1. Incorporating metal bioavailability into permitting – UK experience
Paul Whitehouse
Environment Agency, Uk

2. Classification and Permitting – the role of EQSs
Permitting: aims to ensure EQS in receiving water is met
Discharges managed to meet permit condition
WASTEWATER TREATMENT
RECEIVING WATER
Classification: sampling of receiving water to assess compliance with EQS
Determines whether or not ‘Good’ status
UNCLASSIFIED

3. Responding to EQS failures - Investigations
Focus on priority waterbodies
Achievability e.g. ‘legacy’ contamination vs ‘active’ emissions
Building confidence e.g. Accounting for local backgrounds, more intensive monitoring of [M] or water quality parameters
Prioritise
Identify sources
Modelling (e.g. SAGIS), local knowledge, past incidents
Options appraisal (cost-benefit)
Options for mitigation and likely benefits of taking action
e.g. national measures, permit review, protection zones, best practice
Mitigation

4. Permitting hazardous pollutants
Hazardous pollutant in discharge liable to cause pollution?
Step 1
Screening
Step 2
Modelling
Step 3
Determine Emission Limits
Yes
Our current permitting procedure for hazardous pollutants discharging to freshwaters has three steps, which I will describe in more detail in a moment.
Steps 1 and 2 assess whether the substance in the discharge is present at a load that could have a significant effect on the receiving watercourse.
If the substance is not significant, then it does not need to be controlled on the permit.
If it is significant, in Step 3 we calculate a numeric emission limit to impose on the environmental permit.
For installations BAT is a precursor to this process. No
Permits ensure EQS compliance in the receiving water and “no deterioration” against EQS
No emission limit set on permit

5. Bioavailable metals: the challenges for permitting
Metal bioavailability is dependent on site-specific physico-chemical conditions that vary in time and by location - pH, dissolved organic carbon (DOC) and hardness
Data on these important parameters have not been collected routinely (so far)
Discharges can affect the downstream metal concentration and the conditions that influence bioavailability (DOC in particular)
We need to move away from permitting total metal concentrations (focus on dissolved and bioavailable)
The shift to bioavailability-based standards has implications for our current discharge permitting for three reasons:
Metal bioavailability is dependent on site-specific chemical conditions that vary in time and by location - pH, dissolved organic carbon (DOC) and hardness
Discharges might themselves have an effect on the downstream metal concentration and the conditions that influence bioavailability (DOC in particular)
Bioavailability focuses on particular forms of the metal (relationship between dissolved and bioavailable metal)
UNCLASSIFIED

6. Distributions of flows and quality upstream and in discharge are used to produce distribution of downstream quality
Permit based on point from downstream distribution c f T F
This slide shows how our Monte Carlo tool works now
Distributions of upstream flow and quality, and effluent flow and quality, are combined, and a distribution of the total downstream concentration is calculated.
We then compare this downstream concentration against the EQS to see if the substance could have a significant environmental impact C

7. C F T Bioavailable metals d c f d d
The prototype metal permitting tool has adapted Monte Carlo to allow us to input additional quality statistics for pH, Ca and DOC upstream and in the discharge
This means that we can now calculate downstream concentrations and how much of the metal will be bioavailable, using the same calculations which are used in MBAT. T C d
extra distributions are needed for conditions
that influencing bioavailability

8. Permitting bioavailable metals: how are we addressing the challenges?
We have developed a prototype tool that performs Monte Carlo simulation on all the upstream and discharge parameters of interest (flows, metal concs, DOC, pH, hardness)
Output is a downstream distribution from which we can estimate a permit condition
Assumptions:
Effluent DOC behaves in similar way to ‘natural’ DOC
Allow for all DOC present in discharge
Express permit as dissolved concentration - modelling suggests little exchange between dissolved and particulate metals
The shift to bioavailability-based standards has implications for our current discharge permitting for three reasons:
Metal bioavailability is dependent on site-specific chemical conditions that vary in time and by location - pH, dissolved organic carbon (DOC) and hardness
Discharges might themselves have an effect on the downstream metal concentration and the conditions that influence bioavailability (DOC in particular)
Bioavailability focuses on particular forms of the metal (relationship between dissolved and bioavailable metal)
UNCLASSIFIED

9. Permitting bioavailable metals - where are we now?
Engagement with stakeholders and permitting specialists – broad acceptance of the approach
Requires more intensive data collection (dissolved metal, DOC, pH, hardness) - inputs to permitting tool
Pilot study in 2014?
“Line of sight” from the science through to policymaking, permitting processes and implications for end-users is important in implementing bioavailability-based approach