LICENSING AND RESOURCE USE
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LICENSING AND RESOURCE
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USE
ENVIRONMENTAL LICENSING PROGRAMME MEMORANDUM
1. Background
Waterford City Council was granted a Waste Water Discharge Licence (Reg. No. D0022-
01) for Waterford City on 6* January 2010. A wastewater treatment plant (Wwrp)
providing secondary treatment, and with a design capacity of 190,600p.e. was
commissioned in mid 2010. The agglomeration loading as provided in the licence
application is 122,588p.e. The WWTP primary discharge is to the Lower Suir Estuary,
3km downstream of Waterford City. (See Map in Appendix 1to this memo). The plant is
being operated by Celtic Anglian Water, in accordance with a Design, Build and Operate
contract. The licence requires the Wwrp to achieve effluent standards of 25mg/1 BOD,
125mg/I COD, 35mg/I Suspended Solids, lOmg/l Ammonia, and 15mg/l Total Oxidised
Nitrogen (TON). Waterford City Council (hereafter referred to as WCC) is the lead
authority and Kilkenny Co. Co. and Waterford Co.Co. are licensees.
2. Requested Amendment
A technical amendment request was received from WCC on lo* February 2011 for the
removal of emission limit values for Ammonia and Total Oxidised Nitrogen, as WCC
considered the limits to be 'onerous and unnecessaw. WCC were requested by the
Agency on 12* May 2011 to identify achievable emission limit values for Ammonia and
TON and to demonstrate that such limits would not compromise achievement of the
objectives as required by the Environmental Objectives (Surface Waters) Regulations
2009, S.I. No. 272 of 2009. A response was received on 07"' July 2011.
WCC has proposed emission limits of 25mg/1 Ammonia, 35mg/I TON and 35mg/1 Total
Nitrogen for the Wwrp and maintain that these limits would be unlikely to prevent the
Suir from achieving its water quality objectives. They state that there is currently no
provision for nitrogen removal, but that these limits could be achieved without additional
treatment. The WWrP was reported by WCC to be achieving a good level of nitrogen
removal as the activated sludge process is under-loaded. It is receiving less than 5,000
kgBOD/day, compared to the design loading of 11,436kg BOD/day. WCC expects that as
the influent loading increases in the future, that the operational flexibility of the plant will
reduce, and that without significant investment in nitrogen removal the licence limits for
nitrogen may be exceeded. From monitoring results provided by WCC the ELV for TON
(15mg/tN) was marginally exceeded on four occasions since July 2010.
Page 1 of 7I n support of their request WCC submitted results of dispersion modelling for the treated
effluent discharge to the Suir Estuary. This model was applied as part of the EIS for the
WWrP (1998). A dispersion modelling study was provided in support of the licence
application, however the information relating to nitrogen was only provided as part of
the amendment request. The model has predicted increases in nitrogen concentrations
above background levels at a number of locations along the Suir Estuary.
3. Assessment
No treated effluent standards for nitrogen were provided in the wastewater licence
application. The WWrP discharges to the Lower Suir Estuary, a 'transitional' waterbody,
which meets the Barrow Nore Estuary at Cheekpoint. This flows to Waterford Harbour, a
coastal waterbody, 15km downstream of the WWrP. The Environmental Objectives
(Surface Water) Regulations (S.I. No. 272 of 2009) specify a standard for Dissolved
Inorganic Nitrogen (DIN)' for coastal waters. There are no nitrogen standards for
transitional waters. The licence limits for Ammonia and TON were specified having
regard to S.I. No. 272 of 2009 and information provided in the licence application.
The receiving water at the WWTP discharge point (SWl-Future) is not designated
sensitive under the Urban Waste Water Treatment Regulations, as amended. The
nearest sensitive water is approximately 2.7km upstream of SWl-Future: Suir €stua/y
(Upper) - from Coolnamuck Weir to Newtown. This was designated under the Urban
Waste Water Treatment (Amendment) Regulations, 2010, after the licence was granted.
