EPA Waste Water Discharge Licence Application

Transcription

1 Duleek Waste Water Treatment Works EPA Waste Water Discharge Licence Application ARTICLE 16 COMPLIANCE REQUIREMENTS Meath County Council EPA Document Ref: D Section A: Non-Technical Summary Update the non-technical summary to reflect the information provided in response to this notice. An updated non-technical summary is attached in appendix 1. Section B - General Information Please provide the name of the agglomeration to which the Waste Water Discharge Licence Application relates. The agglomeration named in the application refers to the waste water treatment plant. Agglomeration name: Duleek and Environs The name of the agglomeration on the Waste Water Licensing Web based data tool has been amended. Provide the most recent planning permission including a copy of all conditions and where an EIS was required, copies of such EIS and any certification associated with the EIS. Attached in appendix 2 is a certificate from Meath County Council confirming that the Part VIII planning document (File Reference: P803031) was passed on the 1 st March As per S.I. No 600/2001, Planning and Development Regulations, 2001, Schedule 5, Part 2, an EIS is only deemed necessary for Wastewater treatment plants with a capacity greater than 10,000 population equivalent as defined in Article 2, point (6), of Directive 91/271/EEC not included in Part 1 of this Schedule. The upgraded Duleek WwTW will have the capacity to cater for a maximum population of 7,000. As this does not exceed the threshold criteria for the provision of an EIS, as set out above, an EIS was not required. Provision has been made in the design to allow for a possible future expansion to 10,500p.e. Should this phase 2 expansion ever be required then an EIS would have to be undertaken at that stage. Section C: Infrastructure and Operation In relation to the plant which is currently in operation, provide a description of the plant, process and design capacity for the areas of the waste water works where discharges occur, to include a copy of such plans, drawings or maps, (site plans and location maps, process flow diagrams), and such other Page 1 of 19

2 particulars, reports and supporting documentation as are necessary to describe all aspects of the area of the waste water works discharging to the aquatic environment. Maps and drawings must be no larger than A3 size. The existing wastewater treatment works was built in 1977 with refurbishment works completed in It is an extended aeration process with a design capacity of 2,500 p.e. The existing population equivalent is estimated as 4,645. The existing wastewater treatment plant is currently overloaded. It is however providing a high level of treatment during dry weather conditions. The current operational plant consists of; Extended aeration Basin (using a diffused air aeration system) Volume = 660m 3 Liquid depth = 1.8m Clarifier Phosphate Removal (Ferric Dosing) RAS pumps (Return Activated Sludge) Control Room (along with the control panels this also houses the air blowers and ferric dosing equipment) The effluent is pumped, from the existing pump station in the town via the existing rising main, directly to the extended aeration basin. Here it is aerated using a diffused air aeration system in a carousel type extended aeration basin. Ferric sulphate is dosed into the flow between the extended aerator and the clarifier. This dosing facility was added in 2000 to aid phosphorus removal. In the clarifier the sludge settles, allowing the clear, treated effluent to be discharged to the River Nanny (as per drawing DL-DK-12 in appendix 3) Some of the settled sludge is returned to the aeration tank, via the RAS pumps. The remaining sludge (WAS Waste Activated Sludge) is drawn from the clarifier to the sludge holding tank. From here the sludge is tankered to the main Sludge Acceptance Centre for County Meath, at Navan WwTW. The latest County Council sampling results from the Duleek WwTW are as per table Aug Sep Oct Nov Dec Jan-09 Parameter Inf Inf Inf Inf Inf Inf BOD mg/l COD mg/l TSS mg/l Tot P mg/l Tot N mg/l Parameter Eff Eff Eff Eff Eff Eff BOD mg/l COD mg/l TSS mg/l Tot P mg/l Tot N mg/l Table 1.1 Meath County Council Effluent Results August January 2009

