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

  • BPopov
  • BPopov's Avatar
  • Ecologist involved with ecosanitation in Ukrainian Carpathians
  • Posts: 141
  • Karma: 7
  • Likes received: 48

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

Hi Dean!
I have no practical experiece yet with building aerated constructes wetlands. The inforamtion on the forum is here
forum.susana.org/component/kunena/36-con...gineered-wetlands-ew

I believe that one possibility is to aerate is through perforated pipes inserted directly in the substrate or have the the air supply from underneath the supporting structure like it done in industrial trickling filters. If we have the air cavity between the walls it would also help


Or it can be a cobination with the perforated pipes protruding through support layes vertically.
As far as I know pressurized air can be produced directly by windmils or hydropower pumps bypassing electricity.

I think in cold climate design active aeration could be a must since insulation also means restricted air flow from outside.
Regards
Bogdan

Bogdan Popov
The Ecosolutions Forge
www.ecoforge.org
Attachments:
You need to login to reply
  • goeco
  • goeco's Avatar
  • Self employed innovator with an interest in wastewater treatment systems and recycling of nutrients
  • Posts: 259
  • Karma: 7
  • Likes received: 142

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

Hi Bogdan,

I'm not in a cold climate but was thinking that a well insulated reactor would only require ventilation when it warms up. Very little biological activity would happen say below 6 degrees C so the ventilation system could be set up to switch on once above that temperature. This could be passive, such as convection (a black pipe that warms with the sun and draws air into the reactor), or a small solar panel and fan that runs during the daytime? In small systems I don't think air pipes through the media would be necessary, especially if the media basket has air flow under and around the sides and the media course. However, anything that improves the efficiency of the system is good!

cheers
Dean

Dean Satchell, M For. Sc.
Vermifilter.com
www.vermifilter.com
The following user(s) like this post: BPopov
You need to login to reply
  • BPopov
  • BPopov's Avatar
  • Ecologist involved with ecosanitation in Ukrainian Carpathians
  • Posts: 141
  • Karma: 7
  • Likes received: 48

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

Hi Dean!

Thanks for the useful input! Yes it would be really intresting for me to build this one in the cold conditions where sometimes I work with -20 C outside for prolonged time during winter. There is not much sun to take into account for the passive ventilation.
Does this process release considerable heat? Probably one can expect more heat from black water vermifilter than from a grey one.
What do we have here a compost pile with a bit of worms or rather worm nest eating up feces with a bit of compost?

Regards,
Bogdan

Bogdan Popov
The Ecosolutions Forge
www.ecoforge.org
You need to login to reply
  • goeco
  • goeco's Avatar
  • Self employed innovator with an interest in wastewater treatment systems and recycling of nutrients
  • Posts: 259
  • Karma: 7
  • Likes received: 142

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

Hi Bogdan,
No I don't believe the process releases much heat. Certainly oxidation means generation of heat, but I don't think the wastewater would increase much in temperature during the process because of flow and volumes involved. Although the wastewater influent has a very high biological oxygen demand (BOD), which directly results from dissolved and suspended organics, if actually quantified as organic matter content, this is not much compared with the solids pile. The issue is that the amount of oxygen that water can contain or "dissolve" is very little compared with what is in air. This means that the oxygen needs to be replenished several times in wastewater for aerobic decomposition to be completed, if only taking place in the water. The biological process is that the bacteria degrade the organics in the wastewater and consume oxygen. What little oxygen is dissolved in the water is quickly depleted, rapidly leading to anaerobic conditions unless aeration takes place. I've tried to explain this here . Filtering solids out and providing air to the decomposing bacteria is quite different than decomposition taking place within the water... a big advantage with vermifiltration over traditional wastewater treatment.

However, if the water is already cold the process will inevitably be slow (even slower under anaerobic conditions). This means a capacity issue if the environment is cold for long periods.

By providing ventilated media and wastewater flow with lots of "food" (organics), bacterial slime builds up on the media and consumes the dissolved and suspended organics. I favour the recirculating vermifilter because oxygen will dissolve into the wastewater with each pass. I just don't think that the quantity of organics in the filtered wastewater will be sufficient to generate much heat. The solids pile on the surface of the primary treatment vermifilter would produce some heat but this does not decay rapidly like a compost heap. A normal compost heap decomposes very rapidly from the inside out because there is plenty of air inside it and the heat generated increases the rate of decomposition. The "wet" compost heap on top of the primary treatment vermifilter doesn't have air inside it, it relies on the worms to introduce air from the outside (especially underneath) and so the process is slower. It would generate some heat but maybe not as much as you require to increase rate of decomposition in cold conditions.

Okay, so insulation would be required to ensure the worms don't freeze. However, ventilation shouldn't be required when conditions are cold because there is so little biological activity taking place anyway and the oxygen wouldn't get depleted in the reactor. You could introduce a heat source to generate the required biological activity and treatment level, but I'm thinking you could automate ventilation to open when the sun does shine or when temperature does get above say 5 degrees, you just need capacity because when its cold not much will be happening.

Just some ideas, it doesn't often get below zero degrees C here!

Dean Satchell, M For. Sc.
Vermifilter.com
www.vermifilter.com
The following user(s) like this post: BPopov
You need to login to reply
  • BPopov
  • BPopov's Avatar
  • Ecologist involved with ecosanitation in Ukrainian Carpathians
  • Posts: 141
  • Karma: 7
  • Likes received: 48

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

Thanks again Dean!
This all is very very interesting.

