The Tribune (NZ) - - VIEWS -

Re­gard­ing the city dis­charge into the Manawatu River.

Many sys­tems for treat­ing dis­charge are avail­able, and from what I can dis­cern, these fun­da­men­tals ap­ply to all sys­tems: How long the dis­charge is treated; the amount of bac­te­rial ac­tiv­ity – which in turn de­pends on aer­a­tion and the bal­ance of nu­tri­ents.

In­creas­ing these in­creases the qual­ity of the dis­charge.

The costs cor­re­late with con­struc­tion and ma­te­ri­als, the cost of the lo­ca­tion, and the area re­quired.

New Ply­mouth is tri­alling dis­charge flow­ing through bark waste. Could this be im­proved by hav­ing col­umns of bark wrapped in ge­o­desic cloth? The dis­charge would be pumped in at the top and fil­ter down through the bark nod­ules.

This would mean am­ple aer­a­tion due to the per­me­abil­ity of the cloth and a slow­ing of the flow be­cause of the lumpi­ness of the bark.

The bark pro­vides a por­ous nodu­lar medium for the bac­te­ria to colonise. Sev­eral col­umns could be ar­ranged closely to save space, and fed from a pump or auger.

With time the col­umns could be utilised as a fer­tiliser, and be­ing mod­u­lar, their re­place­ment wouldn’t in­ter­fere with the run­ning of the plant.

These ma­te­ri­als would cost much less than con­ven­tional ma­te­ri­als.

Kevin Wells Palmer­ston North

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