The Coxmoor Publishing Company book titled ‘Hydraulic Fluids – A Practical Guide’, by Allan Barber, Nigel Battersby and David Phillips, and published in association with the BFPA, is a handy source of information on its subject. Below is an extract from the publication, looking at the theme of disposal regeneration and recycling. At some stage the user of hydraulic fluids will be faced with the need to either dispose of aged or contaminated fluid or to recondition (recycle) the product for further use. Disposal of used hydraulic fluids and their containers Increasingly, restrictions are being imposed on the disposal of all waste materials. Hydraulic fluids are no exception, and users have a ‘duty of care’ to dispose of used fluids correctly, pursuant to local regulations. Waste oils, including used hydraulic fluids, are designated as ‘special wastes’, and users are required by law to keep records of how and when they dispose of these materials. It should be noted that in the European Union, even when a contractor specialising in waste oil disposal is involved, the fluid user has a legal requirements to ensure that the waste fluid is disposed of in an appropriate manner. Many fluid suppliers also operate a fluid disposal service. Levels of oil and other materials being discharged into waste water may also be closely monitored by environmental agencies, and anyone discharging unauthorised materials (or even unauthorised materials beyond agreed limits) can be prosecuted and heavy fines imposed. Once collected, there are several acceptable ways to dispose of waste hydraulic fluids, the three main routes being: energy recovery, regeneration and recycling. Energy recovery In the UK the vast majority of waste industrial oil is burnt as fuel by industries such as power generation, road-stone coating and cement manufacturing. Most waste hydraulic fluid will therefore undergo some basic treatment to remove water and particulates, before being burnt as ‘recovered fuel oil’. Although mineral oil-based hydraulic fluids are not normally mixed with any other type of used hydraulic fluid, small volumes of other non-aqueous fluids (HEES and HFDR) can be co-disposed without a deleterious effect on energy recovery. Oil-in water (HFAE) and water-in-oil (HFB) emulsions are usually disposed of by splitting the emulsion with acid. The oil can then be burnt (or recycled), whilst, after neutralising, the water can be discharged into the sewer for processing. This would have to be in accordance with local regulations and is normally subject to a specific ‘trade waste’ agreement with the local water utility. Regeneration The key to successful regeneration (or recycling) is the careful segregation of each type of used fluid. For example, mixing with metalworking fluids such as cutting oils or coolants will render the used hydraulic fluid unfit for reclamation. Regeneration (otherwise known as laundering) involves the removal of water, particulate matter and acidic degradation products. The fluid is then returned to the user. Additive levels may be replenished after consultation with the fluid supplier. For users of large volumes of hydraulic fluids, on-site reconditioning is now a feasible option that saves the cost of transportation to off-site locations for processing. Recycling Recycling (also known as re-refining) involves the complete removal of the additives and contaminants. This subjects the used fluid to a range of chemical treatments to remove impurities, followed by distillation of the base oil from the additives. The preferred option for disposal of water glycol (HFC) fluids is to recover the base stock components. This involves filtering the used fluid to remove wear metals, sludge and other contaminants. The glycol and water are then separated by distillation; the glycol is recovered and the water recycled or disposed of. The small amount of polymer-based sludge that remains and the solid material from the filtration process should be disposed of through a specialised contractor. Most water glycol fluids are readily biodegradable and are therefore amenable to disposal through the waste water treatment plant. As stated earlier, this would have to be in agreement with the local utility. The fluid can be supplied to the waste water treatment plant either by tanker or through the sewer network. Heavy metals and other contaminants would have to be removed from the waste fluid (e.g., by filtration) prior to disposal. HFC fluids should never be discharged to a watercourse as this could cause a major pollution incident due to the high biological oxygen demand. This is also true for environmentally acceptable fluids (HETG, HEES and HEPG). Containers Medium - large containers, such as 200-litre drums or IBCs (intermediate bulk containers), should be emptied and returned to the supplier or a specialist reconditioner. It is important that the container still retains its original label or markings to identify the previous contents. To obtain a copy of ‘Hydraulic Fluids – A Practical Guide’, contact the BFPA on 01608 647900 or email: enquiries@bfpa.co.uk.