Conceptual Approach / Conceptual elements

We assume that, in our case, an entrepeneur can treat the feces of at least 1000 people what is equal to a total amount of 137 liter a day. The entrepeneur collects the urine and feces in the toilets once in the 1 - 2 days by emptying the toilets in a vehicle. On the vehicle are 2 oil drums, 1 for the urine and 1 for the feces. The oil drum with the feces is transported to the workshop of the entrepeneur. For this activities the entrepeneur is paid by his customers.

How he may collect and treat feces

Idea #1: The feces are collected in drums that are placed in an oven (tekening van de oven) and heated until sufficiently dry to be burned. The caloric value of the wet feces has to be sufficient for this. The oil drum with the dried feces is taken out of the oven and the content is put on the fire. Important note is that the whole treating proces is no-contact and the pathogens in the feces are killed by the fire in the oven. The amount of ash from the burned feces is very small and easy to be dealt with. The oil drums with the urine can be emptied in a nearby river, sewage system or diluted with water to create a fertilzer. A more complex option of treating urine in slums with the help of algae is described below at Phase 2: urine. The treating of urine with the help of algae can be considered as phase 2 in the businessplan of treating excreta in slums.

Idea #2: A simple way to treat the feces is to collect all feces from 1 day in a ventilated, black, oil drum. After a period of 2 months the feces are so dry that they are easy to burn and the drum can be used again for the same purpose.The amount of properly guarded space for the storage of the drums should be regarded.

Idea #2: Another option is to put the total amount of feces, 137 liter a day on a compost pile with the same amount of additional green waste, soil, sawdust, etc. for a good composting process. The compost pile need to be well build for a good composting process. In good circumstances (high temperature of 50-60 degrees, ventilated) the compost will be pathogen free in about 2 months. In this case a lot of compost piles will have to be build. After 2 months the compost can be used as a fertilizer on the surrounding farm land. When there are no farming conditions in the area the compost can be re used as part of fresh compost piles to stimulate the composting process. Important note is that the compost piles need to be covered when a lot of rain falls because of water with pathogens may not enter the neighborhood. There also have to be taken measures to keep the compost piles free from rats and other disease spreading animals.

How he may collect and treat urine

Phase 2: Urine

The treating proces of urine with algae is more difficult then the proces of treating feces by burning them. However the treatment of urine can be very interesting because urine contains a lot of valuable compounds which can be used for soil improvement and/or animal food. We choose for the use of algae in the treating proces because algae can add the valuable compounds (N,P,K).

The urine is collected in oil drums as described at phase 1. The urine is lead in algal ponds and treated in a batch proces. We assume that the urine have to be diluted a maximum of 10 times with (waste)water to produce a good liquid for algae growth. This makes a daily amount of 13.700+1370 = 14.070 liter of liquid (see above)

The surface of the algal pond, when 30 cm deep, has to be:

• With a depth of 30 cm, 1 m^^2^^ contains 300 liters of liquid.
• 14.070 / 300 = 46,9 m^^2^^. (say 50 m^^2^^)
• The pool size = 10 meter in length and 4,69 meter in width.

There has to be a system of at least 2, but possibly 4 ponds, to give the algae the time to grow and add the biggest part of the urine compounds. The waste gasses from the feces treating proces can be used in the algal growing proces. In order to deal with smell problems in the feces treating proces there are ventilation pipes connected to the oil drums when putted in the oven. The pipe for the fresh in-going air has a little electro motor. The outgoing air is led through the urine ponds with a pipe causing CO__2__ and movement to enter the algae process and speeding it up.

When the process is finished the algae can be retrieved from the water with a sieve or by a little centrifuge.
4 Ponds require a total surface area of 4 x 50 m^^2^^ =200 m^^2^^. This is a 200:3300= 6,06 % of the densily populated area to be serviced. Clearly this option of processing urine needs a more effective, space saving method.
The final product, dried algae, can be used as a kind of fertilizer or green material, as it contains useful fertilizer components as Nitrogen, Phosphorus and Potassium.

Conceptual Approach / Conceptual elements