Yesterday we published Part 1 of Stinkin’ Pipes, Kathy Webb’s investigation into the viability of Hastings’ new sewage treatment plant in East Clive … a design to be copied by Napier.
Here’s Part 2, the continuation of her examination. Or you can download the entire article here.
Stinkin’ Pipes! (Part 2)
By Kathy Webb
$27m down the toilet?
Environmental watchdog David Renouf says Hastings has effectively thrown $27m down the toilet. Bio-trickle filtering without a first-stage settling process and a third stage clarifier to remove all the filtered sludge is a waste of money, he says, because large amounts of the biomass that removes nutrients from the raw sewage are flushed out of the tanks along with the filtered liquid, on to the seabed.
“It’s a bit like vacuuming your lounge, then emptying the bag all over the floor,” he says. He believes the bio-trickle plant and its accompanying “Papatuanuku Channel” were the $27m price tag for Maori agreement to a sewage-disposal solution for Hastings.
But he says Maori were misled into believing there is no human waste in the filtered discharge to sea, because although it might not be raw anymore, it is part of a chunky glutinous mass that will take a lot longer to disperse than milliscreened sewage. It’s unknown what effects biomass will have on the marine environment, because not enough tests have been done yet to prove it is harmless. And it still contains heavy metals, viruses, parasites and suspended solids that the filters have not dealt with.
Mr McLeod rejects any notion of “a $27m spend just to satisfy cultural concerns,” and says the project was necessary to meet conditions for the plant’s resource consent. The Council’s tangata whenua wastewater committee has yet to sign off on the new bio-trickle plant, but if it refuses to do so, “we’ll have to work through the whys and wherefores.”
Group asset manager David Fraser says the concept of changing the form of human waste into biomass came from Monty Paku, one of the wastewater committee members, and he’s confident the system will get the final seal of approval.
The Papatuanuku channel is an open drain studded with rocks that were blessed by Maori and are now generally referred to as “sacred,” although the Council itself does not use that word. The rocks were brought from a quarry at Linton, near Palmerston North, to spiritually cleanse the filtered discharge before it heads out to sea. It is “more symbolic than anything,” Mr Fraser says. But it is a “standard concept across New Zealand , with slightly different perceptions between iwi.”
He rejects Mr Renouf’s criticism. The filter tanks can be compared to a “quick composting” bin in a garden, turning waste into another form, but much more quickly.
“What’s coming out is bugs’ waste.” he says, and the Council is monitoring the seabed around the sewage outfall 2.5km out at sea “to see if there are any adverse changes.”
So far, the Regional Council has not replied to BayBuzz requests to see the monitoring data.
In a magazine article headlined “Cultural dreams become a technical reality with innovative wastewater treatment,” Mr Fraser describes the new Hastings system as “a model that others can follow.” “Essentially, we have secondary treatment for half the cost of primary, or one third the cost of the traditional configuration for biological trickling filters.”
The Maori cultural element focused on avoiding the transport of sewage sludge on roads past homes, marae, etc, and required “a great deal of lateral thinking and discussion from within the Maori community,” which eventually aligned the bio-trickle process with “the long drop approach, in which human waste was allowed to grow old and become inert with dignity.”
The Council’s legal adviser, Mark von Dadelszen, is more effusive. In a written article he describes the consultation and co-operation that led to the construction of Hastings’ novel take on bio-trickle filtering as an historic blend of Maori spirituality and modern science.
The Papatuanuku channel was the solution, he said, by invoking the sons of Papatuanuku ( Maori God of the Earth) to purify and spiritually cleanse the sewage, with “Tanemahuta providing biomass to transform kupara (faeces) by removing the mauri (spirit) of human wastes. Tangaroa (the sea) receives the transformed waste after passage through Papatuanuku and heals himself through movement of the ocean, and Tawhirimatea (god of the winds and weather) agitates the surface of Tangaroa and through a synthesis of air and water completes the cleansing process.”
Des Ratima, a member of the District Council’s Maori Joint Committee, is less than impressed by the lateral thinking and consultation that led to the construction of a waste disposal channel named Papatuanuku.
