Wastewater Treatment

Fibreglass Flume for metering wastewater flow from new prison complex in Auckland

Project Date




Sewage Networks

Flume Station


A flow metering flume was required for a new prison complex in Auckland. The flume had to be installed in difficult soil conditions in a short timeframe.

In order to be accurate, flumes must be built to strict dimensional tolerances. Achieving this in a below-ground installation using traditional methods can be difficult and time consuming, especially when the soil is loose volcanic scoria. In addition, personnel access to the flume is generally required for monitoring and maintenance.


Armatec¹s fibreglass flumes are built using precise moulds so every flume produced is dimensionally accurate. The flume can be incorporated into a fibreglass manhole to provide the access needed. This is all done off-site at Armatec¹s factory, minimising site works.

These features meant that the contractor was able to excavate the hole, install the flume, connect the pipes, place concrete around the flume, and backfill in just a single day. This saved both time and money on the project, and helped to avoid delays due to inclement weather.


A cost-effective and well-constructed flume installation that allowed accurate metering of wastewater flows.

Fibreglass Cover Installation at Careys Gully, Wellington

The two sludge tanks at Carey’s Gully store sewage sludge pumped from the Moa Point wastewater treatment plant located about 10 kilometers away. Due to the age of the sludge, considerable quantities of corrosive hydrogen sulphide gas are released within the tanks. H2S concentrations over 50 ppm have been recorded, and resulted in severe corrosion to the concrete walls and concrete roof of these two tanks. 

Ammonia Scrubber and Fibreglass Ducting at Wastewater Treatment Plant

Air given off from the biosolids treatment plant at Watercare’s Mangere wastewater treatment plant contains ammonia and odours. This air had to be captured and ducted away for treatment in soil bed filters. However firstly the ammonia had to be removed as it would have had an adverse effect on the soil bed filter biology.

All Fibreglass Pump Station for Residential Wastewater

There are two problems faced by all wastewater pump stations: corrosion and odour. Typical concrete pump stations corrode within 20 years of installation, and do not meet the requirement of a 50 year design life required in municipal applications. Corrosion is worse when there are long residence times in the system, as the wastewater can go anaerobic and produce significant quantities of corrosive hydrogen sulphide.