OOil, fats and hydrocarbons commonly comprise around 2% of wastewater content. These organic compounds can present a challenge for traditional wastewater treatment systems due to the toxicity of the sludge by-products that remain after treatment. In Spain, according to data from the National Registry of Sludges, around 1.2 million tonnes (dry matter) of this sludge is produced annually and 8% of it is dumped in landfills. New solutions for treating oil, fats and hydrocarbons in wastewater are needed in order to find ways of reusing the organic compounds and reducing pressure on landfill.
The main objective of the LIFE-PURIWAT project was to design and develop a pilot plant, with a treatment capacity of 5 000 dm3 per hour, which would be able to remove between 97% and 99% of hydrocarbons, oil and fats from wastewater, thereby satisfying the requirements of current European directives. The project’s aim was to implement a pilot plant using a filter made from a specific elastomeric material and a biodegradation system comprising microorganisms that can degrade or remove contaminants. This would enable the target organic materials to be either separated and reused for secondary purposes, or eliminated altogether. The project planned to test its technology on different types of wastewater to demonstrate its broad potential application.
The LIFE-PURIWAT project achieved its main objective of designing and developing a demonstrative pilot plant capable of purifying 5 000 dm3 per hour, which removed between 97% and 99% of oils, fats and hydrocarbons present in wastewater.
The project team developed a novel filter capable of retaining natural organic contaminants from wastewater. The project team designed and constructed a pilot plant, which was operated at the Los Arcos wastewater treatment plant in Navarra, Spain. It included the new filter made using an elastomeric material and a biodegradation system that uses microorganisms capable of degrading the fats, oils and hydrocarbons present in the wastewater after the filtration stage. As a result of the project’s technology, there was a reduced discharge of oil, fat and hydrocarbon contaminants in the processed wastewater, estimated to be below 2%. This purified wastewater was therefore of a higher quality than wastewater from traditional plants and can be used for a wider range of applications, including irrigation.
The project team achieved a technology capable of being applied in different sectors, which could be located in strategic places to manage the separation of these contaminants from wastewater. It gives a high added-value and provides recycled water for common applications. This type of pilot plant offers advantages in different sectors that nowadays have problems with the separation of wastes from water. The adaptability of the plant for different installations, to enable the treatment of wastewater from different sources, demonstrated a considerable replication and transfer potential.
The project beneficiaries also studied the recyclability and reuse of the elastomeric material and the filtered organic waste. Sludge is the main by-product generated, which is a potentially important source of organic matter and nutrients.
The project’s technology offers significant environmental benefits. Used oils, in particular, are one of the most abundant wastewater pollutants, but traditional treatments for water purification do not resolve acute pollution or problematic pollutants. For hydrocarbons, the project’s technology offers a more efficient solution, to replace the use of several different techniques that are currently used together in existing plants.
Key project innovations were the: 1) development of a new cost-effective tertiary wastewater treatment to meet specific demands for the removal of oils, fats and hydrocarbons from wastewater; 2) development of a new application technique to reduce the environmental impacts arising from the discharge of oil; and 3) development of a novel absorbent elastomeric material.
The beneficiaries developed the elastomeric material in the laboratory and scaled up the process for use in the pilot plant. This involved, for example, a roller system for natural rubber mastication; and the optimisation of a mixture of the necessary reagents (antioxidant, zinc oxide, stearic acid, sulphur, accelerant, foaming agent). The most suitable materials were also identified for the encapsulation of the bacteria (starch and a sodium alginate suspension) in the biodegradation system.
The project’s wastewater purification technology will make useful contributions to EC directives, particularly the Water Framework Directive (2000/60/CE) and the Urban Waste Water Treatment Directive (271/91/CEE).
In terms of socio-economic impacts, the benefits to be gained are mainly through the increase of available resources. The water filtered and refined through the pilot plant brings significant advantages compared to water leaving traditional wastewater treatment plants: it ensures a higher quality resource is available for reuse; the regenerated water can reduce the exploitation of already overexploited aquifers; it will provide ecological water flows; its use in agriculture can help decrease the consumption of fertilisers; and it will provide alternatives to the discharge of treated water in areas where it is difficult. Reclaimed or reused water capitalises the processes, making it economically viable. The project therefore provides a valuable technology and a pioneering approach for the rational management of water resources. Finally, the implementation of the modular pilot plant was shown to be feasible in the geographical area of northern Spain, where it will be further developed to benefit the population and the economy of the area.
Further information on the project can be found in the project's layman report and After-LIFE Communication Plan (see "Read more" section).