Controlling Midge Niusance at Mangere - 10 Years of Operational Experience

The Mangere Wastewater Treatment Plant at Mangere was initially commissioned in 1960 with the main treatment process consisting of large oxidation ponds, and the non-biting midge species Chironomus zealandicus has been a nuisance since that time. The oxidation pond system was decommissioned in 2002 and the practices for controlling C. zealandicus changed accordingly. Initial success was met when the viable habitat was substantially reduced, but for operational reasons, a Final Effluent Channel (FEC) and Intertidal Storage Basin (ISB) remained and provided 19 ha of viable habitat. In 2005 an integrated midge control program (IMCP) was created to target multiple life stages as well as discouraging dispersal into neighbouring areas. The two pillars of this program are the frequent dosing of slow release methoprene pellets and contact insecticide sprayed onto strategically planted vegetation. Since 2005 there has been a trending reduction in complaints with zero received in the 2012-13 and 2015-16 seasons.

This paper summarizes the current IMCP, the methodology for measuring midge numbers, the successes, failures, and the lessons learned over the past 10 years. This paper also summarizes how Watercare Services Ltd engages with the community and pursues its vision of being a good neighbour.