Project Appreciation and Objectives
Regulation 26 (or Regulation 27 in Wales) requires disinfection by-products (DBPs) to be kept as low as possible without compromising disinfection. Focus has been on the regulated DBPs, mainly the trihalomethanes, but the increasing emphasis on a risk-based approach for water supply management is likely to make consideration of other DBPs a regulatory priority. The very wide range of known DPBs makes routine monitoring for them all impractical. However, applying knowledge of the factors which lead to formation of specific types of DPBs would allow Drinking Water Safety Plans to identify which DBPs pose the greatest risk. These factors include:
- raw water quality and precursor concentrations,
- treatment design and operation,
- ability of treatment processes to remove precursors and DBPs.
The objective of the work is to allow water companies to demonstrate compliance with regulatory requirements for minimising DBP formation for specific water treatment works, without the need for widespread sampling and costly analysis.
Business Benefits to Clients
- Demonstration to regulators that an appropriate range of DPBs have been included in DWSPs risk assessments.
- Defence against future public concerns arising over DBP risks.
- A much more cost-effective approach than sampling and analysis for specific DBPs.
This work will develop a detailed risk assessment process for incorporation into DWSPs to ensure that regulatory requirements for minimising DPB formation are identified for specific treatment works. This will be achieved through:
- A review of published information on DBPs worldwide, to identify water quality and treatment conditions influencing formation, and evaluate relative toxicity.
- Identification and prioritisation of those DBPs of potential concern under UK water supply conditions.
- Development of a risk assessment process to identify and prioritise risk for defined water quality and treatment conditions, taking into account toxicity of the individual DBPs identified and mitigation measures, including through treatment modification or catchment management.
Project Output and Implementation
A risk assessment and mitigation framework for inclusion in company DWSPs to allow risks from a wide range of DBPs to be identified and managed. Detailed implementation guidance, with supporting information on types of DBPs, precursors, routes of, and factors influencing, formation, removal by treatment and toxicology, will enable those responsible for maintaining and applying DWSPs to quickly get benefit from this work.
Related WRc Work
- Development of best practice guidance on disinfection for water treatment.
- Management of the UKWIR Toxicity Datasheets and toxicology support service to the industry
- Development of risk assessment approaches for water supply.