Pressurised pipe cleansing services - Water Industry

Description

Severn Trent Water wishes to improve its ability to cleanse pressurised wastewater assets rising mains (RM) and clean water mains to address potential problems within its asset base. Failure to do this could otherwise result in wastewater assets presenting with rising main blockages, asset failure and lead to further problems such as blockages/pollution/sewer flooding. Within the clean water network this is to remove biofilms and the risk to water quality. Part of the solution to achieving this goal is to have a way of cleansing these pressurised pipes which, in some instances are >500m long and only have one means of insertion and one means of extraction sometimes ~2km away. STW would like to move into a proactive space for asset cleansing without causing disruption through asset failure. We currently do not have a similar solution within the business and are therefore looking to explore delivery solutions as part of this pre market engagement. Lot 1: Assumptions & Constraints • Wastewater rising mains are generally 80mm to 400mm in diameter and lengths typically range from ~500m to 2km, with some being 5km. They generally only have one access point on the RM and the intention is to cleanse the pipe without the need to cut in every 50-200m as would be required with traditional jetting techniques. • Connection points such as bower couplings and/or air valves are assumed to be present near the wastewater sewage pumping station (SPS) to allow insertion of pipe cleaning. Basic adjustments will be the responsibility of the contractor i.e. connection to or removal of bower, but significant adjustments of pipework will be the responsibility of STW. • The pipe material will have been identified prior to cleansing and it is expected that the cleansing will work on the majority of pipe materials. Asbestos may require additional H&S measures, and ductile iron mains, which typically experience galvanic corrosion may be excluded. • Flow and pressure (or assumed) will be provided prior to cleaning works and work is expected to be carried out within acceptable limits to prevent the cleansing works as not to risk, bursting the main. • Assets along the rising main length will be identified where present, especially where the RM length is >500m, although it is assumed that any assets do not have isolation valves present on the RM itself, rather only on the spur so unlikely to be of use for insertion/extraction. Where present these will be identified. Air valves should have been inspected/serviced prior to cleansing. • Rising mains will have been selected for cleansing on the basis there are restrictions assumed to be as a result of blockages / sedimentation, which the cleansing will remedy. • Flow management of existing flows to the SPS will be an important consideration. Solutions where the rising main can be kept in service are preferred, although solutions where reduced tankering can be used, or even isolation of the main itself for the duration of the cleansing. Flow management is the responsibility of STW unless otherwise agreed. • Customer management will be the responsibility of STW. • Traffic management will be the responsibility of STW. Access is expected to be available within 30m of the SPS or clean water insertion point, and access is also expected within 30m of the discharge/extraction point for removal of arisings. • Contractors will be responsible for Health & Safety and will comply with STW safe systems of work including confined spaces, where necessary. • For clean water sites it is assumed that STW operatives will isolate the sections of pipe prior to cleansing. They will also ensure the area is rezoned accordingly to ensure or customers are informed as necessary. • Following the cleansing of a water main, STW will take water quality samples to prove the main holds water that is 'good to drink', no taste & odour concerns, no chemical or biological residuals on the main before a return to service. • Extraction of waste arisings will be undertaken by the contractor so that the arisings do not pass down the system. Where the rising main discharges into a trunk sewer that goes directly to a large works this requirement may be forfeited. • The contractor will provide a written report within 2 weeks of completion with a description of the works, photos and results. This will be cross referenced with STW flow & pressure readings to demonstrate the benefits. Minimum Viable Product (MVP) Criteria Improvement in flow: The cleansing of the rising main must produce improvements in flow, (Reduction in pressure) and/or reductions in pressure. Sediment removal: The cleansing should demonstrate removal of arisings at the discharge. Flow/Pressure one week on: The improvement in flow/reduction in pressure should last more than 7 days. Failure to do so would suggest that cleansing is not the root cause of performance, rather pump issues, trapped air or other. Water Quality (Clean only): Reduction in coliforms (or other water quality metrics). ADDITIONAL CONSIDERATIONS The following considerations are not compulsory for the MVP, but would add to the value of the solution should they be incorporated into the design: • Management of flows whilst cleansing activities are undertaken • Ability to be re-located / re-used, and number of vehicles being used OTHER / OPERATING CONSIDERATIONS Consideration should also be given to the following environmental factors: • Ensuring the debris removed from cleansing works does not block the sewer   INSTALLATION / EXTRACTION METHOD We are interested in hearing from Suppliers who have experience in pressurised pipe cleaning and would like to discuss further.