Solutions for planning sustainable sanitation for a dense settlement on hilly area

  • goeco
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Re: Solutions for planning sustainable sanitation for a dense settlement on hilly area

npopat,

With hilly terrain gravity can be used to advantage for treatment systems requiring no energy input. I would suggest that the key sustainability objective is to avoid direct discharge of wastewater into waterways, and the other key sanitation objective would be to avoid direct community contact with the wastewater. All at low cost of course...

Open drains are not viable going forward because rainfall will inundate the system they discharge into. Rocky terrain would be problematic for constructing pipework, but smaller pipes mean lower costs and buried pipes might not always be necessary. Pipes will be necessary to convey wastewater from highly populated areas because if directly discharged the capacity of the soil matrix will not be sufficient to avoid contaminating groundwater.

I assume there is a water supply for domestic greywater and blackwater generation. Can I assume a community preference for flush toilets?

What is the geography below the settlement? Less hilly land with more soil, used for agriculture? Does the soil get less rocky down the slope? Is the land densely settled all the way down to the waterway with no opportunity to discharge treated wastewater to land?

cheers
Dean

Dean Satchell, M For. Sc.
Go-Eco Sustainable Solutions
www.go-eco.co.nz
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  • euisochoi
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Re: Solutions for planning sustainable sanitation for a dense settlement on hilly area

I do not understand the exact situation of the hilly regions, but it reminds me of my application of rorck filte system which was applied to hilly areas without any supports from electrical and mechanical equipments. The basic idea include a combination of septic tank + rockfilter + wetland system.
Unlike trickling filter, no primay and final settling tanks are furnshed in this system. The septic tank works as primary and sludge treatment facility and the wetland works as a final settling tank as well as as final polishing unit as attached article. The rock filter is single pass flow and nitrification may not be possbile. The wetland must be designd to remove nitrogen as well as phosphorus removal.

Euiso Choi
Director of innovative water center (iWc), NPIC
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  • goeco
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Re: Solutions for planning sustainable sanitation for a dense settlement on hilly area

The issue with septic tanks as primary treatment is that sludge needs to be dealt with. With vermifiltration the product is humus, so meets npopat's criteria of "sustainability" by requiring no further treatment for use as a soil conditioner.

A "rock filter" could also be a vermifilter, because without worms the bacterial slime will build up and slough off, requiring further treatment stages. Worms maintain the biofilm by grazing it and converting this to humus. I prefer an organic substrate such as bark or biochar rather than crushed rocks because the buildup can be removed and used directly as a soil conditioner. However, if crushed rock is more available then that would be suitable as a substrate.

A wetland should only be used if the treated effluent is then discharged to a waterway, and therefore the nitrates need to be removed. A more sustainable solution would treat the nitrates and phosphates as a resource and retain these within the water for irrigating productive plants. Vermifiltration offers a solution that retains the plant nutrients in the water, reducing BOD and pathogens sufficiently to meet regulations, then the wastewater is used for surface irrigation of crops. If good treatment levels are achieved (capacity is matched to influent level), food crops could also be irrigated.

cheers
Dean

Dean Satchell, M For. Sc.
Go-Eco Sustainable Solutions
www.go-eco.co.nz
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