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