Research Paper Anaerobic digestion of cheese dairy wastewater following chemical oxidation Apostolos G. Vlyssides*, Emmanuil S. Tsimas, Elli Maria P. Barampouti, Sofia Th. Mai National Technical University of Athens, School of Chemical Engineering, 9, Heroon Polytechniou St., Zografou, 15700 Athens, Greece article info Article history: Received 30 March 2012 Received in revised form 25 July 2012 Accepted 1 September 2012 Published online 6 October 2012 As global cheese production has gradually increased there has been a proportional increase in the wastewater produced which poses serious environmental problems. Conventional anaerobic treatment processes are often used for dairy wastewaters. However, lipids inhibition and high suspended solids concentrations are the main operational problems for anaerobic digesters treating dairy wastewater. The performance of a pilot scale cheese production wastewater treatment plant that includes an oxidation pretreatment stage and a UASB (upflow anaerobic sludge blanket) reactor was investigated. Monitoring was performed during the start-up period, the fully operational period and the period following wastewater depletion. The data from this six month period are presented and evaluated. The mean composition of raw wastewater was: chemical oxygen demand (COD) 20,314 mg l 1 , total organic carbon (TOC) 7920 mg l 1 , total Kjeldahl nitrogen (TKN) 285 mg l 1 , total phosphate (TP) 85 mg l 1 , fats 1931 mg l 1 and pH 4. In the oxidation pretreatment stage fats presented a significant reduction that reached 80% and the sharp peaks of the all pollution parameters of the raw wastewater were adequately smoothed. The anaerobic digester performance was considered satisfactory, since the COD reduction >90%. A significant fraction of the input carbon was retained in the sludge bed as “absorbed” carbon and then hydrolysed slowly following first order kinetics with a hydro- lysis rate constant of 0.0036 d 1 . The pilot plant operation showed that the proposed technology could be sustainable not only in terms of the treatment of cheese-dairy wastewater but for their energy utilisation as well. ª 2012 IAgrE. Published by Elsevier Ltd. All rights reserved. 1. Introduction In many parts of the world, the dairy industry is a major source of food processing waste. The European Union (EU) is the dominant global milk producing region with 143 MT per year, or 23% of world production, with India (88 MT) and the United States (77 MT) also being substantial producers, while production in China is increasing rapidly. Overall, about one third of world production is consumed as fresh milk and the rest as various dairy products. A wide range of products can be manufactured ranging from fresh milk and short shelf-life milk products (e.g., flavoured milk and yogurt) to longer shelf-life products such as butter, cheese, and milk powders (Liu & Haynes, 2011). The principals of cheese making are similar for all types of cheese but limitless variations exist in all stages of the process, resulting in the production of many different types, often from the same factory. Cheese is produced by coagulation of the * Corresponding author. E-mail address: avlys@tee.gr (A.G. Vlyssides). Available online at www.sciencedirect.com journal homepage: www.elsevier.com/locate/issn/15375110 biosystems engineering 113 (2012) 253 e258 1537-5110/$ e see front matter ª 2012 IAgrE. Published by Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.biosystemseng.2012.09.001