Choice of treatment plants

[Stones]

Prices are for 6 person units, Ex VAT but include £140 delivery charges to Orkney.  Free delivery seems to apply to a large % of the mainland.

 

8 hours ago, SteamyTea said:

They basically work by agitating and aerating the sewage.  So bubble size should not make any difference (within reason) as it is the total energy needed, not the instantaneous energy.  So a simple timer is probably all you need to 'clean' each 'batch', think of it as a multiple batch process rather than a continuous process.  So air volume x time is the important metric rather than bubble size, which is a proxy for surface area (small bubble, greater area, but less energy).

Keeps as many things that have to be changed out of the ground (so all pumps, gears, switchgear in 'the shed).

 

As for shape, spherical or conical, this may make a difference for smaller volumes.  Just a case of knowing the sizes and volumes.  A sphere will have a greater top surface area than a cone for any given height, volume or in this case, the mass of waste in it.

 

 

From what you say, the shape of the unit is going to make much difference, it's the ratio of air in vs volume of sewage that's important? Just wondering whether the conical design effectively guides sewage to a concentrated point directly over the air diffuser, thus ensuring that there is even aeration?

 

8 hours ago, ProDave said:

If you turn off the air blower, would there not be a danger of sludge settling on the air vents and blocking them?
 

 

That's the concern I have going down this road and why i wondered whether varying the amount of air going into the treatment plant was the better option.  Not sure how the air blowers would react / perform if one were to fit a variable resistor to limit its power.

[SteamyTea]

4 hours ago, Stones said:

Just wondering whether the conical design effectively guides sewage to a concentrated point directly over the air diffuser, thus ensuring that there is even aeration?

That was my thinking at first, it really comes down to the design I think.

 

 

[Stones]

Spoke to the Vortex people today about servicing.  Apart from the air blower itself (filter and diaphrams), and a test of the treated effluent for suspended solids to determine when desludge required, no other maintenance required.  

 

They did say in the first few months there may be some adjustment needed in terms of the amount of air going into the unit.

 

I specifically asked about the air diffusers but they were clear that there was no service requirement for these.  They did advise that the diffuser would eventually need replaced as over time it would silt up or the rubber in it would perish, but to date, they hadn't had to replace any.

 

Remote support available by phone and online.  They said sending in a video of how the unit was operating was probably the best way of them being able to assist in diagnosing any issues.

 

I have to say I'm not entirely convinced about the air diffuser not requiring, at the very least, an annual inspection, especially given that the air diffuser isn't operating 24/7.

[Roundtuit]

On 8/15/2016 at 18:19, Stones said:

From what you say, the shape of the unit is going to make much difference, it's the ratio of air in vs volume of sewage that's important? Just wondering whether the conical design effectively guides sewage to a concentrated point directly over the air diffuser, thus ensuring that there is even aeration?

 

 

Just had a Biopure delivered this morning (by a very helpful driver, with a well practiced techique for unloading safely without the use of a forklift or digger).  Having seen the housing for the air pump under the unit lid, I'm not sure there is any advantage in housing the pump externally; it sits in it's own self-contained box outside of the nasty stuff.  As for shape, he suggested that a conical shape reduces the risk of the tank being lifted out of the ground if the water table rises.

[pauldoc]

slightly different question on this subject, not sure if I need to start a new one?

In respect of the discharge from the plant, I am going into the ground rather than a ditch/stream

I am trying to find a definitive answer on how to do this. Are crate soakaways sufficient? I have seen them online for sale for this purpose but have also read on rival sites that these are illegal. I have read thru the regs and cant find the answer. They say a drainage field is required for a septic tank only as far as I can tell.

I think the crate way will be an easier option for me

[ProDave]

Building regulations have a calculation that tells you the area of ground you need for a soakaway based on the occupancy of the building and the percolation rate for the ground you are discharging to.

 

So your first step is dig the required test holes and measure the percolation rate.  Then you will be able to calculate the area of ground your require, which can be substantial.

 

Crates don't solve the problem and won't reduce the area of land you need.

 

If you find you don't have enough land, then you have to look at alternatives.  No drainage solution = no building warrant = no house (a worrying situation I was in for a few weeks until we found a solution)
 

[pauldoc]

That is worrying, much like almost all aspects of the build! I think I have enough land, I was trying to work out the most economical route really. I have an existing septic tank, not sure if the helps me or not? I'm guessing it doesn't really make a difference. Out of interest what was your solution dave? 

[ProDave]

My solution was discharging to the burn. Originally SEPA said no to a discharge to the burn as they only allow that as a last resort.  I was going to use an above ground filter mound, until building regs changed and it now had to be a greater distance away from the road which didn't leave enough space. I looked at a Puraflow system (similar to a filter mound but using peat in a tank as the filter medium) that would fit into the now reduced space, but building control rejected that. At that point SEPA changed their mind and allowed us to discharge to the burn. I guess we had reached the "last resort" situation.

 

Designing a soakaway system is really not that hard and for a new system building control will want to see it has been properly sized.
 

