Blockchain applicability in the management of urban water supply and sanitation systems in Spain.

Blockchain constitutes a disruptive technology that is currently changing business models and the way organizations operate. This paper explores the applicability of blockchain technology, and of distributed ledger technologies in general, to urban water supply and sanitation services in Spain. The potential of this technology for improving processes in this sector is assessed through a specific methodology of strategic analysis developed for this purpose. First, the technical, legal and managerial factors that condition the potential use of this technology to address the global, operational and governance challenges faced by urban water management are explored. Second, strategic analysis tools (e.g. value chain, factors of competition, and benchmarking) are used to model a water utility organization as a set of processes and characterize blockchain as an enabling technology with both benefits (traceability, immutability, and disintermediation) and limitations. Based on cost-benefit analysis, use cases in which the implementation of a blockchain could improve the organization's performance can be discerned. The results identify the processes and sub-processes of urban water utility management for which the use of a blockchain could improve performance: comprehensive maintenance, the management of serious incidents, and supplier management. Essentially, the methodology developed identifies management processes whose requirements are efficiently met through automation derived from blockchain solutions. Regardless of the management models currently in place in Spain, the traceability and disintermediation benefits of blockchain solutions can help to overcome governance and efficiency challenges associated with the management of urban water supply and sanitation services.

Application of simulation models to the diagnosis of MSW landfills: an example.

Among the landfill simulation programs being developed by several research groups around the world as tools for the management of sanitary landfills is MODUELO, whose second version, MODUELO 2, has been presented elsewhere. It reproduces the operational history of the landfill and its hydrologic and biodegradation processes, allowing the estimation of the flow and pollutants emitted in the leachate and the generated landfill gas over time. This program has been used for a diagnosis study of an existing European MSW landfill. The construction and calibration of the facility's hydrologic model, based on the available data, allowed the detection and quantification of two sources increasing the flows reaching the leachate collection system: a small portion (6-7%) of the runoff over the landfill surface and the contribution of water coming from external hillsides of the same watershed that represent a total surface area of around 20ha. The contrast of the leachate quality (COD, BOD, NH(4)-N and TKN) simulation results and measured data showed the potential of these models for the assessment of other significant aspects in landfill operation such as the potential harnessing of the landfill gas. Nonetheless, in this case as in many others, the accuracy of the simulation results was limited by the scant quality of the available data, which highlights the need for implementing continuous monitoring and characterizing protocols to take advantage of these programs as a tool for landfill optimization.

Sedimentation and prefermentation of domestic wastewater in a fixed bed biofilm reactor.

This investigation was undertaken with the aim of developing a new wastewater prefermentator reactor in order to increase the percentages of sedimentation, hydrolysis and prefermentation of all the organic matter present in the raw wastewater, using only one unit of pre-treatment. The study was carried out using a pilot fixed bed biofilm reactor of 43.3 L in net volume. HRT of 0.5, 1, 2 and 4 h were applied. The reactor has been operating for 403 days during which it has been fed on raw wastewater from the city of Santander, in Spain. The results showed that it is possible to carry out the sedimentation and prefermentation of the organic matter contained in the raw wastewater in this reactor. The TSS average elimination percentage was higher than 50% during the whole testing period. The highest percentage of TSS retained in the reactor was 70% with a HRT of 4 hours and a flow rate of 0.3 m/h. The maximum COD(Total) elimination percentage was 30% for any of the four OL tried. The COD(Particulate) average solubility was greater than 40%. About 44% of the COD(Dissolved) in the effluent consisted of VFA. The highest concentration of VFA measured in the effluent was 44 mg COD/L, applying a HRT of 1 h. The average acidising was slightly higher than 30%. The acetic, propionic, butyric and valeric acids were the species of VFA detected, the acetic acid being the one present in a larger amount (> 50%). The production rate of VFA increases as the HRT decreases.

Population dynamics in an aerobic submerged fixed bed reactor (ASFBR) process.

In this study, an aerobic submerged fixed bed reactor's (ASFBR) population dynamics has been studied in order to know its behavior in different conditions of organic load and oxygen concentration. The reactor was fed with synthetic wastewater. Tested variables and applied values were: 1) Variations in organic load (OL): 16-65 g COD/m2/d. 2) Variations in influent's COD concentration: 40-400 g COD/m3. 3) Variations in specific air flow (SAF): 15-127 m3air/kgCOD. Biofilm samples were taken at the top of the reactor. This study showed important variations in the composition and abundance of the microfauna depending on the experimental conditions. Variations in influent concentration had no significant effect on the abundance of the studied groups. However, differences depending on organic load and aeration conditions were observed. Organic load influenced every group studied but with different results. Sessile cilliates, metazoa and flagellates were abundant in low load, while crawling ones were in high load. Aeration intensity influenced most of the groups except Peranema and Vorticella spp. Despite obtaining good yields, not many protozoa, typical of biofilms under conventional processes, were found. Thus, a great variety of microorganisms, such as many classes of sessile and crawling cilliates, were not found. Important nitrifying activity was obtained at 20 cm depth in a bed. From this point, the heterotrophic and nitrifying populations exist but are inactive.

Reducción simultánea de DBO(C), NH4+, y desnitrificación en un reactor de biopelícula

Se estudió la eficiencia de eliminación de DQO, aminio, nitrificación y desnitrificación de un reactor biológico de lecho aireado sumergido, alimentado con agua residual sintética y operando en estado estacionario, con baja carga orgánica alimentada, y carga de nitrógeno alimentado. El objetivo del trabajo fue correlacionar el rendimiento de reducción de carga orgánica y nitrogenada, nitrificación y desnitrificación con las condiciones de operación

Reducción simultánea de DBO(C), NH4+, y desnitrificación en un reactor de biopelícula

Se estudió la eficiencia de eliminación de DQO, aminio, nitrificación y desnitrificación de un reactor biológico de lecho aireado sumergido, alimentado con agua residual sintética y operando en estado estacionario, con baja carga orgánica alimentada, y carga de nitrógeno alimentado. El objetivo del trabajo fue correlacionar el rendimiento de reducción de carga orgánica y nitrogenada, nitrificación y desnitrificación con las condiciones de operación

Reactor biológico de lecho aireado sumergido (BLAS): Eliminación de DBO (C), NH4 y desnitrificación

El objetivo de este estudio fué caracterizar el proceso BLAS (alimantado con ARS), operando con baja COA (15-20 gDQO/m2 día) y correlacionar el rendimiento de eliminación de carga orgánica y nitrogenada, nitrificación y desnitrificación con las condiciones de operación