Vermi-Trickling Filters (or vermifilters) for Sewage Treatment (looking for help to design)

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Re: Vermi-Trickling Filters (or vermifilters) for Sewage Treatment (looking for help to design)

Hi Dean!

Thank you!

I am involved with developing these kind of public toilets and surge loads is quite challenge for any kind of system (dry or water based) Just wanted to see how in your view vemifiltration could possibly overcome it. Looks like it is also complicated issue.

Regards,
Bogdan
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Re: Vermi-Trickling Filters (or vermifilters) for Sewage Treatment (looking for help to design)

Hi Bogdan,

What about scaling a single digester to the number of users? There would be no problem with high weekend use and then no use during the week.... the worms don't care, that is no different from the same quantity evenly over the week. 300 uses per week is maybe like 30-40 people using it constantly... so 10 x the capacity of a domestic vermifilter... maybe (I'm guessing) 2m high and a diameter of 3m? However, the key would be getting digestion underway rapidly to keep pace with the inflow. On a domestic system one can add a small handful of worms a few weeks after commissioning and it might take months for the population to build, which isn't a problem because there is additional capacity. With a larger system the buffer might not be so large, so the pressure would be to get digestion to keep up with inflow as soon as possible. Could you describe in more detail what you have in mind in terms of a modular system?

cheers
Dean
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Re: Vermi-Trickling Filters (or vermifilters) for Sewage Treatment (looking for help to design)

Hi Dean!

Do you think it is would be technically possible to develop primary vermidigester for public toilet with high number of week-end visitors (say 300 per point of use per day) , long idle period with none of few visitors? The modular system when several vermifilters cells got linked in on demand is what comes to my mind. Having one big vermidegester designed for peak loads doesn't look like a right option. Or what do you think?
Best,
Bogdan
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Re: Vermi-Trickling Filters (or vermifilters) for Sewage Treatment (looking for help to design)

Hi Bogdan, I have to say I prefer settling tanks in series rather than cartridge filters, because filters don't tend to be maintained by users and can affect the reliability of the whole system. Maintenance of settling tanks is minimal, perhaps 5 yearly intervals pumping sediment back to the primary vermidigester.

Also keep in mind that with vermifilters the worms maintain the filter! Settling tanks can also be built cheaply out of used 40 gallon drums. I'll upload some photos some time of a low cost domestic system made entirely out of 40 gallon drums...

Perhaps think about designing systems that malfunction at the source when not maintained... i.e. the toilet overflows because maintenance is required! These are wonderfully foolproof... :-)

cheers
Dean
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Re: Vermi-Trickling Filters (or vermifilters) for Sewage Treatment (looking for help to design)

Hi Dean!

Thank you! This very valuable that you are willing to share your experince here including trials record. It is only through these experiments we can develop new systems "out of septic box")))).

Now I understand much more about your design and why did you put several setlling tanks after the primary digester. This really makes sense. I wonder if there are any very small low wattage small flow sludge pumps produced capable of passing bigger partickles. and run on 12 volts. I haven't seen any here less than 500 watts so far.
Some cartridge type rough filter serviced from outside like septic tank effluent filter is what what comes to my mind when I think of the ways to make things working with the pump. Probably also control system that warns of level raise in the sump when the filter got clogged.

Best,
Bogdan

Bogdan
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Re: Vermi-Trickling Filters (or vermifilters) for Sewage Treatment (looking for help to design)

Hi Bogdan, yes blockage of these small cheap pumps has always been a concern. Indeed they can block with silt building up in the inlet. The pump itself doesn't block, but the buildup of fine particles can stop the water from flowing into the pump which can burn them out. How I've got around that is to use a series of sedimentation drums between the primary and secondary vermifilters. These remove most of the suspended solids. Also, the intake for the pump is below the surface but not too far below. The solids themselves are never big enough to block the pump, with reliability being the key concern.

I'm sure there would be a thousand different ways to design the system... if there were fall then the secondary filter could be directly under the primary filter and thus avoid any need for settling and recirculation. That is not always possible, however. I'm also interested in hearing others solutions to the problem!