In fact, he’s horrified. “It’s not respectful at all. It’s totally inappropriate, almost to the point of being offensive.” Papatuanuku (Mother Earth) is a concept of support and nourishment resulting in a cleansing, “not to take dirty water and make it less dirty,” Mr Ratima says.
He’s surprised the Tangata Whenua Committee allowed what he considers to be a serious spiritual distortion, and intends to consult “a few people whose opinions I respect, and see what they think about it.” A name change for the channel could well be on the cards, he says.
The East Clive treatment plant has already attracted a lot of attention from other councils.
Napier is poised to build an identical system at Awatoto, but its tanks will have lids. Mayor Barbara Arnott says Napier is still watching events at East Clive before seeking its own resource consents later this year. “Everyone’s learned a lot from the Hastings experience.”
Napier should not have the same problems because it has a larger urban area and therefore higher volumes of domestic sewage to maintain momentum in the pipeline and filtering, she says.
It will also have a permit to discharge offensive odours to the air!
A saga of investigation and consultation
In the early 1980s, Hastings was pumping all its sewage out to sea via a 2.75km pipeline, the longest ocean outfall in the country. It was a minimalist approach, relying on oxygen-rich receiving waters and high sunshine hours to provide plenty of ultra-violet light to break down and disperse the sewage.
Milliscreens were added in 1993 to catch the toiletries and other items that sometimes got through the initial screening.
In 1998, the Hastings Council sought a renewal of its resource consent to continue the discharge. Maori objected to a continuation of human waste going straight into the ocean, and eventually the Council was ordered to heed their concerns and consult them.
In 2001, the Council was granted consent to build a new wastewater treatment plant, to be ready by 2007, and the Council-Maori Tangata Whenua Joint Wastewater Committee was formed with the task of ensuring any new system resulted in “the significant removal of kuparu (human waste)” by 2007, and the “complete removal of kuparu” by 2009.
Maori were not happy about the natural settlement system being considered by the Council, so the committee set about finding an alternative to meet everyone’s standards. The stand-alone bio-trickle filter tanks were the result.
Hastings’ resource consent expires in just four years, so the Council must begin a whole new round of public consultation later this year. Mr Chapman says public expectations for sewage treatment have raised the bar a lot in recent years, so he will not be surprised if there turns out to be a mood for even more treatment, maybe sludge removal after filtering, or ultra-violet light.
How it Works
A traditional bio-trickle filter system has three stages – primary treatment such as settling tanks, followed by the trickle filtering, then clarifiers to collect the resulting sludge, which is removed before the wastewater flows on to its intended destination.
Settled sewage is pumped up to the top of each tank, where rotating arms spray it on to some form of media on which sewage-eating microbes, composed of algae, fungi, protozoa, rotifera, nematodes, and aerobic bacteria, live as a slimy substance commonly called biomass. As the wastewater trickles through the media, the microbes in the biomass grab and eat the nutrients in the sewage.
But Hastings does not have a traditional bio-trickle system. Mr Fraser says that is because traditional systems, built when milliscreening was unavailable, went out of vogue as more cost-effective ones were developed. To save money, it dispensed with the usual first and third stages, and built only the second-stage filter tanks. It also omitted lids on the filter tanks and a closed channel to the sea outfall, which it replaced with an open “spiritual cleansing” channel studded with “sacred” rocks from a quarry at Linton, near Palmerston North. The rocks were free, but cost $5000 to truck to Hastings.
Raw domestic sewage arriving at East Clive is screened and pressed to remove the bulkiest of solids, which are then carted off to Omarunui landfill.
The rest is pumped to spray arms at the top of two 37 metre diameter tanks, each containing five million pieces of plastic, nine metres deep. The wastewater takes 12 minutes to trickle down through the plastic.
It’s a complex process. Bio-trickle filters need a critical mass of sewage to keep their biomass alive. Too much or not enough biomass creates odour. Blockages in the media can cause sections to go anaerobic and smelly, so every few hours, the tanks are flushed to remove any lodged solids such as toilet tissue and excess biomass.
[You can download the entire article here.]