Sewage purification plant. The sewage purification system on the west side of Odderøya purifies the sewage from the main parts of Vennesla.. It is a chemical sewage purification plant i.e. the waste in the sewage water sinks by adding the chemical , ironchloride.
Cleaning up. The sewage has for a long time been emptied directly into the Otra or the Byfjord, both from Vennesla and Kristiansand. Because of this there has been no fishing and swimming here in modern times. The drain systems have been relatively simple. Therefore a big effort is needed to collect waste from numerous outlet and lead to the new purification system. Almost 80 million NOK have been invested to renovate the sewage system in Vennesla and Kristiansand. While the pipes were being established, the local industries got hard regulations to limit waste.
Industrial efforts. Industries have taken their share of the environmental program. Hundreds of millions NOK have been invested to reduce the outlet of waste. Hunsfoss Factories have achieved important waste rductions. Norwegian Wallboard has also had considerable decrease of waste material.The outlet from the wood processing industry is however still high. Therefore the local counsil industrial drain pipe to cleanse the Otra is necessary. Falconbridge Nikkelverk A/S has in the program period achieved considerable reductions of harmful waste. Elkem Fiskaa Verk has reduced its damaging environmental waste to the Byfjorden considerably. Environmental initiative at Hunsfos factories Hunsfos factiries - leading producer of paper and paper pulp - use the Otra as power and processing water source.After cleansing the production outflow goes into the river. The outlet of dissolved organic compounds and suspended material from the paper production and the woodfiberproduction at Norwegian Wallboard represent the greatest polutants in the lower Otra area.E.g. the outlet of dissolved organic compounds measured as KOF was 25000 tons in 1989.During the environmental program period these outlets have been considerably reduced. This has to a great extent contributed to improving the quality of the water.However the outlets are much bigger than the goals of the environmental program. In the program period Hunsfoss has spent 50 million NOK in environmental investments. The factory has accomplished the following outlet reductions:
The outlets of suspended material are reduced from 3.9 ton/day to 1.2 ton/day. The outlets of chlororganic compounds are reduced from approx. 5kg/ton bleached material to about 2.8 kg/ton bleached material. From the summer 1993 chlor was no longer implemented. Outlet reductions of Norwegian Wallboard Ltd. This firm has managed to obtain the following reductions inthe period of " the enviromental program". 1: The outlet of dissolved, organic matter is reduced from 8,1 tons to 6,0 tons per 24 hours. 2: The outlet of suspended matter is reduced from 320kgs. to approxi. 200kgs. per 24 hours. In addition to these outlet reductions the firm now recirculate waste from the Hunsfoss and the Wallboard plants.Instead of depositing this waste in spacecraving fillings, it is now being recirculated. Now all the fibre dust , 2 - 300 tons,which was earlier burnt in ovens, goes back into production. Web site maintained by the Vennesla vg. skol- Vennesla
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