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

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

Hi Bogdan,
from memory they are 1m x 1.2m and about 900 high, about a cubic metre of capacity.
I tend to pipe greywater directly to the secondary reactor because the purpose of the primary digester in my design is to filter out and digest solids, not purify the wastewater. Thus kitchen greywater could go through the primary digester to remove any solids, but bathroom/laundry greywater gushing over poo might actually pick up fine solids? Piping laundry/bathroom greywater directly to the secondary filter for purification along with primary-treated blackwater makes more sense to me. I'm sure I could put all my wastewater through the primary treatment vermifilter though and welcome anybody trying out alternatives then sharing the results from these... this is an evolving technology!

cheers
Dean

Dean Satchell, M For. Sc.
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Re: Vermi-Trickling Filters for Sewage Treatment (looking for help to design)

I´ve done that Dean. I´ve set up a vermifilter initially for a local NGO site for black water only, but the system receives high doses of greywater (shower) during the courses they offer there every now and then. I felt that the effluent was not adequate for shallow infiltration because it´s quite near a swimming pond, so I decided instead to add on a constructed wetland as a 2nd stage, before actual infiltration. The vermifilter handles this additional flow quite well during the course of events, which usually lasts no more than 3 days, but one can see that there´s a real restriction on flow throughout theses days.

You can see its overall aspect on the image below. Looks great and no fowl odor at all.

I haven´t had a chance to do lab tests on this one as of yet, but as soon as I do I´ll let you know.

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Guilherme Castagna
Fluxus Design Ecológico
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Re: Vermi-Trickling Filters for Sewage Treatment (looking for help to design)

Hello Guilherme!


Could you please , share what is volume of your primary vermifilter and what was approximate waste water load on it per day including grey water from the shower?

Regards,
Bogdan

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

Hi Dean! Are the worms able to get through the shade cloth when the migrate from one crate to the other? To my memore shade cloth holes are around 3 mm diam. I have seen recently in Norway some kind of heavy duty shade cloth hanging in the building store and really liked it (see picture attached)



Stacking the secondary treatment crate directly under primary one sounds interesting however I would go for some kind timer operated dosing sprinkler for the secondary filter and put respectively accumulating pump/syphon tank before it.
What I would think also about is to have a separate small volume basket primary filter for kitchen sink filled with wood shavings to get rid of the grease and soapy cleaners (an aerobic grease trap). They are quite effective even without worms.

Regards
Bo

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

Hi Bogdan,
keep in mind the primary reactor will be dosed every time you flush, which if stacked would then dose the secondary reactor below. Why would you dose the secondary reactor? Be careful of using sprinkler nozzles, the bacterial slime will block them up. I see dosing as only essential at the outlet where you'd dose surface irrigation drippers.

I reckon the worms should squeeze through the gaps in your shadecloth ;) ...if they ran out of food on one side they might have to slim down a bit before they can get through!

Yes, I have a 230 litre drum-sized vermifilter specifically for my kitchen water. It was going for a few months before I added the worms. The solids and grease built up on the surface of the media (I was shoving anything I could fit down the plughole) so the liquid was then draining through the shadecloth sides, which also got clogged with grease, impeding drainage and making a pool. Once the worms were added they soon dealt with the buildup of solids on the surface and drainage was effective again. The grease condenses on the first surface it finds and in my case almost sealed the filter! Definitely wider filters are always more reliable.

Guilherme, I wonder if you would have better effluent quality if you piped the shower water straight to your wetland rather than through your primary vermifilter? Or set up a dedicated vermifilter for all the greywater that discharges to the wetland? They are so easy and cheap to construct, I'd need convincing that it is a good idea to put shower water through a poo vermi-digester...

cheers
Dean

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

Hi Dean,

The idea is to really separate black and greywater, and direct greywater straight to the constructed wetlands (a floating wetland with emergent species over a bamboo rack, btw), but this involves a future refurbishment that was not possible to happen, as of yet. In other words, this is a temporary solution.

Best to you all, and thanks for your work and attention!

--
Guilherme Castagna
Fluxus Design Ecológico
São Paulo/SP - Brazil

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

Dear Bogdan,

The vermifilter I mentioned was built using 1m (diameter) concrete rings. They consist of 2 rings of 0,5m high put one on top of the other, totalling 1m as well. This was my first vermifilter and I thought, based on the studies I had read by then, that it´d be better to get the effluent applied to an area that would be larger than the plastic tanks I had found so far, but not wide enough to create preferential flows since the effluent comes in from a 100m pipe, straight from the toilet + shower.

As I mentioned to Dave, my original plan was to have it receiving blackwater only, a load varying from 5 PE to 20 PE (person equivalent). It now receives usually 1 PE on a day to day basis, and up to 20 in single events. It has already received the volume of up to 20 showers/day in events, whereas today it´s not more than 8/10, as we have been able to build a separate installation for additional showers, which have helped to reduce the load.

Good work out there, best from Brazil!

