Sewage treatment plant - air blower electricity costs

[David Essex]

We have a Mantair conversion unit and a Medo LA-100 air pump running 24/7, costing approx. ~£200 per year on the tariff we were moved to when our old electricity supplier went bust recently.

 

£200 for peace of mind is fine, but if prices e.g., double next year and we’re then paying £120 for a service, £150 to desludge, and £400 in electricity costs - the whole thing is starting to get a bit expensive. And I really feel for the poor sods who have recently installed ASHPs.

 

The advice we were given from the people who service the Mantair is that the air pump should be on 100% of the time, possibly tolerating a 9:1 on/off ratio.

 

I’m considering putting it on a timer and using a 7:3 ratio - 21 mins on, 9 mins off.

 

I was wondering if anyone here has experience in reducing their air blower on/off ratio successfully without breaking their system? Or is this just a bad idea?

[JohnMo]

I hadn't though about the compressor running costs, so watching with interest

[nod]

Pennys 

[SteamyTea]

These pumps draw about 100 W.

Can you get a couple if PV modules and a second pump that runs when the sun is out, and switches off the mains powered pump.

Edited November 28, 2021 by SteamyTea

[ProDave]

Before I moved in i checked with just the treatment plant operating and it was clocking up 2kWh per day, so currently about 40p per day so about £146 per year.

 

The metered units was very different to what I expected just be measuring the current drawn, no doubt due to power factor.

[David Essex]

1 hour ago, SteamyTea said:

These pumps draw about 100 W.

Can you get a couple if PV modules and a second pump that runs when the sun is out, and switches off the mains powered pump.

 

Yeah, I'm half looking into this but don't know much about the tech - I'd need a PV panel with an integrated microinverter? Plus mount / installation etc. Not sure what the outlay would be.

 

I'm not sure describing the potential ongoing savings as “pennies” is entirely accurate, though. My napkin maths is:

 

- 100W device running 24/7 consumes 2.4 kWh per day

 

- 2.4 x £0.22 = £0.528 per day = £192.72 per annum

 

When prices rise (as they inevitably will do next year) then the annual cost could be, what, 2.4 x £0.30 = £0.72 per day = £262.80 per annum. More?

 

Reducing the power consumption by 30% = an ongoing saving of £78.84 per year. Enough to fund my gin consumption for a few weeks. That’s worth doing if I’m not going to break the system. I’m just interested if anyone has bothered trying.

 

The guy I spoke to who serviced the treatment unit said that problems could occur with sludge making its way back and eventually blocking the airlift inlet. He didn't seem too concerned about the effect on the bacteria colonies.

 

No big deal! Just interested to know. Thanks for your responses.

 

[Stones]

A lower power air pump ?

 

Our treatment plant uses a 60W Secoh air pump.  At the price cap that works out around £120 per annum.

 

The capital cost of buying a new pump would pay for itself in a year.

[markocosic]

Following with interest - also a new aerobic tank owner that raised an eyebrow at a 50W pump!

 

 

Wastewater aeration is a huge deal - bubbling sludge is easily over 1% of western electricity demand so monitoring bacteria in commercial plants and minimising the leccy used to aerate them is worth a fortune.

 

https://www.ssiaeration.com/improve-aeration-efficiency/

 

Dunno how you do this on a domestic scale. We were advised to run 100% for the first month of use then 30-on-30-off. I suspect the amount of shite matters quite a lot...

[Iceverge]

1 hour ago, markocosic said:

 We were advised to run 100% for the first month of use then 30-on-30-off. I suspect the amount of shite matters quite a lot

 

I'm also interested. Ours is €127 per year. Do you have any further guidance on intermittently running? 

[Ian]

Our Bio Pure 1 came with a Secoh JDK-S-60 air pump which only uses 40 W.

[SteamyTea]

Usually a race to the bottom is a bad thing.

But not here.

[Gone West]

One of the problems with cycling on and off is that as the level of solids builds up so there is more back pressure each time you restart the pump. This causes premature failure of the diaphragms in the pump. There is a thread on here somewhere where this was discussed in the past and Jeremy designed a pressure sensor which would warn when the pressure was too high.

[joe90]

But if you are off the sewerage grid what are your options? What would your charge be if you were connected to mains drains? Mine runs 24/7 but don’t know it’s consumptions. I guess it’s either solar or the lowest pump consumption you can get. I would want to see more evidence before timing mine.

