Drinking Water Safety Plans, Disinfection of Drinking Water & Revised EPA Disinfection Manual Dr. Suzanne Monaghan Office of Environmental Enforcement, Environmental Protection Agency
Presentation Water Safety Plan approach Guidance on Water Safety Plans Disinfection Revised EPA Disinfection Manual
Water Safety Plan Approach Recommended by WHO Water not only safe but also secure All potential risks identified in the supply from source to consumer NFGWS QA Scheme Moving away from monitoring only Small and large supplies
Potential Hazards What do we mean when we talk about potential hazards? Any potential risk to human health Hazards can be present at any stage, catchment, intake, treatment, distribution. Some we are aware of, some we are not
Catchment Hazards
Treatment Hazards
Assess Risk One step further than QA system assess risk Ask how likely is it that this hazard will occur, and how severe would the consequences be if it did occur? Establish the risk category of each hazard Low High Put in appropriate controls
Likelihood Assess Risk using Table Is animal access a risk? Severity/Impact of Consequence Insignificant Minor Moderate Major Catastrophic 1 2 3 4 5 Almost certain 5 5 (L) 10 (M) 15 (H) 20 (VH) 25 (VH) Likely 4 4 (L) 8 (M) 12 (H) 16 (VH) 20 (VH) Foreseeable 3 3 (L) 6 (M) 9 (M) 12 (H) 15 (H) Unlikely 2 2 (L) 4 (L) 6 (M) 8 (M) 10 (M) Most unlikely 1 1 (L) 2 (L) 3 (L) 4 (L) 5 (L)
Likelihood Reassess Risk using Table Is animal access a risk? Severity/Impact of Consequence Insignificant Minor Moderate Major Catastrophic 1 2 3 4 5 Almost certain 5 5 (L) 10 (M) 15 (H) 20 (VH) 25 (VH) Likely 4 4 (L) 8 (M) 12 (H) 16 (VH) 20 (VH) Foreseeable 3 3 (L) 6 (M) 9 (M) 12 (H) 15 (H) Unlikely 2 2 (L) 4 (L) 6 (M) 8 (M) 10 (M) Most unlikely 1 1 (L) 2 (L) 3 (L) 4 (L) 5 (L)
Monitor, Record and Document Test new controls - validate Operational monitoring to verify controls and to ensure that problems show up early Record operational monitoring results Document everything - supply details, monitoring results, actions to be taken in normal and incident conditions (SOP s)
Benefits of a DWSP? Improved water quality and incident reduction Safe and Secure Deficiencies in controls, procedures and training will be highlighted Catchment improvements Clearer, prioritised investment Regulator and Consumer confidence 14
Guidance WHO Manual
DWSP Guidance EPA DWSP letter Sept 2009 Section 10 in EPA Handbook Pilot study with Galway City Council EPA have prepared guidance from this study - brief Advice Note: List of ALL potential hazards, matrix, template action sheet
Disinfection What is the goal of disinfection?
Disinfection and the DW Regs Reg. 4 Water shall be regarded as wholesome and clean if (a) it is free from any micro-organisms and parasites and from any substances which... constitute a potential danger to human health, and (b) it meets the quality standards specified.. in Part 1 of the attached Schedule
Sources of contamination?
E. coli The presence of E. coli is an indicator of faecal contamination 31.4% of Private Group Schemes detected E.coli at least once in 2007 (35.8% in 2006) If you detected E.coli you would: Review the effectiveness of the disinfection system is it robust?
Disinfection systems Remove or inactivate contaminants Chemical disinfection (e.g. chlorine) Physical removal (coagulation and filtration) Other (UV, Membranes) All treatment options have their limitations... disinfection by-products
EPA Disinfection Guidance Disinfection Manual (1998) being revised Handbook: Section 6: Procedures for noncompliance with standards Drinking Water Advice Note No. 3: E.coli in Drinking Water EPA Circular on Chlorine Monitors
Revised Disinfection Manual Alternative disinfection technologies Verification of effectiveness Emphasis on risk based approach to water treatment (DWSP) Integration with overall treatment, the multibarrier approach. Cryptosporidium
Revised Disinfection Manual Consultants, Steering Committee - NFGWS, CCMA, WSA, DoE, Industry, WSTG and HSE Started in September 2009 4 meetings, final meeting held in August Publication end 2010/start 2011
Disinfection Technologies Chlorine Chloramination Ozone Chlorine Dioxide Non-chemical (UV, Membrane) Other
Chlorine Chlorine most widely used disinfectant Range of technologies: Chlorine Gas Sodium Hypochlorite Calcium hypochlorite Effective against bacteria and viruses By products e.g. THM s
Disinfection Performance Determined by C and t product of which is Ct WHO recommend 0.5mg/l (C) X 30min (t) = Ct of 15mg.min/l Tool in manual to calculate t and Ct on-site Verified by monitoring of C
Practical Guidance Disinfection Performance Troubleshooting disinfection malfunctions Daily check sheets can build up over time Chemical storage Calibration and maintenance of equipment
Revised Disinfection Manual Not a design manual aid to decision making Training roll-out in 2011