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Wetlands trial impresses international expert

18 Mar 2016

Wetlands trial impresses international expert

The standard of the wetlands trial under way at the city’s wastewater treatment plant is of top international standard, according to visiting biologist Steen Nielsen.

The Danish biologist, who has nearly 30 years’ experience in the construction and operation of Sludge Treatment in Reed Bed Systems, says the Gisborne trial has been particularly well set up and constructed.

“I’m impressed by the standard. This is a very good test site, the data from which will be most valuable and will be able to be trusted. This is much more ambitious than many I have seen around the world with better opportunities to get more information because it’s working with several plants species and filter media.

“Such a trial is essential before going ahead with a full-scale system.”

The trial is a joint project between Gisborne District Council, NIWA, ESR and the Centre for Integrated Biowaste Research aimed at further improving the city’s treated wastewater.

Mr Nielsen was in Gisborne to peer review the trial and fine-tune its operation, and deliver a paper on Sludge Treatment in Reed Bed Systems (STRBS) to the three-day NZ Land Treatment Collective conference.

Providing his expertise at this early stage will help prevent problems later on.

He is involved in all aspects of a STRB system from working out the dimensions required, construction, design, two-year run-in and loading programmes – the rate at which sludge trickles through the reed beds – and staff education.

“The system has huge economic and environmental benefits. It reduces the volume and improves the quality of sludge, uses little energy and no chemicals, effectively reduces pathogens and hazardous organic compounds, has a minimum of CO2-emissions and has no odour.

“As there is no need to touch the sludge for many years, it makes for a better working environment.”

The reed bed system provides long-term treatment of sludge produced in wastewater treatment plants by drainage, evapotranspiration and decomposition.

“The processes go on naturally without input from us.”

He says there is huge interest internationally for treating sludge from wastewater and water treatment plants in the reed bed system. Through Orbicon, the company he works for in Denmark, he has helped develop about 80 systems over the past 28 years in Denmark, Sweden, Norway and England. He is overseeing trials in Australia and New Zealand, and looking at projects in China.

Mr Nielsen has written more than 30 international papers on the subject and presented at more than 35 international conferences. 

Biologist Steen Nielsen

Biologist Steen Nielsen