This document discusses methods for reducing copper levels in distillery effluent discharge to meet tightening regulations. Initial tests found that adjusting pH to 8-8.5 and using aluminum-based coagulants and polymers could remove over 90% of copper. Additional dissolved air flotation and biological treatment could further reduce copper levels. Trials at several distilleries successfully reduced copper discharge by 30-70% using this chemical and physical treatment before existing biological systems. The treatment may help distilleries meet lower discharge limits but future technologies may be needed for further reductions.

2. The pH was typically reduced by 1pH so even at a high pH of 12; the chemical treatment on its own was good enough to take the pH to within discharge consent.

3. There was a reduction in Chemical Oxygen Demand (COD), although a generous allowance of 5,000mg/l, a general reduction of the order of 20% means that as the site is under Scottish Water Mogden Formula charging then there is an additional cost saving by reducing the COD

4. The same applies to the Suspended Solids (SS) allowance, again a generous consent of 2,000mg/l, but again as the SS reduction is substantial (65%) then this contributes again to a reduction in the effluent charging to siteOverall so far, sites own figures have found that the reduction in Copper has been in the order of 30%, this is mainly due to working at the high pHs<br />It was found that in future should site be required to reduce their discharge consent for say Copper from 10mg/l down to 5mg/l then by refining the pH to within 8 – 9.0 pH was adequate to strip out more of the Copper.<br />To demonstrate this samples were taken at various pH’s these were then treated at their current pH range, as previous and then as part of the initial treatment, Hydrochloric Acid (24%) was used to take the pH lower and then the already suggested chemical treatment programme was introduced. The results were extremely encouraging and show that maybe when the goal-posts are narrowed by Scottish Water in the future, then this treatment programme can assist this particular site in achieving it next anticipated discharge consent.<br />Hydrochloric Acid was used as there are no issues with chloride consent in the site’s discharge and 24% is still classed as irritant rather than corrosive as Hydrochloric Acid is at higher strengths.<br />With regard to the future using this technology, there is already interest from several other distilling companies to install this system mostly alongside technologies, predominately biological, and usually as an initial treatment stage to take off some of the loading to the biological programme on sites<br />That said there are still several sites with currently no effluent treatment, where with the Scottish Water discharge consent being between 5 – 10mg/l, there is no reason why this technology on its own would not be able to assist these sites meet their discharge consents.<br />Longer term it is felt, that whilst this technology has a place, it is not good enough to entirely strip out the whole of the Copper, and certainly in terms of COD reduction 60 – 70% is the maximum ever likely to be achieved. Therefore should discharge licences be reduced even further in the future, it is suggested that technologies such as micro-filtration, or electro-coagulation might be possible solutions if the effluent is treated by physical/chemical processing first to keep the loading off such systems.<br />The process outlined is in itself also not reducing the Copper it is merely transferring the Copper (and other parts of the effluent) from one area to another, and still has to be disposed of in a sludge form. Although currently the majority of the sludge goes for land spreading there is nothing to say that long term this route may change and as a result the process, whether chemical or physical might have to change also.<br />Alternatively processes such as anaerobic digestion, working alongside this technology should be adequate. Indeed anaerobic systems are already in use within some distilleries, although sadly the claims made by the companies selling such systems have not lived up to the expected return on investment, certainly in terms of energy return, leading to some scepticism on some part as to the value of this treatment<br /> However for now we will have to wait and see what the full implication will be of European Legislation such as the Priority Substance Directive, and to see how Scottish Water and SEPA interpret this legislation.<br />In conclusion I would like to thank Farid Turan of Wehlre Environmental who was instrumental in starting this project and to the staff at the various distilleries where this technology is being used for having the confidence to stick by us. <br />