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Location of the Roof Water Harvesting Centre:
The Roof Water Harvesting Centre (RWHC) is a College of Health research centre situated on the Massey Wellington Campus and is administered from within the School of Public Health. The main physical components of the RWHC is the rainwater tanks facility situated on the western side of Block 2, and the research laboratories of the School of Public Health situated in Block 3. The RWHC is a purpose built facility consisting of 13 rainwater storage tanks incorporating various rain harvesting components and monitoring devices for measuring physico-chemical and microbial levels under a variety of experimental conditions.
The RWHC is situated approximately 3 km from the centre of Wellington city and is positioned 30 meters from a major arterial road and is adjacent to two bus stops. The catchment surface of the RWHC comprises a galvanised iron roof and copper and PVC gutters with a roof area of approximately 400 m2 consisting, on one level, of north and south panels and at a lower level, a smaller west facing panel. A purpose built aluminium ladder is attached to the lower level to facilitate the seeding of the roof surface with microorganisms as well for use in enticing birds to the roof with food.
Plumbing, storage tanks, and accessories:
Roof top rainwater is harvested from the north and south panels via copper gutters into two 80 mm diameter PVC down-pipes that distributes the water onto the lower west roof panel through eight equally spaced horizontal 80 mm diameter spreader pipes. The rainwater from this west panel then runs into another 150 mm half-round PVC gutter that feeds 100 mm PVC down-pipes for the supply of roof water to 13 polyethylene storage tanks. The down-pipes, each containing debris screens (0.95 mm stainless steel mesh) drop down into 100 mm diameter pipes that split into equal 80 mm outlets, each containing its own isolator valve and / or gate valves so that the roof-collected rainwater can be diverted to any tank individually or simultaneously to all thirteen tanks. Water inlet pipes (80 mm diameter) to 11 of the 13 tanks are located at the top of the tank but in one tank the water enters the storage tank via a calmed inlet located at the bottom of the tank so as not to disturb any sediment that may accumulate in the bottom of this tank. Each tank has a 50 mm PVC vent cowl with a light-proof cover allowing the flow of fresh air into the tanks and reducing the possibility of pressure build up. All of the tanks are also fitted with water level indicators (flagged-topped sliding rods on polystyrene floats) and the six 25,000 litre tanks each contain Minisonde 5A multiprobes (Hydrolab) with sensors for temperature, pH, conductivity, turbidity, dissolved oxygen, and ORP, LDO measurements.
- A 25,000 litre tank containing a tank vacuum (bottom overflow) - system designed to automatically vacuum the sediment off the bottom of the tank in the area of the out-take pipe every time the tank overflows. The bottom of the 90 mm vacuum pipe is attached to a notched coupling with 30 mm serrations where it sits on the tank floor. This tank also contains a Level Troll for recording gravitational as well as syphonic flows in the tank when these events take place.
- A 25,000 litre tank containing attached to an Aqua Filter. The roof-collected rainwater enters the Aqua Filter before entering the storage tank.
- A 5,000 litre tank containing, as mentioned earlier, a calmed inlet pipe located at the bottom of the tank as well as a floating valve out-take pipe (suspended just below the water surface) that feeds water to the second tank via a 50 mm diameter connecting pipe 100 mm from the base of both tanks.
- A 5,000 litre tank that is linked in series (as described above) to another 5,000 litre tank.
- A 5,000 litre tank that is linked to a first flush diverter. The diverter is 300 mm diameter pipe 1.5 meters in length and has a flush volume capacity of 120 litres. This self-draining first flush diverter is fitted with five different sampling ports for the automatic sampling of ten 2000 ml volumes of roof runoff. Water quality, catch efficiencies and leakage rates are determined through the use of different bore size slow release valves, with diameters of 0.25 mm, 0.5 mm, 0.75 mm, 1.0 mm, 1.25 mm, 1.5 mm, 1.75 mm and 2.0 mm.
- A 5,000 litre control tank.
Each of these six tanks described above is fitted with 4 equally spaced sampling taps. The discharge overflows from all six tanks are through 80 mm diameter PVC pipes linked to 100 mm diameter storm water drainpipes.
The seven additional 1000 litre tanks are linked to a variety of plumbing configurations and pre-treatment devices including:
- 15 and 25 litre self-draining first flush diverters
- 15 and 25 litre manually operated diverters
- Screened inlet pipe system without first flush diverters
- Mains water tank top-up systems
Each of these seven tanks have equally spaced top and bottom sampling taps.
The research laboratories of the School of Public Health on the Wellington Campus are well equipped for water quality monitoring in the fields of microbiology, chemistry, molecular biology, cyanobacteria, and ecotoxicology. The very close proximity of these laboratories to the rain water tanks facilitates the collection, processing and analysis of water samples. The staff have considerable expertise in laboratory techniques for the isolation and identification of indicator organisms, pathogens, chemicals and agents in recreational and drinking waters. The water research laboratory has gained national and international recognition for its research work with the defined substrate technologies Enterolertä and Colilertä for water quality monitoring. Based largely on Massey University Wellington research, Enterolertä is now the Ministry for the Environment’s recommended method for monitoring marine recreational waters and Colilertä is the Ministry of Health’s referee method for monitoring drinking water quality. Similarly, major research on toxic cyanobacteria, especially in terms of the identification of toxic species, characterization of the toxins and methodology for routine monitoring of water bodies has been carried out in School of Public Health laboratories at Wellington. The detection, isolation and genetic analysis of Cryptosporidium and Giardia in water samples is carried out on the Palmerston North campus in the laboratories of the Institute of Molecular Biosciences (IMBS) and the School of Veterinary Science.
Page authorised by Head of Institute, Institute of Food, Nutrition and Human Health
Last updated on Wednesday 03 January 2018