Two-Phase Acid/Gas Anaerobic Reactor for Industrial Wastewater of Food & Drink SME Industries

Food and beverage wastes are rich in organic material such as carbohydrates, proteins, oils, fats, sugars and others. Those high levels of organic material translate in high amounts of chemical oxygen demand (COD) and biochemical oxygen demand (BOD) which cause several pollutions problems, such as water quality degradation and air pollution. Anaerobic digestion (AD) appears as a great solution given its ability to treat and convert organic matter into biogas. The current objective is to use a two-phase AD to treat wastes from juice (apple pulp) and winery industry (winery waste with grape concentrated (WWGC)) in order to convert as much COD into biogas. For this, several operational conditions were studied. Firstly, biogas was produced when treating waste apple pulp. The best conditions for the acidogenic phase were: Organic loading rate (OLR) of 35.05±2.30 g COD/(L.day); Hydraulic retention time (HRT) of 1 day; T 30ºC; pH of 5.45. The yield in terms of VFAs conversion from sugar was 0.46 g ΔVFA COD/g sugar COD. For the methanogenic phase, the best conditions studied were: OLR of 7.26±0.38 g COD/(L.day); HRT of 2.5 days; T 37ºC; pH of 7.5. The methane yield achieved was 0.32±0.03 L CH4/g COD. Secondly, WWGC was treated using the two-phase AD producing biogas. In the acidogenic phase, the optimum conditions were: OLR of 23.20±6.51 g COD/(L.day); HRT of 1 day; T 30ºC; pH of 5.45. The yield of VFAs conversion was 0.50±0.23 g ΔVFA COD/g sugar COD. In the methanogenic phase, the highest methane yield achieved was 0.34±0.03 L CH4/g COD with the following conditions: Organic loading rate of 9.70±0.81 g COD/(L.day); HRT of 2 days; T 30ºC; pH of 7.5. Optimization of the operational conditions lead to a better performance of the two-phase AD process when treating both wastes tested. A significant COD removal and a high methane yield were achieved for both wastes