In New Zealand, a CST Wastewater STU/CR combined inlet screen and grit removal package plant has been installed as part of a sewage treatment system. The town of Te Aroha on the North Island previously used oxidation ponds to handle the effluent. Now the treatment process culminates with a Membrane Biological Reactor (MBR). The ponds have been retained for stormwater storage. The Matamata-Piako District Council, servicing a municipality of 4000 people, commissioned the upgrade in 2006. According to the company, the council examined the performance of the screen and grit removal system. It found that there was only a small amount of fibrous material in the water and tiny particles in the sludge at the bottom of the tanks. The system is designed to remove 95% of particles above 250µm in size. The council’s analysis found a median particle size of 100µm. This ensures that the MBR does not get blocked. The STU/CR plant uses a stainless steel tank and a shaft-less spiral screw made from micro-alloy carbon steel. It can handle flowrates up to 200L per seconds.
