natural bugs to eat the poo. one method adds air bubbles to keep it moving and oxygenated. the other i assume uses the principle of enormous areas of surface for it to cling to while eaten.

That logic is good. for many (15+) years I dispensed with oil interceptors on car parks and instead used  natural drainage through lots of gravel. It worked really well and has next to no maintenance or running cost.

The analogy is quite close.

 

 

[RossMcO]

@saveasteading there is a fair amount of first order data on their website, and this video as a high level explanation   

I didn’t find any detail on the make up of their media, but not sure I would expect them to be explicit on that in a public forum anyway.  

Seems interesting as it has even fewer moving parts than the Graf system. 

Ross

[saveasteading]

It seems to be an old-fashioned septic and settlement tank, which will do 90% of the work, followed by the filter chamber. That should work nicely

£3,800 inc vat for a 10 person is not a bargain.

 

The downsides?

The outlet appears to be 2m deep or so, which will limit options and add to drain cost. OR it has a pump, so the avoidance of mechanics is lost.

If anyone was to put bleach or wash out paint brushes etc into the drains, , I think it wold cause more damage in this than in an air mixed tank.....but that's just a feeling.

If it gets heavy use on occasions will it cope?  I think so as the solids stay in tank 1.

How do you change the filter medium bags? will they still be available in 10 years?  Maybe they could be washed out.

[Roger440]

3 hours ago, RossMcO said:

@saveasteading there is a fair amount of first order data on their website, and this video as a high level explanation   

I didn’t find any detail on the make up of their media, but not sure I would expect them to be explicit on that in a public forum anyway.  

Seems interesting as it has even fewer moving parts than the Graf system. 

Ross

Coconut husks or similar i believe.

[SteamyTea]

I don't know a great deal about bio-chemistry, or even organic chemistry (I know (expletive deleted) all about chemistry really, but good at research).

What would happen if an air blower was put into a traditional septic tank?

Would the bacteria change to the ones that like oxygen (aerobic) and if the blower was switched off, who it revert to anaerobic digestion?

[saveasteading]

2 minutes ago, SteamyTea said:

revert to anaerobic digestion?

I don't know, but my vague understanding is that it is one thing or the other. Different bugs are doing the job if it is aerated or not. 

If the air was turned off, the dominant bugs would eventually change, but not suit that machine ideally.

[SteamyTea]

2 minutes ago, saveasteading said:

don't know

You got a bit of land, how about doing an experiment with 3 holes.

One bucket of poo without and aeration, one with  and one that switches every 4 months.

I would do it but my neighbours might get upset.

[Alan Ambrose]

Sometimes you guys worry me...

[SteamyTea]

14 minutes ago, Alan Ambrose said:

Sometimes you guys worry me...

Others are madder.

https://simple.m.wikipedia.org/wiki/Barry_Marshall

[RossMcO]

Have to say, I'm closer to @Alan Ambrose on this one, versus the extreme option of distilling and potentially drinking your own 'liquor', I believe one of the technical terms to be?  But, Barry Marshall got a Nobel prize for his work, so @saveasteading and @SteamyTea should be at least worthy of something similar on successful conclusion of their experiment.  🙂   Photographic/video evidence required mind...

 

Back to reality.  On the topic of longevity, I guess you could just pre-purchase the bags for the next load, and give yourself ~20 years of service. 

 

Depth might be an issue - our site does slope downwards to the water course, but more work would be needed to figure out whether we have sufficient gradient to accommodate outflow to the tank, and then another 2m to the outflow from the tank, and then sufficient drop to the water course.

 

An earlier topic the forum discussed running costs and maintenance, so to add a little bit of information to that discussion, for an aerated tank, for a 9 person Graf system, and intermittent use the estimate was 2 carbon cartridges at £150 per year plus ~£200 service visit per year.  So, an additional £500 annually plus whatever power costs may be.

 

This is not the primary consideration for me as a non-functioning or mal-fiunctioning system would soon consume that much money in call-out costs and aggravation, but I add it here just for the wider knowledge pool.

 

From all of the discussions above, my summary is:

Biodisc, not widely recommended due to mechanical elements.

Aerated: simple easily maintained, but will need careful management and additional expense if left unused for extended periods.

Biorock: maybe, but concerns over depth for gravity feed, consumables, and little/no experience of its use on the site.  

 

I still have some more calls to make, but at the moment, I would be opting for Graf or similar and building in the additional maintenance costs.

 

[saveasteading]

4 minutes ago, RossMcO said:

Aerated: simple easily maintained, but will need careful management and additional expense if left unused for extended periods.

That's all I've ever used. No careful management. The final effluent always looked and smelled completely clean, tho I never tested it.

I don't think unuse matters..the contents will fester slowly until your return.

Neither will it need much maintenance. Just allow for a sucklift every few years and a change of air pump when necessary.

[SteamyTea]

22 minutes ago, RossMcO said:

additional expense if left unused for extended periods.

If you have PV fitted, your running costs, when away, will be lower as little else will be using the power.

24 minutes ago, RossMcO said:

Barry Marshall got a Nobel prize for his work

Off to drink a pint of aqua vita.

(His work cured my stomach ulcer, he is a personal hero to me, 40+ years of thinking that eating and drinking was normally painful, 2 weeks treatment and all gone)

[RossMcO]

Completely agree on his contribution - tremendous benefit.  Touch wood, I don't have that problem (as of now) but what a fantastic shift of the accepted wisdom.