Many health jurisdictions in ...

Many health jurisdictions in North America permit single-family residences to recycle ( i.e. without treatment) greywater  (typically defined as bath/shower, lavatory and laundry drainage) for direct shallow (within the root zone) subsurface irrigation.  There are two Canadian municipalities that  allow recycled greywater to be used for toilet flushing without treatment by capturing bath/shower water and pumping it to the toilet as required.  These are "smart" systems that drain the stored greywater to sewer if the storage time exceeds 24 hours, automatically top up the water in storage with potable water (if  required), and have UPS power supplies in the event of a power failure.  This simple practice could save up to 30% of a household potable water demands and reduce the volume of wastewater generated by the same amount without the burden of treatment costs.  The principal impact on the household is a  more frequent need to clean biofilm from the toilet tank and bowl.  The expressed concerns I have heard are primarily related to the potential for disease transmission as a result of a person coming into contact with droplets of water as a result of flushing.  However, common sense dictates that fecal deposition and bowl contamination from previous users of the toilet are a significantly greater health risk -one that we accept, particularly with respect to public toilets.  Further, intuitively, we can appreciate there is a much greater risk of disease transmission within a family as a result of interpersonal contact and food preparation, that there is with incidental potential contact with bath water used to flush a toilet.but 

Here is a link to the ConservePump greywater recycling system that was manufactured by iDUS Controls designed to recycle bath/shower drainage for toilet flushing.  I am not sure the company still actively markets the technology, but the link provides information on how the system functioned.  It was installed in homes in Nanaimo, British Columbia, and Guelph, Ontario, Canada.

http://www.waterwisetech.net/specs/idus_conservepump_home_product_data_sheet.pdf

An International Association of Plumbing and Mechanical Officials (IAPMO) committee developed a small-scale residential greywater recycling performance Standard 1207, in 2014, that failed to receive approval because of unfounded concerns the practice posed a health risk.

The Sloan AQUS system also directly recycles greywater from lavatories for toilet flushing without treatment, but does incorporate a simple chlorine puck system for disinfection.

https://inhabitat.com/sloans-innovative-aqus-grey-water-toilet-system-makes-every-drop-count/