How about oils and grease? Do they pose threat for the vermifilter and better removed by grease trap before it? I am asking this since in compost pile grease is quite ok and sometimes used deliberately to heat it up.



Regards,
Bogdan

Bogdan Popov
The Ecosolutions Forge
www.ecoforge.org
The following user(s) like this post: goeco
You need to login to reply
  • goeco
  • goeco's Avatar
  • Self employed innovator with an interest in wastewater treatment systems and recycling of nutrients
  • Posts: 259
  • Karma: 7
  • Likes received: 142

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

Good question Bogdan! I wondered about this myself so tested it. I tipped 20 litres of solid rancid fat from a grease trap into my domestic primary treatment vermifilter to see what would happen. It was all digested and gone in about two months. This surprised me because I had heard that worms don't like grease and fat... Not true! Again just not sure how much heat this would generate.

cheers
Dean

Dean Satchell, M For. Sc.
Vermifilter.com
www.vermifilter.com
You need to login to reply
  • BPopov
  • BPopov's Avatar
  • Ecologist involved with ecosanitation in Ukrainian Carpathians
  • Posts: 141
  • Karma: 7
  • Likes received: 48

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

Hi Dean!

This is great experiment! Means it is quite a robust system.
Regards
Bogdan

Bogdan Popov
The Ecosolutions Forge
www.ecoforge.org
You need to login to reply
  • BPopov
  • BPopov's Avatar
  • Ecologist involved with ecosanitation in Ukrainian Carpathians
  • Posts: 141
  • Karma: 7
  • Likes received: 48

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

Hi Dean!

We've been discussing with a colleague the vermifilter issue recently in terms of limitations of this approach and came to conclusion that basically it is fantastic and everything can be solved with cold temperature but the worst thing is when somebody will flush down something nasty that kills or harms the worms. The cleansers or whatever those neat householders use in the bathroom to make it look tidy and fresh. Did you experiment also with that stuff?

Best wishes,
Bogdan

Bogdan Popov
The Ecosolutions Forge
www.ecoforge.org
You need to login to reply
  • goeco
  • goeco's Avatar
  • Self employed innovator with an interest in wastewater treatment systems and recycling of nutrients
  • Posts: 259
  • Karma: 7
  • Likes received: 142

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

Hi Bogdan, vermifiltration has been used for domestic sewage treatment for some time in New Zealand and Australia. I have not heard of any cases where the worms were killed by household disinfectants etc. I would imagine that pouring a fairly large quantity of pure disinfectant down the drain would kill the worms but in common use this would not happen. It appears that standard practices such as washing disinfectant down the sink with water sufficiently dilutes the chemicals to not kill the fauna. I haven't actually tested the limits of this but do use standard household disinfectant and laundry steriliser.

cheers
Dean

Dean Satchell, M For. Sc.
Vermifilter.com
www.vermifilter.com
You need to login to reply
  • BPopov
  • BPopov's Avatar
  • Ecologist involved with ecosanitation in Ukrainian Carpathians
  • Posts: 141
  • Karma: 7
  • Likes received: 48

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

Hi Dean !

Thank you! Sounds good again.

I wanted to ask you about the profile of your vermifilter. Do use wood chips all the way down both as bedding and drainage or still have some kind of gravel underneath for drainage? If so what is grain size of the gravel and what its depth? Do you have some kind of collecting perforated pipe underneath?
Regards,
Bogdan

Bogdan Popov
The Ecosolutions Forge
www.ecoforge.org
You need to login to reply
  • BPopov
  • BPopov's Avatar
  • Ecologist involved with ecosanitation in Ukrainian Carpathians
  • Posts: 141
  • Karma: 7
  • Likes received: 48

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

I agree with you Dean in terms of proprietary issues applied to vermifiltration. You can't patent worms, plants, bacteria and water -- it's like trying to patent nature itself. We are to achieve nothing in terms of solving global water and sanitation challenges if resort to this attidude.

Bogdan Popov
The Ecosolutions Forge
www.ecoforge.org
You need to login to reply
  • goeco
  • goeco's Avatar
  • Self employed innovator with an interest in wastewater treatment systems and recycling of nutrients
  • Posts: 259
  • Karma: 7
  • Likes received: 142

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

I wanted to ask you about the profile of your vermifilter.

We probably should be discussing primary treatment and secondary treatment vermifilters separately. In a secondary treatment vermifilter you don't need much space above the media because solids don't really build up over time. This is because only liquid circulates through the secondary treatment module. Depth of media is also important.

On the other hand, primary treatment vermifilters need lots of space above for buildup of solids, they should be wide to allow the solids to spread out rather than build up, and they don't require much depth of media.



Media basket using plastic mesh, shadecloth, polythene pipe and plastic cable ties




Basket installed in 250 litre plastic drum



Coarse pine bark media installed in basket

Because there is air surrounding the media there is no need for a coarser drainage layer at the bottom. I do use a free draining media that doesn't impede percolation and air penetration into the media though. If you use a fine media such as peat or sawdust, you might need a coarse gravel drainage layer at the bottom. Keep in mind that using a basket means that impeded drainage doesn't result in over-saturation/flooding. You can't drown the worms this way and the environment always remains aerobic. Also note that I drill lots of fine holes in the drum to allow ventilation (but not flies). In your case you'd have insulation and a ventilation system to ensure the reactor doesn't freeze.

cheers
Dean

Dean Satchell, M For. Sc.
Vermifilter.com
www.vermifilter.com
Attachments:
The following user(s) like this post: guilherme, BPopov
You need to login to reply
Share this thread:
Recently active users. Who else has been active?
Time to create page: 1.972 seconds