Sanjay,It seems that you have ...

Sanjay, It seems that you have before you the whole range of sanitation alternatives: from ventilated pit privies or lagoon treatment to membrane bioreactors or granular sludge systems. I suggest that you follow a systematic consideration of a wide range of possible solutions starting with a coarse screening to determine the most feasible alternatives and then proceeding to more detailed evaluation of these. If you are not familiar with it, you might start with the EAWAG Sanitation Systems Compendium (http://library.eawag.ch/EAWAG-Publications/openaccess/Eawag_08276.pdf). This gives a basic description of many systems. I produced a similar document in the 1990s for the UNEP (http://www.cep.unep.org/pubs/Techreports/tr40en/chapter1.html) but the EAWAG document is more current and of higher quality! Clearly your environmental conditions are challenging and should be the start for your analysis. Starting from the most low tech of solutions you might consider an anaerobic pit system followed by a facultative lagoon. Snow cover may require long-term winter storage, however. This system will produce basic treatment with little or no power required, but with rock in the environment, excavation could be very expensive. This type of system is the typical system in small villages in the Kathmandhu Valley. At the high tech end of the spectrum membrane bioreactors are very compact and produce excellent water quality effluent, but at the cost of high power consumption. If a powered system is not out of the question, the most up-to-date approach these days might be a granular sludge system (http://www.royalhaskoningdhv.com/en-gb/projects/nereda-the-natural-way-of-treating-wastewater/106). You might also consider one of the "Reinvent the Toilet" solutions, for example, EAWAG's Blue Diversion toilet: http://www.bluediversiontoilet.com/on-site-recovery.html. Best wishes in your search. Regards, Randal