The development will allow Pan Pac - an active forest grower and wood processor - to convert some of its Pulp-Mill capacity to the manufacturing of high grade Bleached Chemi Thermo Mechanical Pulp (BCTMP). This in turn will allow for the production of higher quality pulp for packaging materials, which sees an expansion into alternative markets from Pan Pac's valued base product of wood-pulp produced for newsprint manufacture.
Ovivo are helping to secure the future of the local environment and to facilitate Pan Pac's expansion by designing, constructing and installing the waste water process. The upgrade includes a new primary FlooDAF® (dissolved air flotation) which uses micro fine bubbles, and along with an upgraded polymer system which improves flock formation and aids in floating the particles, creates a floating sludge blanket. The FlooDAF uses top rollers to move the sludge across the top of the DAF into the sludge reservoir, as well as scrapers mounted on the bottom of the FlooDAF which remove settled sludge from the bottom of the DAF.
Once the effluent stream has passed through the FlooDAF it is pumped nearly 400m through underground pipework to an equalisation basin for automatic pH correction to neutralise the flow, and a cooling tower ensures that the flow entering the FlooBed® BAS process is maintained at an optimal temperature for the biofilm to work at its most efficient state. The FlooBed BAS process consists of a compact and high rate FlooBed Moving Bed Biofilm Reactor (MBBR) and a mediumloaded
activated sludge system. The process enables the client to achieve excellent performance of the plant, to reduce energy consumption and to minimise the required footprint and civil works. The FlooBed MBBR contains plastic biofilm carriers which provide high protected surface area for the biofilm to grow, with a series of porous plastic tube diffusers to ensure high aeration efficiency and mass transfer in biofilm. An activated sludge basin for secondary biological treatment incorporates fine bubble diffusers to keep the micro-organisms aerated. The basin is covered in AquaConsult AerostripsTMwhich are designed and manufactured in Austria and provide world class oxygen transfer efficiencies. The optimum oxygen level is maintained automatically using Dissolved Oxygen (DO) probes to control feed from the blowers.
The flow from the Activated Sludge basins is then gravity fed to a 35m diameter Ovivo clarifier which will remove solids to allow the discharge of clean water. The sludge in the clarifier settles and is drawn from the bottom of the tank via rotating suction scrapers and either sent to waste where it will be dewatered or pumped back into the start of the MBBR to stimulate biofilm growth.
Finally sludge from the FlooDAf and wasted sludge from the clarifier are mixed in sludge tanks. The sludge mixture is pumped through a flocculation tank where polymer is added and then gravity feeds into a Rotary Screw Thickener and then into a Screw Press which has an operating weight of 47 tonne. The sludge that exits the Screw Press will then be conveyed to Pan Pac's boilers where it will be used as fuel to produce steam and electricity for their site.
Some unique technologies have been incorporated in the design including the Ovivo proprietary FlooBed® MBBRTMand FlooDAF® MicroflotationTMdesigned in Finland. In addition, Pan Pac has opted to take up the latest in blower technologies to reduce their energy consumption. This has involved the first use in New Zealand, of large turbo blowers that operate with approximately 30 per cent less power for the same air delivery. As a bonus, each unit comes complete with variable speed to allow turndown for reduced loadings and to maintain efficiency.
Stage one of the project will be up and running by March 2012 treating the current flow of 7.2ML a day and Stage two will allow for the treatment of 12.4ML a day.
In constructing the waste water process Ovivo have spent more than NZ$9m in the local area on goods and services, including the main concrete tanks and the mechanical and electrical install. And the extensive project has utilised 8,000 m³ of concrete, 1,100 tonne of reinforcing steel and 15km of cabling!