3 As can be seen from the results above, the effluent standard currently being achieved is consistently within the statutory requirements. Please note that the new treatment works facility is due to be operational by January For the Duleek pumping station provide details of the measures to be undertaken in the event of a power failure or pump malfunction; The pumps at the existing Duleek pumping station are controlled at the pump station only. The pump station is checked regularly by the caretaker and a pump malfunction or unexpected power failure would be dealt with at this stage as there is no alarm out facility. Generally speaking, notification is given in the event of any power outages and generators would be organised to provide temporary power. Clarify as to whether the emergency overflow from the Duleek pumping station has been known to activate in the last 12 months. If so, provide the reason for the activation and details of the frequency, duration and discharge volume; The emergency overflow was activated on the 22 nd August As it is not monitored the duration and discharge volume is not known. This was during a sustained period of extremely heavy rainfall. After investigation, it was concluded that the pump sump filled up with river water causing the emergency overflow to activate. There is an open, elevated manhole adjacent to the River Parmadden close to the pump station. Due to the extremely high water level, on that day, this manhole was submerged allowing river water into the collection network and ultimately going to the pump sump. As part of the Network Contract, currently ongoing, this manhole will be eliminated, preventing any further such incidences. The network upgrade contract is due to be completed by mid Clarify whether there are screens on the stormwater overflow (SWO) and identify if the SWO may be impacting on surface water quality; On completion of the upgraded works all influent to the Duleek Wastewater treatment plant will be screened at the inlet works. Stormwater will only overflow post inlet works. The stormwater will be mechanically screened. There will be 2No. Mechanical Screens each with the capacity to handle in excess of 8 DWF. They will be in a duty assist arrangement, thereby allowing even greater screening capacity in the event of extreme storm conditions. There will also be a manually raked by pass 6mm bar screen with a capacity of m³/h. Hence, all stormwater discharge will be screened and will not impact on surface water quality. Evidence of any hydraulic modelling or design discharge frequency of the SWO in order to ascertain whether it complies with the definition of a storm water overflow. The WwTW was not modelled as part of the Duleek Catchment Model Study. A Storm tank will be provided at the wastewater treatment plant to reduce the potential for overflow from the wastewater treatment plant. Page 3 of 19

4 Formula A as detailed in the Department of the Environment Procedures and Criteria in Relation to Storm Water Overflows relates to storm overflows within the sewerage network rather than at wastewater treatment plants. There are no storm overflows within the sewerage network. All flows are transferred to the wastewater treatment plant in Duleek. The storage volumes stated in the Department of the Environment Procedures and Criteria in Relation to Storm Water Overflows have been used to provide an evaluation of the adequacy of the storm tanks provided for Duleek. Formula A = DWF P + 2E Daily domestic flows = m 3 /day Daily non-domestic flows = m 3 /day The flows are based on a flow of 225 litres per PE per day The 95%ile flowrate in the River Nanny at the discharge point of the overflow from the storm tanks is: 0.06m 3 /s The Dry Weather Flow to the wastewater treatment plant is; 18.23l/s = m 3 /s. The dilution factor in the River Nanny is: 0.06 / = 3.29 The required storage volume based on a dilution rate of >2 = 80l/hd (UWWTD 91/271/EEC, Table 3). The required storage volume = 80l/hd x 7,000pe = 560m 3 The volume of the stormwater tank is 980m 3. The stormwater tank capacity is approximately 43% larger than that required and therefore complies with the design criteria as per Procedures and Criteria for Storm Water Overflows, published by the Dept. of the Environment, Section D: Discharges to the Aquatic Environment Provide date(s) when all monitoring was carried out in Table D.1 (i)(b) and Table D. 1 (i)(c); The monitoring was carried out on the 21 st and 22 nd August The results entered are the average over the 2 days sampling. Clarify the name of the River 'into which the SWO at Easting and Northing ; 'SW2' discharges. The Storm Water overflow SW2 connects to the Primary discharge pipeline and is discharged with the final effluent from the treatment plant into the River Nanny. Section E - Monitoring Assimilative capacities - provide workings in relation to Suspended Solids. The allowable level of suspended solids in the effluent from both the existing and upgraded wastewater treatment plants is 35mg/l. Page 4 of 19

5 WWTP Flow (m 3 /day) = 1,575 m 3 /day Level S.S. = 35mg/L Effluent load to the River; (35 x 1,575)/1000 = kg/d 95%ile Flow of River Nanny = 0.06m 3 /s Increase in River 95%ile flow; x 10 6 /[0.06 x (3 x 3600 x 24)] = 10.63mg/L There is no background monitoring of suspended solids in the river. However, the increase in suspended solids due to the effluent is low relative to the limit of 25mg/L. As attachment E4 of the WwDL application shows, 83% of the Meath County Council Final effluent samples were significantly below the required 35mg/L TSS, therefore the effluent limit of 35mg/L is considered acceptable. Also note, as per table 1.1 above, all Meath County Council Final effluent samples from August to December 2008 are significantly below the effluent limit of 35mgTSS/L. Section F: Declaration Complete Section H: Declaration and scan the signed declaration for electronic submission. A signed copy of Section H is attached in appendix 4. Page 5 of 19

