ANNEX C INFRASTRUCTURE & OPERATION

Transcription

1 ROSCOMMON COUNTY COUNCL MONKSLAND WASTEAWATER DSCHARGE LCENCE ANNEX C NFRASTRUCTURE & OPERATON

2 Roscommon County Council WWD Application Attachment to Form C1.1 Design Criteria The Monksland WWTP is situated on a c2.75ha site in the Monksland ndustrial Estate, off the Tuam Road (R362). The plant was upgraded to a capacity of 10,515 PE in An extension to this upgraded works to facilitate treatment of additional process waste from Élan Corporation was commissioned in May 2003, increasing the capacity of the plant to 14,381 PE. The design loading of the existing plant is summarised in Table C-1.1. Table C.1.2 gives the effluent standards that the plant is designed to achieve. ` Parameter BOD 5 Parameter Suspended Solids COD Phosphorous Design Loading of WWTP Equivalent Population (BOD 5) 14,381 Equivalent Population (Hydraulic) 11,667 Existing Units persons persons Total BOD kg/day Total DWF 2,100 m³/day Peak Flow 45.6 l/sec Table C.1.1 Design Loading of Existing WWTP Table C.1.2 Design Effluent Standards C.1.2 Plant Equipment Minimum Standard 20 mg/l 30 mg/l 125 mg/l 2 mg/l The existing municipal treatment works comprises the following elements; Preliminary equipment including 6mm spiral screen and flow measurement Balancing tank and associated pump sump 2 no. high rate biofilters and associated recirculation chamber Humus/intermediate settling tank and associated sludge draw off chamber Aeration bypass chamber Fine bubble diffused aeration tank Attachment C.1 Operational nformation Requirements C- 1/5

3 Roscommon County Council WWD Application Attachment to Form Secondary settling tank Activated sludge return chamber Sludge thickening and dewatering plant Phosphate removal facilities Control building Workshop building Sludge dewatering building Effluent measurement and sampling chamber. C.1.3 Plant Process Flow enters the wastewater treatment works by gravity and is directed to the inlet works. After passing through the spiral screen, flows in excess of 2.5 times dry weather flow (DWF), overflow to the balancing tank. Flows up to 2.5 times DWF are then pumped to the high rate biofilter. Flow collects in the base of the tank and is directed to the recirculation chamber. An actuated valve located in this pump sump maintains a recirculation rate of 10 litres/second. This valve closes when flow into the sump exceeds 10 litres/second, thereby forcing flow over a weir and into the humus tank. The valve opens when the flow drops below 10 litres/second and returns filtrate to the pump sump within the balancing tank. The biofilters are currently achieving up to an 80% BOD removal rate. Settled effluent overflows to the aeration tank via the aeration bypass chamber. The aeration tank has a duty/standby variable speed blower system with dissolved oxygen (DO) control. Air diffusion is achieved via 225 membrane diffusers. From here, mixed liquor drains to the secondary settling tank. Sludge is drawn off from the humus tank to the humus sludge pumping station and mixed with surplus activated sludge, from where the mixed sludge is pumped to the sludge thickening tank. The thickened sludge is drawn off daily and dewatered by a belt press located in the sludge dewatering building on the site. Attachment C.1 Operational nformation Requirements C- 2/5

4 Roscommon County Council WWD Application Attachment to Form Phosphate reduction is achieved by dosing ferric sulphate into the effluent at either the recirculation chamber or the aeration bypass chamber. Final effluent is discharged to the Cross River. The process flow diagram below details the various processes Supernatent Dried Sludge Removed By Specialist Contractor Sludge Dewatering Supernatent Sludge Holding Tank Sludge Sludge PUMPNG CHAMBER BALANCE TANK BOFLTERS (2 No.) NTERMEDATE SETTLNG EXTENDED AERATON 2.5 DWF NLET m m 3 133m 2 kg/day 3 295m C.1.4 Effluent Standard OVERFLOW FNAL SETTLEMENT The existing plant has been designed to the following final effluent specification; Biochemical Oxygen Demand < 20 mg/l O 2 Suspended Solids < 30 mg/l SAMPLNG CHAMBER & FLOW MEASUREMENT CROSS RVER Chemical Oxygen Demand < 125 mg/l O 2 Total Phosphorus < 2 mg/l Results from the plant over the past 18 months indicate that the following final effluent parameters are being achieved in general; Biochemical Oxygen Demand < 5 mg/l O 2 Suspended Solids < 20 mg/l Chemical Oxygen Demand < 56 mg/l O 2 Ammonia < 1 mg/l Total Organic Nitrogen < 25 mg/l Total Phosphorus < 2 mg/l Attachment C.1 Operational nformation Requirements C- 3/5

5 Roscommon County Council WWD Application Attachment to Form C.1.5 Process Control Most elements of the treatment works mentioned in C.1.2 are monitored by the SCADA system in place at the treatment works. There are two full time staff employed at the plant supported by a technician who is responsible for overall process control at Monksland Wastewater Treatment Works and all other wastewater treatment works in Roscommon County Councils functional area. The Technician is based in Roscommon Wastewater Treatment Works where there is a SCADA linkup. All data can be viewed in Roscommon but no changes to the control philosophy can be made at this remote terminal. The full time staff includes a caretaker who carries out his duties under the guidance and instruction of the Monksland Area Engineer.The caretaker makes any process alterations requested by the Technician and carries out day to day maintenance works including the operation of the sludge dewatering facilities. An Assistant Caretaker assists the caretaker with his duties and provides cover during the caretaker s absence and at weekends. Both caretaking staff can monitor alarms from the works via mobile phone. C.1.6 Description of Overflows There are emergency overflows included in the pumping stations at Bellanamullia, Cushlea and Summerhill. Three other pumping stations controlled by the Roscommon County Council do not have overflows. These overflows are described in more detail in Section C.2. There are no storm overflows associated with the works. C.1.7 Laboratory Testing and Facilities. There are flow monitoring and sampling points located at both the inlet and outlet to the treatment works. The monitoring points are to measure and record flow data of the influent and effluent flow lines. There is a fully equipped laboratory at the Monksland Waste Water Treatment Works. Most of the samples taken are tested in the Roscommon County Council laboratory in Roscommon. Attachment C.1 Operational nformation Requirements C- 4/5

6 Roscommon County Council WWD Application Attachment to Form Composite samples of the influent and effluent are tested on site for COD and suspended solids. Phosphate levels of the samples are also tested on site to determine phosphate removal. Samples are taken from the intermediate clarifier at the point where effluent leaves the channel and the ph of the influent as well as the dissolved oxygen levels in the aeration tank are monitored continuously. There is a sampling point located upstream of the primary discharge point (at Burnbrook Bridge) and downstream of the primary discharge point (at Crannagh Bridge). Grab samples are collected from the river via bucket and rope from the respective bridges and are taken for analysis to Roscommon County Council laboratory. 1 litre sample bottles are rinsed out with the sample, filled and labelled with the location and date of the sample. All information is recorded in the field sheet. Sample details are entered into Labinfo and given a unique reference number. All relevant information is recorded in the Samples log book. The sampling procedure is Standard Operating Procedure (SOP) 900. Refer to Attachment E.2 for a detailed description on Roscommon County Council s laboratory procedures. Attachment C.1 Operational nformation Requirements C- 5/5

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