Receivina waters
The Upper Suir Estuary is from above Carrick-on-Suir to Fiddown and under the Trophic
Status Assessment Scheme it was 'Potentially Eutrophic' in 2007-2009. The Middle
Estuary extends approximately 25km from Fiddown to Little Island (2.7km upstream of
the WWrP discharge) and it was 'Eutrophic' in 2007-2009. This was due to winter DIN,
Chlorophyll and Dissolved Oxygen. The WWrP discharge is to the Lower Estuary, which
was 'Intermediate' in 2007-2009. I n the same period Waterford Harbour was
'Unpolluted'. For 2008-2010 the trophic status for the Estuary and Harbour were
unchanged compared to 2007-2009. However improvements were found for BOD, DO
and summer DIN levels for the Middle Estuary.
The Water Framework Directive (WFD) status was determined by the Agency in 2011,
based on 2007-2009 data. The Middle Estuary had 'Moderate' status due to
unsatisfactory BOD and DO levels. The Lower Estuary had 'Good' status. Waterford
Harbour also had 'Good' status in 2011, with 'High' for MRP and BOD and 'Good' for DIN
and DO. Under the WFD the objective is to protect 'Good' status where it exists. I n the
Transitional and Coastal Waters Action Programme the objective for the Middle Estuary is
to 'restore' to 'Good' status by 2021.
Table 1 summarises the trophic status, WFD status monitoring data for DIN. The data
indicates that nitrogen contributions from the Suir catchment upstream of Waterford City
are having an impact on nitrogen levels in the Middle and Lower Estuary. Nitrogen
concentrations are less elevated in the Lower Estuary and Waterford Harbour. I n the
Lower Estuary there has been an improvement in nitrogen concentrations in 2009-2010.
This may reflect flows being directed to the WWrP in early 2009 and commissioning in
mid-2010. I n 2007-2009 the thresholds for DIN were exceeded for winter (2.304mg/I)
and summer (1.770mg/I), but in 2009-2010 the winter level improved to 1.622mg/I.
DIN is the sum of nitrate (NO3), nitrite (NO2) and ammonia (NH3), and represents nitrogen available for plant uptake.
Page 2 of 7Table 1. DIN, Trophic Status and WFD status- Suir Estuary & Waterford Harbour
Water body DIN (mg/lN Trophic Status WFD Status
2007-2009 1 2007-2009 (01/04/2011)
(mg/lN) (and 2008-2010)
Upper Suir W: 3.330 ' 2.6 Potentially Moderate
Estuary S: 2.960 ' 2.600 Eutrophic
Middle Suir W: 3.740 ' 2.6 Eutrophic Moderate
Estuary S: 2.795 2.600
Lower Suir W: 2.304 ' 1.824 Intermediate Good
Estuary (Little S: 1.770' 1.682
Island to W: 1.622 *
Cheekpoint) S: 1.776
Barrow Suir Nore W: 1.755 ' 1.4 Intermediate Moderate
Estuary S: 0.870 1.017
Waterford W: 0.379 ' 0.506
Harbour S: 0.150 ' 0.506 Unpolluted
1: Water Quality in Ireland 2007-2009, Appendix-5-1JraC.xla. W: Winter, S: Summer.
Good
2: 2009-2010 data provided by Agency (OW)to Waterford City Council.
3: Figures in bold are DIN concentrationsthat exceeded the TSAS threshold levels.
I n an Agency report? the water quality benefits due to the characteristics of the
Suir/Barrow/Nore Estuary are large water volume turnover, large tidal excursions and a
well-mixed estuary with short retention times. Because of the long narrow estuaries and
strong tidal action sediments tend to become resuspended resulting in high turbidity and
low transparency. This limits light penetration and can result in reduced productivity.
Urban Waste Water Treatment (UiWWr) Reaulations
The UWWT Regulations, as amended specify the following waters as sensitive:
S.1 No. 254 of 2001: the 'Suir Estuary (Upper) - h m Coolnamuck Weir to Mount
Congreve'. Mount Congreve is 15km upstream of SW1-Future.
S.1 No. 48 of 2010: the 'Suir Estuary (Upper) - h m Coolnamuck Weir to Newtown:
Newtown is 2.7km upstream of SW1-Future. This replaces the
'sensitive area' in the 2001 Regulations.
The following are reievant sections of the 2001 Regulations (Article 4).
