The existing Wastewater Treatment Plants (WWTPs) are in the range of 20 to 30 years old and have all been based on relatively old, low end, low cost pond technology.
Because of the high intensity loading at certain times of the year (particularly in the summer holidays), all have been equipped with aerated lagoons. In addition, Whangamata and Pauanui plants have relied on pumped discharge through irrigation systems.
More recently, all sites have been provided with ultra violet disinfection systems, adding more power costs along with the annual cost of replacing lamps.
In short, all of the plants have significant limitations in terms of the capacity to treat the volume of sewage to standards that are environmentally acceptable. With predicted growth in these towns, these issues are only going to intensify.
Tairua/Pauanui
TCDC operates a wastewater treatment plant (WWTP) and associated disposal system in Pauanui for treating raw sewage from both Tairua and Pauanui.
The plant is located between Hikuai Settlement Road (the main road into Pauanui) and the estuary, approximately 1 kilometre west of Pauanui settlement and directly adjacent to Stage 2 of the Pauanui Waterways Development.
Despite additional provision for disposal, both the treatment plant and the disposal system were (and continue to be) unable to cope with peak inflows during busy holiday periods and following heavy rainfall.
A Development Moratorium (or ban on subdivision) was in place in Tairua-Pauanui as a result of the current plant being unable to accept further capacity. However in July 2007 this moratorium was fully lifted by the council with the new plant due to open this year.
Whangamata
Treated wastewater from Whangamata WWTP has been irrigated to commercially-operated areas of the Tairua Forest since 1986. The current resource consent for irrigation expires at the end of this year so a new consent for treated wastewater is required. Future disposal could be via continued forest irrigation, an alternative discharge mechanism, or a combination of forest irrigation and alternative disposal.
The Whangamata plant requires upgrading to provide capacity for an increasing population and to reduce the impact of the treated effluent on the environment.
Whitianga
The Whitianga Wastewater Plant is located on Moewai Road to the west of Whitianga Township. The treatment process consists of an aerated pond followed by a retention/maturation pond. Treated wastewater is disposed of in two ways.
Part of the treated effluent is disposed via spray irrigation to a block of eucalyptus trees to the north of the plant, while the remainder passes through sand filtration and UV, and then is discharged to the Ngarahutunoa Stream. The Whitianga plant requires upgrading to provide capacity for the increasing permanent population and holidaymakers.