Septic Tanks / domestic sewage treatment

BigMonka

I hope you'll excuse the shitty topic of conversation (pun very much intended) but does anyone know anything about septic tanks or small scale sewage treatment? I've got an existing septic tank that discharges to a local ditch, but from Jan 2020 this won't be allowed so I'm looking ahead at what my options are and at the moment it's all a bit overwhelming - particularly as all the useful looking info seems to come from manufacturers who clearly have vested interests.

All help appreciated!

TTony

We've got one.

What do you need to know?

Septic tank just collects all the waste, and so needs emptying regularly.

Treatment plant breaks down the waste (ours discharges clean water into a ditch) and so needs emptying far less frequently.  Minimal maintenance as long as you don't put anything into it that it's not designed to cope with.

What else do you need to know?

munckee

I drove past one being emptied this morning, smelled awful like they kept their poo in there!

BigMonka

Thanks @TTony - do you know anything about what type yours is? Does it have a power supply with a moving disc inside, or one of these ones with a compressor that blows bubbles through it all?
It also seems that a lot of the treatment plants have a bit above ground (for things like power and pump equipment), but they don't all seem to. Ideally I'd want something completely buried so that there's not a box sat in the middle of the lawn or driveway!

TTony

Ours has a pump blowing air through - keep everything moving & bubbling.

The pump is above ground, but it doesn't need to be.  The size of the pump is determined by the size of the tank (in turn determined by the size of the property that its serving), and above a certain size of tank/pump, it's apparently better to have them above rather than underground to guard against the pump overheating.  

Apart from that, it's all buried with a couple of access hatches flush with the ground and a warning indicator that flashes if there's any sort of problem - though the only time that it went off, our noses had already detected that there was something wrong


If you need the plant, I'm guessing that you'll have neighbours with one too.  Ask them who they used to install, service, or empty it and get some recommended firms to quote you.  It's not an expensive thing to sort.

grungebob

Water treatment is what im employed to do.  you have two types, one as a digestion method and one as a filtration method.
each have pros and cons whens it comes to intervention and maintenance. Aerobic digestion is more susceptible to poisoning from chemicals etc and has a higher running cost but should require very little maintenance.  Filtration has lower running costs, is more robust but will require a maintenance/service visit at least annually.

  

BigMonka

TTony said:

If you need the plant, I'm guessing that you'll have neighbours with one too.  Ask them who they used to install, service, or empty it and get some recommended firms to quote you.  It's not an expensive thing to sort.

Cheers for the info Tony. We use the same emptying company as our neighbours, but they don’t do installs. The neighbours installed their own about 15-20years ago so although I’ve asked they’re not up to date on latest technology. They are willing to help us do a DIY install though so that should keep costs down a bit.

BigMonka

grungebob said:

Water treatment is what im employed to do.  you have two types, one as a digestion method and one as a filtration method.
each have pros and cons whens it comes to intervention and maintenance. Aerobic digestion is more susceptible to poisoning from chemicals etc and has a higher running cost but should require very little maintenance.  Filtration has lower running costs, is more robust but will require a maintenance/service visit at least annually.

  

Thanks @grungebob from that it sounds like the filtration system might be better for us. Is the annual service something that a handy DIYer would be able to undertake?
Any products/manufacturers that you’d recommend? Or is all your work much more industrial?

blobb

Hmm, when you say you won't be allowed to discharge to the ditch do you mean you won't be allowed to discharge anything at all, or can you still discharge within some agreed parameters? If you are not allowed a discharge then you have two options:

1. Cess pit - differs from a septic tank as it has no overspill. Big tank, emptied by a tanker on a regular basis, taken away to local treatment works.
2. Connect to local sewer network and pay a collection fee to your utility company. Connecting can be expensive if at all possible. The utility has no obligation to take your connection unless you can swing a section 101a application. you will need a load of other properties to join you to make it worth their while.

If you have an allowed discharge then you can self treat. There's an old saying in sewage treatment that basically goes along the lines of "the bigger it is, the easier it is to treat" i.e. the opposite is also true, the smaller it is the harder it is to treat. On a positive note though, the chances of you being sampled are slim on a private residence.

Self treating (to a consented standard) on small populations (how many of you are there, just your household or a couple of houses?) is a minefield.  As you say, every man and his dog will offer you something in what we call a package treatment plant. 

Look up WPL diamond.

But basically, can you discharge and how many will be connected. Start there.

