To convey a strategy not ...

To convey a strategy not often mentioned, that is to take on full wastewater effluent recycling, solids removed as a source of drinking water by growing algae for biodiesel.

In doing that the algae purifies water better than chemicals and particular species of algae do take up metals and pollutants my studies used 11% oil Spirogyra found in any pond for volume estimates.

This gets the water purity to where a final filtration would produce drinking water, basically too pure so needing minerals for potable, I have a connection to a small wastewater utility wanting to help with the biology they also needing farm spill remediation and these units are semi-portable, we are after a certified drinking water system for home-ranch-farm that scales up.

In any case, the cost of purification without the biodiesel is about what putting in a system to gain the biodiesel would be, in any city a lot of money goes to transportation fuels is the math.

Look at the money spent on city vehicle fuel, when the treatment plant becomes the "oil refinery" the costs are trivial compared to fossil fuels, in Phoenix a local biodiesel producer is at $1.99/gallon retail.

By using biological purification the secondary effluent process to remove dissolved solids doesn't use chemicals so costs are mainly electrical, thus saving a lot over standard methods beyond gaining the biodiesel.

For a city sewage system doing this it's worth about 7.5L/day per person using Phoenix, AZ, and 38M-liters/day of effluent, that's 21,000 tons of dissolved solids to grow algae from daily, it's enough to power all transportation and a lot of home heating in volume for any city.

Consider small cubes full of glass plates means the volume grows like the top 6mm of a pond that stack using fiber-optics for lighting as growing units, insulated, they interconnect, takes 5/person capacity at the plant. For a city that's a lot yet can be added incrementally so self-financing that advised.

It takes about 50w/person to process the ongoing waste for lighting, aeration, fluid pumps & controls. Recent micro-algae harvesting methods use EMF to release the oil using far less energy than centrifuges.

This sounds high tech, it is, yet the units scale from household-farm-ranch to big city. My work was for the home-farm-ranch system, miniaturizing the larger standard. It's easy to grow algae every lab in the world does. Once the units are refined they can be volume mfg'd locally now using 3D-printing.

By putting capital into the system it pays back to society so much more beyond drinking water so wanted to post these thoughts for a viable long-term solution freeing towns from cashflow out of the locale that just for transportation & household cooking fuels.

A related R&D in the switch to biodiesel entails work on soot elimination for anything using it, from cars to porting for home stoves so always considered part of the solution in this strategy.