Purton WTW Electrochlorination

Customer: Black & Veatch

Site Owner: Bristol Water

Value: £516k

FSD were awarded a contract for the electrical and mechanical works associated with the installation of an Electrochlorination plant at Purton Water Treatment Works in Gloucestershire.

Raw water is extracted at Purton from the Gloucester & Sharpness Canal, and disinfection is required during the summer months to control the seasonal growth of zebra mussels, which attach themselves to hard surfaces, clogging inlet pipes and reducing the hydraulic capacity of the system. Previously these were controlled by heavy doses of chlorine at the intake, with the chlorine stored in a bulk storage facility; this is to be replaced by an electrolytic chlorination process to satisfy regulatory H&S issues. This is a prototype process in the UK. The total Electrochlorination package was supplied by Grundfos.

Electrical Scope:

  • Design, supply, installation, termination and testing of all cabling and cable support systems
  • Design, manufacture, testing and installation of the dosing pipe leak detection marshalling box including Hawker DC1/P Level Control Relays (one for each catchpot)
  • Supply and installation of suitable isolation
  • Supply and installation of instrumentation
  • Design, supply, install, test and commission trace heating for Salt Saturators and Hypochlorite Storage Tanks
  • Design, supply, install, test and commission access lighting in the area of the Salt Saturators and the Hypochlorite Storage Tanks
  • Design, supply, install, test and commission a complete lightning protection scheme for the tanks, including the provision of an earth loop around these structures, earth rods as necessary, bonding of the base slab reinforcing and bonding to the main electrical earth

Mechanical Scope

  • Installation of Service Water Panels
  • Installation of Strainer and Water Softening Packages
  • Installation of Water Heating Systems
  • Installation of Brine Transfer Pump Skid Packages
  • Installation of Selcoperm Electrolyser Packages
  • Installation of Acid Cleaning System
  • Installation of free issue 1m3 NaOCL (Sodium Hypochlorite) Intermediate Tank and NaOCl Solution Transfer Pump Packages
  • Installation of one free issue Hydrogen Gas Detection Package
  • Installation of one free issue Emergency Dilution Panel Package
  • Installation of one free issue Dosing Pump Skid inside GRP cabinet
  • Installation of two free issue Dosing Packages each inside a GRP Cabinet
  • Installation of double contained chemical dosing lines including catch pots and final connections; (Just under 1000mts of Flexible Double Contained Pipework fitted with 14 Bespoke Catchpots)
  • Design, supply and installation of all interconnecting pipe work
  • Supply and install valves and fittings between the termination points
  • Design, supply and install trace heating and lagging
  • Design, supply and install all required access metal work.(Including High level Access Platform and Up and Over Stairways to Chemical Bunds)
  • Design, supply and install hydrogen vent pipe work.
  • Design, supply and install Hot Air Ducting to convey hot air from the cooling fans installed in the Rectifiers; the ducting is designed such that the hot air can be diverted from its normal venting to outside atmosphere, to inside the main building to aid with heating during the winter months.

Although the actual process of Electrochlorination is relatively simple, the interconnection of all of its peripherals was complex, and there were additional challenges associated with the design and supply of a completely new plant equipment package.

The interaction between all M&E stakeholders on site was a success, as regular communication between Site Supervisors and both Electrical and Mechanical trades remained constant, resulting in efficient teamwork. Initial client feedback has been extremely positive for the project as a whole.

The Design, Supply and Installation phase of the contract is now complete, with commissioning ongoing.

Additional photographs can be viewed in our Gallery.