Data logging in Ugandan Toilet!

A tricky one for you: I’m working on a project and am quite stuck.

It is for an NGO in Uganda who want to know to get a better idea of what goes into their basic pit latrines (essentially a hole in the ground where waste is flushed into via flushing with a bucket of water).

The setup is pretty much this: http://www.unep.or.jp/ietc/publicati.../2-4/4-1-3.asp

The waste enters via a 110 mm pipe (angle is variable but can be fixed for a trial). The NGO would prefer if the device is something which fits on/around the pipe
I want to measure:
1. At the very least – an approximation of what total combined volume of liquids plus solids is entering the pit (plus timings would be great)
2. In the ideal world – the proportions of water vs urine vs solids entering the pit (and at what time)

I guess the time is useful because maybe through some manipulation of the data I can start to link up a ‘use’ with a volume e.g. if the ‘switch’ which say something passes is activated 3 times in one minute – this could be attributed to one user (the distinction between ‘uses’ and ‘volume’ is difficult in my mind.
This would ideally be transmitted via phone or have collectable data. No mains electricity available.

Any help greatly appreciated – this data will hopefully enable the NGO to work more effectively for provision of sanitation. Keep in mind the basic and rough conditions in a Ugandan toilet pit!

Nicola

p.s. I am not being payed for this work - just trying to help them out.
p.p.s I have some ideas but this post was too long so if someone joins me for a chat about this I'll explain my initial thoughts.
p.p.s please be patient - i have no electronics background - civil engineer