A methodology has been developed in order to evaluate the potential risk of drinking water for the health of the
consumers. The methodology used for the assessment considered systemic and carcinogenic effects caused by
oral ingestion of water based on the reference data developed by the World Health Organisation (WHO) and
the Risk Assessment Information System (RAIS) for chemical contaminants. The exposure includes a hypothetical
dose received by drinking this water according to the analysed contaminants. An assessment of the chemical
quality improvement of produced water in the Drinking Water Treatment Plant (DWTP) after integration of
membrane technologies was performed.
Series of concentration values covering up to 261 chemical parameters over 5 years (2008–2012) of raw and
treated water in the Sant Joan Despí DWTP, at the lower part of the Llobregat River basin (NE Spain), were
used. After the application of the methodology, the resulting global indexes were located below the thresholds
except for carcinogenic risk in the output of DWTP, where the index was slightly above the threshold during
2008 and 2009 before the upgrade of the treatment works including membrane technologies was executed.
The annual evolution of global indexes showed a reduction in the global values for all situations: HQ systemic
index based on RAIS dropped from 0.64 to 0.42 for surface water and from 0.61 to 0.31 for drinking water; the
R carcinogenic index based on RAIS was negligible for input water and varied between 4.2 × 10−05 and
7.4 × 10−06 for drinking water; the W systemic index based on the WHO data varied between 0.41 and 0.16
for surface water and between 0.61 and 0.31 for drinking water. A specific analysis for the indexes associated
with trihalomethanes (THMs) showed the same pattern.