Slaughterhouse wastewater is a difficult to treat because it contains high concentrations of suspended solids and colloidal compounds, such as blood, protein, fat and cellulose. The wastewater is characterized by high loads of biodegradable organic compounds, oil and fats, nitrogen and phosphorus. The treatment train typically starts with a pre-treatment to decrease the high concentrations of solid particles and fats, and is followed by an anaerobic biological treatment system. There is currently no simpler (involving only a single stage) method of effectively treating this wastewater at an acceptable cost.
The technology studied in this TKI project is aimed at treating high-strength slaughterhouse wastewater in a single step. It should also offer the possibility for on-site resource recovery (energy, nutrients).
This project will use a test-site to test and further develop a new, Dutch-developed, anaerobic technology. The technology is a non-conventional, self-regulated anaerobic SBR (sequencing batch reactor), which was developed for high-strength wastewater, such as that produced by slaughterhouses.
Although the system processes the wastewater in batches, what most distinguishes it from conventional anaerobic SBR systems is that it conducts different stages of the treatment process simultaneously per cycle. This means that reaction times are maximised and a complete degradation is achieved, without compromising the total duration of the process.
The treatment of wastewater streams with slowly degradable substrates, such as suspended solids and fat, oil and grease (FOG), presents a major challenge for the food industry. It is particularly difficult to achieve the complete degradation of the compounds in the wastewater, and avoid their accumulation in the reactor. In addition, a variety of undesirable effects, like foaming events, sludge floating, and high long-chain fatty acid concentration, can occur during the course of the treatment. These complications make it difficult to treat high-strength slaughterhouse wastewater efficiently. Although there are other technologies that are able to achieve high biodegradation levels, there is as yet no simple, single-stage method for the effective and efficient anaerobic treatment of slaughterhouse wastewater. The partners in this research project aim to demonstrate a stable/robust pilot reactor for the treatment of a slaughterhouse’s high-strength wastewater, which should ultimately lead to the further scaling-up of the technology for this application.
The successful testing of the described technology will offer sectors such as the slaughterhouses a more effective and, in particular, a less costly solution for direct anaerobic water treatment.
The anaerobic reactor configuration shows an extremely high tolerance potential for fats, suspended solids and fluctuations in the raw wastewater composition. The system is also easy to manage and operate, and provides high treatment performance (90% total COD conversion to biogas), good solids separation and operational flexibility. The technology is designed for a cost-efficient treatment – that is, without pre-treatment or the addition of chemicals – of high-strength wastewater with strongly fluctuating COD (5-50 g/L), and high loads of suspended solids (1-20 g/L SS) and/or FOG (0-4 g/L). The project activities include the testing, evaluation and optimization of the anaerobic reactor system’s operational regime. The pilot tests will take place at a pig slaughterhouse wastewater treatment plant located in the Netherlands. The project will involve the conduct of state-of-the-art research methods and laboratory analyses. These will increase our understanding of the degradation of slowly degradable compounds in slaughterhouse waste streams.