Hydrogen (H₂) as a clean fuel holds global potential and can be produced through bio-processes. To enhance bioH₂ yields, integrated systems have been proposed, combining dark fermentation (DF) of wastewater with a subsequent photofermentation (PF) stage involving purple non-sulfur (PNS) bacteria. Mixed cultures of PNS bacteria and their microbial ecology have been relatively understudied despite the known benefits of mixed cultures in industrial applications. The aim of this study was to obtain various mixed cultures of PNS bacteria under different environmental conditions during the enrichment stage. Four different mixed cultures were obtained (A, B, C, and D). However, in the H₂ production phase, only Consortium A, which had been enriched with malic acid as the carbon source, exposed to 32 W m⁻² of irradiance, and subjected to intermittent agitation, produced H₂ with a yield of 9.37 mmol H₂ g⁻¹ COD. The consortia enriched were a hybrid of PF and DF bacteria. Especially in Consortium A, Rhodopseudomonas palustris was the dominant organism, and various DF bacteria were positively associated with H₂ production, with their dominance comparable to that of PNS bacteria. Despite the reported low yields, optimizing environmental conditions for this culture could potentially enhance hydrogen production from DF effluents.

One of the research areas is the agricultural use of treated wastewaters, because it represents a unique opportunity to solve the problem of water supply for irrigation and at the same time the disposal of treated water. Anaerobic digestion appears as an interesting alternative, since anaerobically treated wastewaters can be used for irrigation purposes. These considerations are applied to the Chilean pisco industry (a traditional alcoholic drink, prepared by distillation of wine made mainly from Muscatel grapes), where high concentrated wastewaters are produced: vinasses originate as a residue from the distillation operation. Two laboratory reactors fed with wine vinasses, a UASB and an EGSB, were used in order to study the anaerobic treatability of the wastewater. Then, a pilot reactor was built (60 m³ UASB digester) and treated water was used to irrigate eucalyptus trees. Finally a 300 m³ reactor, including biogas treatment for its reuse, was developed. Results showed, both at laboratory and full scale, that anaerobic treatment is suitable for pisco's wastewaters, and also that the nutrient content of treated water can be beneficial for plant growth, reducing the need for fertilizers. Another kind of investigation was carried out in order to study the stability of anaerobic granules and how it can be recovered. UASB and EGSB were fed with low, medium and high load wastewaters, in order to evaluate possible fluctuations in the productive process. From these results, it was possible to propose and to apply recovery techniques to the digesters when they are destabilized.