Upgrading of the Motueka WWTP Pond System by Tertiary Processes Including Ultrafiltration Membrane

Annual Conference

Beca was engaged by Tasman District Council (TDC) to review options for upgrading the pond-based Motueka Wastewater Treatment Plant (WWTP) and the treated effluent discharge. An Issues and Options report was prepared by Beca in June 2014, which included a review of earlier reports relating to the Motueka WWTP. Much of the earlier work was focused on land application for wastewater disposal. However, this option had been found to be not viable due to unsuitable land conditions in the local area and predicted sea level rise. TDC and its stakeholders now consider that moving the WWTP to an inland site to allow for future land application could be required, perhaps in a 30 year timeframe.

For the immediate future, continued discharge to coastal water would be required. The Beca 2014 Report considered the treatment required to achieve the treated effluent quality limits that could comply with the required nearshore receiving water criteria, primarily based on the Ministry for Environment/Ministry of Health (2003) shellfish gathering and contact recreation guidelines.

The report recommended a combination of treatment upgrades as follows:

  • Removal of sludge from the main oxidation pond;
  • Pond partitioning to reduce short circuiting and formation of two polishing ponds to
  • reduce algae solids concentration;
  • Increased mechanical aeration and mixing in both the inlet aeration basin and main
  • oxidation pond;
  • Recirculation of final pond effluent over the upper portion of two rock bunds using high
  • volume, low pressure sprays, to reduce ammonia and total nitrogen by nitrification and
  • denitrification;
  • Membrane (ultrafiltration) polishing treatment for algae solids removal and disinfection;
  • Construction of a new outfall pipe with a submerged diffuser in an isolated branch of
  • the Motueka River, directly adjacent to Tasman Bay; and
  • Rehabilitation of the former effluent infiltration basins into stormwater habitat wetlands.

Consents were granted in October 2015 with a 20 year term. The project was delivered through a number of contracts and completed in September 2016 within the $8 million budget. The paper describes the above upgrading methods and presents a summary of effluent quality during the first nine months of operation.

Conference Papers

11.30 Upgrading of the Motueka Wwtp Pond System By Tertiary Processes Including Ultrafiltration Membrane.pdf

pdf
1 MB
06 Nov 2017

11.30am H Archer.pdf

pdf
2 MB
06 Nov 2017