I just wanted to hear thoughts about the fact that our standard flush fixtures reduce water usage by 56 %, without us doing anything. Our toilets are as set at 4-6 liters for a big flush and 2-3 liters at a small flush. This results in savings of 56 % for the 2/4 liter alternative (0.7 GPF), and 34 % saving for the 3/6 liter (1.06 GPF) alternative. The latter of course not enough, but the first one fine.
A discussion is however going on in my country whether the 2/4 liter fixtures work as they should and if pipes will be clogged or not. I have heard many opinions there.

Also the third option above, what exactly is required and which projects is it applicable to. Could a zero-lot-line city project pursue this option? If the municipal water treatment company treats the sludge through anaerobic digestion to retrieve biogas etc, would that comply? After this the remainings are treated and stored for 6 months and later used in agriculture, is this sufficient? This is also standard procedure in my city.