From a satellite perspective, about 20 kilometers east of the central urban area of Nairobi, the capital of Kenya, a large area of organized water stretches out at the edge of the city, with canals crisscrossing and ponds connected. At sunrise, African bald storks, black winged sandpipers, and wild ducks stop on the water surface, while hippopotamuses and crocodiles occasionally emerge from the water. This seemingly wetland area is not a nature reserve, but a Dandora sewage treatment plant repaired and expanded by Chinese companies. Water is the starting point of Nairobi, and the city's name comes from the Maasai language used by the Maasai people in East Africa, meaning 'cool water'. Before the formation of the city, this area was once a grassland, with the Nairobi River winding through it, serving as an important water source for local residents and wildlife. With urbanization and population growth, the pressure on Kenya's water resources continues to increase. In 1992, Kenya was recognized as a water scarce country. The population growth combined with lagging infrastructure construction has led to increasingly prominent pollution problems in the Nairobi River. Due to the accumulation of solid waste and long-term discharge of domestic and industrial wastewater along the coast, the heavy metal and bacterial content in the river water seriously exceeds the standard. The river is silted and blocked, and the water turns black and smelly. Since the 1970s, the Dandora sewage treatment plant located along the Nairobi River has been responsible for approximately 80% of Nairobi's sewage treatment tasks. Despite undergoing multiple renovations and expansions, the problem of insufficient processing capacity is becoming increasingly apparent as the population continues to grow and equipment ages. The turnaround will occur in 2022. Middling coal Construction Group Co., Ltd. (middling coal) in Kenya won the bid for the second phase rehabilitation and expansion project of Dandora Sewage Treatment Plant by virtue of mature sewage treatment experience and better cost scheme. The project is financed by the Kenyan government from the African Development Bank, with an investment of 2.023 billion Kenyan shillings (approximately 108 million yuan). Previously, some equipment imported from Europe by local contractors had poor operating conditions, coupled with a long-term lack of system maintenance, and the dredging facilities were almost scrapped. When the rainy season comes, the pump room is prone to flooding, sewage overflow, and poor construction environment. At one or two o'clock in the morning, the smell can wake people up from their sleep, "said Li Maowu, the head of the project engineering department. The project officially started construction on February 21, 2023. Middling coal has completed the reconstruction and expansion of the intake channel and the construction of pre-treatment structure units, completed the construction of waste spots that meet the daily average of more than 300 vehicles of sewage suction vehicles, and cleared about 600000 cubic meters of sludge in 23 anaerobic ponds. Meanwhile, it has built auxiliary facilities such as control rooms, and improved the plant enclosure, internal roads and protection systems. In terms of equipment selection, the project party combines local pollution characteristics, introduces mature sewage treatment solutions from China, and customizes dredging equipment for the local area. Deputy Project Manager Huang Youming introduced that the newly configured grab type coarse and intermediate grilles, as well as rotary fine grilles, can screen out impurities of at least 6 millimeters, while the updated cyclone sand removal machine can achieve sand water separation of at least 2 millimeters, greatly improving processing accuracy. Simultaneously introducing dredging robots to achieve automated operation of key processes. In April 2025, the Dandora sewage treatment plant renovation and expansion project was completed, with a daily treatment capacity increased from 160000 cubic meters to 320000 cubic meters, making it one of the largest sewage treatment plants in East Africa. After pre-treatment and biodegradation, the sewage is discharged in compliance with standards, and the entire process takes about 40 days to operate. In the past, the smell here was pungent and required manual dredging, but now automated control has been achieved. ”Kenyan employee Margaret Wangechi told reporters that being able to participate in the treatment of Nairobi's sewage "makes me proud". After the completion of the project, middling coal entered the two-year operation service stage, focusing on assisting Kenya to achieve independent operation. Through the "old leading new" approach, Chinese employees provide systematic training to local technical personnel, and currently only two Chinese personnel are retained in the factory area. According to the plan, localized operations will be fully implemented by April 2027. This collaboration with Chinese companies is one of the best experiences of all our collaborations. ”James Muturi, Acting Director of the Planning and Design Department of the Water Supply Project at Asi Water Authority in Kenya, said, "We look forward to continuing to cooperate with Chinese contractors to implement the subsequent expansion plan of the Dandora sewage treatment plant." Nowadays, the Dandora sewage treatment plant is not only an environmental protection facility, but also an important place for public environmental education. Several schools in Kenya organized students to visit, and photography enthusiasts also frequently visited. Three years ago, there were almost no traces of wild animals here, but now it has become an important habitat for various bird species. Dozens of waterbirds stop here to forage, and the once "Black Stinky River" is once again becoming a "cool water". (New Society)