Treatment plant or soakway?

[Thedreamer]

Good morning,

 

We have in our building warrant and SEPA approval for a soakaway from a septic tank. Is the 'end product' that is discharged from a treatment plant better for the environment than a soakway? Would this be seen as positive upgrade by SEPA/Building Control?

 

My limited understanding of treatment plants would suggest you have two different options, one with a electrical feed and other that don't.

 

Could anybody point me in the direction of a treatment plant that would be suitable for a family of four?

 

Thanks

 

Kerry

[Jeremy Harris]

The general rule is that treatment plants are far and away the preferred option, a septic tank with tertiary treatment (usually land drains in aerobic soil) is acceptable if you have the land area for the drains and a cess pit is generally forbidden unless there is no alternative option.

 

A treatment plant discharges treated effluent with a low biological oxygen demand (BOD), so can be discharged to a watercourse (subject to agreement) or can be discharged to a suitable land drain/soakaway arrangement.

 

A septic tank doesn't aerobically treat the effluent, so it's discharge has a very high BOD which needs tertiary treatment.  Traditionally this was done using a leach field of shallow land drains that allowed aerobic soil bacteria to do the final treatment, but these only have a limited life of around 10 to 15 years before they stop working, due to biofilm build up, hence the preference for an aerobic treatment plant.  A septic tank can discharge to an alternative tertiary treatment system, like a reed bed, but although reed beds work well there is quite a lot of maintenance involved and a slight risk of infection when thinning them out and trimming them back.

 

Generally, blower type treatment plants seem to be the best.  There are some non-electrical units around, but opinions on them seem mixed - some have found that they work well when properly set up, others have problems with them.    The ones I would avoid are any that have electrical operated moving parts inside the chamber, as they look to be a maintenance nightmare.  There are lots of well-respected blower units around in the size range you're looking at, and several here have experience of some of them.  We have a Biopure1, that suits 1 to 6 people, and have found it works well.  Ours discharges to a nearby stream; an easier option to get consent for here in England than it is in Scotland, for some bizarre reason to do with different policies between SEPA and the EA.  Others here have used blower units like the Vortex, which is similar to the Biopure but has the option of a timed blower pump (now also an option for the Biopure I believe) that saves energy.

 

The hurdles you face are really to do with where you're going to discharge the output from the treatment plant.  @ProDave had to jump though some hurdles with SEPA, so may be best advised as to how to handle things where you are.  I got consent to discharge to the nearby stream from our EA within an hour of asking, but I gather that SEPA are a lot different to deal with!

[ProDave]

For the small extra cost, I would definitely fit a treatment plant now rather than a septic tank.  We were doing that anyway and it ended up getting  permit to discharge to the burn, which they definitely would not have allowed with a septic tank

 

Our issue with SEPA was building control rejected our soakaway plan and it ended up with no option but discharge to the burn (with a small partial soakaway). SEPA have a presumption against discharge to a watercourse and only allow that as a last resort if all other options have proved unsuitable which is the situation we had reached.

[nod]

6 hours ago, JSHarris said:

The general rule is that treatment plants are far and away the preferred option, a septic tank with tertiary treatment (usually land drains in aerobic soil) is acceptable if you have the land area for the drains and a cess pit is generally forbidden unless there is no alternative option.

 

A treatment plant discharges treated effluent with a low biological oxygen demand (BOD), so can be discharged to a watercourse (subject to agreement) or can be discharged to a suitable land drain/soakaway arrangement.

 

A septic tank doesn't aerobically treat the effluent, so it's discharge has a very high BOD which needs tertiary treatment.  Traditionally this was done using a leach field of shallow land drains that allowed aerobic soil bacteria to do the final treatment, but these only have a limited life of around 10 to 15 years before they stop working, due to biofilm build up, hence the preference for an aerobic treatment plant.  A septic tank can discharge to an alternative tertiary treatment system, like a reed bed, but although reed beds work well there is quite a lot of maintenance involved and a slight risk of infection when thinning them out and trimming them back.

