Bioresources Permitting Worcester STW Substantial Variation Application
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ST Classification: UNMARKED Bioresources Permitting Worcester STW Substantial Variation Application Document No. | 0.1 February 2021 Severn Trent Water Ltd EPR/ZP3498ER Worc ester ST W Su bstan tial Vari atio n App licatio n Sever n Tr ent Wa ter L td Worcester STW Substantial Variation Application ST Classification: UNMARKED Bioresources Permitting Project No: B1958992 Document Title: Worcester STW Substantial Variation Application Document No.: Document No. Revision: 0.1 Document Status: <DocSuitability> Date: February 2021 Client Name: Severn Trent Water Ltd Client No: EPR/ZP3498ER Project Manager: Rob Bainbridge Author: Mark McAree File Name: Worcester application final Jacobs U.K. Limited Jacobs House Shrewsbury Business Park Shrewsbury Shropshire SY2 6LG United Kingdom T +44 (0)1743 284 800 F +44 (0)1743 245 558 www.jacobs.com © Copyright 2019 Jacobs U.K. Limited. The concepts and information contained in this document are the property of Jacobs. Use or copying of this document in whole or in part without the written permission of Jacobs constitutes an infringement of copyright. Limitation: This document has been prepared on behalf of, and for the exclusive use of Jacobs’ client, and is subject to, and issued in accordance with, the provisions of the contract between Jacobs and the client. Jacobs accepts no liability or responsibility whatsoever for, or in respect of, any use of, or reliance upon, this document by any third party. Document history and status Revision Date Description Author Checked Reviewed Approved Document No. i Worcester STW Substantial Variation Application ST Classification: UNMARKED Contents 1. Introduction ............................................................................................................................................................ 3 1.1 Non-Technical Summary ..................................................................................................................................................... 3 2. Technical Description ........................................................................................................................................... 5 2.1 Regulatory listing .................................................................................................................................................................... 7 3. Application Form Questions:............................................................................................................................... 8 3.1 Form C2 ...................................................................................................................................................................................... 8 3.2 Form C2.5 ............................................................................................................................................................................... 18 3.3 Form C3 ................................................................................................................................................................................... 22 3.4 Form C4 ................................................................................................................................................................................... 55 CHP engine 1 ......................................................................................................................................................................................... 66 Boiler 1 .................................................................................................................................................................................................... 67 Boiler 2 .................................................................................................................................................................................................... 68 Appendix A. Figures A.1.1 A.1.2 A.1.3 A.1.4 Process Flow Diagram Appendix B. Certificates Appendix C. Air Dispersion Modelling Report Appendix D. Annex 1 of MCP Appendix E. BAT Assessment Appendix F. H5 Site condition report Appendix G. Odour Management Plan Document No. ii Worcester STW Substantial Variation Application ST Classification: UNMARKED 1. Introduction This application relates to a bioresources treatment permit for the Worcester Sewage Treatment Works, operated by Severn Trent Water Ltd. The site is currently permitted for the import of non-hazardous tanker trade waste for treatment through the aerobic treatment route at the site. This operation remains unchanged by this variation, although a clarified set of EWC codes has been provided, in line with current Environment Agency (EA) guidance. This substantial permit variation application relates to the addition of a listed activity to the site, that of biological treatment of waste under the Industrial Emissions Directive. It relates to the non-urban waste water treatment directive (UWWTD) treatment of indigenous UWWTD derived sludge and imported UWWTD sludges from other works and cess and septic tank imported material which is of a similar composition. Note that these operations are currently operated at the site, under the UWWTD. As part of this installation, there is also the replacement of an existing CHP engine with the replacement being classified as a ‘new’ medium combustion plant and specified generator at the site. This new CHP and aspects of the anaerobic digestion process will require an extension to the current site boundary. The listed activity starts from the point of the separation of the sludge from the main UWWTD treatment stream, through to its storage on the site cake pad, prior to its recovery to land offsite. The additional aspects of the permit includes the biogas handling and treatment system as a directly associated activity, including a biogas fuelled gas engine, covered by the Medium Combustion Plant Directive. A number of other activities are undertaken at the site, outside of the scope of this permit, relating to the treatment of sewage derived materials through aerobic processes. These activities are covered by the UWWTD. 1.1 Non-Technical Summary This application is for a substantial variation to environmental permit EPR/ZP3498ER/V003 under the Environmental Permitting (England and Wales) Regulations 2016 (as amended), following a change of interpretation of the Urban Waste Water Treatment Directive by the Environment Agency. The current permit for the site covers the treatment of non-hazardous tanker delivered trade wastes in liquid and thin sludge form and wastewater, up to a maximum of 150,000 m3 per annum, brought to site for treatment through the aerobic treatment processes on site, as part of the operation of the wider sewage treatment works. Previously, sewage treatment sites operated by sewerage undertakers importing sludges and liquids were only regulated for the import and treatment of these materials to the wider site and indigenous sludges arising from the treatment of sewage were not required to be included in the sludge treatment permit. It has now been determined that indigenous sludges do need to be permitted as they fall outside of the Urban Waste Water Treatment Directive (UWWTD). This variation application is : • To update the tankered trade wastes accepted on site for treatment through the aerobic processes on site; • To incorporate the addition of a new listed activity to the permit, that of biological treatment by anaerobic digestion, to make this an installation permit; • To add the operation of a biogas fuelled Combined Heat and Power unit on the site; and • To amend the site boundary to include the area occupied by the CHP unit, associated pipework and other infrastructure. The installation covers the biological treatment of sewage sludge, both indigenous and imported from other waste water treatment sites, by anaerobic digestion, with a capacity above the relevant threshold. There are a Document No. 3 Worcester STW Substantial Variation Application ST Classification: UNMARKED number of directly associated activities, including the operation of a biogas fuelled CHP unit for the generation of electricity and heat at the site, which is classified as a ‘new’ combustion source under the Medium Combustion Plant Directive. The site is located to the west of the River Severn to the south of the town centre. The waste activity comprises an offloading coupling for tankers to discharge through, located at the works inlet. All tanker trade imports are passed through a logger to record the incoming volume and the company carrying out the import. The import is directly into the works inlet, with no holding or blending tanks before the import. Once the tanker trade waste has mixed with the incoming UWWTD material, its treatment falls outside the scope of the Environmental Permitting Regulations. The installation is for the biological treatment of non-hazardous wastes by means of anaerobic digestion. It comprises a set of three import tanks, for sludge transfers from other waste water works. This material is transferred, via a wet well into a blending tank. The blend tank also accepts the indigenous sludge separated from the main aerobic treatment flow and site derived SAS (surplus activated sludge) from a separate wet well. The blending tank is used to ensure that the incoming materials are properly mixed to give a more homogeneous mixture, prior to transfer to one of the two primary anaerobic digesters located at the site. Both digesters are manufactured of concrete and operate