Designing and building grey water filter for reuse in flush toilets at the tourist hostel in the Carpathian mountains (Ukraine)

  • BPopov
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Designing and building grey water filter for reuse in flush toilets at the tourist hostel in the Carpathian mountains (Ukraine)

Hello everyone!
I am helping to design a rain water harvesting and sanitation system for the tourist hostel up in the Carpathian mountains. The situation with water supply there is rather complicated -- rain water is the main source. There is an idea to reuse the grey water from showers and sinks for the water flush toilets. However grey water needs basic treatment and filtration before pumped back to the toilet cisterns. One of the challenges is that treatment and filtration system has to be installed indoors protected from freezing temperatures thus it should be relatively compact. There are some factory made grey water filters that can do the job but being produced in Scandinavian countries they are too expensive for Ukrainian context and need constant and regular replacement of special filtration material also to be imported and being expensive.
There is a need to design a self built system form locally available materials and components with moderate maintenance input
I would be interested to discuss possible design of this filter and later next year post the reports on building process as I did this before with my public toilets projects. This can be quite an interesting project!
The main issues to consider:
1. The filter can be located on the ground floor directly underneath the showers, sinks and toilets (4 points of each) on the second floor. The grey water should feed filter by gravity and then pumped back to the toilet cisterns. The height of the ground floor to the ceiling is 2.3 m.
2. The grey wat can be rather hot from the showers.
3. The flow can be highly variable from 50 l up to 1 cubic meter per hour.
At the moment I am thinking about using there a vertical up flow filter made in 500 l polyethylene tank filled with 30 cm layers of zeolite with progressively smaller grain size each (8-12mm, 4-8 mm and 2-4 mm) Zeolite is used because it is mined nearby and hopefully will provide better treatment than ordinary gravel. Upflow design is thought since this will allow hydraulic cleaning by draining. Concept sketch is attached.
Looking forward to hear you suggestions and ideas!


Bogdan Popov
The Ecosolutions Forge
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Re: Designing and building grey water filter for reuse in flush toilets at the tourist hostel in the Carpathian mountains (Ukraine)

Hi Bogdan,
Thanks for sharing this! I am just wondering why you chose an upflow configuration rather than downflow? Is that to save on space?

Also that's interesting that you have zeolite available. It might help you also with ammonia removal, have you considered that?
Would your filter require any periodic backwashing to prevent clogging? Would you add some sieves before the filter or at the outlet of the shower maybe?

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Re: Designing and building grey water filter for reuse in flush toilets at the tourist hostel in the Carpathian mountains (Ukraine)

Hi Elisabeth!
Thanks for the responce!

I suggest upflow design mainly because it seems to allow effective non-pressurized backwashing as opposed to down flow one.
This kind of roughing filter had been suggested in many resources like for instance here www.aqsolutions.org/images/2016/12/2000LPD_English.pdf

Actually now I am not too sure if zeolite is the best material for the media.. Maybe regular gravel all is needed. The single goal is to have flush water for the toilet. It should not clog the toilet cistern flush valves , have more or less nice appearance (some turbidity is probably ok) and most important do not stink too strong while rests for some time in the toilet cistern or in the receiving tank after the roughing filter below. The nitrogen content is not an issue at all I guess. Maybe actually UV would deal with the odor but this involves electricity which quite limited in that mountain hostel. What about batch chlorination?

I think a servicesable mesh filter before the equalizing/pressure tank would be good to get read of hairs and fibres
Best wishes,
Bogdan

Bogdan Popov
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Re: Designing and building grey water filter for reuse in flush toilets at the tourist hostel in the Carpathian mountains (Ukraine)

Hi Bogdan, I'm assuming this greywater system is only for washwater rather than kitchen wastewater. A kitchen wastewater vermifilter needs a much larger surface area.

The only way to stop the stink is to ensure dissolved oxygen (DO) levels remain high. There will be demand on that very limited oxygen in the greywater by organisms in the process of breaking down the organics. Your system does not add oxygen to the water so the water in the receiving tank will be very low in DO or even devoid of it. Indeed the system might even operate anaerobically, depending on the levels of organics present and the flow.

