Bogdan, no... vermifiltration retains the nutrients mostly in liquid form. In contrast to other treatment systems most of the nitrogen is retained, so is a good option where immediate irrigation to vegetation is viable. What happens when your septic tanks freeze? Do the underground soakage fields also freeze? How deep under the ground must you go for reliable soakage that never freezes? Is the water table always high when it gets cold?

I'm guessing swampy ground is the exception for communities of people in most parts of the world. Certainly communities living on top of high water tables have "special needs" in terms of wastewater management, but in most other cases dwellings should have sufficient land available on which to surface discharge with secondary treated wastewater. Surface discharge has huge advantages, but does require secondary treatment and of course the surface can freeze. No doubt Ukraine conditions would preclude surface discharge for some (how much?) of the year and I'm most interested in solutions allowing treated wastewater discharge to ground.

What seems to be the general assumption in the sanitation community is that secondary treatment is outside the means of people in developing countries, where not able to access a sewer. Septic tanks are the cost limit, as far as they are willing to go.... apparently without properly designed leach fields in many cases. Addressing one problem with another (very ugly) problem, FSM. Yet domestic scale vermifiltration systems with secondary treatment can be constructed at lower cost than a septic tank, so can be "decentralised" to the household level, provided vegetation is available to irrigate to.

Phillipe, worms are very robust beings, but like any living organism require conditions within their limits, especially with regard to temperature. Freezing them or cooking them is death, although the eggs survive. This just means the digester needs to be insulated in cold climates and given shade in hot sunny climates.

I agree with you that septic tanks are an unreliable interceptor for small-pipe simplified sewers. This is because ignoring the buildup of sediment/solids doesn't directly affect the user, their toilet still flushes. However, importantly, primary vermifilters by design no longer function once full. The toilet no longer flushes away because the inlet to the vermifilter eventually becomes blocked with the growing pile of solids. This makes them eminently suitable for solid-free small-pipe (low cost) simplified sewers. Of course only twin chamber designs should be endorsed, so once full (maybe 6 years depending on capacity) the inlet is simply switched to the other chamber.

A simplified sewer without solids is much lower cost because the pipe size can be dramatically reduced, so would be suitable for peri-urban areas with no available land and those with high water tables.

cheers
Dean

Dear Bogdan, dear Dean,

I would prefer simplified sewer systems not because of costs, but because they are in my view less vulnerable than solid-free sewer systems. Indeed, with the latter, you have to rely on compliance and good behaviour from all the users. If one household does not maintain properly his septic tank/interceptor, or if the design is not good, then quickly clogging issue will appear. Same thing if stormwater enters the system.

Bogdan, it is a good point to mention frost. I think that the problem is the same with both type of sewer systems. Regarding pumps, it will depend on the level of decentralisation you are targeting. Simplified sewer systems may be used at street or neighbourhood level. Bigger than that, we fall into conventional again.

As for vermidigesters in every household, how realistic is that? In theory, it sounds good. But worms are sensitive beings. Besides, they will not treat all the wastewater. How to best to use this emerging technology? And at which level of decentralisation?

Cheers,

Philippe Reymond

Decentral wrote: The reuse of treated water is a viable alternative in arid and warm climates, but in Europe it is possible for a few months in a year, so is a problem as well, which needs to be considered. You are aware that the water quality requirements for irrigation purposes and for discharge are different, the last are much more stringent.

Dear Roumiana!

Thank you for useful links and comments !

This is very important note that irrigation water needed only for few month in cold climate while waste water is produced all year round. We need either a fllexible system that allows changing quality of efflluent or constantly treat it to discharge quality while transfering the nutrients into solid form for storage and later use. Looks like vermifiltration offers this later option. Is it correct Dean?
Regards,
Bogdan

Dear all,

I enter this discussion at a later stage and in general I agree with the first comment of Philippe. Decentralized wastewater systems are a common case in many small population centres and villages in Europe, especially on-site sanitation. However, such solutions are a real problem in areas with high water table or very small plots. Therefore, the choice of appropriate level of decentralization is question of technical and economic analysis, which normally can not be done by the community itself but should be delegated to professionals. Some general points related to decentralized systems can be found at the site Decentralized wastewater systems

The reuse of treated water is a viable alternative in arid and warm climates, but in Europe it is possible for a few months in a year, so is a problem as well, which needs to be considered. You are aware that the water quality requirements for irrigation purposes and for discharge are different, the last are much more stringent.

I am in full support for decentralized solutions but we have to be careful in the choice of the most appropriate one.

Best regards,
Roumiana

All the more reasons to remove the transporter of pathogens- urine. Whilst urine is almost a sterile product ( and useful in its own right) it makes faeces difficult to handle and the volume increase a real problem. Leaching of mixed urine and faeces into waterways is criminal.
Ross

goeco wrote:

Bogdan describes a highly risky approach to fertilising crops, using sludge from septic tanks and pit latrines. This will contain pathogens and will result in disease.

Hi Dean! Thanks for the input!

That's right-- this approach is highly risky but it is here and it might make sense to shape into safe onewhile leaving the pattern of direct linking the households with small farm without intermediate WWTP. If vermidigester can replace the septic that would be great breakthrough, but I am still not convinced that it will be so easy in cold climate. It takes quite an effort to keep vermidigester above 10 degrees, while septic is basically hole in the ground.
Regards,
Bogdan

Bogdan, you're right, wastewater treatment isn't just about toilets, but all household wastewater. Water is always a necessary component, the issue is dealing with it.

