Workshop Module 3: Houses, Water, and Waste Management 105Running this exercise
Take the participants on a walk to do a field survey of the area and explain the reasons
it was chosen and how the amount of wastewater to be treated was calculated.
Work together with the participants to:
- Calculate the size of the hole needed to hold at least 3 times the daily water flow
that has been calculated.- Dig the hole.
- Create an impermeable (water proof) layer using one of the following:
- Clay (10-15cm thick).
- Gley - cow manure (50 parts), organic matter (10 parts) and dirt (40 parts),
mixed together (10-15cm thick). - Ferro cement (7-10cm thick).
- Build an overflow point at the end of the system (using a pipe or a channel)
to control the volume of water in the system. The height of the overflow point
must be lower than the top of the system so that if needed it can be raised. This
overflow point will channel any excess wastewater – the cause of which should be
eliminated as soon as possible i.e. overflow point raised, system size increased, or
use decreased.- Fill the hole with gravel and compost so that plants will have some nutrients before
the system is fully functional.- Plant the gravel with at least 3 types of water loving plants per 1m 2. The root
lengths of the plants should be varied so that the entire system is filled with roots
once the plants have grown. If you use any productive plants make sure that
the harvested parts will never coming in direct contact with the wastewater, for
example coconuts or bananas work well because the fruits are high up and far from
the base of the plant.- Design an absorption trench or irrigation system into which the treated water will
flow.For more ideas, see PC Book MOD 3 – Houses, Water, and Waste Management.