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Whangamata Marina's commitment to a clean harbour

01 October 2014

The new treatment plant for waterblast and hardstand runoff has been a revelation to the Whangamata Marina Society because of the amount of solid waste collected since trialling of the system began in September.

In keeping with the Marina's commitment to their Clean Marina certification, all water collected on the hardstand runs through the treatment plant. To get the plant up to standard some redesign of the construction drainage and catchment areas wasnecessary, including another large catchment pit, pumps, three additional catch pits, another large sump and electrics which make the system almost fully automatic.

Shut off valves have also been installed allowing the yard to be shut off into three sections. The catch pit at the bottom of the yard also has a sediment trap and is the section which most of the dirty work is concentrated.

The first amount of contaminated sludge was in excess of 150kg from 25,000 litres of treated water of which 7,000 litres was contaminated water blast water.

"In essence the batch was regarded as lightly contaminated, it is still early days and we are still undergoing chemical trials. Our aim is to better the Waikato Regional Council resource consent standards, this won't be known until we have trialled a full load," says Whangamata Marina Society's Manager, John Gillooly.

"There is no doubt that, until now, this material has been contaminating the sea," he added.

While this sophisticated treatment process is used in some industrial sites, Whangamata is the first Marina in New Zealand  to install this system.

The treatment plant process:

  • Water from the hardstand is collected in six catchment pits.
  • The contents of the pits and sump are pumped into a 22,000 litre tank.
  • The water is aerated with material being pumped to an adjacent tank.
  • The material is then moved to chemical mixing tanks.
  • Three chemicals (lime - calcium hydroxide, polyaluminium chloride and a polymer are added with the dosage determined by the volume of material to be treated and its perceived level of contamination.
  • Clear treated water is then drawn off and discharged at a measured rate to sewer or sea.
  • Flocculated sediment is drawn off and forced through a multi plate press at up to 100 psi.
  • The resulting material is then compacted into cakes and sent to a landfill that caters for this type of material.

What has this plant cost the Whanagmata Marina Society?

  • $220,000 - ground works and drainage
  • $130,000 - building, pits and bunds
  • $500,000 - the plant itself - pumps, electrics, tanks, pipe work, press and compressor
  • $200,000 - approximately for consultancy, surveys and permits

Whangamata Marina