Interestingly, several AAs were present in hospital effluent that were not observed at all or with very low frequency in community wastewater, likely due to dilution of hospital wastewater with communal discharge (table ). Many AAs and metabolites were also observed in high concentrations. This is likely due to, with shorter sewage residence time, lower volume of flow and concentration of individuals at the source requiring AAs. LZD is an oxazolidinone antibiotic which is used in severe bacterial infections in the UK. It is often prescribed in hospital environments as it requires specialist supervision (National Institute for Health and Care Excellence, n.d.). It can be used to treat serious respiratory illness (pneumonia) and to treat skin and soft tissue infections caused by methicillin resistant Staphylococcus aureus (MRSA). It has also been identified by WHO as a recommended treatment of multi-resistant TB (World Health Organisation, 2019). Whilst LZD was not detected in community wastewater, three of the hospital effluent samples observed levels between 0.03 and 5.2 μg/L. AMX on the other hand is prescribed in both community and hospital settings and is a popular AA due to its effectiveness against both gram-negative and gram-positive infections. AMX was not detected in any samples in community wastewater but was quantifiable in all hospital effluent samples, ranging between 0.3 and 6.0 μg/L. The absence of AMX in community wastewater is likely due to lack of stability of the constrained betalactam ring .