Hajo,
I appreciate the points you make and fully agree with you. The project, which we got involved in the later steps, had this logic of decontamination for water to be discharged to a river. Quality parameters were given, and a plant was purposed to comply with those limits.
If you think about reuse and circularity, conception of the plant would have been different.
I relate this, only a bit, with other projects here in Bolivia, where chlorination is an option only used when water is to be discharged to a water body. In turn, when water is to be reused for crop irrigation, no chlorination is used.

We will monitor the plant, specially water coming out of the vermifilter to evaluate options. That is why I really took interest in Dean's approach (even at a household level). The project in La Paz will teach us a lot.

I'll be posting here when I have news regarding the plant operating.

Hi Alejandro ,

as indicated in my previous posting, I fully agree with the need for the treatment steps before the vermifilter in order to remove all the unwanted 'ingredients' which come with public sewage.

But the following steps (vermifilter, effluent treatment) seem to me being steered by the 'wrong' criteria. I am not a water chemist but think that your emphasis on the quality limits (BOD < 30 mg/l COD < 45 mg/l and SST < 25 mg/l) indicate that the design aims at lowering these values like in 'standard' WWTP. Chlorination should then 'clean' the effluent further.

In my opinion this is the complete opposite of what vermitechnology aims at: to recover as much nutrients as possible taking them back onto the fields and following Albert Einstein who said: We can't solve problems by using the same kind of thinking we used when we created them. The effluent should not be 'cleaned' of nutrients. And the vermifiltration actually does the opposite. As far as I know the nutrient level is even enhanced by the excreta produced by the worms in the process. As indicated by Dean a series of repeated vermifiltration will produce an effluent of sufficient quality for surface irrigation and wanted nutrient level. The 'thinking' of vermifiltration is very different from current 'state of the art' waste water treatment.

In your latest posting you indicate that about 50m3 of humus will be recovered from the vermifilter per year. How is the system designed so that the top layer of applied sewage can rest for long enough for the worms to digest it? You don't want to recover fresh 'shit' from the surface of the filter, or? Either you have to have two filters which are used alternatively or only half of the filter is used at a given time while the other half can rest.

I am very curious to see that the system presented by you really serves as a 'new generation' (vermifilter!) waste water treatment plant for public sewage. Dean promotes his system as a (single) household solution. I want to see whether someone manages to develop vermifiltration as a solution for public sewage making full use of its advantage recovering ALL nutrients (from humus and effluent) for reuse.

ciao Hajo

I was forgetting about the humus. It is expected that a layer of 15 to 20 cm will form every year, that translates to 43 to 57 m3 of humus per year. The humus is collected manually, trying to preserve as many worms as possible inside the system. Any worms removed can be returned to the system while humus is drying.

Hajo and Dean, thank you so much for the continuing discussion and sorry for the late reply.

Addressing some of the concerns (first, I'm sorry the documentation is all in Spanish), while also keeping the discussion alive as I myself don't have many of the answers:
As Hajo just noted in his last reply, we are talking about a public system, and improper use of toilets and sewage are to be expected (or at least accounted for). The ministry of environment published the last inventory of WWTPs in Bolivia back in 2017, which showed that nearly 78% of the plants implemented and operating weren't doing so properly. Most of them due to a lack of proper preliminary treatment (mainly screening and also grit and grease removal) that ended up affecting the proper treatment steps.

Regarding the consideration of the vermifilter as primary only or both primary and secondary, GEMAT previous experiences show that water coming out of the single vermifilter should be of relatively good quality (BOD < 30 mg/l COD < 45 mg/l and SST < 25 mg/l). I do see the need to monitor the quality of the water coming out of the vermifilter prior to disinfect it with chlorine, we sure will make any adjustments if necessary. That's the main reason I pointed out your system was of particular interest to us, as it shows how recirculating vermifilters might be of great help.

Regarding the discharge of the treated water, as you can see in the pictures, the plants are surrounded by small plots producing tall stem crops such as maize as well as ornamental flowers. Although we won't be operating these plants, we do intend that the treated water is made available to the farmers with the necessary measures. The plant next to the river will need an adaptation to the exit tubing as well as investing in a conduction system to downstream plots.
The current configuration was implemented as requested by the client (the public utility), but we will keep trying to convince them into investing into the necessary infrastructure to provide the treated water to downstream farmers.

Regarding the attachments in the posts, I will look into that with the rest of the team.

Eager to hear from both of you!

Hi Alejandro ,

first, which may be of interest to you as a moderator of the forum: I asked for the plans, because that attachment was not visible to me as long as I was not logged in, only the two pictures. Once I logged in I could also see the attached plans. Is there possibly a limitation in the programming which allows guests only to see two attachments?