[David Essex]

9 hours ago, markocosic said:

We were advised to run 100% for the first month of use then 30-on-30-off. I suspect the amount of shite matters quite a lot...

The company that installed your system advised this? And this is working for you is it?

[markocosic]

The company that fitted it advised this yes.

 

Not in operation yet so can't say if it's working.

 

You'll probably know if it's working by the smell and colour though. Anaerobic effluent isn't clear and the smell is awful. Aerobic effluent is clear and doesn't smell awful.

 

Trouble is it takes time to rebuild the aerobic beasties if you've let it go anaerobic, and if you fill a (small) drain field with gunge meant for a leach field you might end up ruining it. Not errors that you want to make!

[David Essex]

8 hours ago, markocosic said:

Anaerobic effluent isn't clear and the smell is awful. Aerobic effluent is clear and doesn't smell awful.

 

Hmms... I'm not sure my aerobic effluent has ever smelt that pleasant.

I'd be really interested to hear how you get on.

 

9 hours ago, joe90 said:

But if you are off the sewerage grid what are your options? What would your charge be if you were connected to mains drains?

 

This is the thing... the water company don't want to connect my "end of the village". It'd involve going under a train line. But, the cost would be significantly less (is it 90% of the cost of water consumed?) than what we pay at the moment and will be paying in the future.

 

On 28/11/2021 at 14:35, Stones said:

A lower power air pump ?

Thanks, yep. It'd have to be the model above that (75W delivers 95 l/min). I'd recoup the outlay more slowly but it's a good idea.

Edited November 29, 2021 by David Essex

[markocosic]

I'll let you know after I take the inaugural poo sometime in 2022... ?

 

Probably not too relatable though as it's a folly / cabin / airbnb / holiday home rather than a permanent house. Load profile will be all over the show.

[dpmiller]

ours does an aerate-settle-pump out cycle, the air pump is off quite a bit of the time

[Ian]

9 hours ago, markocosic said:

I'll let you know after I take the inaugural poo sometime in 2022... ?

 

Probably not too relatable though as it's a folly / cabin / airbnb / holiday home rather than a permanent house. Load profile will be all over the show.

We use ours as a holiday home so it’s only used 2 or 3 days max a week. We have a Bio Pure 1 which has been running now for 5 years with no issues. When I completed the build I rang the manufacturer for advice about the best way to operate the air pump due to the intermittent loading and I was told to put it on a timer set to operate 2 hours on and 2 hours off. It’s been completely problem free with no smells.

 

The added benefit of the timer is that it halves the running cost.

Edited November 30, 2021 by Ian

[ChrisH]

Reduce the time the air blower is on until it starts to smell then increase it just enough to get rid of the smell. I’ve found that 1 hour on and 1 hour off works for me, I’ve had a Charles Austen air blower in my Condor tank for over ten years now and doesn’t smell and it’s never gone wrong. 

[JohnMo]

Sorry bit of a drag up an old thread.

 

We have a Harlequin Hydroclear 6, 2 people in the house.

 

The blower runs 24/7 (55W) so looking to reduce that.  PV covers the running cost during the day, so would leave it running during daylight hours.

 

So what's the best way to add a timer?  Is it a normal time switch?

[joe90]

Yes I also have thought of this now prices are rising so much, rest of the house is quite frugal. Mine, Vortex, has a timer built in to divert bubbles at intervals to two different sections. I guess a timer on the input from the fuse board would do. 

On 05/01/2022 at 17:53, ChrisH said:

Reduce the time the air blower is on until it starts to smell then increase it just enough to get rid of the smell. I’ve found that 1 hour on and 1 hour off works for me, I’ve had a Charles Austen air blower in my Condor tank for over ten years now and doesn’t smell and it’s never gone wrong. 

I might try that 🤢

[markocosic]

In hindsight I'd probably soakaway the grey water and go composting for a toilet in an occasional use building.

 

15 on / 45 off is fine thus far for us fwiw. Will try 15 / 105 next whilst unoccupied.

[Russell griffiths]

My Graf unit comes with a computer control working the timer and pumped outlet. 

It runs for 6 mins on 4 mins off, I was told having it off for longer there is a greater risk of sludge blocking the holes in the air tube. 

[saveasteading]

3 hours ago, markocosic said:

probably soakaway the grey water 

That makes a lot of sense, esp if it spreads the water further and helps the garden to grow. However the operation of the digester needs some balance of water for best results. The manufacturer can advise. I remember needing to increase digester size for a school' use because, excluding detail, the balance of contents differed from a domestic situation.