BioFilter Treatment Questions

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Bob
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Post by Bob » Tue May 29, 2007 9:57 am

An afterthought.

Going back to the page where I describe the biofilter, I note that I did not show ribbon media that I added to the system later. I put it in the downtube in the settling tank (2nd drum).

It is commonly available from aquarium or pond supply sources. I'm not sure it is necessarily the best type of media, but I chose it for this because it has pretty good surface area/volume, and, even more importantly, is relatively easy to clean and maintain -- as seen in this maintenance video. Googling "ribbon media", I find a couple of useful sites, including this discussion, about the advantages and disadvantages of different types of media ...
The most desirable media for a filter meets some, or all, of the following qualifications: provides ample surface area for bacteria to grow on, resists clogging, channeling and compression, maintains loft, is easy to clean, durable, affordable, nontoxic, low density, easy to apply, and readily available. . . . . Below are commonly available filter medias their advantages and disadvantages.
and this interesting page describing how to make your own. (I have had similar ideas, while just cleaning up the waste from cutting & drilling plastic pipe...)

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System Start-up going slowly but progressing.

Post by davidg » Wed May 30, 2007 1:34 am

Bob wrote:Good questions, David.

I think I'd be inclined to just let it keep going as is for a while longer, and wait to see if it clears up as the sludge blanket grows and biological populations mature.
Yes figured as much.
Assuming that the solids in the 3rd tank are settleable -- i.e. not in colloidal suspension, I would think that over time, the surge pump in the 3rd tank should return them to the bottom of the 2nd tank.
I don't think that will happen as the 20L trickle filter contains "aquarium wool" which is catching the larger suspended solids in solution, I suspect I'll have to clean it soon the rate of water flow through it has slowed quite a bit, I now have a continuous puddle on the surface all time now.
What kind of flow rate are you getting from the bottom of the 3rd tank to the trickle filter? Would it be possible to increase this? i.e. by turning up the airflow to the pump?
Um, no the geyser/big bubble pump is flowing about 3-4 litres a minute, I slowed down the surge tank pump slightly as it was really pushing the water through quite quickly reduced it back to an average of approx 120 litres per hour. it was running much faster than that about 4 litres per minute.
From your description, it sounds like the scum layer in the 2nd tank is comprised of settleable solids that are heavier than water, but that had been floated to the surface with rising bubbles (of biogas?). I'd be curious to know what the pH is.
possible. Also, a lot of bacteria as well I suspect, the scum is just under the surface, oh and clings to the sides and anything else it can as it would :), of the (2)tank.

The (3)tank also has similar but to lesser extent and less in solution solids as well. Again I suspect as a result of "start-up" and having no active sludge layer at all to start off with.

We don't use "poisonous" cleaning products anymore and haven't for sometime, all our cleaning, shampoo, soap, etc products are labelled as being "eco or grey-water friendly" and are supposed to be derived from natural renewable materials. Pity I can't say the same for the containers :( .They are mostly plastic at least they are capable of being recycled.

The PH I have not tested it yet.

I should say though that water that exits the system is considerably cleaner than it started in the surge tank so from that point of view it is working OK.

A slight odor is still present after the water exists the (3)tank but it is only about 5% of what it was in the surge tank and the water is fairly clear about 80% compared to what it is in the surge tank. So from that point of view it's working :), I suspect time will help to improve this further.

I'm running the water that exits through another small tank which I'm using to see what "settles out" at the moment. There are micro solids still settling out so this shows that things still need to progress further still.
=========================================

The tanks I used are about twice the size of the ones you used. At the current water levels in them they each hold about 400 Litres of water the surge tank can get to just under 500 litres of water at a pinch. When I was testing things, I found that the surge tank pump at the current setting for the air flow it averages 120-130 litres per hour provided of course there is water to move.

That of course works out at lots (1000's) of litres per day. not required but it can :) which is kind or cool.

With the tanks that I used the cost would be a bit more, about AU$600-$700. This is still fairly inexpensive really.

I have a few people here that have suddenly become interested in my version of this and have expressed an interest in doing something similar, once mine is finished, particularly for some the rural areas where I know a few people, time will tell how these will go.

By the way, the current air pump I use consumes more power than the one you mentioned/used, what I could not figure out is how much air yours pumped in litres per minute or similar, that would have helped a lot.

The air pump, I'm using is able to pump 85 litres of air p/m. I'm using long 4mm black flexible tube used water dripper systems costs about 1/3 of the clear tube UV stabilised as well, each tube is approx 8 metres long, the air pump is inside out if the weather, one spin-off benefit of having long tubes is that the air pulsing has been smoothed out into the pumps the long tubes take the pulsing out which makes the system quite a bit quieter.