4. (1) In the case of urban waste water entering colldng systems, a sanitaty authority
shall prowde treatment plan& which provide for secondary treatment or an equivalent
treatment -
(a) on the commencement of these Regulations, or such later date, not being later
than 31 December 2005, as the European Commision may agree pursuant to a
request under Article 8 of the Dil-ective, in respect of all discharges from
agglomerations with a population equivalent of more than 15,000,
(b) by 31 December 2005 in respect of all discharges fiom agglomerations with a
population equivalent of between 10,000and l&OOO;
(c) by 31 December 2005 in respect of all discharges to kshwaters and estuaries
from agglomerations with a population equivalent of between 2pOO and 10,000.
'Water Quality in the Suir, Barrow/Nore Estuary b Waterbrd Harbour- 2005 (EPA, 2005).
Page 3 of 74. (2)(a)- Notwithstanding sub-arbcle (1) and subject to sub-arbcles (3) and (4), a
sanitary authority shall provide treatment plants which provide more stn’ngent
treatment than secondary treatment or an equivalent treatment in respect of all
discharges &om agglomerations with a population equivalent of more than 10,000KO
sensitive areas or into the relevant catchment areas of sensitive areas where the
C S .
4.(3? Subject to sub-article (4)/ a discharge from a treatment plant required under
sub-article (2)/ shall satism the requirements of Part I and 2 of the Second Schedule
(i.e. et77uent standards fbr Total P and Total N).
4.(4) (a) Sub-articles (2) and (3) shall not apply in respect of individual treatment
plants where the sanitary authority is satisfied that the minimum percentage of
reduction of the overall load entering all urban waste water treatment plants in a
sensitive area is at least
4.(4)(b)- Sub-article (3) shall not operate to require the reduction of nutrients in
discharges to estuaries, bays or coastal waters where Me sanitary authority is satW%d
that such reduction will have no effect on the level of eutrophication in the receiving
waters
The ‘Suir Estuary (Upper) - h m Coolnamuck Weir to Newtown’is 2.7km upstream of
SWl-Future. As the Suir Estuary at SWl-Future is tidal the WWTP discharge is potentially
into the catchment of the sensitive area. However it must be considered whether the
discharge contributes to pollution of the sensitive area, or if nutrient reduction would
have any effect on the level of eutrophication in the receiving water. The effluent
standards applicable for agglomerations > 100,000p.e. are 15mg/l Total nitrogen and/or
lmg/l Total phosphorus depending on the local situation.
The extent of the ‘Suir Estuary (Upper) - from Cmlnamuck Weir to Newtown‘
corresponds with what are the Upper and Middle Estuaries under the TSAS and WFD.
The Middle Estuary was Eutrophic in 2007-2009 and this may have been the reason that
the stretch from Mount Congreve to Newtown was designated sensitive in the 2010
UWWT Regulations. From consultations with OEA (Shane O’Boyle) the downstream half
of the Middle Estuary (from approximately Mount Congreve to Waterford City) is light
limited due to its characteristics, including depth. This part of the Middle Estuary does
not show signs of eutrophication, most likely due to it being light limited. The eutrophic
conditions are in the upstream section of the Middle Estuary (from Carrick on Suir to
Mount Congreve), approximately l5km upstream of SWl-Future. The OEA are
considering revising the waterbody boundaries for the Suir Estuary in light of the
difference in conditions. It is considered that the provision of nutrient removal for
Waterford City Wwrp would have no effect on the level of eutrophication in the Middle
Estuary and therefore the provision of nutrient removal under the U W Regulations is
not recommended for Waterford City W.
Water aualitv modelling
The model predicted increased nitrogen concentrations above background levels at a
number of locations along the estuary. The form of nitrogen (Total Kjeldahl Nitrogen -
TKN) is organic nitrogen plus ammonia. It does not include TON, however nitrogen was
treated as a non-decaying parameter and therefore WCC consider it gives a reasonable
prediction of Total Nitrogen (the sum of TKN and TON). A loading of 1,054kgN/day was
modelled, which is equivalent to the Wwrp DWF in 2025 and an effluent concentration
Page 4 of 7of 38mg/1 Total N. It assumed river dry weather flow and neap tide conditions and is
therefore considered conservative. It did not take into account any reduction in
background levels due to cessation of untreated wastewater discharges.
