The town of Te Aroha in New Zealand’s North Island have installed a modern intensive-treatment sewage system, replacing the facultative or oxidation pond treatment that have been used by urban councils since the 1960s. The new system applicable to Australia and New Zealand uses a combined screening and grit removal package plant, prior to a Membrane Biological Reactor (MBR). The old ponds at Te Aroha have been retained for storm water balancing.
Matamata-Piako District Council (MPDC) commissioned the system in 2006 to service the municipality of about 4000. Kaimai Valley Services (KVS), the Works division of MPDC, undertake operation and maintenance of the plant. A recent assessment by KVS’s wastewater team concluded that the system in general was performing well, with the screening and grit removal performing effectively.
According to Hugh Ratsey, Team Leader, KVS Wastewater, as they were looking at increasing the wastewater throughput of the system, they examined the performance of the screen and grit removal quite closely to see if it could handle the extra load. The wastewater team also carried out an analysis of the sludge at the bottom of the tank and found only fine particles. KVS Wastewater examined the sludge quite closely. The median particle size was 100 microns, which is small. The grit removal plant is designed to take out particles above 250 microns in size.
The CST Wastewater Solutions STU/CR combined inlet screen and grit removal package plant, which was supplied to Matamata-Piako District Council by Smith and Loveless. Similar technology has been employed by CST Wastewater Solutions in Tasmania, Queensland and NSW, including the Olympic site at Homebush.
Following are the functions of Te Aroha installation:
- Screens solids from the raw influent
- Lifts the screenings out of the wastewater and simultaneously washes the screenings
- De-waters the screenings, which are discharged down into conveniently placed skips
- Separates the sand particles or grit
- Lifts and de-waters the grit, which is discharged into the same skip or a separate skip
- Offers optional grease removal
The system handles flow rates up to 200 litres per second, with a 3mm to 5mm circular holes screen, dewatering screenings to between 25% to 35%, and removes 95% of grit particles above 200 microns and SG 2.1.
According to Pieter Groenewegen, CST Wastewater Solutions, key to the STU/C combined inlet screen and grit removal system is that it offers efficient and cost effective solids separation before the wastewater reaches the MBR plant to make sure the membranes do not block. The screen cleanly removes rags and other debris, while the grit removal stage gives good separation of particles from the solution, with no accumulation in the reactor.
Design features of the screening and grit removal plant include a stainless steel tank and a shaftless spiral screw made of micro alloy carbon steel. The plant is prefabricated so that limited civil work is required. Available accessories include screenings washing for faecal removal, a continuous bagging unit on the outlet, and trace heating for cold regions.
CST Wastewater Solutions have been providing a broad range of industrial and municipal water and wastewater solutions. CST Wastewater Solutions are suppliers of wastewater treatment solutions throughout Australia and New Zealand, with projects also completed in Europe, Asia, Africa and America. CST Wastewater Solutions are a member of the Global Water and Energy Alliance, a group of select companies around the world committed to providing solutions in waste and wastewater treatment for the recovery of green energy and water.
CST Wastewater Solutions network of partners includes Smith & Loveless, Berson UV-techniek and Global Water. CST Wastewater Solutions’ broad range of proprietary wastewater treatment equipment is manufactured to ISO9001 and EEC standards of safety and design.
Following are the broad range of proprietary wastewater treatment equipment from CST Wastewater Solutions:
- Water and wastewater screening
- Grit removal and dewatering
- Septic receival stations
- Dissolved air flotation
- Sedimentation systems and clarifiers
- Shaftless conveyors
- Sludge dewatering
- Lime handling and silo systems
- Continuous sand filters
- Micro filters and screens
- Solar-powered circulation
- UV disinfection
- Ozone treatment
- Anaerobic treatment
The CST Wastewater Solutions also provide assistance with equipment and system selection, design, installation and maintenance, as well as operation of wastewater treatment systems and delivery of complete packaged plants.