Tullamore WWTP and Sludge Hub Centre

Link to Built Environment Article Jul-Aug 2012

T J O’Connor & Associates were appointed by Offaly County Council to prepare a preliminary report and Environmental Impact Statement in respect of the proposed expansion and upgrading of the Waste Water Treatment Plant at Tullamore. The preliminary report, completed in 2004, proposed expansion of the plant to 45,000 PE and the construction of a county sludge hub-centre for 80,000 PE.

Approval and funding for the scheme was secured with the preparation of a preliminary report in line with DoEHLG requirements/guidelines. A number of ancillary reports were also prepared in connection with the scheme including polluter pays reports, a public sector benchmark report, procurement options appraisal, etc.

Planning for the scheme was obtained under the 2001 Planning and Development Regulations via two separate Environmental Impact Statements. The EISs had to have regard to the proximity of a number of protected (SAC & NHA) sites to the works and were subsequently certified by An Bord Pleanála.

The second of the EISs proposed the construction of a 3.5 km outfall pipeline to take a proportion of the treated effluent from the plant to a nearby river (the Clodagh) availing of an increased level of dilution. Approval for the outfall required additional studies and consultations with the National Parks and Wildlife Service to facilitate construction through a protected site. This EIS was approved by An Bord Pleanála in May 2008.

The works proposed include the construction of new large diameter inlet sewers to the works, one of which is constructed under the bed of the Tullamore River, the construction of a new inlet pumping station, a sludge digestion and thermal drying facility, an imported sludge acceptance plant and waste water treatment to a tertiary standard in line with the EIS.

Sludge treatment to a class ‘A’ standard was proposed to allow for the beneficial re-use of the sludge as a replacement agricultural fertiliser. Odour abatement measures to be provided include covering of primary settlement tanks and the collection and treatment of exhaust air from various odour producing points around the site.

T. J. O’Connor & Associates’ role also included pre-qualification of contractors, sample design, tendering of works and report and recommendation on tenderers. The contract was awarded in May 2010 under the FIDIC Orange book as a DBO contract. Construction of the works was completed in October 2012.

Start/End Date:

2004 – 2013

Contract Value:



Consulting Engineers and Client’s Representative; PSDP

Key Features:

  • Preparation of a Preliminary Report for the WWTP including recommendations
  • Preparation of two separate EISs to provide planning approval for the works proposed.
  • Assessment of assimilative capacity of receiving waters
  • Coordination of specialist ecological, archaeological, odour, noise assessments
  • Preparation of the Water Services Pricing Policy reports
  • Assistance in the preparation of EU Official Journal (OJ) advertisements on behalf of the local authority
  • Preparation of Pre-Qualification Questionnaire and Pre-qualification of applicants
  • Preparation of a Public Sector Benchmark Report (PSB) for the works
  • Site Investigation contract
  • Preparation of draft and tender documents, including liaison with the DoEHLG
  • Assessment of tenders received including report on tenders – engagement of legal services


  • Construction of a 45,000 PE WWTP comprising:
  • Preliminary treatment including grit removal, screening, pumping, storm water over flow – capacity 1.2m3/s
  • Landfill leachate acceptance plant
  • Primary settlement via 27m diameter settlement tanks
  • Aeration/activated sludge treatment via fine bubble diffuser air in aeration basins each some 2,000m3 capacity
  • Chemical dosing using ferric sulphate
  • Activated sludge treatment
  • Secondary settlement
  • Inter-stage pumping and tertiary treatment via disc filtration system
  • Final effluent discharge including splitting of flow
  • Construction of an 80,000 PE sludge treatment works to provide for treatment to a class A standard including:
  • Imported sludge reception (cake and liquid)
  • Sludge thickening, dewatering and digestion
  • CHP units, bio-gas storage
  • Thermal drying of sludge via a belt dryer with a 1.25 tonne/hour evaporative capacity
  • Construction of new large diameter inlet sewers and a new inlet pumping station

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