 

Generally, blower type treatment plants seem to be the best.  There are some non-electrical units around, but opinions on them seem mixed - some have found that they work well when properly set up, others have problems with them.    The ones I would avoid are any that have electrical operated moving parts inside the chamber, as they look to be a maintenance nightmare.  There are lots of well-respected blower units around in the size range you're looking at, and several here have experience of some of them.  We have a Biopure1, that suits 1 to 6 people, and have found it works well.  Ours discharges to a nearby stream; an easier option to get consent for here in England than it is in Scotland, for some bizarre reason to do with different policies between SEPA and the EA.  Others here have used blower units like the Vortex, which is similar to the Biopure but has the option of a timed blower pump (now also an option for the Biopure I believe) that saves energy.

 

The hurdles you face are really to do with where you're going to discharge the output from the treatment plant.  @ProDave had to jump though some hurdles with SEPA, so may be best advised as to how to handle things where you are.  I got consent to discharge to the nearby stream from our EA within an hour of asking, but I gather that SEPA are a lot different to deal with!

The plot of land that we bought was part of a large garden

There was two tankks that had been fitted 10 years ago that were problematic It was upto us to put a treatment plant in for ourselfs and re route the neibouts drain and install anew tank

The difference between the tank and treatment plant was a thousand Same labour and concrete I asked the neibour to put  500 to and I would install treatment plants for both of us

NO Eighteen moths on they are kicking themselves 

I’d no option but to install a treatment plant 

But I’m glad I did 

[joe90]

We have just installed a treatment plant called a vortex and it discharges to a ditch that is dry for a couple of months a year. I didn’t think septic were allowed for new builds any more( but may be wrong) . Because the ditch dry,s for a while during the summer the pipe to the ditch is called a rumble drain, a pipe with holes In it and set on drainage stone. We are very pleased with ours.

[Thedreamer]

Thanks for the helpful comments chaps.

 

If we were to install the treatment plant it would be similar to @joe90 setup. 

 

I think I'll have a call with SEPA tomorrow and do some research on the various options. I like the idea of the non-electrical ones.

[joe90]

11 hours ago, Thedreamer said:

I like the idea of the non-electrical ones.

 

So did I  but I was not convinced by the theory.

[Jeremy Harris]

11 hours ago, Thedreamer said:

I think I'll have a call with SEPA tomorrow and do some research on the various options. I like the idea of the non-electrical ones.

 

A chat with SEPA would definitely be a good start, after the hassles that @ProDave had in sorting out how to discharge the treated effluent. 

 

I also was very drawn to the non-electrical ones, and went to look at one locally installed unit, a BioRock.  It was working OK, but the owners had spent a fair bit of time getting it to operate correctly.  They still had a mild odour problem from it when I went to see them, and were in the process of trying to arrange for a different vent pipe arrangement to overcome that.  They had also had to have the media replaced (under warranty) because of an initial problem.  I believe someone here has one, and had a few teething troubles in getting it to work OK.

 

One things seems clear, they are very critically dependent on getting good natural airflow over the media, and the positioning of the vents to allow this seems quite critical.  Local wind conditions can seemingly have a significant impact on effectiveness, as all these units rely on stack effect to drawn air in at a low air inlet and out at a higher one, with the air flowing over the media in order to allow aerobic bacteria to do their stuff and break everything down.

 

I remain sceptical that there will be a consistent enough airflow under all local wind conditions to allow effective, odour-free, treatment, I'm afraid.  The big advantage of all the pumped air systems is that there is always a surfeit of air, which not only keeps the unit working properly but also means there is virtually never any noticeable odour.

[ProDave]

You have to satisfy SEPA and Building control.  So exactly what you are allowed to have might not be agreed until your building warrant is processed. 

 

I can say our air blower plant (Conder, very similar to the Bio Pure) is working very well. There is no odoor and what comes out into the burn is a clear odourless liquid.

[joe90]

Like Jeremy above I think local conditions apply, we may have been ok because it’s mostly windy here (near coast) but Jeremy is in a valley that suffers from stagnant air (bonfires cause big problems as the smoke does not blow away).