6 APPENDIX 1 UPDATED NON-TECHNICAL SUMMARY Page 6 of 19

7 NON TECHNICAL SUMMARY 1.0 Introduction The waste water works serving the town of Duleek comprises of a network of sewers, a pumping station and a wastewater treatment facility. The wastewater treatment facility, currently in construction, is replacing the older facility that was built during the 1970 s and is now overloaded. The new wastewater treatment plant is due to be completed and fully operational in January Duleek town is located in the eastern part of County Meath. It is on the R150 to Laytown and close to the R152 to Drogheda. Duleek lies approximately 8kms from Drogheda and 19kms from Navan. The River Nanny runs through the town. The location of the town close to the M1 Dublin-Belfast motorway and the Drogheda by-pass means that it has experienced a significantly higher growth in population than other parts of the county. The new wastewater treatment plant includes storm tanks, inlet works, anerobic, anoxic and aeration tanks, sludge pumping station, sludge holding tank, sludge dewatering building, administration building etc. all of which are contained within a land area to the south west of the existing plant. The existing population equivalent of the town is approximately 4,645p.e. Phase one of the new treatment plant is designed for 7,000p.e. The new WwTW is designed and will be constructed to facilitate a future phase 2 expansion to 10,500p.e. should the demand for same arise. The existing pumping station will be upgraded to handle the increased pumping capacity. This will include the installation of 3no. VSD pumps. New twin rising mains will be constructed up to the new wastewater treatment plant. The existing and only pump station emergency overflow is to the River Parmadden. 2.0 Summary of Current Waste water treatment works Currently the influent to the treatment plant is treated in an extended aeration process with a design capacity of 2,500 p.e. The existing population equivalent is estimated as 4,645. The existing wastewater treatment plant is currently overloaded. It is providing a high level of treatment during dry weather conditions. The new wastewater treatment plant is due to be completed and fully operational in January The current operational plant consists of; Extended aeration Basin (using a diffused air aeration system) Page 7 of 19

8 o Volume = 660m 3 o Liquid depth = 1.8m Clarifier Phosphate Removal (Ferric Dosing) RAS pumps (Return Activated Sludge) Control Room (along this the control panels this also houses the air blowers and ferric dosing equipment) The effluent is pumped, from the existing pump station in the town via the existing rising main, directly to the extended aeration basin. Here it is aerated using a diffused air aeration system in a carousel type extended aeration basin. Ferric sulphate is dosed into the flow between the extended aerator and the clarifier. This dosing facility was added in 2001 to aid phosphorus removal. In the clarifier the sludge settles, allowing the clear, treated effluent to be discharged to the River Nanny (as per drawing DL-DK-12 in appendix 3) Some of the settled sludge is returned to the aeration tank, via the RAS pumps. The remaining sludge (WAS Waste Activated Sludge) is drawn from the clarifier to the sludge holding tank. From here the sludge is tankered to the main Sludge Acceptance Centre in Navan, Co. Meath. 3.0 Description of Waste Water Treatment Works (in construction) The treatment plant in construction consists of preliminary and secondary biological treatment with nutrient removal and is designed to cater for a population equivalent of 7,000. The plant will include the following: Sewer Network The wastewater collection and disposal system discharges by gravity to the main pumping station in the town. From here it is pumped to the wastewater treatment plant. This collection system and pumping station is currently being upgraded and expanded to cater for the projected population in the town. Pumping station 3No foul pumps (duty/assist/standby) Storm screen (6mm mesh size) Pump sump over flow The wastewater is pumped from the main pump station to the treatment plant proper via 2No. 300mm diameter rising mains. In the event of pump failure, power failure or extreme storm conditions the pump sump will overflow through a Page 8 of 19

