Millicent Mill Historic waste water quality improvement summary

Transcription

1 Total Nitrogen concentration mg/ L Total Phosphorous concentration mg/ L Millicent Mill Historic waste water quality improvement summary Over the past 0 years of Pulp and Tissue Manufacturing, Millicent Mills total nitrogen and total phosphorous concentrations have declined to the point where Millicent Mill is releasing half of the limits agreed with the EPA, as illustrated in the following graphs Kimberly Clark Millicent Mill Total Nitrogen and Total Phosphorus Concentrations 004 to 0 Tantanoola Mill Liquor Neutralisation Commenced August 008 Tantanoola Mill Shut operations in November 0 Total Nitrogen Total Phosphorous Year Figure - Total nitrogen and total phosphorous concentrations 004 to Key strategies that reduced total phosphorous included changing an anti-scale compound from a phosphorous based chemical to an organic acid in March 009, changes to the ph of liquor firing at Tantanoola Mill. Total nitrogen was reduced by introducing a liquor neutralisation loop at Tantanoola Mill in August 008, and further reduced by asset closures. Bore water extracted from the aquifer, for use at the Mill contains base concentrations of total nitrogen measuring.88 mg/l and total phosphorous at 0.09 mg/l. The following table illustrates bore water, clarifier and main drain contribution of total phosphorous and total nitrogen measured in 0 and 04.

2 Total phosphorous concentration mg/l Table - Changes in total nitrogen and total phosphorous concentration in 04. Bores Clarifier Main Drain Total phosphorous concentration mg/l 0.09* Total nitrogen concentration mg/l.88* * measured in 0. Bore water contributes approximately 6% total phosphorous and 8% total nitrogen. The remainder originates from Mill operations and sludge inside the ponds. Concentrations of total phosphorous and total nitrogen from waste water entering the Mill, via the clarifier, compared with what is leaving the Mill from the ponds, in 04 is illustrated below Total Phosphorous concentration 0.5 EPA Agreed Continuous Upper Limit Main Drain Clarifier Figure. Total phosphorous concentration in 04

3 Total nitrogen concentration mg/l Total Nitrogen Concentration EPA Agreed continuous Upper Limit Main Drain Clarifier Figure - Total nitrogen concentration in 04. Approximately 55% of total phosphorus is picked up from the ponds. Sludge from the ponds adds % total nitrogen to the Mill waste water discharge. In addition to the dramatic reduction in nutrient loads historically measured, other improvements in waste water quality include: Table - Comparative water information 00 to 05. Waste water parameter Units Average results in 004 Average results in 04 Waste water flow ML/day 0 Conductivity µs/cm Colour 95 nm) HU 58 9 BOD mg/l 0 COD mg/l 95 0 AOX mg/l DOC mg/l 9.* 4.5 TOC mg/l 5.5* 9.4 * Results were only available for 00. Changes in waste water properties were attributed to closure of major assets. In May 0, two Tissue Machines, a Thermo-Mechanical Plant and other utility services were closed down at Millicent Mill. Tantanoola Mill operated a pulp bleaching plant producing up to 65,000 tonnes per annum of bisulphite pulp using thinning from the local forest industry. In November 0, Tantanoola Mill closed down after 0 years of operations, marking the end of a significant era in the Pulp and Paper making industry.

4 Sludge Height (m) Waste water from Tantanoola Mill was treated together with effluent from Millicent Mill, through primary clarification and secondary treatment in three air stabilisation basins. Over the course of time, pulp from the Tantanoola and Millicent Mills have settled at the bottom of the three air stabilisation basins and is now slowly releasing nutrients, together with the Mills waste water into Lake Bonney. Figure 4 shows the decline in pond sludge depth over the past 5 years Average Sludge Height In Ponds Year Pond Pond Pond Total Figure 4- shows the decline in pond sludge depth over time. Since the closure of Tantanoola Mill, Millicent Mill's waste water quality has improved to the point, where in 0, waste water passed all conditions for potable water quality except for traces of bacteria- E.coli, from ducks using the ponds. Currently, the limiting factors governing nutrient emissions are the ground water concentrations of both total nitrogen and total phosphorous, and the pulp sludge left inside the ponds, slowly releasing additional nutrients from the Mill. Pulp sludge volume within the ponds is continuing to decline as illustrated in figure 4. In Summary Concentrations of total nitrogen have reduced from ~ 9.4 mg/l in 004 to ~.5 mg/l in 04. Concentrations of total phosphorous have reduced from ~. mg/l in 004 to ~ 0. mg/l in 004. Bore water contributes the majority of total nitrogen, at approximately.88 mg/l. 8% of effluent total nitrogen is sourced from bore water entering the Mill. Historical sludge residue in the ponds contributes 55% of the total phosphorous in the discharge leaving the Mill. Millicent Mill has undertaken significant process changes including closing assets which have progressively reduced the volume and improved water quality leaving the Mill. Successive pond surveys have shown, pond sludge depth is declining. 4

5 Water quality tested in 0 met Australian Drinking Water Guidelines (except for E.coli) Total nitrogen and total phosphorous are still well within agreed limits under the new EPA licence. The Mill remains committed to continuous improvement in the environmental impact of operations. Future Waste Water Quality initiatives Millicent Mill is engaging the assistance of the University of South Australia through a PhD study to investigate and improve waste water quality even further. Once completed, the study report will provide the basis for decisions on economic solutions to further progress the Mills waste water quality in consultation with the EPA. This course of action will ensure that Millicent Mill adheres to the conditions of its licence and seeks the best available, practical and scientifically valid ideas to further enhance its reputation for environmental governance and responsibility. 5