Regards David

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Post by Bob » Wed May 30, 2007 10:00 am

...as the 20L trickle filter contains "aquarium wool" which is catching the larger suspended solids in solution, I suspect I'll have to clean it soon the rate of water flow through it has slowed quite a bit, I now have a continuous puddle on the surface all time now.
It sounds like you might want to try experimenting with a different kind of media, something that still has a lot of surface area, but that allows sluffed solids to fall through it without clogging it up.
The air pump, I'm using is able to pump 85 litres of air p/m.
Wow. That is far more than mine. This is an area that could use a lot more experimentation and testing to optimize. Do you have pump curves for that pump that show air flow against head? 85 lpm at what pressure? And what is the wattage?

I've been experimenting with various different air pumps, trying to come up with an optimum airflow/energy use combination. At first, I was using multiple (3) single-outlet Rena 301's, one for each pump and one for aeration in tank3. The only specs I have on it say max 325 LPH, but I haven't actually measured airflows at different depths. It draws 6 watts. I love these pumps. I've had some of them running continuously for 10 years without a failure.

More recently, I've been experimenting with larger cheaper pumps made in China -- connecting a single pump to a manifold. The example shown in the pictures draws 25 watts and produces about 8 LPM at 3 PSI (the V201 in the chart). What I don't know yet about these pumps is their reliability. (6 months so far, without a problem...) Also, 25W running 24hr/day is higher than would be ideal for most off-grid people.

Image

Another downside of using a single pump with manifold is that one of the three airflows (i.e. the pump in the surge tank) will vary widely depending on depth of water over the diffuser. This affects the output of the other two, which I would prefer to remain constant.

The ideal pump -- what I'd like to find -- would be a low wattage, inexpensive, high reliability DC pump with three independent outlets. Independent so that variable resistance on one outlet doesn't affect the output of the others.

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A few more questions

Post by blimpyway » Sun Jul 15, 2007 2:32 pm

Hi again Bob,

what is the role of pvc ribbons (those you clean on the video)?
Wouldnt the dissolved oxigen flowing out of trickle filter be consumed anyway in the sludge at the bottom of the 2nd tank? Hopefully the bottom sludge will develop a small aerobic colony, without needing pvc ribbons on the input vertical tube.

Another question - do you have any figures regading daily BOD / amonia load on your biofilter system?

What is the surface area of the media in trickle filter and how much volume/area would need a biofilter for treatment all sewage (toilet flush also) from two persons, at a total water flow rate of 80 galons/day

Thanks for your patience,
cezar

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Post by Bob » Mon Jul 16, 2007 10:55 am

what is the role of pvc ribbons (those you clean on the video)?
Wouldnt the dissolved oxigen flowing out of trickle filter be consumed anyway in the sludge at the bottom of the 2nd tank?
Good questions, cezar, and not ones I'm sure I have a good answer to. The added media was a bit of an afterthought, something I thought I'd just try, to see how or if it changed the performance. My thinking was that it would add just that much more 'habitat' for colonization, adding to solids retention time, and insuring that the sludge that reaches the bottom is anaerobic by the time it gets there. (But lacking money for lab testing and a control to compare it to, I don't have a clear answer to performance. I suspect the difference in performance is minor -- maybe not worth the additional cost or maintenance it requires.)
Hopefully the bottom sludge will develop a small aerobic colony
Why?
Another question - do you have any figures regading daily BOD / amonia load on your biofilter system?
No. But compared to sewage it is quite low. The design is based on the basic idea that it is much harder and more complicated to try to separate all the constituents of sewage from each other after they have been mixed together than it is to avoid combining them in the first place and treating each separately. (Which also follows logically from the 2nd Law of Thermodynamics)

By itself, urine is easily dealt with. It is sterile, nutrient rich and solids-free (i.e. does not clog small pumps or pipes). It is a valuable soil amendment. It's highest and best use is to dilute it and apply to plant roots (subsurface) immediately before the nitrogen is lost to the atmosphere. Compared to what it takes to remove it from combined sewage this is trivially easy to do. The majority of pharmaceuticals, antibiotics, pesticides and synthetic hormones (mutagens) that we consume is also excreted in urine. These are things that pass through conventional sewage treatment plants and into the food chain.

Human feces (combined with kitchen scraps) is easily composted aerobically -- far more easily than if combined with urine, which adds salts (which kill earthworms), extra nitrogen load (which creates suboptimal C/N ratio, ammonia and odors), and excess liquid (which makes it harder to keep the pile aerobic, requires energy for evaporation and/or drainage, both of which add cost and complication).

