The Estuary is acknowledged as having international significance as a wetland, and although the present discharge removes 99.9 per cent of pathogens, the nutrients within the discharge have a significant effect on the ecology of the Estuary.

Because the Estuary is a shallow, relatively enclosed body of water, it supports a wide range of flora and fauna which is affected in different ways due to the low dilution the Estuary provides for these nutrients. Removal of the nutrients, it is believed, will reduce sea lettuce growth by a minimum of 50%, and reduce anoxic areas where sea lettuce accumulates.

Juvenile fish have also been identified as likely to benefit from removal of exposure to the low levels of ammonia in the discharge. The colour and clarity of water within the Estuary will also improve by removal of the discharge which contains green algae.

From an ocean outfall the dilution achieved by the time the discharge reaches the surface would be approximately 100 times, making the effect of nutrients and any remaining pathogens minor.

The modeling conducted on an ocean outfall to date indicates that on the infrequent occasions the discharge would go directly to the New Brighton beach (under certain conditions, over a period of about four tides) it will be safe to gather shellfish at the foreshore. In fact the model suggests that an ocean outfall will have significantly less impact on shellfish on the beaches than an Estuary outfall.