The monitoring stations used are from 43. Mount Congreave (upstream of Waterford
City) to 60a. Cheekpoint Pier (approximately 4.5km d/s Wwrp discharge). The Wwrp
discharge was predicted to result in an increase in concentration of 0.19mg/lN (mean) at
the outFall in the vicinity of 57. Lime Island The predicted increase at 60a. Cheekpoint
Pier was 0.14mg/l (mean). I n 2007-2009 the mean background DIN concentration at
60a. Cheekpoint was 2.0mg/lN3, therefore 0.14mg/l represents an increase of
approximately 7% over the background DIN at this location.
The model report includes a graph of predicted increases in TKN concentrations to the
outer edge of Waterford Harbour (approximately 22km d/s of the WWTP). The predicted
increase at the inner extent of the Harbour (approximately 1Okm d/s of Cheekpoint) is
less than 0.09mg/lN. It predicts no increase in concentration at the outer edge of the
Harbour. I n 2007-2009 the median DIN (Winter) for Waterford Harbour was 0.379mg/lN
and the threshold for ‘Good’ status was 0.506mg/lN, i.e. exceeding this would result in a
deterioration to ‘Moderate‘ status. Based on the predicted increases it is considered that
the Wwrp discharge would not compromise meeting the Good status EQS for DIN. This
approach is considered conservative as the background data for 2007-2009 includes the
discharge of untreated wastewater. Ambient concentrations in the estuary are likely to
reduce to reflect provision of the WWTP. Also even when the WWTP reaches its design
capacity the contribution 1,054kgTN/day will be less than the untreated discharges,
which contributed l,677kgTN/day. Also when wastewater was receiving no treatment
the trophic status of Waterford Harbour remained unpolluted.
The Lower Suir Estuary, the Barrow, Nore Suir Estuary or Waterford Harbour are not
classed as eutrophic or potentially eutrophic. Although the DIN levels in the Lower Suir
Estuary were somewhat elevated in 2007 -2009 there is no evidence of eutrophication or
excessive algal growth, possibly due to the light limiting conditions. Taking into account
that there is no evidence of eutrophication, and based on the additional information
provided it is considered that installing nutrient removal to achieve the current licence
limits would not be justified. The approach of the Agency is to set ELVs for TON and
Ammonia for discharges to coastal waters. Although the discharge is to a transitional
water, it is recommended that nitrogen limits be maintained in the licence to limit the
discharge of nitrogenous compounds and to protect Waterford Harbour.
~ ~~~
Physico-chemical data for Suir Estuary 2007-2009 from EPA Laboratory, Kilkenny.
Page 5 of 7On consideration of the information from the kensee, I am of the view that it is
appropriate to deal with this request by way of Technical Amendment. It has been taken
into consideration that the information provided by the licensee was not supplied as part
of the licence application. The requested ELVs of 35mg/I TON (as N), 25mg/I Ammonia
(as N), and 35mg/I Total Nitrogen are recommended to be included in SLbed.de A.1 of
the licence. These limits will allow greater flexibility in operation of the Wwrp and in the
proportions of nitrogen in the effluent, as well as protecting the receiving waters.
It is considered that the limits will not compromise the achievement of the surface water
objectives for Waterford Harbour, i.e. it would not result in the waterbody deteriorating
from 'Good' to 'Moderate' status. This is taking into account the water quality modelling,
the characteristics of the Suir Estuary apd Waterford Harbour and the distance from the
Wwrp discharge to Waterford Harbour. The monitoring specified in the licence is
appropriate and no changes are recommended.
4. Consultations
I consulted with Brendan Wall, Senior Inspector, in the Office of Environmental
Enforcement (OEE). It was confirmed by OEE that the requested change could not be
accommodated under the existing licence (00022-01). Ialso consulted with Shane
O'Boyle in the Office of Environmental Assessment with regard to the transitional and
coastal waters. I have taken into account consultations with OEE and OEA and
comments received regarding the catchment of the sensitive area and provision of
nutrient removal under the UWWT Regulations, as amended.
5. Recommendation
Irecommend that the licence amendment, under Regulation 33(l)(c), be approved as
set out in the attached recommended Technical Amendment. Such an amendment does
not result in the relevant requirements of Regulation 6(3) of the Waste Water Discharge
(Authorisation) Regulations, as amended ceasing to be satisfied.
Signed,
&- 0-4
Marian Doyle
Inspector
Environmental Licensing Programme
Page 6 of 7Appendix 1:W a t e h r d City WWTP discharge and k i v i n g waters
r- -
Page 7 of 7I
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