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AECOM
Project: Meary Veg WwTW - Sludge Import, Thickening and Storage Facility
Subject: Planning Design Report Prepared by: Martin Weeks Reviewed by: Nick Robinson Approved by: Mark Badcock Date: 8th August 2012 Date: 8th August 2012 Date: 8th August 2012
BACKGROUND
The Isle of Man Government is providing significant investment in the Island's wastewater network and sewage treatment works, to improve water quality around its shores. A key part of this investment is the Sludge Import, Thickening and Storage Facility located within Meary Veg WwTW. This new facility will receive sludge from satellite treatment facilities, constructed as part of the islands improvement works. The facility will also provide additional benefit to the sludge treatment process at Meary Veg WwTW by providing greater flexibility in the management of surplus activated sludge from the process stream.
FACILITY DESCRIPTION
The proposed Sludge Import, Thickening and Storage Facility at Meary Veg WwTW will allow sludge, from satellite treatment works, and septic waste from around the Island to be imported. In addition sludge storage tanks will provide a means of storing and gravity thickening both the imported and indigenous sludge before it is transferred to the sludge treatment process. Septic Waste will be stored in a balance tank before being pumped to the treatment process at a controlled rate.
The imported streams comprise:
Sludge or septic waste will be unloaded from tankers and passed through a screen where any rag contained within the sludge will be removed. The screened sludge will gravitate to a small tank from where it will be pumped to the sludge storage tanks.
3 no. 600 m³ Sludge Storage Tanks will be installed within the facility. Two of the tanks will be used to store and gravity thicken the sludge. The third tank will be used to store the thickened sludge prior to transfer to the treatment process.
1 no. 100 m³ septic waste balance tank will be installed within the facility to store imported septic waste, prior to being pumped into the wastewater treatment process.
Transfer pumps and mixer pumps will be installed externally to each of the tanks to allow the contents to be mixed and pumped to the downstream process.
Direct Tel: +44 (0)1392 66 3227 T +44 (0)1392 663200 F +44 (0)1392 663299 E [email protected]
Belvedere House Pynes Hill Exeter EX2 5WS United Kingdom
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AECOM
3 no. pumps will be installed to pump the thickened sludge to the downstream process. 1 no. Odour control system will be installed to provide mechanical ventilation to the sludge storage tanks and equipment. 1 no. Motor control centre will be installed to provide control and monitoring of the equipment installed within the facility. The colour of all exposed surfaces of tanks and kiosks will be dark green.
The location of the sludge import facility has been selected to limit the distance that sludge needs to be pumped between processes while ensuring safe access for sludge tankers and safe working areas for operatives.
All structures and equipment used for the conditioning and storage of the sludge are sealed from the atmosphere and linked to a mechanical ventilation system. The mechanical ventilation creates a negative pressure within the structures and equipment thus preventing release of odours. The extracted air is transferred to a two stage odour control (removal) unit before being released into the atmosphere.
Rag removed from the imported sludge, as it passes through the import screen, will be washed before being compacted and discharged into continuous polythene bag system. This system eliminates the risk of odour discharge from the screenings.
Where possible the equipment has been located to allow gravity flows between the process elements. Storage tanks are constructed above ground level to enable decanting (draining of liquors above the settled sludge) to be under gravity conditions. Further benefits of above ground tanks, in addition to reduced construction costs associated with sub surface structures, are the following operational and maintenance benefits:
Storage tanks are protected from any potential impact, resulting from tanker movements or site vehicles, by the nature of their location or the installation of protective barriers or bollards.
The external lighting design approach ensures nuisance lighting is avoided. External lighting will be installed within the facility to provide safe access for the tanker deliveries and operatives during times of low light levels. Where changes in level exist, on access paths within the facility, occupancy sensing
Direct Tel: +44 (0)1392 66 3227
Tel: +44 (0)1392 663200
Belvedere House
Pynes Hill
Exeter
www.aecom.com
Page: 2 of 3
Doc. F8/13 Revised April 2009 www.aecom.com
EX2 5WS
United Kingdom
01/120608 Meary Veg WwTW Planning Design Report M6.doc
using Passive InfaRed (PIR) sensors will be installed to activate walkway lighting. General lighting for the facility will be activated by manual switching. All lighting will be automatically switched off during normal day light hours and following expiry of a timer following activation.
The project will include the excavation of material from the site as part of the construction works. At this stage it is estimated that approximately $4,400 \mathrm{~m}^{3}$ will be excavated. This material has been previously tested and been found to be inert (i.e. not contaminated). Options for the disposal of this material will be determined at the construction phase, but may include the deposition of the material on agricultural land adjacent to the site. If this is the case, this will be subject to separate planning application.
Sapling trees which have been recently planted by the Department of Environment Food and Agriculture (DEFA), that are affected by the scheme, are to be uprooted and replanted elsewhere on the site.
The scheme design has been subject to an environmental impact assessment covering noise, odour and trafficking. Through the selection of equipment and location of plant, the impact on the environment has been minimised.
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