NWGEAR Posted January 17, 2020 Share Posted January 17, 2020 Hello, my architect is recommending a GRAF One2Clean 7 person sewage treatment plant and I'd like to research alternatives for the sake of due diligence. Any recommendations? The property is off-grid so it'll be powered by solar PV/battery and also holiday home rate of usage for 5 people, at least for the next 10 years. Scotland regs apply and my understanding is sewage treatment is the only allowed tech these days. I'll be digging the hole myself after dicovering the joy of excavator hire. Outlet will be an open field drainage ditch, very rural. Link to comment Share on other sites More sharing options...
ProDave Posted January 17, 2020 Share Posted January 17, 2020 The Graf is one of the ones that operates on the air blower principle. So is one I would recommend (I don't like the ones based on moving mechanical parts) Others to look at are the BioPure, Vortex and the one I have the Conder. I believe these are all available as 6 person sizes which will suit your 5 person occupancy. But first have a look at @Crofter blog. He built a holiday home. Have a look at what he chose as I seem to remember it being suitable for intermittent use. Check also that SEPA are happy for you to discharge to a open ditch? I thought it had to be a flowing watercourse in Scotland. Link to comment Share on other sites More sharing options...
NWGEAR Posted January 17, 2020 Author Share Posted January 17, 2020 Righto, will check those. Yes the GRAF is blowing air. I've yet to see the open ditch run dry as its in Dumfries & Galloway ? Pretty sure SEPA will be ok with it. Building warrant details nearing completion! Link to comment Share on other sites More sharing options...
jamieled Posted January 17, 2020 Share Posted January 17, 2020 13 minutes ago, ProDave said: Check also that SEPA are happy for you to discharge to a open ditch? I thought it had to be a flowing watercourse in Scotland. Their policy currently requires tertiary treatment (rumble drain or reed bed) where the flow is either low or potentially intermittent. This is because of the low, or non existent dilution. 1 Link to comment Share on other sites More sharing options...
ProDave Posted January 17, 2020 Share Posted January 17, 2020 9 minutes ago, NWGEAR said: Righto, will check those. Yes the GRAF is blowing air. I've yet to see the open ditch run dry as its in Dumfries & Galloway ? Pretty sure SEPA will be ok with it. Building warrant details nearing completion! Then don't describe it on any paperwork as a ditch. It's a burn. And yes ours also goes through a "partial soakaway" first. Link to comment Share on other sites More sharing options...
NWGEAR Posted January 17, 2020 Author Share Posted January 17, 2020 Noted. The architect did mention a possible coconut husk filter or some such. I like the 'Burn' approach. SEPA should just require occupants to down a pint as reassurance of the quility of output. Link to comment Share on other sites More sharing options...
jamieled Posted January 17, 2020 Share Posted January 17, 2020 Good luck to you downing a pint of sewage treatment plant output! Link to comment Share on other sites More sharing options...
nod Posted January 17, 2020 Share Posted January 17, 2020 I’ve a bio pure that I installed myself Probably new less than you about treatment plants when I started As Dave has already stated Moving parts are a real no no Our bio has a blower which I set up in our garage about ten mtrs from the plant and simply plunged it into an electrical socket It’s been running without any problems for 18 months One thing I would say is some manufacturers claim you can dig a hole and site the tank in pea gravel No chance I sat ours in two metres of concrete and fill it with water and left it filled A friend who had been fitting tanks for more than twenty years recons they can pop up like a cork Link to comment Share on other sites More sharing options...
SteamyTea Posted January 17, 2020 Share Posted January 17, 2020 when you say off-grid, do you mean sewage or power. If power, then you need to reliably supply ~300W (I think @Jeremy Harris monitors his power requirements). Supplying that sort of power constantly is not easy, probably need a combination of solar or wind with batteries, plus a good generator. Link to comment Share on other sites More sharing options...
