Fecal Sludge (FS) in India and Emerging Hazard Crisis with Few Solutions

India has rapidly installed millions of household twin-pit toilets at densities of 2500-5000/km².   These discharge fecal sludge (FS) once every 2-3 years (2-4kL per pit @2-5% TS) and disposed on open land for drying for form a cake and then returned to soils for recycling and reuse. However, because of its microbials and heavy metals sustainable solutions are not in sight.  The problem stems from rapid digestion of food materials left out by human GI tracts, creating a build-up of heavy metals and potential risks of live pathogens residual in dried sludge. Anomaly arises from the fact that much of the constituents of original food materials emerge from agricultural soils and most of food consumed easily pass these heavy metal permissible limits.  In the absence of an animal food as an intermediary, all heavy metals are conserved in the system as humans directly eat grains, fruits and vegetables that are generally 98-99% digestible.  The residual human waste thus concentrates the heavy metal by at least 100 times. If disposed in wet conditions direct to agricultural fields this does not contravene too many regulations. However, current regulations on dry wastes pronounce this as hazardous and therefore does not allow its use in dry form.  Killing possible pathogens require it to be dried and pasteurized. This brings in a Catch-22 situation to be addressed soon, especially when all the new toilets put up by the hundreds of millions will begin to discharge FS.