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30 water treatment plants released 11 billion liters of raw sewage in a year, study suggests | rivers
Eleven billion liters of raw sewage were discharged from a sample of 30 water utility treatment works in one year, a new study suggests.
The study aimed to find out the volume of discharged effluent released from storm floods by water companies. Companies are not obliged to indicate the volume of raw sewage released during discharges. Regulators are only required to provide data on the number of downloads and their duration.
Recommendations by MPs on the environmental audit committee that volume monitors be installed by water companies have so far been rejected by ministers.
In a study of 30 treatment works in 2020, run by nine out of 10 water and sewerage companies in England and Wales, the volume of raw sewage discharged was estimated at 11 billion litres, or the equivalent volume of 4,352 Olympic swimming pools .
Professor Peter Hammond, a mathematician who analyzes data on sewage discharges, carried out the research. He has previously given evidence to MPs to reveal that the rate of illegal discharges of raw sewage by water companies is 10 times higher than official figures suggest.
Hammond said it was vital to determine the volume of wastewater discharges from water companies. He said his research suggested the government’s target to reduce raw sewage discharges to 20 per year by 2025 was not strong because there was no requirement to disclose the volume of raw sewage discharged. for each download.
No data is yet available showing the volume of untreated sewage discharges, he said. The water companies have an idea, but the regulators [Ofwat and the environment agencies in England and Wales] and the government [the Department for Environment, Food and Rural Affairs] maybe i have no idea. Wastewater residues in rivers, beaches and seas provide data but may not reflect the volume of discharges.
So what is the potential discharge volume for 20 overflow spills per year?
Of the 30 treatment works analysed, only one Mogden sewage treatment works in west London has volume monitors fitted. In 2020, Mogden, which serves more than 2 million people, released a volume of raw sewage equivalent to 2,768 Olympic swimming pools.
The average volume of wastewater discharged for discharge from the other 29 treatment plants in 2020 was 1.3 Olympic swimming pools. The government’s target of 20 spills a year by 2025 will still involve large volumes of untreated sewage, according to the analysis.
Even if the government’s target of reducing stormwater discharges of 20 outfalls a year were met, some treatment works could still discharge a volume equivalent to 26 Olympic-size swimming pools of untreated sewage a year, Hammond said.
Measuring the volume of discharges was vital to determine their environmental impact on rivers, he said. Individual rivers receive direct, simultaneous discharges of untreated sewage from multiple storm surges during their journey from source to sea, Hammond said. So, during longer floods, a river’s downstream may already be polluted by upstream discharges, when even more downstream floods discharge untreated sewage.
The River Nidd in North Yorkshire, one of the river catchments studied by Hammond, receives untreated sewage discharges from at least seven treatment works. Calculations were possible on estimated volumes for four treatment works: Pateley Bridge, Harrogate North, Darley and Kirk Hammerton. Hammond estimated that the river received the equivalent of 317 Olympic swimming pools of raw sewage from those works in 2020.