Next, the capacity of your receiving tank (and received water volume) will be greater than what you use for flushing. Therefore you will need an overflow to soakage. Importantly, the longer this "stored" water remains therein the tank depleted of oxygen, the more it will stink as the anaerobic organisms work on the remaining dissolved organics.

Vermifiltration, on the other hand, oxygenates the water at the same time as the aerobic organisms are working on the organics. The oxygen demand is reduced at the same time as oxygen is being dissolved into the water, in one simple process. Most people don't understand this which is why outdated technologies continue to be used and promoted.

With vermifiltration your receiving water tank will hold oxygenated water with a greatly reduced oxygen demand. Provided you don't hold it for too long, the water will not stink. That is, there will still be a residual oxygen demand and dissolved organics, so DO will reduce over time. What I would suggest is to limit the capacity of your receiving water tank so that the flush-water doesn't sit there too long and is being replenished with "fresh" well oxygenated water from your vermifilter.



This design has a fairly small diameter (maybe 1m) but as much depth as you can provide. Note the air cavity between the wall of the vessel and the media, and there also needs to be good ventilation so this air can be constantly replenished. Zeolite will be fine as the medium, but of more importance than the composition is the size. Powdered zeolite will not have sufficient flow for 1 cubic metre per hour unless the vermifilter vessel is much much wider. Coarse granules would have too much flow and therefore not reduce the oxygen demand sufficiently with one pass. Sieved to be small-granular will be fine and layering with different sizes is not necessary when packing the vermifilter. Test the zeolite granules first in a bucket with flows equivalent to the actual system and (unlike in my diagram) allow capacity at the top of the vermifilter so the maximum dose volume doesn't overflow. 

Dean Satchell, M For. Sc.
Go-Eco Sustainable Solutions
www.go-eco.co.nz
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Re: Designing and building grey water filter for reuse in flush toilets at the tourist hostel in the Carpathian mountains (Ukraine)

Dear Goeco.
Grey water is once used water from certain cleaning up operation.

In kitchen , bath . laundry wash waters optimise the use of detergents and soaps - awareness in communities.

If you have control in the community and can ensure use of bio-soaps and hot water with degreaser.

Then the effluent in the last stage can have phyto remediation ie use of appropriate plants foliage etc..
This wwtp plant can be effective.

Well wishes
Prof Ajit Seshadri
Vels Unversity. Chennai .
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Re: Designing and building grey water filter for reuse in flush toilets at the tourist hostel in the Carpathian mountains (Ukraine)

This is very interesting goeco. I have one question, can the worms live directly in the zeolite? don't you need something like sawdust or humus? Maybe I didn't get it just right. Thanks for any clarification you can provide.

Gustavo Heredia
Director
AGUATUYA Bolivia
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Re: Designing and building grey water filter for reuse in flush toilets at the tourist hostel in the Carpathian mountains (Ukraine)

Hi Gustavo,
I haven't used zeolite but my understanding is that worms don't care whether they are in mineral or organic media, what they require is moisture and media surface area that has biofilm growing on it to feed on. They would need to be able to burrow and I can't see why zeolite wouldn't work. Of course the worms will create humus so this will accumulate and eventually the media would be mixed mineral and organic. I assume that Bogdan wants to use zeolite because of its high cation exchange capacity and surface area, but also because it is locally produced. This appeals... using what is available locally... whether zeolite... pumice... scoria, gravel, pine bark, sawdust or even peat. To me the main thing is to get the porosity right which means the right granule size for a mineral substrate.

cheers
Dean

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Go-Eco Sustainable Solutions
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Re: Designing and building grey water filter for reuse in flush toilets at the tourist hostel in the Carpathian mountains (Ukraine)

Hi Dean !
Thank you for the input!
The vermifilter design for treating of grey water for reuse in the toilets is very interesting. However, I see certain challenges when using this approach in this specific case
1) Highly variable unpredictabe flow. The hosel might stay empty for weeks and then suddenly suffer pick loads of 20-30 people. For the idle period recirculation might be needed to keep the biota alive and in proper population size (both bacteria and worms)
2) Hot water temperature from the showers (>40 degrees) might be a problem as it would flow directly to the vermifilter in your design/ I would put some kind of cooling equalizing tank before. Maybe also a horizintal inlet pipe with heat exchanger that coils around the vermifilter tank to keep it warm during cold time (some way of dumping that heat outside should be thought of for the summer-- maybe heating the water supply for the showers).
3) Sump below the ground is not possible already since it is on the rock and there already concrete slab poured on the first floor.



