By Karel Mulder – For many protestants, the phrase ‘swimming the Tiber’ meant returning to Catholicism. Well, whatever one might think about religion, literally ‘swimming the Tiber’ is definitely not a good idea. The reason is obvious. As a tourist put it on TripAdvisor: “At some point of time during your stay in Rome you will come across the Tiber. It is a historic river, today a filthy green flowing body cutting through Rome.” Well one might argue that Rome receives already far too many tourists now, and so the low water quality of the Tiber might prevent additional tourists from completely blocking the center of the city. However, the river’s bad water quality is also harming recreation options for Romans. The small beach area, called Tiberis, that the city each summer constructs near the Marconi bridge, strictly forbids any swimming. And not only the Tiber River is polluted: Italian scientists detected fecal bacteria and staphylococci during a prolonged sampling period at Latium beaches Although the origin of the bacteria has not been studied, the pollution of the Tiber River could be a main candidate.

Rome has a great reputation for sanitation: Every sanitation textbook treats the Cloaca Maxima as one the first sanitation systems in the world. Its remains can still be seen today, and some small parts are even still in operation. Over time, with growing population, tourism and industrialization, more and more sewage was produced that often killed river life. Especially cities which were located far from the seashore, or which were not at the riverbanks of a major river, could hardly get rid of their sewage. Cities like Berlin, Paris and Manchester spend much efforts to deal with sewage. London invested in pumping stations that removed the sewage far outside the city, before flushing it into the Thames.

Activated sludge sewage treatment was developed in the 1920s and was rather generally applied by the end of the 20th century. However, cities that freely emitted sewage, without much harm for local interests, were reluctant to give up this ‘free’ solution. However, untreated sewage causes damage to ecosystems, to fisheries and to tourism, but very often in other communities. Hence communities investing in modern sewage treatment do have very few benefits themselves from this investment. Soft pressure or even force is often required to prevent harm and allow bathing. In the Netherlands, the city of The Hague was the last to stop emitting raw sewage in 2006. The city had long struggled against pressure to treat its sewage, and had emitted it further offshore. But this only prevented peaks of nearby shore pollution, while spreading the pollution to a longer coastline.

Rome has not only a long history of sanitation, but also a long history of river pollution: the aqueducts were certainly not constructed without a very good reason: the Tiber was polluted, and still is. Main reason: the capacity of the Rome sewage system is inadequate. Before Rome, the quality of the water of the Tiber and its main tributary within Rome, the Aniene, is excellent. However, when they merge, the Aniene is heavily polluted. Illegal emissions (the river cuts through an industrial site) and inadequate connections (e.g., mixing up sewage end rainwater) are a main cause. But the outlets of the Waste Wate Treatment Plants (WWTPs) are also a main cause. The total treatment capacity for Rome is sufficient for 2.78 million inhabitants. The number of inhabitants is about 2.9 million inhabitants, excluding tourists (domestic and international on average 100.000 at any moment) and illegals. Moreover, everyday Rome attracts thousands of commuters, students, etc. Finally, also companies discharge into the sewage system which is not included in normal capacity calculations. Rome’s WWTPs are terribly overcharged. As result, the WWTPs are the main source of river pollution. Comparing it to my own region, The Hague, the region has about 25 % more treatment capacity than its number of inhabitants. Rome probably has a significant capacity deficit. The errors in the sewage system end its management, make things worse, and cannot be undone by the use of reserve capacity.

This is the main reason for the Tiber’s problems. The problem is imminent given the low Tiber summer flow rates that we have to expect: What if the Tiber will consist of more than 10 % of ill-treated sewage? That might lead to ‘avoiding the Tiber’, whatever the religious connotation might be of such a phrase.