For the nerds out there, the aerated system is called a Submerged Aerated Filter (SAF), but it's not a filter at all
The rotating disc is called a Rotating Biological Contactor (RBC), again not a filter.
These are called attached growth systems, they grow bacteria on plastic media which eats your poo.
You don't want to filter sewage.

blobb

https://s3-eu-west-1.amazonaws.com/wplltd/wp-content/uploads/2018/04/24153218/WPL-Diamond-Brochure-UK.pdf

grungebob

blobb said:

Hmm, when you say you won't be allowed to discharge to the ditch do you mean you won't be allowed to discharge anything at all, or can you still discharge within some agreed parameters? If you are not allowed a discharge then you have two options:

1. Cess pit - differs from a septic tank as it has no overspill. Big tank, emptied by a tanker on a regular basis, taken away to local treatment works.
2. Connect to local sewer network and pay a collection fee to your utility company. Connecting can be expensive if at all possible. The utility has no obligation to take your connection unless you can swing a section 101a application. you will need a load of other properties to join you to make it worth their while.

If you have an allowed discharge then you can self treat. There's an old saying in sewage treatment that basically goes along the lines of "the bigger it is, the easier it is to treat" i.e. the opposite is also true, the smaller it is the harder it is to treat. On a positive note though, the chances of you being sampled are slim on a private residence.

Self treating (to a consented standard) on small populations (how many of you are there, just your household or a couple of houses?) is a minefield.  As you say, every man and his dog will offer you something in what we call a package treatment plant. 

Look up WPL diamond.

But basically, can you discharge and how many will be connected. Start there.

For the nerds out there, the aerated system is called a Submerged Aerated Filter (SAF), but it's not a filter at all
The rotating disc is called a Rotating Biological Contactor (RBC), again not a filter.
These are called attached growth systems, they grow bacteria on plastic media which eats your poo.
You don't want to filter sewage.

 you can filter sewage with a biological MBR system( technically not filtering raw sewage but I didn’t want to bog people down with unrequired jargon)but I don’t know if these have made it to private sector yet and are probably still large scale industrial. 

Im guessing the OP meant he’s not allowed to discharge untreated effluent but like you said the chances of being sampled is remote. The cheapest of all options would be fit a septic tank and have it emptied every 18 months or so, shouldn’t cost more than £250-300 each empty which is less than you’d have paid your local municipal, the other advantages are zero running costs or maintenance. 

blobb

...not in your backyard you can't.

grungebob said:

you can filter sewage with a biological MBR system

but, agreed, discharge (or not) is important.

blobb

looks like the agency are clamping down on private discharges, but doing it through building regs.

'In 2015, the Environment Agency introduced ‘general binding rules’ that state certain septic tanks are, by law, no longer allowed to be discharged into a watercourse such as a river or a canal.

By 1st January 2020, all homes that do this must either connect to the main sewage network, create a drainage field or replace the existing septic tank system with a small sewage treatment plant.'

Interestingly, this allows drainage fields (soakaways) to be used. Strange, they stopped us using these, they block easily.

I can't see why they are on the warpath against septic tanks, standard solution for very small pop for us, so long as the consent is not too strict, say 40:60, possibly with a reed bed on back.

Also strange that you can get away with a system that meets 'British Standards' and does not 'Pollute local watercourses' (huh, define pollute?) otherwise you need a permit to discharge (consent) which could open a whole other can of worms.

All my time doing small works I've never known a private consent be monitored anything like we get. Which means basically you could put a pipe in and so long as no one notices or complains you get away with it.

What line are you in @grungebob, if you don't mind me asking?

grungebob

@blobb Suez/GE water 
I dabble in refinery ETP’s and power sector steam generation so filthy to nuclear clean. 

Yourself?

grungebob

blobb said:

...not in your backyard you can't.

grungebob said:

you can filter sewage with a biological MBR system

but, agreed, discharge (or not) is important.

Are there not nano or UF filtration systems on the market yet? One plant I’ve just worked on has 1 x common masserator to aerobic and 1 x rotating screen to enzyme holding to UF with 5-10% reject (sludge cake). FM ratio is good and consistent and the cake is taken off site easily enough with a low hazard EWC. 

gusman2x

I share one with my neighbour. He (like many others I know) think it's acceptable to only empty it every 10 years or so.