[Tyke2]

With a treatment plant is there any restriction on the cleaning products etc you use in the house? For instance will my wife have to give up on her love of bleach?

 

[Ed Davies]

I'll have a treatment plant (BioPure 1). Vendor's planning permission in principle specified a rumbling drain. Though the BioPure and the like are supposed to give an output suitable for discharge to a watercourse SEPA like a rumbling drain as a backup. The 50 metre length they ask for seems a bit much, just about OK on my site but must be awkward for many. Asked BC during warrant discussion exactly what they were looking for. “Ask SEPA”. Went to talk to SEPA, very helpful on the paperwork side of things (how to apply for consent to discharge, etc) but as to the practicalities of the rumbling drain: “Ask your BCO”. Made up a drawing/specification of what I thought was reasonable (100mm holy pipe wrapped in 2" clean and geotextile). BC accepted it happily enough.

[Jeremy Harris]

1 hour ago, Tyke2 said:

With a treatment plant is there any restriction on the cleaning products etc you use in the house? For instance will my wife have to give up on her love of bleach?

 

 

 

Very small amounts of well-diluted bleach you can just about get away with, but in general you need to avoid anything that has a powerful biocide in it from going down the foul drain, and that includes stuff like Jeye's Fluid, as well as any cleaning products that contain chlorine.  If you use chlorine based products (as I do occasionally to disinfect pipes etc when doing any work on our borehole system), then you can just leave the waste water with the chlorine in it in an open bucket for a few days and it will break down, leaving the water relatively harmless.  I tend to use any water with chlorine in to wash down our stone paths, as it's pretty good at cleaning up the sandstone.

[joe90]

I too have a missus that loves to use bleach and I have had to rein her in on cleaners around the house.

[ProDave]

1 hour ago, Ed Davies said:

I'll have a treatment plant (BioPure 1). Vendor's planning permission in principle specified a rumbling drain. Though the BioPure and the like are supposed to give an output suitable for discharge to a watercourse SEPA like a rumbling drain as a backup. The 50 metre length they ask for seems a bit much, just about OK on my site but must be awkward for many. Asked BC during warrant discussion exactly what they were looking for. “Ask SEPA”. Went to talk to SEPA, very helpful on the paperwork side of things (how to apply for consent to discharge, etc) but as to the practicalities of the rumbling drain: “Ask your BCO”. Made up a drawing/specification of what I thought was reasonable (100mm holy pipe wrapped in 2" clean and geotextile). BC accepted it happily enough.

"rumbling drain" is a new expression to me?  care to explain?

 

SEPA gave permission (eventually) for out Conder plant (very similar to the BipPure) to discharge to the burn, but insisted on a partial soakaway preceding the discharge.  That actually works very well, in the dry season (when the burn flow is low) not a lot makes it past the partial soakaway into the burn.  But in winter when the water table comes up and the ground is saturated, most of it just goes straight through the partial soakaway, but the burn is at full flow and dilution is high.  So the partial soakaway makes sense and seems to work well.

[Crofter]

The question isn't really 'treatment plant or soakaway'- it should be 'treatment plant or septic tank'. Both solutions need to discharge the effluent somewhere, and the generally preferred method is a soakaway. You are allowed a 25% reduction in soakaway area if you use a treatment plant, but otherwise it's all much the same.

 

The reasons for not using a soakaway would be if you don't have enough space for one, or if the ground conditions are unsuitable (e.g. high water table, slow draining clay soil, rotten rock which drains too fast). The backup option is to discharge to a watercourse, which I don't think is possible with a septic tank.

From my experience of building in Scotland, you won't be allowed to discharge effluent (from either a septic tank or a treatment plant) straight into a drying ditch.

I was allowed to use a partial soakaway which in wet weather overflows to a ditch- in wet conditions there will be plenty of flow in the ditch for dilution.

The partial soakaway does not seem to attract the same degree of scrutiny as a full sized soakaway- I was given very vague instructions on what sort of size to make it.