I like the idea anyway and think that it is worth developing and experimenting. However so far for this specific case I lean so far towards simple mechanical filtration in the upflow or downflow roughing gravel filter and subsequent automated chlorination like it is used in the pools. Aeration also possibly can be reached through running the water through cascade aerator like something described in the book " Simple methods for treating drinking water" by Gabriele Heber which also acts like a roughing filter

Best,
Bogdan

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Re: Designing and building grey water filter for reuse in flush toilets at the tourist hostel in the Carpathian mountains (Ukraine)

Dear BogdanPopov,

It is an interesting read and find that the same vertical layout could be made out horizontally, pl assess and adapt.

Do you have control over soaps & detergents used in hostels , then you can opt for usage of bio-soaps and hot water and bio-de greasers.
This would be more amenable to natural treatment in your chambers.
In vermi-pits to use - soap-nuts and legumes etc, would be accepted well by worms.
As regards the digestion by worms, the bio-matter require to be 50% decomposed, for worms to accept it as food for them.

Use of organic food ( ex. soapy, legumes wastes and others ) will not contain strong bleach- Cl2, NH3, HCl.. which releases gases not amenable to worms, whereas good draft of fresh air with desired air changes are ensured.

The regime of worms would be an eco system, very vibrant- productive enough, and sustained due to food - 50% decomposed bio matter being regularly available, worms die, and these matter also are consumed by others .
In the secluded regions not rich in organic content, the worms will shift to nutrient rich zones,
The totally consumed organic matter is turned into matter resembling earth/ soil rich in nutrients and minerals.
This remains are removed regularly and new food is introduced tot he worms to carry on the process.

The specie of worms are selected and uni-culture is followed, pl avoid introduce another specie, as this would be detrimental.

The above notings are issued for providing guidance, and pl do apply prudence and practices for your specific site conditions.
The practices are documented including any adaptations, and try follow a set pattern for optimum benefits.

well wishes,
Prof. Ajit Seshadri,
Vels University, Chennai, India.
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Re: Designing and building grey water filter for reuse in flush toilets at the tourist hostel in the Carpathian mountains (Ukraine)

Hello everyone!

I think I need to draw a simple plan how the whole setup looks like.

Best,
Bogdan

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Re: Designing and building grey water filter for reuse in flush toilets at the tourist hostel in the Carpathian mountains (Ukraine)

Excellent! I am looking forward to trying a vermifilter at home. I have my grey water separated already so it should be straight forward!
Cheers and thanks for your help!

Gustavo Heredia
Director
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Re: Designing and building grey water filter for reuse in flush toilets at the tourist hostel in the Carpathian mountains (Ukraine)

Dear BPopov.
Its nice to see a sketch for a plan.

How much would be the flow in cbm per day. Pl afford 4 to 6 days HRT for retention of water being remedied in tanks.

You can have the process in 6 stages :
pre process - large holed mesh striner
Primary stg-equlzng tk anaerobic
Secndry - large sized stones/:boulders
Tertiary- gravel, sand aerobic in nature
Finishing - vermi beds for remedied water with bio matter from primary stage bottom of tank.
Polishing- can include an over head tank with aeration and providing a constant head for flush water.

At each tank at lower level could have sunk pit and sludge suction pipe to draw out sludges . All sludges taken for process with bio matter - ( food matter. foliage from campus. etc ) from your solid waste mngmnt path.

You should try to evolve a Smart Complex at the hostel premises.
As an attachment I will share information as to how 6 odd green initiatives are done at your campus.

You may assess , plan and attempt the easily doables first, then efforts can be made for doing other tasks.
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Well wishes
Prof Ajit Seshadri
Vels University. Chennai. INDIA.

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