This kind of environmental engineering was most often done during the era of a fully planned economy in East Africa. Many cities in East Africa have similar sewage treatment plants, as a key feature of the planned economy era was not considering costs.
Of course, not considering costs doesn't mean they don't exist; it's just that these costs are not directly in the form of money. Labor, materials, and other investments are allocated through administrative means.
Labor costs in East Africa have always been low. Initially, there were Black slaves to fall back on, and later, with the population boom in East Africa, labor prices were not considered too high. Materials are even less of a concern, as resources like land and minerals were controlled by the East African government.
