Let's see: There are 640 acres per square mile. In the 25 or so square miles around where I live, there are maybe 4 people per house with one house per acre f

Let's see: There are 640 acres per square mile. In the 25 or so square miles around where I live, there are maybe 4 people per house with one house per acre for 4 * 640 = 2,560 people per square mile. The land area of the US is about 3.797 million square miles. Since the land area of India is 1/3rd of that, the land area of India is about 3.797/3 = 1.266 million square miles. Since the population of India is 1.3 billion people, the population density in India is about 1.3 * 10**9 / (1.266 * 10**6) = 1,027 persons per square mile. That would be the population density everywhere in India if the density were uniform. In that case, septic tanks would work for all of India much like they work for all the people within a few miles of me. But likely the population density of India is not uniform which means that some areas of India have population density less than 1,027 persons per square mile, and in those areas, and likely more up to a density of about 2500 persons per square mile, again septic tanks and drain fields should work well. For people in India who walk out at night to use the woods as a toilet, as in the OP, then if only from the woods there should be land area for those people to use septic tanks. I'm not suggesting septic tanks for Mumbai or New York City. Hmm .... On second thought, given my view of New York City, maybe I'd like to see everyone there using septic tanks, especially all using the same tank, a small one! Naw, then too many of them would want to live in my neighborhood -- no thanks; I like my current neighbors!