Now to the design and partially also referring to Dean's comments.

I guess that the steps of 'treatment' before the vermifilter, become necessary because the system treats sewage from a public sewer. And as 'usual' customers dispose off all sorts of rubbish through the toilet: from condoms, sanitary towels, nappies to plastic bags, solid waste - whatever can be flushed. This waste has to be separated from the fluid and that is what the steps do before the vermifilter. I guess in the 'homogenization tank' could be a pump with a cutter head which ensures that all remains are cut small enough not to block the nozzles of the sprinklers. These are considerations you have to take if you operate a public sanitation system, not a private household system. Dean will always make sure not to put such trash into his toilet

The core purpose and advantage of a vermifilter system is that you want to recover and make use of the nutrients in the human excreta. It does not make sense to flush them into surface waters (lakes, rivers, oceans). It is a waste of nutrients, a waste of water for flushing and pollution of the environment.

In this I agree with Dean that the plans give the impression that system may not make full use of the fundamental advantage of vermifiltration by recovering and reusing the nutrients.

Therefore my questions from a previous post still stand (and somehow in line with Dean's comments):

1.  how is the vermifilter bed maintained, i.e. how is the humus recovered which is produced by the worms' digestion and the decomposing of the filter bed (I assume wood chips not saw dust, or?)
2. Why is the effluent 'chlorinated' and not treated by steps of vermifiltration? The latter would be more environmentally, maintain or even increase the nutritional value of the effluent and allow surface irrigation.

ciao Hajo

Hi Hajo, Alejandro has attached drawings to his post, they are in Spanish but I used google translate.
Cheers
Dean

hi Dean..  where did you get the (readable) plans? .. can you please send me or post here on the forum?
thanks and ciao
Hajo

Hi Alejandro,
from your plans I struggle to make sense of the stages prior to the vermifilter. From manual pretreatment to pumping sump, to static sieve, to homogenization tank... these don't seem to provide any level of treatment. I've heard this style of uncovered vermifilter with sprinklers is common in Chile, using plastic pallets underneath and "snorkels" or ventilation tubes and sawdust media. We use the Chilean system here in New Zealand for treating agricultural effluent, but it is only primary treatment. Thus your chlorination stage... or in the case of TOHA an anaerobic DEWATS after the vermifilter, followed by disinfection. Not making sense to me at all... the primary treatment should be followed by recirculating vermifilters in series to achieve the level of treatment required for surface irrigation. I just don't think these companies get it...
Cheers
Dean

Hi Alejandro ,

thanks for your response.. although no drawings attached..

I found the GEMAT website and in it a description of the TOHA system (  www.gemat.cl/sistema-toha.php )   ... unfortunately my Spanish does not exist...  and the picture of the TOHA system cannot be enlarged to make the descriptions readable...

What happens in the system with the humus produced by the worms digesting the sewage and what happens with the effluent?

ciao Hajo

Hi Hajo,

I am attaching a couple drawings of the plants, as well as some pictures while delivering the plants, sadly they won't be operating for a couple months until sewage works are finished.
The plants were designed in cooperation with GEMAT (a small Chilean company) as they have a lot of background with vermifilter plants at this scale (Toha system).

The plants basically consist of a preliminary treatment system + vermifilters + disinfection.
Looking forward to your comments!

Hi Alejandro ,

I like it that you try to upscale vermitechnology from household to community level what looks like treating sewage from the village.
Would you mind to share your setup here on the forum?

ciao Hajo

Hi Dean,
Awesome adventure you embarked on! Thanks for sharing.

• Here in Bolivia, we haven't dealt with open defecation properly.
• Regarding sewage treatment, barely half the population has access to proper sewage, and most of the sewage systems end up in a deficient treatment plant or directly discharged into a water body.
• If you add all that to the fact that many productive regions are in severe need of irrigation water and will use any they can their hands on, you are talking about very unsafe practices and products with serious health risks.

We have been tackling these issues one step at a time, often through decentralized systems, which are definitely more agile and allow even small municipalities/communities to start dealing with unproper access to sanitation and unsafe discharge/reuse practices.
These implementations have a clear focus on circular economy as well as innovation.
A couple weeks ago, we finished implementing two vermifilter municipal plants, each serving a population of around 1.000 people. Plants are a couple months from commissioning due to sewage networks not being quite ready yet, but learning from your experience is quite helpful to us! And I will definitely keep you posted on this.

A question I do have:
Have you ever needed to remove some of the worms due to excess population?

Best regards.