Research on the anaerobic treatment of raw cheese whey started in 1990 with the objective of developing a technology suitable for medium size cheese factories that have growing disposal problems and cannot afford high investment costs for whey valorisation technologies (such as whey protein and lactose recovery, spray drying, etc.). In order to couple process stability and high loads, a new downflow-upflow hybrid reactor (DUHR) has been designed. The reactor was able to reach B(v) values around 10 g COD·1-1·d-1, with 98% COD converted to gas and effluent soluble COD values close to 1,000 ppm; no external addition of alkalinity is required to maintain a stable pH that was constantly around 6.5-6.7 in the downflow pre-acidification chamber and around 7.5 in the bio-methanation upflow chamber. The high strength of the cheese whey treated gives an effluent that still contains high amounts of COD, ammonia nitrogen and phosphorus and therefore a post treatment is required in order to meet standard limits. Tests of post treatment were carried out during two years with a Sequencing Batch Reactor (SBR). The SBR was tested at various F/M values with different durations of anoxic-anaerobic-oxic cycles, obtaining, under certain conditions, more than 90% removal of COD, nitrogen and phosphorus.

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