[mafaldina]

Crates or tunnels really don't work, the water/effluent not in enough contact with soil, and they won't let you do them. You probably don't need as much space as you think. Go 900mm gravel filled trenches, they should let you do 1m between each (edge), if you herringbone it helps a lot on space. Remember that if it's a treatment plant the magic figure is .2 not .25. Check out flows and loads 4. I have to do one for a 3 bed + 3 bed +2 bed, all in one, they will let me do it as 12 population but I will size it up a little.

[Ferdinand]

Since this conversation has diversified, where does something like an Aquatron fit into this mini-zoo of waste-processing options?

 

Website:

http://www.aquatron.se/start/

 

It is described as a "composting toilet using ordinary water closets".

 

At the old house, my father replaced our previous septic tank with one in the late 1990s (estimate), and just put it on the end of our waste pipe about 30m from the house at an appropriately lower level to allow gravity feed - essentially beyond a ha-ha / retaining wall. It was the kind of obscure but reasonably sensible idea he *would* come up with; such ideas *usually* worked.

 

The Aquatron has a spiral centrifugal separator to separate liquids and solids - solids fall into a composting chamber with worms, and liquids end up in a drainage field. The only maintenance was digging out the compost every year or so. No power consumption, and cheaper than any treatment plant afaik.

 

We had no problems before we sold in 2013, though if I put one in now I would probably insulate it (zero centigrade kills the worms).

 

Perhaps the only limitation is land for the leach-field, or if regulations have significantly changed. The liquids would probably be the limitation.

 

There is an excellent old thread on Aquatrons and other things at the other other place.

http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=1414

 

Ferdinand

 

Edited August 17, 2016 by Ferdinand

[Ferdinand]

Let me add one more reference - a system called "Trench Arch", which is exactly what it says and needs zero power or maintenance.

 

There is an excellent paper here discussing the various possibilities for rural churches with an excellent description and photographs.

 

http://www.gloucester.anglican.org/content/pages/documents/1352755360.pdf

 

Ferdinand

[pauldoc]

12 hours ago, mafaldina said:

Crates or tunnels really don't work, the water/effluent not in enough contact with soil, and they won't let you do them. You probably don't need as much space as you think. Go 900mm gravel filled trenches, they should let you do 1m between each (edge), if you herringbone it helps a lot on space. Remember that if t's a stp the magic figure is .2 not .25. Check out flows and loads 4. I have to do one for a 3 bed + 3 bed +2 bed, all in one, they will let me do it as 12 population but I will size it up a little.

If I am understanding you correctly, it will be a 5 bed , so a 7 person treatment plant.

Am I worrying too much about this? There are thousands of these all over the country. When I spoke to the EA they didn't seem overly concerned as I met the general binding rules.

Does it come down to regs alone?

I haven't as yet done a percolation text, but I think the soil is ok from the evidence of the footings and also the existing property was built in the 30's and had no problems with the septic tank. Does anyone have a rough idea as to the area I am looking at for the soakaway?

 

[mafaldina]

Go to: http://www.britishwater.co.uk/Publications/consumers-guides.aspx

 

First file, Flows and loads 4. 

 

Formula is:

The calculation gives the area (A), in square metres, required for the soak away trench.

V = The time in seconds for the water in the test hole to drop by 1mm. p = The maximum number of persons that the unit is designed to serve.

For sewage treatment units Area (A) = Vp X 0.20

For septic tanks Area (A) = Vp X 0.25

Further calculations are required to give the length of pipes required depending on the width of the trench, e.g. for a 600mm (2ft) wide trench, the area would be divided by 0.6.

 

For guesstimate make your V=36 (worse than average, should cover you). You can make trench up to 900mm, minimum between edges of trenches 1m. Must use perforated rigid pipe. Max length of pipe 30m, must run in a loop not dead end.

 

Hope this makes sense.

[ProDave]

For an estimate, our existing 5 bedroom house (that in Scotland must be sized for an occupancy of 8 people) has a soakaway area of 85 square metres.  In this case it is under the field behind us.
 

[pauldoc]

2 hours ago, mafaldina said:

Go to: http://www.britishwater.co.uk/Publications/consumers-guides.aspx

 

First file, Flows and loads 4. 

 

Formula is:

The calculation gives the area (A), in square metres, required for the soak away trench.

V = The time in seconds for the water in the test hole to drop by 1mm. p = The maximum number of persons that the unit is designed to serve.

For sewage treatment units Area (A) = Vp X 0.20

For septic tanks Area (A) = Vp X 0.25

Further calculations are required to give the length of pipes required depending on the width of the trench, e.g. for a 600mm (2ft) wide trench, the area would be divided by 0.6.

 

For guesstimate make your V=36 (worse than average, should cover you). You can make trench up to 900mm, minimum between edges of trenches 1m. Must use perforated rigid pipe. Max length of pipe 30m, must run in a loop not dead end.

 

Hope this makes sense.

thanks, might have to give it to my son to work out!!

Joking aside that is really helpful. So is this the calculation building regs will use?

