No one has published enough about UK wastewater analysis to assures me they can make accurate comparisons between areas over time, or confidently relate unexpected changes in a particular area to actual infection levels. For example, sewage systems n different locations would be expected to respond differently to varying inputs over time, and the type of properties, urban/rural setting etc would affect this.
This is what the
gov say:
"Estimating infection rates
Some studies have shown SARS-CoV-2 RNA concentrations to correlate with COVID-19 cases. However, exact infection rates cannot yet be calculated from SARS-CoV-2 wastewater monitoring. This is because calculating exact infection rates from a sample relies on knowing how much virus is released from faeces and/or urine during different infection stages and how long it can persist in different sewer networks. Researchers do not know this yet for SARS-CoV-2. Instead, scientists are starting to estimate viral RNA concentrations per inhabitant based on wastewater monitoring. For this, scientists need to know how many people are contributing to a wastewater sample and if rain and/or industrial wastewater diluted the sample. This is important so that monitoring results can be compared over time and across different regions...."
All sorts of things can affect the dilution and degradation of RNA in sewage systems, from rainfall to whether the local authority puts bleach block toilet cleaners in school cisterns or whatever.