Ian Posted January 18, 2020 Share Posted January 18, 2020 2 hours ago, SteamyTea said: when you say off-grid, do you mean sewage or power. If power, then you need to reliably supply ~300W (I think @Jeremy Harris monitors his power requirements). Supplying that sort of power constantly is not easy, probably need a combination of solar or wind with batteries, plus a good generator. I’ve got the same Biopure and the pump is 27W Link to comment Share on other sites More sharing options...
Jeremy Harris Posted January 18, 2020 Share Posted January 18, 2020 9 hours ago, SteamyTea said: when you say off-grid, do you mean sewage or power. If power, then you need to reliably supply ~300W (I think @Jeremy Harris monitors his power requirements). Supplying that sort of power constantly is not easy, probably need a combination of solar or wind with batteries, plus a good generator. Yes, that's right, our whole house averages around 300 W to 350 W, but would need to be lower than this to be off grid, I think. The fixed loads that are on 24/7, and that I can't do much about are the ~30W for the treatment plant pump, and ~50 W for the MVHR. Getting the other background loads down was really just a bit of detective work going around finding things that used more power than they should and finding a solution that reduced the load. For example, I had a plethora of power adapters running things like the VDSL modem, router, a couple of Ethernet switches etc, and these were all replaced with a single battery-backed supply that feeds power via PoE to all the connected devices. The vampire load from a single supply is significantly lower than that from four or five separate supplies. Installing all LED lighting helped a fair bit (mainly in winter), but one of the other big savings was getting rid of the large PC and replacing it with a small fanless unit. The performance of the small fanless box is slightly better, and it saves a lot of energy. The old PC would idle at around 60 W and peak at around 150 W, the small fanless box idles at about 6 W and peaks at 15 W. Link to comment Share on other sites More sharing options...
SteamyTea Posted January 18, 2020 Share Posted January 18, 2020 30 minutes ago, Jeremy Harris said: Yes, that's right, our whole house averages around 300 W to 350 W, but would need to be lower than this to be off grid, I think. The fixed loads that are on 24/7, and that I can't do much about are the ~30W for the treatment plant pump, and ~50 W for the MVHR. Must have got a bit muddles, it is 300W for whole house. My current usage is 750W, this is for everything. That drops to 200W in the summer. Link to comment Share on other sites More sharing options...
dpmiller Posted January 18, 2020 Share Posted January 18, 2020 In some of the newer plants, the pump doesn't run full time I believe. Certainly the air outputs are rested for periods. I'll hopefully be able to confirm this in the next couple of weeks with our Solido Smart. Link to comment Share on other sites More sharing options...
Jeremy Harris Posted January 18, 2020 Share Posted January 18, 2020 Yes, there are a few around that use some form of pulsed pump operation, although whether they are better than some of the newer, lower power pumps, I don't know. One of the issues that the pulsed pump systems have to deal with is sludge settling time - if the sludge settles around the aeration outlet holes during the pump off time, then there is a risk that the pump won't develop enough pressure to blow it away and restart the sludge circulation pattern. Pumps have failed because of sludge build up like this. At least one of the pulsed systems uses solenoid valves to direct air selectively around the unit, and this may be to enable the sludge circulation bit to keep working OK, as well as the aeration bit. I was planning on trying pulsed power to our unit, but in the end just swapped the pump for the much lower power version of the same output Secoh pump. IIRC, the original pump was around 50 W, the newer version is a bit under 30 W for the same pressure and flow rate, so more of a power saving than pulsing the pump would have achieved, with none of the risks associated with possible sludge settlement. Link to comment Share on other sites More sharing options...
Gone West Posted January 18, 2020 Share Posted January 18, 2020 12 hours ago, NWGEAR said: The architect did mention a possible coconut husk filter or some such. If I was going to fit a replacement for ours it would probably be a Viltra's Oxtec which appears to have tertiary treatment in the one tank. https://www.viltra.co.uk/products/sewage-treatment/oxtec Link to comment Share on other sites More sharing options...
