CASE STUDY: HAZOP Study of a Biothelys Thermal Hydrolysis Plant for Oxford Sewage Treatment Works

HAZOP Facilitation and Recording

Thames Water had awarded a design and build contract to KE Water (a joint venture between Enpure and Kier Construction) to design and build a new Sludge Treatment Facility at Oxford Sewage Treatment Works (STW). This new facility included a Thermal Hydrolysis Plant (THP), the design of which had been produced by Veolia Water Services (VWS).

Subsequently Enpure went into administration, leading to the dissolution of KE Water. However, Kier Construction maintained its commitment to the project through a new joint venture company with AECOM.

This was only the second time that VWS had designed such a plant for operation in the UK and so the technology was still considered to be relatively novel. It was therefore important to ensure that any risks (whether inherent in the design or with the potential of manifesting themselves during operation of the plant) would be identified and managed adequately within the overall design process. Egerton Consulting Ltd was therefore commissioned to facilitate a HAZOP Study of the THP design and to record the findings from that Study.

THP HAZOP facilitationThe objectives of the HAZOP Study were to:

  • Identify all possible ways in which the THP plant design proposed for Oxford STW could deviate from its design intention and lead to significant safety, environmental or operability consequences for the site as a whole
  • Decide whether design changes were required and recommend modifications where appropriate
  • Provide an audit trail for assurance that hazards and operability issues had been identified and addressed within the project.

The HAZOP Study followed the standard HAZOP Study approach as detailed in the HAZOP Studies Application Guide BS IEC 61882:2001. Thames Water, VWS and the joint venture company were all represented on the HAZOP Team. Workshop meetings were held over seven days and were led by HAZOP Facilitator Amanda Egerton from Egerton Consulting, with an exhaustive record of the meeting discussion being made by Martin Egerton (also from Egerton Consulting) as HAZOP Secretary.

The actions produced during the HAZOP Workshop meetings were assigned to various members of the HAZOP Team and led to either

  • a better understanding of the potential for (or consequences of) various process deviations, or
  • design improvements to reduce the potential for (or consequences of) the causes of identified deviations.

A formal report of the HAZOP Study and its findings was produced by Egerton Consulting for the joint venture company and their client Thames Water.

Further information about the Oxford STW upgrade can be found here.