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.

In this work the anaerobic monodigestion for the treatment of turkey manure was evaluated, without its codigestion with another substrate. The effect of the organic loading rate (OLR) and the substrate concentration (high total solids (TS) concentration) or product concentration (high volatile fatty acids (VFA) and/or ammonia (NH(3)-N) concentrations) was studied. The results show that for a continuous stirred tank reactor (CSTR) operation, a maximum of 40 g/L of TS and 4.0 g/L of ammonium (NH(4)(+)) was required. In addition, the maximum organic loading rate (OLR) will not exceed 1.5 kg VS/m(3)d. Higher TS and NH(4)(+) concentrations and OLR lead to a reduction on the methane productivity and volatile solids (VS) removal. During the CSTR operation, a high alkalinity concentration (above 10 g/L CaCO(3)) was found; this situation allowed maintaining a constant and appropriate pH (close to 7.8), despite the VFA accumulation. In this sense, the alkalinity ratio (α) is a more appropriate control and monitoring parameter of the reactor operation compared to pH. Additionally, with this parameter a VS removal of 80% with a methane productivity of 0.50 m(3)(CH4)/m(3)(R)d is achieved.

This work demonstrates the possibility to make a full valuation of a solid waste such as turkey manure, to obtain methane and a soil conditioner/fertilizer from turkey manure anaerobic digestion in a mesophilic pilot-scale continuous stirred tank reactor at different organic loading rates (OLR) (from 0.5 to 2.5 kgVS/m 3 d). The application of the anaerobic mono-digestion for the turkey manure treatment was an efficient alternative, because high volatile solids removal and methane were obtained in addition to obtaining a stabilized solid waste that can be applied as soil conditioner, based on its nutritional parameters and humic substances content. In this way, the turkey manure anaerobic digestion can be applied avoiding the co-digestion of the manure with other wastes and allows a process devoid of pollutant emissions, obtaining two products. The reactor operation depends on the OLR, and its operation does not allow an OLR above 1.5 kgVS/m 3 d. Higher OLR produced a decrease in the TS and VS removals and methane productivity.

The operation of two different reactor configurations (UASB and EGSB), while treating medium and low concentrated wastewater (MCW and LCW, respectively), was studied. The MCW (5 g COD/l) was initially supplied for reactor start up and granule maturation, being subsequently changed to the LCW (0.5 g COD/I), with which led the reactors to an unstable state associated with the deterioration of granule characteristics, in terms of extracellular polymeric substances (EPS) content and composition. The addition of pectin as an exogenous EPS was considered as a way to directly act on granule characteristics and its effect was studied by monitoring the operational parameters as well as by following the EPS content and composition within granules and the dynamics of microbial populations. The effect of adding pectin led to a significant recuperation of the operational performance in both reactors, associated with the increase in Archaea relative abundance, this likely related to the major presence of Methanosaeta-like microorganisms in granules with higher activity and stability.

Anaerobic digestion development has been marked by a constant evolution. Initially it was born as an efficient way to solve environmental problems, but later, a more comprehensive vision was adopted with the inclusion of the issues of biogas, bio-solids and irrigation water utilization. Later on, energy issues started being more relevant and to gain strength. Currently, a new concept has been included as a fundamental variable in environmental processes, namely, the reduction of greenhouse gases. In fact, the regulated/voluntary carbon market has a diversity of developing projects that otherwise would not be possible to be developed. In other words, anaerobic digestion must be viewed as a technology that must be thought about from a systemic viewpoint, where not only a contribution to the waste problem is made, but in addition, a contribution is made to the Planet's environmental and energy sustainability. In this work a new systemic approach for biogas projects is shown. How the carbon market can help to solve environmental and energetic problems, especially in under developed countries. Finally, a real project is described as an example in order to validate this approach.