This water treatment system is designed for, and sized to handle gray water without either urine or feces in it -- which allows it to be smaller, simpler and less expensive than one that must handle raw sewage.
What is the surface area of the media in trickle filter
I don't know. But, just on visual appearance, I will argue that it is very high for it's volume -- and cost. (I would love to be able to perform -- or see someone else perform some rigorous controlled experiments comparing different media -- especially inexpensive "home made" media. Any volunteers?)
...and how much volume/area would need a biofilter for treatment all sewage (toilet flush also) from two persons, at a total water flow rate of 80 galons/day
As noted above, I intentionally avoid mixing feces and urine with used wash water, thus drastically reducing the loading (both hydraulic and organic), enabling the design to be smaller, simpler and less expensive.

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Post by blimpyway » Wed Jul 18, 2007 6:46 am

Bob,
is true that your waste-management design decisions might be very good, but what is a natural step for an ecological-conscious person might be a too large leap for humankind, or at least for most people in my country :wink:

That's why I'm trying to figure out is what parameters needs to have a DIY household biofilter for all sewage treatment. Knowing these parameters then trying to figure if, and at what costs (investment + recurring energy & maintenance) it can be acomplished.

I'm searching for something more ecological than a septic tank or pit latrine, yet cheaper and using less energy than a household activated sludge aerobic plant.

And an open design that can be shared and implemented by anybody.
cezar

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Post by Bob » Wed Jul 18, 2007 9:57 am

what is a natural step for an ecological-conscious person might be a too large leap for humankind, or at least for most people in my country
Yes, very true. We in the west have such a long history of putting our shit in our drinking water that it is now taken as a given. To suggest that if we just stop doing that, everything becomes much simpler and cheaper ignores the psychological and cultural obstacles and the vast existing supporting infrastructure (e.g. water flush toilets, piped sewers, conventional treatment methods, academia, regulatory agencies, etc.) that support the current insanity. Like the QWERTY keyboard, it is locked in.

That said, if your goal is to reclaim water for reuse, this system, with some minor modifications, could be used to treat septic tank effluent (rather than gray water) to advanced water quality. A few years ago I developed a similar system just for that purpose. Here is an excerpt of a proposal I submitted to the US EPA that describes the basic concept. (They declined to fund it).

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Post by blimpyway » Thu Jul 19, 2007 7:41 am

Yes, I'm interested in water recovery, to the level of making it acceptable for watering the garden. What "acceptable" means - food that is supposed to be cooked.

Dominant in country side here are outhouses/pit latrines in old houses and open-bottom "septic" tanks for newer ones. Since we joined EU, this situation is legally unacceptable yet, except for new houses, litle hope to change soon.

thank you,
cezar

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Post by Bob » Thu Jul 19, 2007 8:18 am

Does the system described in the document I pointed to look like a feasible possibility?

Users would have to install regular (closed) septic tanks, then pump settled effluent from them into this unit for further treatment and reuse.

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Post by blimpyway » Thu Jul 19, 2007 9:04 am

Bob wrote:Does the system described in the document I pointed to look like a feasible possibility?
I dont know, mabe. I think we use an average 180l (~50 gal) / day /person, yet the norms specify a minimum of 300 liter.

I also know the cheapest aerated active sludge residential plant can be purchased for a bit under $2500, for 5 persons. It uses 60 watts power, but I could not find wether this is continuos or not - there is a batch program that provides for anaerobic stage and a settling one, during these I suppose the power use is minimised.

An 1100l (300gal) plastic septic tank can be purchased for ~$1500.

These prices do not include the drainage field, although aerobic active sludge manufacturers claim the effluent can be used for subsurface irrigation.
Users would have to install regular (closed) septic tanks, then pump settled effluent from them into this unit for further treatment and reuse.
I noticed that's how many (if not all) secondary treatment solutions work.

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Post by Bob » Sat Jul 21, 2007 8:47 am

I think we use an average 180l (~50 gal) / day /person, yet the norms specify a minimum of 300 liter.
That sounds pretty typical. The need to design for worst case and safety factor is discussed in the proposal. If a full backup system is in place (a drain field), then the reclamation system doesn't need to be designed for worst case and can be smaller and less expensive.

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Post by blimpyway » Fri Jul 27, 2007 4:02 am

I'm however curious about the required parameters (e.g. free volume, retention time, total area, flow speed, and whatever else is rlevant) a trickle filter should have for full blackwater treatment, either separately from greywater or all waste water together.

And then choosing to treat it partially or entirely. That depends on the costs implied.
But first I'm aiming to find a cheaper (investment & energy) DIY alternative to residential aerated sludge plants comercialised here.
A trickle biofilter can be such an alternative?

cezar

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