Ed Davies Posted January 18, 2020 Share Posted January 18, 2020 (edited) Biopure do an option with lower-than-standard power consumption which I'll look into when it comes time to order for my off-grid house. https://webuildit-ltd.co.uk/domestic-sewage-treatment-plants/running-costs/ Edited January 18, 2020 by Ed Davies Add link Link to comment Share on other sites More sharing options...
Jeremy Harris Posted January 18, 2020 Share Posted January 18, 2020 25 minutes ago, Ed Davies said: Biopure do an option with lower-than-standard power consumption which I'll look into when it comes time to order for my off-grid house. https://webuildit-ltd.co.uk/domestic-sewage-treatment-plants/running-costs/ That uses the Secoh pump I switched our older BioPure unit to. It's also a bit quieter than the original Secoh pump that was supplied with it: https://webuildit-ltd.co.uk/product/secoh-jdk-s-eco-air-pump-60/ If anyone has one of the older BioPure units, they can swap the pump over for one of the newer Secoh JDK-S Eco pumps and gain a worthwhile reduction in electricity usage. The swap is easy, as they are the same size and have the same pipe fittings. 1 Link to comment Share on other sites More sharing options...
Crofter Posted January 18, 2020 Share Posted January 18, 2020 I used a 'Puraflo' system. These originate in Ireland and have been around for at least a couple of decades, so it's fairly well tested technology. You still have a conventional septic tank, but the outflow from this is pumped into one or more Puraflo 'modules', which are big plastic tanks full of peat fibre matting. This is an aerobic envoironment where bacteria can get to work breaking down the effluent, and what comes out the holes in the bottom of the tank is sufficiently treated that it can be disposed of into the ground. Essentially the Puraflo is doing the exact same job as a soakaway/leachfield, but in a much more compact space, and it does not require any particular ground conditions. My site actually had percolation rates that were too fast for a conventional system- under a thin layer of top soil I hit fractured rotten rock, and the water just disappeared into it. This risks the effluent popping up again somewhere else, and it isn't spending long enough in the aerated topsoil layer to be properly broken down. The big advantage of the Puraflo over a treatment plant is that it appears to be more resilient to periods of non use, or fluctuating usage. As I was building a holiday let this was quite an important consideration. Link to comment Share on other sites More sharing options...
Ed Davies Posted January 18, 2020 Share Posted January 18, 2020 By the way, my rule of thumb for off-grid power is that it costs about £30/W so going from 44 W for the standard Biopure down to 27 W for the -E model drops the cost by about £500 less whatever the extra cost of the lower-power pump might be. Sometimes the equation is not so simple because the extra power is dissipated in the house so contributes to the heating but that doesn't make much sense from a practicality and noise point of view in this case. Link to comment Share on other sites More sharing options...
Crofter Posted January 18, 2020 Share Posted January 18, 2020 One other point about the Puraflo if going off grid- you can probably just gravity feed it and dispense with the pump, so there is no power consumption. The supplier I dealt with didn't recommend this as he felt there would be a better distribution of effluent through the module if it was pumped. He's probably correct, but if you are going off-grid cutting power consumption might be a higher priority, even if it shortens the lifespan of the (replaceable) peat fibre. Link to comment Share on other sites More sharing options...
Stones Posted January 19, 2020 Share Posted January 19, 2020 22 hours ago, Jeremy Harris said: That uses the Secoh pump I switched our older BioPure unit to. It's also a bit quieter than the original Secoh pump that was supplied with it: https://webuildit-ltd.co.uk/product/secoh-jdk-s-eco-air-pump-60/ If anyone has one of the older BioPure units, they can swap the pump over for one of the newer Secoh JDK-S Eco pumps and gain a worthwhile reduction in electricity usage. The swap is easy, as they are the same size and have the same pipe fittings. We opted for the lower power version ourselves when we ordered and seems to work fine. Interestingly, if we had opted for the next unit up, capable of dealing with a higher population load, the only difference was pump size (the physical tank itself was the same). I can only surmise that the opposite would therefore work as well - for a lower population load you would have a perfectly functioning system with a lower powered pump. 1 Link to comment Share on other sites More sharing options...
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