Pollution questions

Mark Hall’s statement (Letters, November 7) that the NPDC sewerage treatment process does not produce methane is deliberately misleading.

Along with methane that is being produced from the moment the raw ingredients are flushed into the sewers, the plant in its aerobic phase is producing greater volumes of CO2.

Activated sludge fertiliser? – The

sludge digestion process is anaerobic and generates methane.

And it’s laden with industrial contamination such as aluminium oxides, heavy metals, petro-chemical residues, and traces of birth control pill hormones.

Then at the end of the process the remaining water is dosed with caustic soda and chlorine to kill every last vestige of biological life before being pumped out to sea.

Out of sight, out of mind.

What lives around the end of the outlet pipe?

Which begs another question: What are the level ranges (PPM) of nitrates (nutrients) in the plants discharge, and does the maxim ‘‘the solution to pollution is dilution’’ still apply with discharge to sea?

Surely, Mr Hall is aware of the documented effects of excessive nitrate contamination from the Manukau Harbour and its contribution to toxic algae bloom?

Auckland and Waiuku ‘treated’ sewage disposal to sea using similar process to New Plymouth.

Then there is Lake Taupo, Rotorua, Ellesmere, Firth of Thames, Omapere,

Doubtless Bay – all suffering from the effects of excessive nitrate levels

Tim W Busby, Egmont Village