development of a qualitative risk assessment …development of a qualitative risk assessment...

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


EU Framework


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


EU Framework


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…


EU Framework


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


EU Framework


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


EU Framework


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


EU Framework


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


EU Framework


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


EU Framework


Figure 1: Overview of

aspects with the

potential to impact on the

fate of CECs during

agricultural irrigation with

treated wastewater


EU Framework


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


EU Framework


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


EU Framework


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 ……..


EU Framework


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


EU Framework


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

???


EU Framework


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


EU Framework


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

development of a qualitative risk assessment …development of a qualitative risk assessment...

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