The construction industry must meet current environmental requirements, mostly those pertaining to the reduction in construction and demolition waste and the consumption of raw materials. The use of recycled concrete aggregates can be part of the solution, but one question that arises is how many times recyclables can be recycled. This unknown involves other related queries regarding the properties and possible uses of repeated recycled concrete aggregates. This research is derived from the precast concrete industry, where multi-recycling is a pressing need. From good-quality parent concretes, three cycles of recycled concrete aggregates were produced and analysed. The final results are promising due to the good quality of the recycled and multi-recycled concrete aggregates obtained. Not only can they be used in low-level applications (backfilling) as usual, but they can also be used for more demanding purposes, such as graded aggregates, cement-treated road bases and concrete pavements. Their use in structural concrete is feasible, but it will be dependent on the water absorption level and the amount of recycled aggregate substitution. This research proves the viability of multi-recycled concrete aggregates with all of the associated environmental benefits.

The treatment of wastewater from small towns supposes problems of economic efficiency, leading to very high environmental costs in areas with low population density. Constructed wetlands (CW) seems to be the more suitable solution for this kind of situation, but further investigations are needed regarding their efficiency under different climatic conditions. This work presents the results concerning urban wastewater treatment by means of two different constructed wetlands using macrophytes: horizontal subsurface flow (HSSF) and free water surface (FWS). The systems are located in a Mediterranean continental climate area and are fed by a by-pass at the entrance of a wastewater treatment plant. A four-year sampling campaign at the outlet of the CW allowed verifying their relative effectiveness in removing pollutants in the different seasons of the year. BOD₅, COD, and TSS were significantly removed (with average reductions of 55%, 60%, and 57%, respectively) by these natural phytodepuration systems, with HSSF being more efficient during plants’ dormancy than FWS, but the concentrations of nutrients indicated that cumulative effects occur in CW with the need of adequate annual maintenance. It was found that the main factors controlling the efficiency of such systems throughout the year are the period of vegetative development, the presence/absence of a solid substrate, and the pollutant load of the wastewater inlet.

This study aims to analyse the effect of partially clogged inlets on the behaviour of urban drainage systems at the city scale, particularly regarding intercepted volumes and flood depths. The main challenges were to represent the inlet network in detail at a rather large scale and to avoid the effect of sewer network surcharging on the draining capacity of inlets. This goal has been achieved through a 1D/2D coupled hydraulic model of the whole urban drainage system in La Almunia de Doña Godina (Zaragoza, Spain). The model focuses on the interaction between grated drain inlets and the sewer network under partial clogging conditions. The model is fed with data obtained on field surveys. These surveys identified 948 inlets, classified into 43 types based on geometry and grouped into 7 categories for modelling purposes. Clogging patterns were derived from field observations or estimated using progressive clogging trends. The hydrological model combines a semi-distributed approach for micro-catchments (buildings and courtyards) and a distributed “rain-on-grid” approach for public spaces (streets, squares). The model assesses the impact of inlet clogging on network performance and surface flooding during four rainfall scenarios. Results include inlet interception volumes, flooded surface areas, and flow hydrographs intercepted by single inlets. Specifically, the reduction in intercepted volume ranged from approximately 7% under a mild inlet clogging condition to nearly 50% under severe clogging conditions. Also, the model results show the significant influence of the 2D mesh detail on flood depths. For instance, a mesh with high resolution and break lines representing streets curbs showed a 38% increase in urban areas with flood depths above 1 cm compared to a scenario with a lower-resolution 2D mesh and no curbs. The findings highlight how inlet clogging significantly affects the efficiency of urban drainage systems and increases the surface flood hazard. Further novelties of this work are the extent of the analysis (city scale) and the approach to improve the 2D mesh to assess flood depth.