A video explaining changes to the city's sewage has been released after news half New Plymouth's effluent will be piped 450m off a New Plymouth beach was made public.
On Saturday the New Plymouth District Council issued a warning to beachgoers after announcing partially treated effluent will be pumped into the ocean off Waiwhakaiho while one of the treatment plant's two aeration basins is taken out of service for the next four months so it can be cleaned and upgraded.
In the video council water and wastes manager Mark Hall clarifies what the sewage treatment process will look like while an aeration basin is offline.
Mr Hall explains that during a normal cycle sewage goes through a three-step process of screening, biological treatment and disinfection.
In the first step waste water is screened for anything larger than three millimetres before being pumped to the biological process which happens in the aeration basins.
In the aeration basins oxygen is added and naturally occurring bugs consume organic material.
Once this is finished the sewage is moved to the disinfectant process where chlorine is added.
Chlorine is added at a check stage, before the sewage moves on to a chlorine tank where its levels are measured and more is added if needed.
Treated water, or effluent, is then piped out to sea.
During the four months when the aeration basin is being cleaned all sewage will go through the screening process before it gets split at the biological process, Mr Hall said.
Half the sewage will go through the biological process and the other 50 per cent will bypass it.
The two groups of sewage will then be combined together again at the chlorine check before going to chlorine tank for testing before being piped 450m off Waiwhakaiho.
Even though the sewage will still go through the screening and disinfecting stages, with 50 per cent having biological treatment as well, the council is warning swimmers of the potential risk.
In their media release the council said there was a higher risk of illness and skin irritation from swimming and gathering shellfish in the area from Monday when the project begins.
If water quality becomes an issue New Plymouth's Fitzroy and East End beaches will run the risk of losing their Blue Flag accreditation.
Foundation for Environmental Education NZ Blue Flag chairman Rob Acton said if the quality of the water declined the beaches' Blue Flag status could be revoked.
To receive and keep a Blue Flag, a beach must meet strict criteria including the measuring of water quality, the provision of environmental education and information, environmental management, and environmental safety.
Mr Hall said the council was working with Blue Flag and would document in the next Blue Flag application what had happened and make sure the public were aware of the potential impact on bathing.
"If it has a negative effect on the water quality readings then the blue flag would be taken down during this time and information placed on the Blue Flag board to state why the flag has temporarily come down."
But Taranaki Regional Council director environment quality Gary Bedford said he did not expect the discharged sewage to have any effect on the quality of beach water.
"The general movement of water on our coast is from Fitzroy past the Waiwhakaiho, past the wastewater plant and towards Bell Block, so there's no reason any change should affect Fitzroy or East End."
There are also concerns from lifeguards that the public will avoid the city's patrolled beaches.
Todd Cations-Velvin, president of Fitzroy Surf Lifesaving said avoiding Fitzroy and East End in favour of a cleaner swim at Back Beach or other unpatrolled beaches could be dangerous.
"It puts people at a higher risk of drowning."
- © Fairfax NZ News
Should the NPDC councillors get iPads?Related story: Tech-wary councillors hedge their bets