Estefanía Bonnail

Separated liquid digestate management is a major challenge for anaerobic digestion facilities because of the digestate’s high water content, nutrient load and potential environmental impacts when land application is not adequately controlled. This preliminary single-batch case study evaluated the application of Adiabatic Sonic Evaporation and Crystallisation (ASEC) treatment to an animal-derived separated liquid digestate, focusing on water recovery and the production of a dried nutrient-rich solid fraction. The raw liquid digestate, the ASEC-recovered water and the recovered solid fraction were characterised using physicochemical and microbiological indicators. The recovered water stream showed a strong reduction in electrical conductivity from 11,289 to 42 µS/cm, with turbidity Salmonella spp. or Legionella spp., absence of intestinal nematode eggs and Escherichia coli). The recovered solid fraction contained 95% dry matter (dm), 53.5% organic matter, 3.87% total N, 36,090 mg P₂O₅/kg dm and 32,800 mg K₂O/kg, supporting its preliminary classification as candidate organic-mineral NPK fertilising material. Metal(loid)s were below the contaminant thresholds used as references in the EU for solid organic fertilisers. For a 100 m³/d treatment scenario, the estimated NPK nutrient replacement value was 63,543 USD/year; however, this value should be interpreted as a scenario-based estimate rather than a measured process-scale economic return.

The discharge of acid mine drainage (AMD) from abandoned mining sites remains a major cause of water quality degradation, particularly in mine-affected regions such as the Iberian Pyrite Belt. The effectiveness of a full-scale passive treatment plant employing the Dispersed Alkaline Substrate (DAS) technology was assessed through a combined chemical and biological monitoring program at the Esperanza Mine (SW Spain). Water samples were collected at an abandoned mine shaft, at the output of the treatment plant as well as at the discharge point into the receiving river. Physicochemical analyses revealed the DAS system successfully neutralized acidity, reduced electrical conductivity, and substantially lowered the concentrations of dissolved and bioavailable metals, including Fe, Zn, and Cu. Acute toxicity tests conducted with a range species (Vibrio fischeri, Raphidocelis subcapitata, Lemna minor, Artemia sp., Corbicula fluminea, and Gambusia holbrooki) showed a clear improvement in organism survival and physiological responses post-treatment. In addition, passive samplers settled in test samples to determine metal availability showed good performance for most elements (especially for Cu), but some limitation with the very acidic pH test samples. Multivariate statistical analyses distinguished acidity and metal load as the primary drivers of toxicity, both effectively mitigated after the DAS treatment. Although treated waters approached the quality of natural reference sites, residual sublethal effects suggest the need for continued ecological monitoring. These findings demonstrate the potential of DAS-based passive treatments to restore chemical and ecological conditions in AMD-impacted systems and contribute to broader environmental objectives, including compliance with the European Water Framework Directive.

Textural and geochemical analysis of intertidal sediments in the southern Atacama region makes it possible to identify sites primarily affected by mining-related pollution, based on a multivariate statistical analysis of the concentrations of five elements (Fe, Cu, Zn, As, Pb) and their geoaccumulation indices. These concentrations are not correlated with grain size, which is dominated by the sandy fractions. Spearman’s matrix and principal component analysis make it possible to distinguish between two groups of elements (group A: Fe-Cu-As; group B: Zn-Pb), with a strong correlation between them (ρ ≥ 0.51; p < 0.01) and the first two components explain 96.3% of the variance. Three heavily polluted sites (Playa Blanca, Bahía Sarco and Chañaral de Aceituno; I_geo Cu > 8) have been identified linked to waste from the washing of tailings, a copper smelter and frequent boat trips. In addition, four moderately polluted sites (Playa Grande, Balneario Caldera, the mouth of the Copiapó River and Carrizal Bajo; 1.7 < I_geo Cu < 8; 1.2 < I_geo Pb < 2.6), mainly due to activities associated with mining and oil refineries, have been identified.

Scientific knowledge of Andean salt flats remains limited, especially for those lacking formal protection, despite growing industrial interest in their mineral resources. This study presents new ecological and environmental data for the Salar de Loyoques (also known as Quisquiro), located in the northern Chilean Altiplano. We conducted seasonal field surveys assessing hydrochemistry, vegetation, birds, and reptiles, and compared our findings with existing literature. We recorded 18 bird species, including three flamingo species, six of which are classified as vulnerable or endangered, and confirmed a new record of the vulnerable reptile Liolaemus audituvelatus. Vegetation cover was sparse; Azorella compacta, a vulnerable species, was observed. Hydrochemical analysis showed predominance of chloride and chloride-sulfate water types, with elevated levels of B, As, and K. These hydrochemical conditions appear to influence the presence and distribution of sensitive species, particularly those dependent on wetlands and brine pools. The Salar functions as a crucial biological corridor for species of conservation concern. Our results underscore the urgent need for formal protection of this unique high-Andean ecosystem. This study fills a significant gap in knowledge about understudied Andean salt-flats, providing baseline data to inform future conservation and monitoring efforts.

This communication analyzes the distribution of benthic foraminifera in the infralittoral zone of northern Chile located between 26° and 29°S at depths between 7 and 12 m. Twenty-six taxa have been identified, whose density is mainly conditioned by grain size and hydrodynamics of the environment. A comparison with other coastal sectors of the Pacific coast of South America allows us to identify the most representative species of this area from southern Chile to Colombia. The results obtained are very interesting for their possible application in the reconstruction of Holocene paleoenvironments in the Atacama Desert.

Infralittoral ostracods from the southern Atacama Desert

The Adiabatic Sonic Evaporation and Crystallization (ASEC) technology was developed as a disruptive zero-liquid discharge system to treat contaminated mining effluents. This study evaluates its ecotoxicological efficacy using Lemna minor, a freshwater macrophyte, as a sensitive bioindicator. Acute growth inhibition tests were conducted using OECD Guideline 221. Lemna minor was exposed for 7 days to untreated and treated effluents from the Tharsis mine and the Tinto River in southern Spain. The results revealed 100% inhibition of frond growth and biomass in untreated samples (pH < 2.6), indicating acute toxicity. In contrast, effluents treated with ASEC showed growth and biomass accumulation statistically indistinguishable from the control, confirming the system’s efficiency in reducing toxicity and restoring water quality. These findings support the environmental viability of ASEC technology for mine and port effluent treatment.

Seawater desalination is considered the first option to meet the domestic and industrial requirements of freshwater in desert areas, such as the Atacama Desert (Chile). However, its environmental implications remain poorly characterized. This study evaluated the effects of brine discharge from a desalination plant located in Caldera Bay, where fishing and tourism coexist. Sampling was conducted at increasing distances from the outfall to assess physicochemical parameters, sediment metal content, and nutrient concentrations. The results revealed a clear spatial gradient: salinity decreased from 57.75 to 34.87 PSU and nitrate from 10.49 to 4.05 µM. The sediment samples near the outfall showed elevated concentrations of Al, Fe, and Cr(VI). These findings suggest that brine discharge alters water chemistry and sediment quality. This study highlights the need for long-term environmental monitoring and regulatory frameworks to ensure sustainable desalination in sensitive coastal systems.