Cost-efficiency is the single big issue with regards to scale. The only reason to go more centralised (bigger scale) is to reduce costs per participant. Theoretically the plant itself is more cost efficient but the sewer pipes do get expensive.

Then there are the products from waste. Products such as biogas require greater than household scale today, but maybe not tomorrow with technological advances? Products within the nutrient cycle might have different applications on a single household level compared with the community level...

Phillipe, I assume your preference for a "simplified sewer" is mainly driven by cost constraints for on-site treatment? What if a household system were available that was cost-competitive with larger scale alternatives involving pipes? One that produced no sludge, with no leachate contaminating groundwater or water courses.... A simple and reliable system requiring minimal maintenance, where the characteristics of the treated wastewater were of a standard suitable for irrigating food crops and rich in plant nutrients?

The golden egg? Nope, its horses for courses. Sufficient land is required to discharge to if the wastewater is rich in nutrients. No good in peri-urban Lusaka! What about Ukraine? I would suggest that in most cases there will be sufficient land with vegetation for households to discharge to in Ukraine...

The problem with fully centralised systems is one created by the very existence of cities. Lack of land. The cost of transporting the treated wastewater and sludge out to where land is available for cropping can be ignored because there is an alternative... treating the wastewater to remove the plant nutrients (in particular N) and discharging to the nearest waterway. Cheaper than reusing the nutrients on crops. Won't be a good look going into the future though, breaking the nutrient cycle is not sustainable into the long term.

I'm not convinced that simplified sewers without interception are the answer, maintenance is required which means management. That will be a weak link in some cultures, with failures imminent. Maintenance free is good. Intercepting the solids at the source would increase reliability and reduce cost of pipes. However, septic tanks are a ridiculously primitive way of intercepting solids.

Bogdan describes a highly risky approach to fertilising crops, using sludge from septic tanks and pit latrines. This will contain pathogens and will result in disease. The problem of FSM exists because most of humankind haven't found a better way of getting rid of their waste on site. One problem generates another problem. Yet vermifiltration offers a solution that is lower cost than the septic tank and generates no fecal sludge, only safe humus. Primary vermidigesters just intercept the solids and decompose them, so offer a solution allowing discharge of liquids into low cost small-diameter pipes for removal to a community treatment facility. Secondary vermifiltration offers a reliable low cost method for treatment on site.

The problem I see is that researchers are mostly unaware of the breakthroughs being made with this technology.
cheers
Dean

Dear Philippe!
Thank you for very useful input!
Probably the quantities and characteristic of average household waste water in rural Ukraine would be standard as soon as this household has the flush toilet, washing machine and shower
I agree that avoiding septic tanks at each yard make sense But what about the cost of simplified sewer compared to solid free one especially when pumping stations needed? Also frost protection issue during the cold season?
I try to base my suggestions for the small-scale farm integrated WWTS on what already exists to somehow develop it into sustainable system. What I see is that quite many village houses with flush toilets inside have septic tanks (or kind of them) in their yards with pipes to the open ditches along the streets to take the effluent away (eventually to the river). When septics got overfilled the sludge is put to the gardens – same done with the content of pit latrines. Use of human manure for fertilizer is in the local culture.
Another thing I observe is a big demand for manure from the small commercial family farms involved with vegetables growing due to high fertilizer cost. They travel around for 40-50 km to buy any manure including pit latrines content. The demand for manure is rising also since cattle population is steadily declining. The small-scale vegetable farming though is developing especially associated with glass-house growing
I think the right match could be small-scale WWTS and small-scale family farming. Then products and needs might be in comparable quantities.
Regards,
Bogdan

Morning Philippe.
The question of the need for treatment of effluent becomes much more reduced if urine is diverted at the source. This means that the valuable urine can be collected as a raw material requiring no separation at a treatment plant. I agree that treatment plants require a large area of land and the primary reason for this is the mixing of urine and solids at the source.
Regards Ross

Dear Bodgan,

Difficult to say from the distance if it is realistic. It depends so much on the community and local context. What would be interesting as a first step is to estimate the quantities and characteristics of wastewater to be produced. This would help define the most appropriate technical options as well as the feasibility of the whole concept. If possible, I would rather go for simplified sewer systems, and avoid septic tanks or interceptors in front of each house. Basically, I think that one should go for systems with as little input as possible from every household, to lower the risk of failure. Then comes the question of enduse: who will use the biogas and how? Which area of land can the treated effluent irrigate? Are the farmers eager to cease land for this activity and maybe to shift to a crop that can be safely irrigated with treated effluent?

Reuse often implies adaptation and efforts, and the quantities of treated effluent and nutrients are often little compared to the needs. The right incentives need to be identified.

Best regards,

Philippe

Dear Ross!

You are 100 % right. We should tell people about the alternatives and promote waterless toilets in every possible way.
But unfortunately there is a huge gap between Ukraine and Australia about the level of environmental awareness you can rely on. It needs decades of economic, social and other development untill it somehow arrives here. So instead of beating our heads against the wall we might choose to do at least something during our limited lifetime.

On the other hand water toilets can potentially be part of non-polluting and nutrient recycling system. It's a challenge for us to offer those solutions.
Regards,
Bogdan

From my experience in Australia as a manufacturer of Composting Toilets, the main reason why want waterless toilets is the fact that flushing toilets inevitably end up using drinking water to flush, and that this is objectionable. The second main reason for purchasing a composting toilet is a huge move away from inground septic systems that leak and contaminate streams and ground water.
While ever we just sit back and say that people "like" flushing toilets and say nothing about the downstream problems we are abrogating our environmental responsibilities. We at least should be telling people that there is another way, and a way of re-using what others call human waste.
Regards Ross