November 29, 2004

Reverse Osmosis treatment of DNS Waste stream

OsomoTech proposed the use of reverse osmosis to treat the DNS effluent in Jan 98. At the time they did not supply equipment with sufficient capacity to deal with the 165t effluent produced daily. They go on to say that a 70t set-up would cost 495K including installation. Assuming a 165t set up would cost double, this would cost £990K. Osomotech advice using membrane modules at a cost of £3800 that have an unknown working life and may need changing frequently. Sodium Sulphate may also cause problems with the membranes resulting in appriciable downtime.

In terms of colour reduction, reverse osmosis is efficient and meets the EA quota but in terms of COD it does not meet the guidlines (report uses conc factor vol/vol 1, 2 and 5.9). This may be improved by using a lower conc factor.

Ozone Treatment of DNS Waste Stream

A report by CleanZone in Jun 97 proposed the use of Ozone to treat the DNS waste stream. It quoted a capital investment of £2.5 million including all equipment and installation. CleanZone also supply Oxygen at a cost of 3.4p/Kg for two years after installation. The process of converting oxygen into Ozone is 10% efficient and yields an oxygen rich gaseous waste stream. The electricity required for this process is 18.7 Wh/gO3 costing £0.00004/Wh.

Colour reduction, at best, is 97.2% and 98% at 420nm and 580nm respectivley. However COD reduction is, at best, 53.4%. In terms of colour reduction ozone treatment is extremely effective but in terms of COD reduction, it does not meet the new EA guidlines.

November 26, 2004

Electrolysis Treatment of DNS

Yo Lou this is what we need doing for the other two treatments….....

A report on electrolytic treatment of the DNS waste stream was proposed by ElectroClean in Feb 97. This report estimates the cost of a comparable unit to that required to be £700K and is inclusive of general electrochemical hardware and installation, however pumps, pipework and tanks for controlling effluent flow are not included. Aditionally, PbO2 anodes, supplied by ElectroClean, cost £4000/m2 in 1997 and have a working life of between 4 and 10years. Assuming a working anode area of 67m2, this adds £268K to the total cost. Processing takes 48hrs and the total electricity cost is calculated to be £170.

Colour reduction measured at 550nm was shown to be 95% efficient and COD was reduced by 65%. In conclusion, electroltic treatment meets the key environmental criteria.

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