Intermittent Discharges
(inc CSOs)
Paul Simmons
Environment & Business, NW Region
What are intermittent discharges?
Existing Standards
Outcome of the Standards Review
Implications
Intermittent Discharges - The Scale of the
Problem
6,500 sewage treatment works
25,000 intermittents
8,000 have been improved
since 1995 – cost approx £3.5Bn
50% of bathing waters affected by CSOs
~320 waterbodies impacted by intermittents
High Profile discharges
M due for
monitor
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350 CSOs requiring
improvement
320 WFD WBs at risk
Impacts of intermittent discharges
UPM (Urban Pollution Management)
Standards
FIS – Fundamental intermittent standards which are directly related to the characteristics of events which cause stress in river ecosystems. These standards are expressed in terms of concentration-duration thresholds with an allowable return period or frequency. Dissolved Oxygen, unionised ammonia.
High percentile standards (99 percentiles) based on a direct extrapolation of the 90/95 percentile thresholds from other standards. BOD, ammonia.
Review of UPM Standards against WFD
requirements
Task A –Carry out a literature review/data collection.
Task B – Establish an effects matrix.
Task C – Compare the effects matrix against existing standards.
Task D – Propose UPM standards for WFD.
Un-ionised ammonia – sustainable
salmonid fisheries FIS
FIS for Sustainable Salmonid and Cyprinid fisheries are suitable for WFD
Taxa Species Type of
organism 24-hour LC50 (mg NH3-N/l)
Reference
Fish S.salar Atlantic salmon 0.12 Alabaster et al (1979)
Invertebrate V.iris Mussel 0.22 Mummert et al (2003)
Fish O.tshawtscha Chinook salmon 0.30 Harader and Allen (1983)
Invertebrate L.fascioloa Mussel 0.32 Mummert et al (2003)
Invertebrate A.ligamentina Mussel 0.47 Wang et al (2007)
Fish H.molitrix Silver carp 0.48 Xu et al (1994)
Fish O.mykiss Rainbow trout 0.53 Milne et al (1992)
Fish N.guentheri Killifish 0.57 Shedd et al (1999)
Invertebrate L.siliquoidon Mussel 0.60 Wang et al (2007)
Fish S.trutta Brown trout 0.60 Milne et al (1992)
Fish L.guntea Guntea loach 0.61 Sangii and Kanabur (2000)
Fish C.carpio Common carp 0.68 Xu et al (1994)
Invertebrate L.rafinesqueana Mussel 0.68 Wang et al (2007)
Fish L.cephalus Chub 0.76 Gomulka et al (2011)
Algae S.costatum Diatom >1.00 Livingston et al (2001)
Fish P.promelas Fathead minnow 1.22 Markle et al (2000)
Fish P.reticulata Guppy 1.35 Rubin and Elmaraghy (1976)
Invertebrate M.rectirostris Cladoceran 1.61 Gyor and Olah (1980)
Invertebrate D.magna Cladoceran 1.74 Kaniewska-Prus (1982)
Invertebrate L.stagnalis Snail 1.92 Williams et al (1986)
Invertebrate P.tennuis Turbellarian 1.95 Williams et al (1986)
Invertebrate L.intermis Insect 2.18 Williams et al (1986)
Invertebrate P.fontinalis Bladder snail 2.20 Williams et al (1986)
Invertebrate B.rhodini Mayfly 2.30 Williams et al (1986)
Invertebrate L.hoffmeisteri Tubificid worm 2.80 Williams et al (1986)
Invertebrate C.riparius Midge larvae 3.00 Williams et al (1986)
Invertebrate B.rubens Rotifer 3.20 Snell and Persoone (1989)
Invertebrate G. pulex Amphipod 3.20 Williams et al (1986)
Invertebrate E.ignita Damselfly 3.29 Williams et al (1986)
Invertebrate A. aquaticus Isopod 4.04 Williams et al (1986)
99 Percentiles for WFD
99%iles for BOD
y = 1.9727x + 1.3939
R2 = 0.9822
02468
1012141618202224262830
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16
90%ile mg/l
99%
ile m
g/l
RE1
RE3
RE2
RE4
RE5
HIGH
GOOD
How will the standards be used?
Design Standards, not classification
Water company improvements / investigations for PR14
Need driven by WFD classification, use is through modelling
WOE / risk-based approach –
- Confidence in relevant element(s) not achieving Good status
- Significance of the contribution of intermittent discharges to the problem
Implications – application of FIS
In England and Wales the salmonid standard will
replace the cyprinid standard for some waterbodies
Information for 320 Waterbodies identified in Reasons for Failure Database with intermittents as cause
Current Fish Directive Designation Expected Prevalence of:
% No Fish Class points 314 314 314
No. Sample points 620 probability level 0.25 0.5 0.75
Salmonid 229 37 Salmon 90 29% 61 19% 20 6%
Cyprinid 391 63 Trout 253 81% 200 64% 142 45%
12 % to 44 % of waterbodies may require tighter FIS
standard for WFD.
40 to 140 of these 320 waterbodies where salmonid
standards will now apply instead of cyprinid
Implications – 99 percentiles
Steep, fast flowing rivers
Low confidence in detailed river modelling
Standards derived for high, good, moderate, poor status
Good status standards for old RE3, RE4 objectives are tighter
Good status standards for old RE1 and RE2 objectives are less stringent
1,000 to 2,000 km of river may require tighter standards (England and Wales)
Questions / Comments
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