COST is supported by the
EU Framework
Programme Horizon 2020
Development of a qualitative risk assessment
approach for treated wastewater reuse with a
focus on chemicals of emerging concern
Lian Lundy and Mike Revitt
Middlesex University, UK
COST is supported by the
EU Framework
Programme Horizon 2020
EU NEREUS COST Action (2014-2018)
Multi-disciplinary treated wastewater (TWW) reuse network:
• 380 researchers, policy-makers, practitioners from 43 countries
• 5 Working Groups – WG1 Antibiotic resistant bacteria and genes in TWW and
downstream environments
– WG2 Uptake and translocation of contaminants of emerging concern (CECs) in crops
– WG3 Effect-based bioassays required for TWW reuse schemes
– WG4 Treatment technologies to meet the current wastewater reuse challenges
– WG5 Risk assessment and policy development
COST is supported by the
EU Framework
Programme Horizon 2020
Driver: opportunity for transformative action!
• Use of TWW varies e.g. 0% (Ireland) - 100% (Cyprus); EU MS
average: ~2%
• Increasing water scarcity vs an under-exploited resource
• ‘Pockets’ of expertise, experience and accrued knowledge
• TWW can contain CECs – is this a concern for human health
and/or environmental compartments?
• Limited data, knowledge gaps, methodological uncertainties
• Decision-makers are required to develop policy now…
COST is supported by the
EU Framework
Programme Horizon 2020
What can we do?
• Develop a systematic approach to screen TWW uses
• Apply a source-pathway-receptor (SPR) approach – are
there complete SPR chains?
• Develop a qualitative approach to consider:
– the likelihood of occurrence of a specific substance
– its magnitude of impact
• Widely used approach in health and safety sector
COST is supported by the
EU Framework
Programme Horizon 2020
How did we do this?
• Co-development of a ‘long list’ of aspects which would
influence the behaviour of CECs within TWW used to
irrigate crops
• Developed grading system to qualitatively assess – or rank
- on a per use / per protection goal basis:
– the likelihood of occurrence of a specific substance
– its magnitude of impact
COST is supported by the
EU Framework
Programme Horizon 2020
Overview of the potential factors, processes, pathways and endpoints to be considered within an assessment of the risks of reusing TWW
Wastewater characteristics
Source;
treatment; transport;
storage etc.
Bio/chem/phys characteristics
CEC (e.g. Koc, Kow); Receiving compartment (e.g. pH, CEC)
Indirect pathways
e.g. soil-
plant
Direct pathways
e.g. TWW-soil;
TWW -plant
Management practices
Irrigation; Ploughing; Fertiliser
Protection target /
receiving compartment
Humans; Soil;
Aquifer; Surface water
COST is supported by the
EU Framework
Programme Horizon 2020
Table 1. Guide to how the likelihood of a specific CEC
occurring in TWW at point of use could be graded
Possible descriptors for relative grading
Ordinal value associated with likelihood
Likely (expected to occur) 4
Possible (may occur sometimes) 3
Unlikely (uncommon but known to occur) 2
Rare (lack of evidence but not impossible) 1
COST is supported by the
EU Framework
Programme Horizon 2020
Table 2. Example of descriptors to benchmark
progressively increasing magnitude of impact
Possible descriptors for relative grading
Ordinal value associated with magnitude of impact
High (irreversible effects) 4
Medium (reversible effects) 3
Low (effect detected but not at concentration thought to cause harm)
2
Very low (no obvious and direct impact) 1
COST is supported by the
EU Framework
Programme Horizon 2020
Figure 1: Overview of
aspects with the
potential to impact on the
fate of CECs during
agricultural irrigation with
treated wastewater
COST is supported by the
EU Framework
Programme Horizon 2020
Figure 1: Overview of
aspects with the
potential to impact on the
fate of CECs during
agricultural irrigation with
treated wastewater
COST is supported by the
EU Framework
Programme Horizon 2020
Likelihood of CECs reaching the
soil environment
Aspects considered in developing a scoring system :
• Source of wastewater
• Level of wastewater treatment
• Storage prior to use
• Type of irrigation
COST is supported by the
EU Framework
Programme Horizon 2020
Magnitude of impact of receiving soils
on CEC bioavailability
Aspects considered:
• CEC load in TWW
• CEC bioavailability in the soil
• Bio-solid/fertiliser addition to soils and ploughing
COST is supported by the
EU Framework
Programme Horizon 2020
Overall risk rating matrix
Example of how scores can be interpreted • 12-16 = high probability of the occurrence and bioavailability of a CEC in
soil resulting in potential for uptake
• 9-11 = possibility ……..
• 5-8 = unlikely (or limited possibility of) …..
• 1-4 = only on very rare ……..
COST is supported by the
EU Framework
Programme Horizon 2020
Worked example: clarithromycin
Hypothetical scenario
• Wastewater from a residential area
• WWTP - secondary treatment with membrane bioreactors
• TWW piped and stored in a closed tank
• Used for spray irrigation within 24 hours.
• Irrigated crops are growing in a neutral sandy soil
• No fertilisers applied but the land ploughed
Calculated a risk score of 6 = limited probability of the
occurrence and bioavailability of a CEC in soil resulting in
potential for uptake
COST is supported by the
EU Framework
Programme Horizon 2020
List of parameters to extend current approach to
human and environmental receptors from CECs
within TWW used in agricultural irrigation
Protection target Parameters Data availability
Plants (crops or non-
target vegetation)
Species (and genotype?) Limited number of species tested for a
limited range of CECs
Plant physiological status Limited understanding of its role
Soil organisms Species Limited number
Species specific PNEC vs PEC
per receiving compartment
Limited data on PNECs (no data for
many species); limited data on PECs
(no data for many CECs in many
receiving compartments)
Humans (crop
consumption and
occupational and non-
occupational exposure
pathways)
Mass of CEC consumed (per
year or day?) in comparison to
therapeutic dose; CEC load
within TWW re: occupational and
non-occupational
Available for a limited number of CECs
in only a few crops; source-pathway-
receptor linkage identified for
carbamazepine; lack of dose-response
models for many CECs
Animals (consumption
of crops / water)
Mass of CEC consumed (/yr or
/d) relative to therapeutic dose
per animal type e.g. sheep, cattle
???
COST is supported by the
EU Framework
Programme Horizon 2020
What do we know about antibiotic resistance?
Antibiotics:
• Occur in TWW-irrigated soils
• Alter the soil microbiome
• Accumulate in/on edible plants
• Ecological impacts reported
• No data on many antibiotics in many environments
Antibiotic resistant bacteria / antibiotic resistant genes
• Occur in TWW irrigated and non-irrigated soils
• Potential to accumulate in plants demonstrated
• Potential to colonise the gut: unknown
• Ecological impacts: unclear
COST is supported by the
EU Framework
Programme Horizon 2020
Outcomes and conclusions
• co-identified a list of parameters for use within a RA framework
• example application – clarithromycin – as far as soil
• output: a ranking of hazards not an assessment of risk
• currently insufficient data to apply approach to further protection
targets
• strongly support use of the precautionary principle
• time /cost of developing necessary data sets – support use of
integrated chemical and ecotoxicological approaches