Sand Filter for Grey Water Storage

[Barney12]

I'm sure I've read something by the venerable @JSHarris on this subject but I cant locate it. It might have been on the old forum. Anyway to get to it:

 

The garage and bat house surface water (and the flat above the garage grey water; kitchen sink, washing machine, shower) currently heads into a 2000ltr grey water storage tank further down the garden. Its a pretty simple Heath Robinson affair: 110mm Inlet pipe into several huge concrete rings which have been waterproofed. the (higher) outlet heads off to the soakaway once its full. 

 

The one thing that was never done was any form of inlet filter. So any crap (and there are a lot of trees around the garage) or solid (and potentially grease if someone puts it down the sink!) that enters the system ends up in the tank. With the groundworks now in full flow and the diggers onsite this is my last chance to fit some form of filter. Google doesn't really turn up much so is this something I can roll myself? It needs to be below ground, ideally with a small inspection chamber lid. In fact I'm wondering if a small inspection chamber, modified and filled with sand might work? I assume the media needs to be fairly course to allow for what can be a fairly fast flow in a scenario such as its raining and someone is using the shower?

 

Sorry and one more point: This stored water is only for irrigating the garden. So its purely to stop crap building up in the tank. There are no issues with water quality. 

 

Any pointers welcome! 

 

 

Edited July 26, 2019 by Barney12

[Jeremy Harris]

I think you'll forever be backwashing a sand filter to try and keep it clean.  Do you need to filter down to that fine a level, though? 

 

A easily removable and washable mesh debris filter would work OK for keeping leaves etc out.  When you say "grey water", if this has shower waste then it's really foul water, I think (shower and bath water is deemed to have some faecal content), plus grey water that comes from a washing machine will have a high BOD, so really needs treatment before going to a soakaway.  If building control were OK with it then I guess it's fine, but my experience of trying to store/treat grey water is that it can get to be a messy and smelly job (pretty sure it's the relatively high BOD that creates much of the problem).

 

Grease capture needs some form of grease trap.  These can be purchased easily enough, as I think they are mandatory for places like restaurants now, as pre-treatment before discharge to a sewer.  We made one for the caving club drains, using a brick chamber fitted with an old metal milk crate.  This would clog up with fat and every month or two the crate would be pulled out and put on a fire to burn off the grease.  Worked OK, but the commercial units are probably a lot easier to fit and maintain.

[ToughButterCup]

I was going to cobble something together based on an amalgam of the simplest ideas here ....

The issue isn't so much the grease trap: it's

• how to reduce the amount of grease 'thrown away'
• what do you do with the fat ball once you've got it
• how on earth do you get the damn thing out of the trap?

I'll sit back and watch you struggle with it first  though.... ?

[Jeremy Harris]

5 minutes ago, AnonymousBosch said:

I was going to cobble something together based on an amalgam of the simplest ideas here ....

The issue isn't so much the grease trap: it's

• how to reduce the amount of grease 'thrown away'
• what do you do with the fat ball once you've got it
• how on earth do you get the damn thing out of the trap?

I'll sit back and watch you struggle with it first  though.... ?

 

 

The milk crate in a chamber system worked well, but it was dealing with high volumes of cooking fat (loads of cavers having big fry-ups for breakfast).

 

It was easy to clean, just hoik the crate out, burn the fat off and put it back again.  Not exactly environmentally friendly, though...

[Barney12]

On 26/07/2019 at 13:56, JSHarris said:

I think you'll forever be backwashing a sand filter to try and keep it clean.  Do you need to filter down to that fine a level, though? 

 

No not really. Mesh would be fine thinking about it.

[Barney12]

4 hours ago, JSHarris said:

A easily removable and washable mesh debris filter would work OK for keeping leaves etc out.  When you say "grey water", if this has shower waste then it's really foul water, I think (shower and bath water is deemed to have some faecal content), plus grey water that comes from a washing machine will have a high BOD, so really needs treatment before going to a soakaway.  If building control were OK with it then I guess it's fine, but my experience of trying to store/treat grey water is that it can get to be a messy and smelly job (pretty sure it's the relatively high BOD that creates much of the problem)

 

Ok, you’ve got me.....BOD?

[Jeremy Harris]

9 minutes ago, Barney12 said:

 

Ok, you’ve got me.....BOD?