--
Guilherme Castagna
Fluxus Design Ecológico
São Paulo/SP - Brazil

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  • AditiOS1
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Re: Vermi-Trickling Filters for Sewage Treatment (looking for help to design)

Dear Dean,

We did a pilot based on the inputs provided by you, the results are definitely more encouraging. We are now looking at replicating the same for a slightly bigger scale (10,000 litres per day) , the effluent from the existing septic tank would be taken into the vermifilter using a feed pump and sprayed evenly over the active bed. Trying to work out on the recirculation rates, what percentage of the water should be recirculated and how many passes should we design for to get optimum quality of water. Should the recirculation spray be done alternatively or simultaneously with the raw sewage spray over the bed ? We are also getting yellowish tinge in the water how to reduce the same ???
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Re: Vermi-Trickling Filters for Sewage Treatment (looking for help to design)

Hi Aditi
Are you pumping from the outlet of the septic tank up into the inlet of the vermifilter which has an outlet that then drains back into the inlet of your septic tank, or do you have two pumps, one for pumping the effluent from the septic tank into the vermifilter and another to recirculate from a sump below the vermifilter back into the top of the vermifilter? Is your septic tank system baffled with one chamber? How many stages (chambers) are there?
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Dean

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

Dear Dean,

The septic tank has three baffles (4 chambers) and has about 2 days of retention (approx effective volume 20,000 litres). we have put a submersible pump in the last chamber from where we would pump the water on the vermifilter bed. The drainage from the bottom of the vermifilter flows into another holding tank from where we can pump the effluent back for recirculation.

The organic media that we are planning to use is wood chips mixed with humus and earthworms. Sugarcane baggase is also available but I am not sure if such a complex organic matter would be a good choice for treating inlet BOD levels of 80-100 mg/l.

For the inorganic filtration media we are using river bed gravel. However, I am not sure about the long term availability of this material. Can we use construction gravel or fly ash instead ?

You mentioned using fruit crates as the holding tanks, we thought about replicating that on a larger scale to basically cut down on the hassles of changing the media using shovel and hands. What do you think ???

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

Dr. Aditi.
I am not too friendly in answering in weblinks. If it disappears pl feel free to email .. This email address is being protected from spambots. You need JavaScript enabled to view it. .... For your design you need to take care of HRT say the plant capacity in volume ought to be 7 to 8 times to bring raw sewage mixed with sullage waste water... say inlet BOD to plant may be 400-500ppm..
then you can get < 30ppm( less than). Have it in 3 phases.. Simple anaerobic septic tank with 1 or 3 baffles can be more.. next have stone, pebble& sand fllteration filters .. lastly phyto r use plants for r- remediation.. store the outlet water for settling- curing & maturing .. then this water can be re used for secondary uses viz. landscapes. ponds. fountains. Shallow aquifer recharge.. prudently.. w wshs..
Prof. Ajit Seshadri.
Vels University.
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Re: Vermi-Trickling Filters (or vermifilters) for Sewage Treatment (looking for help to design)

Hi Aditi,
okay, so I'm assuming you will have a float switch on your pump so will be pumping the same volume from the septic tank into your vermifilter as your wastewater inflow and it will be dosed.

With only two days residence time you won't be getting a high level of treatment from your septic tank, but you could take advantage of it being multi staged by recirculating (with a constantly operating pump) from the 4th stage through the vermifilter and back into the 3rd stage of your septic. This would take advantage of the capacity in the septic tank by making the 3rd and 4th stage aerobic, which will be more efficient, while also treating the wastewater through the vermifilter. A 10 watt 12v pump does about 10,000 litres per day which is the capacity of those two stages. Maybe aim for two cycles per day, with a 20 watt pump at a 2 m head (2 fruit baskets stacked)?


Brushless 12 v pump. This is $30, 12 watts, 650l per hour with a max head of 3.8m

You could even have two vermifilters operating, one recirculating from and back to the 3rd stage, the other from and back to the 4th stage. Less equipment, lower cost.

Yes, you can feed the output from the septic tank through a vermifilter and recirculate back through this using a holding tank.

Working out recirculation rates, vermifilter capacity and septic tank capacity will be trial and error. Given a set capacity for both septic tank and vermifilter and with a constant hydraulic loading rate (i.e. sewage influent volume per hour or day), recirculation will increase hydraulic retention time. The more volume you recirculate, the higher the hydraulic retention time, therefore the higher the level of treatment. Keep in mind that hydraulic retention time can also be increased by having less porosity in the media, but this entails a higher risk that hydraulic loading could exceed hydraulic retention time. Greater depth of media (or stacked fruit crates) also increases hydraulic retention time but the increased head means more energy is required for the same volume recirculated.

A higher level of treatment is also achieved by increasing capacity of either septic tank or vermifilter. Therefore, to achieve higher level of treatment your options are either increased capacity or increased recirculation or both. Think about costs for each of these and make the right trade off. Pumping has a cost over time whereas capacity is capital outlay. Perhaps fine tune the system by using modular reactors that can be added if required. Stacked fruit crates + recirculation pumps...

Fruit crates make the greatest vermifilters, they can be shifted with forklifts and stacked into towers, several high if necessary. They have been my best kept secret till now... you must promise to open source what you learn! You can use corrugated plastic as the outside covering, screwed on to the crates for easy dismantling.

I'd recommend the woodchips, bagasse might decompose too quickly. Sawdust is good. If you use fruit crates then don't bother with the inorganic layer. Baskets don't need it, they have air underneath.... provided you provide sufficient ventilation around them.

Don't forget to share your findings. We're all learning.

cheers
Dean

Dean Satchell, M For. Sc.
Go-Eco Sustainable Solutions
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