With this system, every 5 years (when I rotate primary vermidigesters) I pump the sediment from the settling drums back into the primary vermidigester. Depending on how well your primary vermifilter removes suspended solids, the buildup of sediment should be quite slow. I don't try and achieve high levels of removal at the primary stage, and with settling drums the secondary vermifilter is not primarily for removing suspended solids, but more to aerate the wastewater and remove BOD, pathogens and smell for subsequent surface discharge.

cheers
Dean
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Re: Vermi-Trickling Filters (or vermifilters) for Sewage Treatment (looking for help to design)

Hi Bogdan,
I originally had the small baskets working in series, it was a long plastic tube made out of 40 gallon drums and I pushed the next empty basket in from one end under the inlet, which pushed all the baskets toward the other end. Was just an experiment... which failed because the composting process was too slow and the tube needed to be too long with too many baskets for my liking. What I learned was that working in shifts is the best option because the worm population builds up. You just need a way for the worms to migrate from one basket to the other... with enough capacity for your rotation length.
cheers
Dean
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Re: Vermi-Trickling Filters (or vermifilters) for Sewage Treatment (looking for help to design)

Hello Dean!

Could you tell please, how well these fountain pumps you use for the recirculation tolerate particles in the vermidigester/vermifilter leachate? Did you have any problems with pump clogging?
Best,
Bogdan
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Re: Vermi-Trickling Filters (or vermifilters) for Sewage Treatment (looking for help to design)

Hello Dean!

Yes, it is very helpful. Thank you very much! I see what you mean from this pictures. It should be a basin rather than bucket. I thought about making a small demo model from 120 l low and wide barrels available but now understood that it wouldn't work for digester. For the vemifilter it will robably be ok though . By the way did you practise rotation of the vemifilters cells as well or kind of make them working in shifts to recoverbetween cycles?

Best,
Bogdan
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Re: Vermi-Trickling Filters (or vermifilters) for Sewage Treatment (looking for help to design)

Hi Bogdan,
Wet composting seems to work differently than ordinary composting. With wet composting the heap degrades from the outside-in compared to inside-out with ordinary composting. I trialled 70 litre baskets a few years ago and didn't have very good results, degradation was slow so the baskets filled rapidly. I attribute that partly to lack of time for a stable population of worms to develop (the baskets filled too quickly) but more importantly, in smaller baskets surface area to volume is reduced.


(I'm discussing primary digesters here where toilet paper is used. A heap is inevitable.)

Pretty rough drawing, but the area highlighted in orange is the area that the worms work. They don't venture into the core because it doesn't have enough oxygen, so they work from the outside. See how the small basket has a very large core and a small outer area for the worms to work?

With lots of area for the heap to expand outwards, it tends to "flatten" as it spreads. This ensures fast degradation.

Helpful? What is your cunning plan?

cheers!
Dean
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Vermifilter.com
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  • Marine Chief Engineer by profession (1971- present) and at present Faculty in Marine Engg. Deptt. Vels University, Chennai, India. Also proficient in giving Environmental solutions , Designation- Prof. Ajit Seshadri, Head- Environment, The Vigyan Vijay Foundation, NGO, New Delhi, INDIA , Consultant located at present at Chennai, India
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Re: Vermi-Trickling Filters (or vermifilters) for Sewage Treatment (looking for help to design)

Hi. Researchers & Developers. It is great to note the deliberations on vermi filter. In certain of our sites in India we use say 20% by volume -
partly cured excreta from cattle. A lot of benefits and if bio mass is available use them also. All this is required to keep e - worms healthy and well at their work. As saying goes if worms are good both in quantity and quality then the filter will be very fine... w wshs from Prof Ajit Seshadri. Vels University.Chennai.India.
Prof. Ajit Seshadri, Faculty in Marine Engg. Deptt. Vels University, and
Head-Environment , VigyanVijay Foundation, Consultant (Water shed Mngmnt, WWT, WASH, others)Located at present at Chennai, India

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Re: Vermi-Trickling Filters (or vermifilters) for Sewage Treatment (looking for help to design)

Hi Dean! Thank you !

But what if we go for more often switch say 1 month or even less and have more than two digesters? What I am interested in is what in general the minimal volume for the biological process of vermidigestion to happen. I know that 100 l is enough volume for composting to happen (though not so fast as in a bigger pile). Or it possible on condtition that you add there enough worms right from the start?

Best,
Bogdan
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