My concerns with Dr. Cuello’s approach are:

Rural communities don’t have sewage treatment plants. At best, they have pit latrines.
Plants that emit carbon dioxide at scales large enough to economically capture and channel through algae ponds are few and far between.

I like the idea of using brackish water in particular, don’t know about recycled water availability.

What would be even more interesting would be the ability for rural communities to acquire appropriate technology to extract oil from algae and produce fuel in small yet economically viable quantities.

Noble idea nonetheless.