I have gone through the ...

I have gone through the detailed comments from my colleagues. I would like to enlighten some of the real facts pertaining today; There are two type of Issues at the moment, 1) Selection of the right low Energy Treatment Technology (obviously it must be low cost as well) 2) Selection of the Energy Source 1) Low Energy Treatment Technology Most of the times in Rural Areas, almost in all countries there is ample land available depending of the cost of the land. Thus Shallow Facultative Ponds, Constructed Wetlands, Trickling Filter Wells (Towers) are some of the almost no energy solutions. Even Decentralized Septic Tanks are one of the promising solution. But when we come to City Areas, then the land is not available or if available then of unbearable cost. Interestingly the wastewater generation from the urban areas are also much higher than the rural areas. Here come the Energy Consuming Technologies, you talk about MBBR, SBR, EA, EAAS, CMAS, TF, RBC whatsoever in Aerobic System most of the power consumed in Aeration and Pumping. 2) Energy Source Still Solar Energy proves to be an expensive solution considering the CAPEX and also long run OPEX. One Sq. Meter of PV Cell could produce just only 300 - 600 watts so producing producing 1kW you need a space of 2 Sq. meter. A small plant of capacity 1MGD normally requires 4,000 to 5,000kWhr a Day so one can easily estimate how much space you would require to produce such energy. Space is one aspect. Now come to Solar Power, normally Solar Power Productive Intensity is considered just 6 - 7 hrs a day in Summer in South East Asia, if you go to Europe then forget about this much intensity duration. And if you talk about Winter, the intensity and angle of sun light also not of much use. This is second aspect. Now consider the Energy Storage (Battery Backup). This is one of the most expensive part and count for huge OPEX. Wet Batteries have effective life not more than 1 - 2 years and if we come to Dry Batteries, that could go some more but still are much expensive. For a very small example, I was just trying to have a 400 gallons per day product water Solar Based Tubewell Plus RO for a remote area and the cost with such system came unbearable even sourcing from China. If some scientist can develop a Very Economical Battery Back Up System; then Solar Panel with inveter could come down to US$ 1 - 2/Watt. Lets hope for the best to utilize this Divine Free Energy Source economically.