 

Plenty of people are still fitting conventional septic tanks, and they can offer the cheapest solution if you have the right plot. However there's no denying that the effluent from a treatment plant is far less nasty, and the difference in cost is nothing really in the scheme of a whole house build. Don't worry too much about avoiding electricity use, it's never going to add much to your bills.

 

FWIW I went with a slightly unusual system called a Puraflo, which is quite popular on Skye. This involves installing a normal septic tank, and then downstream of this is a pump chamber feeding into a big box full of peat fibre. The outflow from the septic tank is pumped into this and it trickles down through the aerated fibres, emerging from the bottom as relatively benign effluent- on a par with the best treatment plants. I chose this system as it is supposed to be quite tolerant of intermittent usage patterns.

 

Finally, when comparing treatment plants, you need to look at three figures: suspended solids, biological oxygen demand, and ammonia (abbreviated as SS, BOD, and NH3). If a supplier doesn't deal in these terms, run away, they are probably snake oil salesmen

[Ed Davies]

54 minutes ago, ProDave said:

"rumbling drain" is a new expression to me?  care to explain?

Yes, was new to me, too, and didn't respond well to web searches. It's sort of like a French drain where the output of the treatment plant gets mixed with surface water and has a chance to clean naturally before it reaches the watercourse. Specification I submitted to building control attached.

 

57 minutes ago, Crofter said:

The reasons for not using a soakaway would be if you don't have enough space for one, or if the ground conditions are unsuitable (e.g. high water table, slow draining clay soil, rotten rock which drains too fast).

First question SEPA asked was “has a percolation test been done?”. For me the test had been on behalf of the vendor and found it didn't - there's solid clay just below the surface (on top of rock only about 500mm down). If the ground percolated they'd have wanted some sort of leach field/soakaway rather than going to a watercourse.

Perihelion Rumbling Drain.pdf

[Crofter]

@Thedreamer have you done your Trial Site Assessment Hole, and your percolation tests, yet?

[ProDave]

Thanks @Ed Davies  Not seen that name for it before, but it is exactly what we did, though it was all on our own land and only 10 metres long and we described it as a partial soakaway.

 

There is this really bizarre thing in building regs saying a soakaway must be >10 metres from a watercourse. I argued that since what comes out of the end of the soakaway is being piped directly into the watercourse, it would make more sense to continue the partial soakaway right up to the edge of the burn which would have in our case doubled it's length, but I was told no you can't do that. 

 

In our case it was high water table in the winter.  The percolation tests (only done in a shallow pit) showed the drainage to be quite reasonable.

[Thedreamer]

Percolation tests were done in 2013 and although we have clay soil the results were okay.

 

Unlike some plots space is not an issue for us.

 

I am keen to explore the treatment plant solution. The ditch that it would drain into has water running down about 1/2 the year the ditch then disappears at the bottom of a wooded area of the croft.

 

I have building control and SEPA approval for a full soakaway so not too concerned at this stage.

 

 

 

 

[ProDave]

8 minutes ago, Thedreamer said:

I have building control and SEPA approval for a full soakaway so not too concerned at this stage.

 

 

Then I would install a full soakaway, possibly with the backstop of a pipe from the very end of it out to the ditch just in case.

 

Definitely install a treatment plant not a septic tank.

[joe90]

10 hours ago, ProDave said:

Definitely install a treatment plant not a septic tank.

 

I agree. Our rumble drain is10 meters long from the  treatment plant to a ditch that runs 3/4 of the year, it then goes into a road drain for 30 meters then into another ditch eventually heading (as a blue line on ordinance survey maps) west. When I applied for permission for the plant I was asked for the name of the waterway it went to but it was so small it had no name. The lady dealing with our application was so helpful, on the document she supplied when she granted permission I noticed she named the watercourse as “river Tamar” which is miles away but I guess that’s where it ends up eventually. We are on heavy yellow clay under only 200mm of topsoil.

 

 

[ProDave]

Our discharge permit gives it as "unnamed tributary of the River Alness" and gives an 8 digit grid reference.