Wellington Scoop

Fix the smell! Regional council’s instruction to Wanganui city council

News from Horizons Regional Council
The Wanganui District Council has been issued with an abatement notice by Horizons Regional Council following on-going objectionable odour from its wastewater treatment plant.

The notice is a legal directive requiring Wanganui District Council to cease causing an objectionable odour beyond the boundary of its wastewater treatment plant within the next four weeks. It follows a formal warning issued by Horizons in December.

Horizons group manager strategy and regulation Dr Nic Peet says while Horizons recognises that mitigating or solving issues at the plant may be difficult, the odour is objectionable and its on-going impact on the people of Wanganui means it must be resolved.

“Industrial processes like those occurring at the wastewater treatment plant will always produce an odour. It becomes an issue when an objectionable odour extends beyond the property boundary affecting other residents and businesses as is clearly the case in Wanganui,” Dr Peet says.

“We know the district council is taking steps to address the issue and is keeping Horizons staff appraised of progress. It is a complex problem but the district council is in breach of regional rules around air quality and as the regulator we need to act accordingly.”

Dr Peet says Horizons will continue to support the district council as they take steps to mitigate and solve problems at the plant and understands that Wanganui District Council will be looking at the design and functioning of the plant as soon as possible.

“The district council has identified that unusually large amounts of trade waste entering its plant have resulted in the recent widespread objectionable odour problems. Horizons understands that Wanganui District Council will be ensuring that the industries discharging industrial waste to the plant do not exceed the conditions set in their consents with the district council.

“However, the plant has had a number of problems since it opened which mean that it has not being functioning as it should. This raises the fundamental question of whether the plant, as it is currently designed, can cope with even normal consented amounts of industrial and domestic waste water and, if not, what needs to be done to fix it. ” he says.

But can they fix it?

1 comment:

  1. Keith Davis, 11. January 2013, 13:53

    In the late 1960s, I carried out the original sewerage investigations for the Whanganui City Council. The original proposal was to first rid the city of the combined wastewater/stormwater system, screen, and pipe the waste to the sea offshore just south of the airport. During a discussion with the then City Engineer, Brian Jackson, I warned him of possible odour problems if lagoons or aerated lagoons were to be considered as a treatment option. However, nothing came of the discussion.
    The problem as I saw it was based on my experience as a chemist working at the Mangere treatment plant in Auckland in its early days when there were three major meat works in operation. I moved to a staff house on site and worked on the problem for about two years but admittedly the plant was not the only culprit. The Upper Manukau Harbour mudflats and the build up of solids from the meat works also contributed to the odour problems.
    The meat works are now long gone and so have the lagoons or oxidation ponds as they were generally termed then.
    I have been in the wastewater and water treatment game for now over 60 years and have also seen lagoon problems overseas and when I became involved in Wellington in the early 1980’s there was talk of a combined Hutt-Wellington scheme for Gollan’s Valley. In 1988 I went on a study tour of lagoons in the USA and as a result I canvassed councillors to forget lagoons and each council concentrate on its own scheme. The harbour crossing also did not fit well in my view.
    No wastewater treatment plant can be 100% odour free. Straight domestic waste can be best managed but when there is a substantial industrial component such as meat, fish, canning or allied to meat waste such as tannery waste there are likely to be problems. No matter how many calculations are carried out there can be no complete answer.
    I do not know what the %age the industrial component is but from memory it would be quite considerable. It is not just hydrogen sulphide that causes the problem but also other reduced sulphur compounds that are not soluble in water and are discharged directly to the atmosphere. In such cases the aerators are acting as an odour liberating device not a treatment device. temperature and bottom sludge build up also contribute to bacterial activity.
    I am afraid that the only answer is to bypass the plant. I know that this may be environmentally unacceptable but it has to be done. A complete review of the scheme is warranted if this situation has been going on since 2007.
    In retirement I have been working here in Wellington as a tutor in water science and more lately on the odour problems associated with the Moa Point wastewater treatment plant. Here with two hi-tech odour management plants in place it has taken some 14 years to achieve an almost nil discernable odour. it must be remembered that many of the odour-causing compounds can be detected in the parts per billion range and it takes some doing to completely remove any odour that is objectionable.
    As I have no knowledge on the various loadings on the existing plant or its design I cannot comment further apart from reitterating my earlier comment that the existing plant must be bypassed asap if the problem is to be resolved for this coming summer.
    Keith Davis
    Dip Chem, FCIWEM, CWEM, C Env
    Retired pro water and wastewater treatment plant/manager chemist