9 6mm mechanical mesh and out to the River Parmadden via a 600mm diameter overflow pipe. Treatment Plant Preliminary treatment to include screening, grit and grease removal Biological treatment and phosphorus removal Liquid sludge storage Sludge dewatering and cake storage Imported sludge facilities Storm treatment. The sources of emissions from the waste water works Primary Discharge Effluent Outfall from Treatment Plant Proper Treated effluent will be discharged from the wastewater treatment plant to the River Nanny via a single outfall. For the new treatment plant a new outfall will be built approximately 50m upstream of the current outfall point. The outfall currently in use will be made redundant once the new one is operational. Storm Water Overflows Should flows to the inlet works exceed the capacity, the peak design flow of 197m3/h, then excess sewage overflows to the storm tank via a storm overflow wall in the inlet works channel. The effluent outfall pipe shall be designed to incorporate the screened storm tank overflow and shall be below the water level of the river at all times of the year and shall include a diffuser on the outlet. Secondary Discharge Not Applicable Existing Sewerage Network Overview The existing wastewater collection and disposal system discharges by gravity to the main pumping in the town. From here it is pumped to the wastewater treatment plant. New twin rising mains will be constructed up to the new wastewater treatment plant from the pumping station. Page 9 of 19

10 3.0 The nature and quantities of emissions from the waste water works (into the receiving aqueous environment as well as identification of significant effects of the emissions on the environment) The existing plant has a design capacity of 7,000pe and a design effluent quality (to the primary discharge point) as follows; Parameter Concentration BOD 5 (mg/l) 18 Total Suspended Solids (mg/l) 30 COD (mg/l) 125 Total Nitrogen (mg/l N) 20 Total Phosphorus (mg/l P) 1.0 As can be seen, the Duleek treatment facility complies with the requirements of the Urban Waste Water Directive, which stipulate; BOD 25mg/L Total suspended solids 35mg/L 4.0 Identification of significant effects of the emissions on the environment Emissions from the WWTW are to the River Nanny. There are EPA monitoring stations, on the River Nanny, up and down stream of the primary discharge point. Upstream Monitoring Station Q value = 3-4 Downstream Monitoring Station Q value = 4 Provision of this performance based treatment system will significantly improve the quality of the effluent to the adjacent River Nanny. The Treatment Works will be required to meet the effluent quality standards as set out in the Urban Wastewater Treatment Regulations, 2001 and in all current regulations governing discharges to freshwaters. 5.0 The proposed technology and other techniques for preventing or reducing emissions/pollution from the waste water works The existing wastewater treatment works was built in 1977 with refurbishment works completed in It is an extended aeration process with a design capacity of 2500 p.e. The existing plant is providing a reasonable level of Page 10 of 19

11 treatment during dry weather conditions. During wet conditions, the plant is hydraulically overloaded and unable to provide adequate treatment. The plant is currently being replaced and the provision of the new works will significantly improve the quality of the effluent to the adjacent River Nanny. This waste water discharge licence submission is based on the treatment plant currently under construction. A Design, Build, Operate (DBO) contract to provide a new pumping station and treatment plant commenced in November The contract was awarded to EPS. EPS took over the operation of the plant in March Commissioning and operation of the new plant is due to commence in December 2009 and EPS will then be responsible for the operation and maintenance of the new WwTW and pumping station for 20 years thereafter. 6.0 Measures planned to monitor emissions into the environment As a minimum the following instrumentation is being provided in the new treatment plant; (i) ph measurement of influent and effluent. (ii) (iii) Flow measurement for influent, flow to full treatment, flow to storm tank, storm return, final effluent, return activated sludge, surplus (waste) activated sludge, supernatant return and flow to dewatering. Dissolved oxygen and suspended solids measurement shall be provided for each biological treatment unit. (iv) Ultrasonic level measurement in all pump sumps, the stormwater tank and in the sludge holding tank. In addition, fixed refrigerated automatic flow proportional composite samplers shall be provided for the influent and effluent. 7.0 Other The existing wastewater treatment plant provides effective wastewater treatment for Duleek. However, due to recent developments in the town, the plant is currently overloaded. EPS Limited is operating the existing wastewater treatment plant until the new wastewater treatment plant is fully operational, due January The new wastewater treatment plant and main pumping station will provide effective treatment of wastewater from Duleek with a capacity which is Page 11 of 19

12 anticipated to be sufficient for a 20-year horizon. The provision of increased capacity at the main pumping station in Duleek will reduce the potential for any stormwater overflows within the sewer network. Page 12 of 19

13 APPENDIX 2 PLANNING PERMISSION Page 13 of 19

14 Duleek WwTW WWDL Application - Article 16 Reply Page 14 of 19

15 APPENDIX 3 DRAWING NO DL-DL-11 (Layout of Existing Sewerage Treatment Works) DRAWING NO DL-DL-12 (Existing WwTW Primary Discharge Point) Page 15 of 19

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18 APPENDIX 4 SECTION H: DECLARATION Page 18 of 19

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