 

56 minutes ago, ProDave said:

For an estimate, our existing 5 bedroom house (that in Scotland must be sized for an occupancy of 8 people) has a soakaway area of 85 square metres.  In this case it is under the field behind us.
 

That sounds big! 

I am just still puzzled that the existing septic tank has nothing like that sort of size soakaway but was functioning fine

sorry if i am repeating myself ! My builder is looking into it, but he said the only time he had a problem with the soakaway was clay soil which we dont have. Its free draining

He has spoken to a building inspector who has said crates are ok. So i am really confused!

I will continue to investigate

[PeterW]

Although it would still be working, it would just be pushing effluent into the leach field rather than treating it first in the tank. The purpose of a septic leach field is very different to that of a package treatment plant that discharges virtually clean water. 

 

They degrade over time and if it's already 20 years old it will be well past its best. If you have the budget, just replace the tank with a package plant and it will be good for another 30-40 years at least. 

[pauldoc]

2 minutes ago, PeterW said:

Although it would still be working, it would just be pushing effluent into the leach field rather than treating it first in the tank. The purpose of a septic leach field is very different to that of a package treatment plant that discharges virtually clean water. 

 

They degrade over time and if it's already 20 years old it will be well past its best. If you have the budget, just replace the tank with a package plant and it will be good for another 30-40 years at least. 

I am replacing it with a new plant. My head scratching is down to the size of the soakaway. It seems to be very large considering as you say that the water is virtually clean.

On other thing is i have alot of trees which i would have thought would improve things?

[PeterW]

Has the manufacturer sized it..?

 

And if you have trees then put root guard sleeves on the soakaway pipes or you will have a pipe full of roots in no time ..!

[mafaldina]

If your soil is free draining, say 20secs then it would work out at 28m2, if you use the 36 it is 51.Good scenario 28 = 31m2 of  900mm trenches.

 

Worst case scenario 51 = 57m of 900mm trenches. If the trenches were say 10m long then the total area would be around 10x10m, if you herringbone you can reduce that a fair bit something like 10x5ish (either way round).

 

I can see your thinking on 'trees good', and they would be for uptake of water but, and very big but, their roots destroy the leach field. So no trees within the area, and leave a good gap around the edges too. Hope this helps.

[pauldoc]

thanks to both of you really appreciate your help

I will continue on my quest! Will talk to BC about the calcs you have provided. I am rapidly going of trees!

God knows what people do on smaller plots!

[ProDave]

6 minutes ago, pauldoc said:

 

God knows what people do on smaller plots!

Up here, a common solution is to get permission to put a soakaway under an adjacent field. Obviously that only works if there is an adjacent field. You don't need to own it, just have a deed of servitude or equivalent to do so.

 

Lack of space for drainage can render a small plot undevelopable (is that a word?)  It's possible to get planning permission to build, but not be able to get a building warrant if there is no drainage solution.  I guess it then comes down to dry composting toilets etc if there is no other solution (dry toilets are allowed by building control)
 

[Ferdinand]

13 hours ago, pauldoc said:

thanks, might have to give it to my son to work out!!

Joking aside that is really helpful. So is this the calculation building regs will use?

 

That sounds big! 

I am just still puzzled that the existing septic tank has nothing like that sort of size soakaway but was functioning fine

sorry if i am repeating myself ! My builder is looking into it, but he said the only time he had a problem with the soakaway was clay soil which we dont have. Its free draining

He has spoken to a building inspector who has said crates are ok. So i am really confused!

I will continue to investigate

 

If it helps, I always visualise areas in "parking spaces".

 

75-85sqm is roughly 5 reasonably generous spaces. Unless you are in a Tonka Tank when they are less generous.

 

Ferdinand

Edited August 19, 2016 by Ferdinand

[Ferdinand]

11 hours ago, ProDave said:

Up here, a common solution is to get permission to put a soakaway under an adjacent field. Obviously that only works if there is an adjacent field. You don't need to own it, just have a deed of servitude or equivalent to do so.

 

Lack of space for drainage can render a small plot undevelopable (is that a word?)  It's possible to get planning permission to build, but not be able to get a building warrant if there is no drainage solution.  I guess it then comes down to dry composting toilets etc if there is no other solution (dry toilets are allowed by building control)
 

 

"Deed of Servitude" - what a glorious legal phrase !

[Ferdinand]

Semi-serious suggestion, because I would like to know.

 

If the output from a Treatment Plant is actually so squeaky clean, is there anything to stop it being recirculated back into the input water for the dwelling in some form?

 

Suspect things would be an outlier in the data set of properties.

 

Ferdinand

[Crofter]

36 minutes ago, Ferdinand said:

Semi-serious suggestion, because I would like to know.

 

If the output from a Treatment Plant is actually so squeaky clean, is there anything to stop it being recirculated back into the input water for the dwelling in some form?

 

Suspect things would be an outlier in the data set of properties.

 

Ferdinand

 

I was told, in the context of investigating discharge to a dry ditch, that the effluent is 'clean' i.e. no pathogenic organisms, but it is full of organic matter which will quickly turn to slime. So, whilst it may be 'safe to drink', I wouldn't!