Environmental projects like this were carried out most extensively during East Africa's era of complete planned economy. Many East African cities had similar sewage treatment plants. After all, one characteristic of the planned economy era was its disregard for cost.
Of course, disregarding costs did not mean costs did not exist; it merely meant those costs were not visibly expressed in monetary terms. Labor, materials, and other inputs were allocated through administrative measures.
Labor costs in East Africa had always been low. In the early days, there had been Black slaves holding up the bottom; later, East Africa's population exploded, and labor prices still could not be considered high. As for materials, there was even less need to mention them—resources such as land and minerals were all controlled by the East African government.
Naturally, such a model clearly could not last. Even the Black slaves exploited as oxen and horses by the East African government had inevitably embarked on the road of resistance, let alone now, when the number of Black slaves was wholly insufficient to support East African social development.
"Dar es Salaam city has three sewage treatment plants in total. Around them are industries with severe pollution, such as aluminum smelters, textile mills, chemical plants, and so on."
"As times have changed, demand for aluminum products has grown higher and higher—electricity, automobiles, kitchenware, and so on. This has brought a metal that was still extremely precious in the last century fully into the era of large-scale industrial production."
Aluminum's influence on the development of the aviation industry was also quite prominent. However, East African aircraft manufacturing was still in its industrial incubation stage, so its impact on total demand was not yet very significant, and ordinary people had little contact with it.
Take East African civil aviation industry