• Energy Research

This review article compiles the various advances made since 2008 in sustainable high-rate anaerobic technologies with emphasis on their performance enhancement when treating agro-food industrial wastewater. The review explores the generation and characteristics of different agro-food industrial wastewaters; the need for and the performance of high rate anaerobic reactors, such as an upflow anaerobic fixed bed reactor, an upflow anaerobic sludge blanket (UASB) reactor, hybrid systems etc.; operational challenges, mass transfer considerations, energy production estimation, toxicity, modeling, technology assessment and recommendations for successful operation

This review article compiles the various advances made since 2008 in sustainable high-rate anaerobic technologies with emphasis on their performance enhancement when treating agro-food industrial wastewater. The review explores the generation and characteristics of different agro-food industrial wastewaters; the need for and the performance of high rate anaerobic reactors, such as an upflow anaerobic fixed bed reactor, an upflow anaerobic sludge blanket (UASB) reactor, hybrid systems etc.; operational challenges, mass transfer considerations, energy production estimation, toxicity, modeling, technology assessment and recommendations for successful operation

Abstract Municipal sludge from primary settling tanks of the Sewage treatment plant (STP) is a potentially important bio mass for the production of bio gas. Large amount of sludge is daily produced at wastewater treatment plants (WWTPs) where anaerobic digesters are located. Coupling the waste water treatment plant with the micro-algal culture is currently considered one of the most promising avenues towards the production of renewable bioenergy, either in the form of biodiesel or biogas. Research on anaerobic digestion of microalgae and sewage sludge will be important for the future of WWTPs because it could be a key step for recycling nutrients for algal cultivation as well as for energy recovery. Any co-substrate can have a co-effect in the sense that they stimulate enzymatic synthesis that can also improve the anaerobic digestion yield. Studies have shown that co-digestion can increase the anaerobic digestibility of algae by improving the substrate composition. Early studies have shown that due to the difference in anaerobic inocula, waste composition, and the experimental environment the quantity and the quality of the methane production vary widely. Sewage Sludge improves the digestibility of microalgae and enhances the production of methane. Co-digestion of waste paper and algal sludge could efficiently balance the feed stock Carbon–Nitrogen(C/N) ratio between 20–25 likely to benefit the methane production rate. This paper reviews recent experimental findings of the co digestion of algae with sewage and several substrates and the methods to enhance the methane production and the factors affecting the augmentation of the bio gas.

Abstract Municipal sludge from primary settling tanks of the Sewage treatment plant (STP) is a potentially important bio mass for the production of bio gas. Large amount of sludge is daily produced at wastewater treatment plants (WWTPs) where anaerobic digesters are located. Coupling the waste water treatment plant with the micro-algal culture is currently considered one of the most promising avenues towards the production of renewable bioenergy, either in the form of biodiesel or biogas. Research on anaerobic digestion of microalgae and sewage sludge will be important for the future of WWTPs because it could be a key step for recycling nutrients for algal cultivation as well as for energy recovery. Any co-substrate can have a co-effect in the sense that they stimulate enzymatic synthesis that can also improve the anaerobic digestion yield. Studies have shown that co-digestion can increase the anaerobic digestibility of algae by improving the substrate composition. Early studies have shown that due to the difference in anaerobic inocula, waste composition, and the experimental environment the quantity and the quality of the methane production vary widely. Sewage Sludge improves the digestibility of microalgae and enhances the production of methane. Co-digestion of waste paper and algal sludge could efficiently balance the feed stock Carbon–Nitrogen(C/N) ratio between 20–25 likely to benefit the methane production rate. This paper reviews recent experimental findings of the co digestion of algae with sewage and several substrates and the methods to enhance the methane production and the factors affecting the augmentation of the bio gas.

An anaerobic fixed bed reactor, filled with small floating supports of polyethylene material (Bioflow 30) as inert media, was operated for 6 months to treat vinasse (wine residue after distillation). Bioflow 30 has a density of 0.93 and a specific area of 320 m2/m3. The experimental results showed that the efficiency of the reactor in removal of soluble COD was very good with a maximum organic loading rate of more than 30 g of COD/L.d and a COD removal efficiency of more than 80%. Bioflow 30 showed a high capability of biomass retention with 4–6 g of dried solids per support. Thus, at the end of the experiment, the fixed biomass represented 57 g of solids/L of reactor. The visual observation of the supports and the specific activity (0.54 g COD/g solids.d) of the fixed solids, which remained close to the values obtained with suspended biomass, showed that entrapment was playing an important role in the retention of the biomass inside the reactor. It was then possible to operate the reactor with a very high loading rate as the result of the increase of the solids in the reactor and the maintaining of the specific activity. Bioflow 30 is then an excellent support for use in a high rate anaerobic fixed bed.

An anaerobic fixed bed reactor, filled with small floating supports of polyethylene material (Bioflow 30) as inert media, was operated for 6 months to treat vinasse (wine residue after distillation). Bioflow 30 has a density of 0.93 and a specific area of 320 m2/m3. The experimental results showed that the efficiency of the reactor in removal of soluble COD was very good with a maximum organic loading rate of more than 30 g of COD/L.d and a COD removal efficiency of more than 80%. Bioflow 30 showed a high capability of biomass retention with 4–6 g of dried solids per support. Thus, at the end of the experiment, the fixed biomass represented 57 g of solids/L of reactor. The visual observation of the supports and the specific activity (0.54 g COD/g solids.d) of the fixed solids, which remained close to the values obtained with suspended biomass, showed that entrapment was playing an important role in the retention of the biomass inside the reactor. It was then possible to operate the reactor with a very high loading rate as the result of the increase of the solids in the reactor and the maintaining of the specific activity. Bioflow 30 is then an excellent support for use in a high rate anaerobic fixed bed.