 

 

BOD = Biological Oxygen Demand

 

It's one of the primary reasons for treating effluent by aeration, as by aerating it, aerobic bacteria use up most of the nutrients (and stuff like washing machine and shower effluent has a fair concentration of nutrients) during treatment.  Doing this means that the discharged, treated, effluent doesn't have the potential to reduce the oxygen level in wherever it ends up, so is more or less harmless.  The reason that fish die when effluent ends up in rivers is almost always because the BOD of the effluent is high, which promotes aerobic bacteria growth in the river, which then uses up the dissolved oxygen, so the fish suffocate.

[Barney12]

Ok, so I’ve been doing a good degree of reading (thanks Google) and it seems my early attempts to store grey water were a little flawed ( it was on the recommendation of a ground worker I had on-site years ago at the very early stages of owning the plot) and in fact may have been missing the bloody obvious!

 

@JSHarris comment re BOD tells me that I really could now do with diverting the utility room outlet in the flat to the treatment plant (which wasn’t installed when the flat was built). Not a huge job but a certain amount of buggering around involving a digger. 

 

But then today I was chatting to a neighbour about my quandary and he said “why are you not simply taking water from the leat?”. I of course looked at him blankly and said “can I do that?” To which he replied “yes, 20 cubic meters a day without a licence”. 

 

Now the good bit is the leat is at the top of my plot and crosses my steeply sloping land. So gravity is on my side! I also have plenty of space for some storage tanks. 

 

So so now my mind is turning to “abstraction”. The source is on the open moor. In short in summer it can be a gentle trickle, in winter a torrent! I’m thinking that some form of dam that creates a holding area (mini reservoir?) which I can then draw from? I have gravity on my side so some form of filter in the dam that runs to storage tanks using MDPE pipe? 

 

This is all about being able to irrigate a massive landscaping project. 

 

Have I gone mad? Too many G&T’s?

 

 

[Cpd]

You would be amazed at how much water a “little trickle” actually ads up to. I have a spring at the top of my property that produces a minimum of 8500 litres a day and the overflow goes into my pond / moat. A friend the other day pointed out that I could also excavate a new pond below the spring as an added feature and I love the idea. So I don’t think it’s a crazy idea but you would need to look at lining the storage area if you wanted to minimise losses. My biggest loss is from the huge area of reed-bed that just sucks up the water....... but it looks great and is a big part of my wildlife garden plan.  

[ProDave]

I don't know about irigation, but I would be thinking hydro power.

[PeterW]

I buried this beast - one good rain shower and it was half full, god knows what it’s like now after a day and a half of rain..!!

 

How much storage do you need ..??

[Onoff]

7 minutes ago, PeterW said:

I buried this beast - one good rain shower and it was half full, god knows what it’s like now after a day and a half of rain..!!

 

How much storage do you need ..??

 

2000L?

[Barney12]

7 minutes ago, PeterW said:

I buried this beast - one good rain shower and it was half full, god knows what it’s like now after a day and a half of rain..!!

 

How much storage do you need ..??

 

 

Working on the assumption of a hosepipe using 1000ltrs an hour (which seems to be want google suggests) then I think in reality I need 2000ltrs of storage per day in the summer months. This of course is if the weather is dry. Once the garden is established then it will reduce. 

[Barney12]

2 minutes ago, Onoff said:

 

2000L?

 

I think those cubes are one cubic meter.

[PeterW]

Yep they are. There is a standard set of calculations as to how much storage you need somewhere. I’ll see if I can find it.  

[Ferdinand]

On 26/07/2019 at 15:41, JSHarris said:

It was easy to clean, just hoik the crate out, burn the fat off and put it back again.  Not exactly environmentally friendly, though...

 

Could one burn it off in situ, assuming a concrete container?

[Jeremy Harris]

3 hours ago, Ferdinand said:

 

Could one burn it off in situ, assuming a concrete container?

 

Probably not, as the lower part of the chamber is sat in was filled with waste water.  The crate sat in the top to sort of skim off the solidified fat that floated up in that chamber.

 

On the topic of rainwater storage, we have just under 4,000 litres of surge attenuation storage under our drive.  That was just enough for the run off from our roof and drive for our area.