The Aquatron separates solids and liquids using the sticking properties of liquid. The liquids stick to the sides of the Aquatron and the solids fall down the centre into a composting chamber.
An Aquatron must be less than 25m (and ideally less than 15m) from the toilet, so that solids and liquids are still separate (have not become too mixed). You need to try to avoid bends in the sewage pipe and ideally the waste should enter the aquatron at a five degree angle.
Nearly all pathogens are broken down by composting. The compost should be left for at least a year before using and should be used on crops where it doesn't come into direct contact with the edible part of crops.
Sizing the system
Urine separated chambers can be as small as 1/8m3 (cubic metres) per person (about 50cm x 50cm x 50cm). Standard chambers should be sized at about 1/3 to 1/2 m3 per person (that is around 0.75m x 0.75m x 0.75m). The larger the chamber, the more forgiving the system.
Vents reduce problems with bad odours and flies and help prevent saturation of compost mass. Can use powered vent or passive vent. The best passive vent is a straight pipe of at least 110m diameter, reaching well above the roof line and with a rotating cowl. Paint the top of the pipe black to assist with thermal draw. In our AtEIC toilets (between shop and top station) we have a 10W fan in the compost loo.
Composting toilets produce leachate which will contain pathogenic material. You must have drainage if you're not separating urine, but drainage is advisable even in urine seperated toilets. So you'd need to include this in the design and allow for pipes, etc.