With regards to the legislation, I think it's highly unlikely anyone will challenge you. Is the discharge/soakaway on your land? If so, I'd probably just do nothing (and I'm quite a nervous person).

blobb

grungebob said:

Are there not nano or UF filtration systems on the market yet?

not for wastewater applications and far too complex for a private residence if they were. Even a small SAF is pushing it on private. The WPL diamond is hybrid affair i.e. a SAF with no media in it - an aerated septic tank if you like. Single dwellings struggle to keep load on the plant to give the bugs food.

Consent is everything, I would say get a septic tank that meets building regs if that's an option and avoid any complexity. If no one is going to sample it then just tick the appropriate box.

grungebob said:

Yourself?

Wastewater process Designer / troubleshooter - amongst other things, ex-Severn Trent small works lead, but we play a different game to domestic application. We actually get sampled!

BigMonka

gusman2x said:

I share one with my neighbour. He (like many others I know) think it's acceptable to only empty it every 10 years or so.

With regards to the legislation, I think it's highly unlikely anyone will challenge you. Is the discharge/soakaway on your land? If so, I'd probably just do nothing (and I'm quite a nervous person).

We were told that ours wouldn't need emptying due to it being massively oversized compared to the size of the house - not sure that's true at all, but we're having it emptied this week for the first time in 7years and it hasn't caused any problems yet.

Having a drainage field (not using a soakaway - that's only allowed for rain water) on your property is fine. But at the moment ours and our neighbours both go to a local culvert in a field (as does the rainwater), which isn't allowed under from a basic septic tank from 2020 so we need to change something. If we ever come to sell the house then it would be highlighted as a problem, and if that was after 2020 so it was clear that we hadn't complied with the regs then who knows what the Environment Agency fines would be.

m_c

A suitably sized septic tank can run for years without needing emptied, provided it's not getting filled with junk that won't breakdown. I know some of my parents neighbours who'd stayed in their houses for over 10 years, and never even knew they had septic tanks.


I do wonder how they're going to enforce this. My parents septic tank feeds into a pipe that is shared with 4 other houses (3 of which share a single septic tank) and a solitary road drain (I suspect strategically added to periodically flush the pipe), before ending in an open ditch 300 metres away, which is also used for field drains.

blobb

gusman2x said:

I share one with my neighbour. He (like many others I know) think it's acceptable to only empty it every 10 years or so.

With regards to the legislation, I think it's highly unlikely anyone will challenge you. Is the discharge/soakaway on your land? If so, I'd probably just do nothing (and I'm quite a nervous person).

I think you are probably right, so long as you have the paperwork to meet the new regulations then I can't see the Agency having the resources to go out sampling everybody. From the looks of it, there is the option to meet the regs OR apply for a discharge permit. Presumably you don't need a discharge permit if you meet the regs?

I wouldn't change a certified septic tank route for a soakaway, they tend to smell when they get clogged and the solids need to come out somehow.

I've known septic tanks that have never been emptied. They work by capturing some of the settleable solids and providing a degree of anaerobic treatment, the sludge cold digests in the tank the longer you leave it and, if you are not loading it up then the sludge will be eaten before it needs to be removed. Cold digestion of sludge releases ammonia back into the effluent so you have to be careful if you have an amm consent, unlikely on private system. As above, avoid applying for a permit, keep it descriptive under building regs.

BigMonka

blobb said:

gusman2x said:

I share one with my neighbour. He (like many others I know) think it's acceptable to only empty it every 10 years or so.

With regards to the legislation, I think it's highly unlikely anyone will challenge you. Is the discharge/soakaway on your land? If so, I'd probably just do nothing (and I'm quite a nervous person).

I think you are probably right, so long as you have the paperwork to meet the new regulations then I can't see the Agency having the resources to go out sampling everybody. From the looks of it, there is the option to meet the regs OR apply for a discharge permit. Presumably you don't need a discharge permit if you meet the regs?

I wouldn't change a certified septic tank route for a soakaway, they tend to smell when they get clogged and the solids need to come out somehow.

I've known septic tanks that have never been emptied. They work by capturing some of the settleable solids and providing a degree of anaerobic treatment, the sludge cold digests in the tank the longer you leave it and, if you are not loading it up then the sludge will be eaten before it needs to be removed. Cold digestion of sludge releases ammonia back into the effluent so you have to be careful if you have an amm consent, unlikely on private system. As above, avoid applying for a permit, keep it descriptive under building regs.

The problem is if I come to sell the house further on down the line.

Thanks for the WPL diamond recommendation @blobb , I'll look them up. I think my current preference will be to ditch the current ancient septic tank and install a domestic sewage treatment plant. Not cheap, but probably less hassle long term then trying to put in and maintain a drainage field.