Saturday, January 20, 2018

Shithole countries

This is a section through a mulberry log.  Somehow it seemed like an appropriate, G-rated, picture to lead this essay.
Let's look at Senegal, West Africa.

Completely ignoring culture, what would it take to fix the "fecalized environment"?

Wastewater treatment
The state-of-the art is activated sludge bio-degradation of human wastes.  The wastewater, a slurry of water and "other stuff" is run into a settling pond.  The "other stuff" is quantified in terms of Biological Oxygen Demand or BOD.  BOD is the amount of oxygen that the slurry would suck out of the water if it were dumped into a river.  That loss of oxygen typically results in fish kills.
Oxidization Ditches where the effluvia recirculates is considered one of the more appropriate technologies for austere environments.  Each "ditch" should be wide enough for a Bobcat to enter and scrape out.  Multiple ditches allows the system to keep running even when part of it is being maintained.

Approximately half of the BOD is removed from the wastewater after 24 hours in a settling pond.  The liquid is then sent to ponds where air is forced into the water.  Some systems use bubblers, others use paddlewheels or vertical turbines.  Some use jets of water to entrain air bubbles, much like a Jacuzzi.

Finally, the water is treated with chlorine or UV light and released to the wild.

How much power does it take?
A significant portion of Senegal's electrical production is from hydroelectric sources.  Once exploited, it is rarely possible to "scale up" the production at a site.
According to the CIA Factbook, the average daily electrical power consumption of a Senegalese is 0.50 kW-hr.  This is a bit of a myth because a few, rich city people use far more than that and the vast majority of the rest of the people use far less.  Approximately 40% of the population live in rural areas and have almost no access to electricity.  But let's go with the average because it is what we have.
Senegal is not even that bad, relatively speaking.

The average African produces twice as much fecal material as the average North American due to the higher fiber content of their food.  Constipation is rarely a problem in Africa.  That equates to about 0.25 lbs of fecal dry matter per person per day.

According to the Army Corp of Engineers it takes between 0.20 kW-hrs and 0.55 kW-hrs to deliver the air necessary to digest one pound of BOD.  That means that simply injecting the air in the activated sludge digester would consume  0.05 kW-hrs per person per day.  (0.25 lbs/person X 0.5 left in the settling pond X 0.40 kW-hrs)

That is 10% of the electrical produced in Senegal for just one stage of the wastewater treatment.

One reason shithole countries are shithole countries is because they have almost no economy.  Technology is a wonderful thing but it stands on a foundation of infrastructure...including electrical production.  To provide a useful frame-of-reference, the average electrical consumption in the US is about 65 times as much, per person, as in Senegal.

1 comment:

  1. I've been to a few shithole countries. It's an apt term. half of Indians don't have access to a toilet. They use RR tracts. Works well as the trains don't have toilets either, just a hole in the floor.
    The reason they are shithole countries is because of the people in them - no other reason.

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