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Sewage in UK waters: a raw deal for wild swimmers

2022; Royal College of General Practitioners; Volume: 72; Issue: 723 Linguagem: Inglês

10.3399/bjgp22x720833

1478-5242

Richard Armitage,

Fish Ecology and Management Studies

Alarming news reports depicting copious volumes of raw untreated sewage being actively discharged onto the beaches of storm-battered England have recently generated concerns for the safety of open water swimming.But what are the health benefits of this increasingly popular sport?What threat does pollution pose to its participants?And what are the consequences for general practice and public health? THE UK's SEWAGE SYSTEMThe majority of the UK is covered by an elaborate sewage network that simultaneously deals with both rainwater and wastewater in the same interconnecting lattice of sewers and pipes.This combined sewage system, which was initially constructed in the Victorian era, collectively carries both precipitation runoff from roads and other surfaces, domestic effluence from bathrooms and kitchens, and industry wastewater from factories and plants to one of some 9000 sewage treatment works across the UK. 1 Each day, around 11 billion litres of wastewater from across the country are collected and carried through the 350 000 kilometres of sewers and pipes directly into these works, where they are subjected to primary treatment (the settling out of solid matter), secondary treatment (the usage of bacteria to break down organic substances), and tertiary treatment (the disinfection of water and removal of nitrophosphates), before the resulting effluent is discharged into inland lakes, rivers, and the open sea. 1 During episodes of particularly heavy rainfall, especially when the ground is especially dry and unable to rapidly absorb precipitation, the local capacity of this sewage system can become quickly overwhelmed.This risks the network becoming severely inundated and a subsequent overflow that causes homes, highways, and other open spaces to be flooded.This outcome can be avoided by directional spillage in which the additional water volume is channelled away from valuable assets and infrastructure prior to the completion of its various treatments.These combined sewer overflows (CSOs) act as safety release valves, the activation of which directs excess wastewater away from homes, businesses, and vital infrastructure and directly into seas and open waterways instead.CSOs are a necessary part of