This paper focuses on the legal and institutional framework of urban water services in Spain, emphasizing water sanitation by using proposals that would positively contribute to wastewater management in Brazil. The recent Brazilian Federal Law No. 14,026/20 aims to encourage investment in water sanitation, promoting public-private collaboration formulas so that service management is viable even in economically less-favored regions. In Spain, sanitation policies are aimed at fulfilling the set of obligations and objectives imposed by European Union Directives within the environmental policies of the Union. From an economic point of view, supply and sanitation water services are classified at European legal framework as “services of general economic interest” (SGEI), not subject to harmonized regulation and open to a natural monopoly provision regime, which they admit various types of management formulas, public and private, based on the ownership and public intervention of the service, both at national and European level. We believe that the Spanish experience in this field, beyond its singularities, can serve as a useful reference for Brazilian’s urban wastewater new regulation for several reasons: (1) Because of the decentralized political scheme that both countries share and the need to articulate an adequate system of competencies in consequence; (2) Because of the international experience that Spanish companies have at the sector’s technological forefront, they are very competitive; (3) Due to the adequate functioning of the Spanish legal and organizational framework since, despite its shortcomings, as we later will comment, it has managed to develop successful financing formulas and management models that, in general terms, have allowed to ensure with reasonable efficiency, continuity, stability and sustainability in the provision of urban water services. Full article

Sulphide build-up in pressure sewers has been identified as the main cause for the occurrence of odour and corrosion in sewer systems. Despite the efforts to optimize commonly used control technologies such as nitrate and iron salts to reduce sulphide emission, continuous addition of these chemicals is still required. A biocidal agent such as free nitrous acid can be added intermittently, less frequently, and in smaller quantities whilst achieving total sulphide control. So far, laboratory and field studies in Australia and the USA have successfully proven and applied the use of this control technology, exhibiting its strong biocidal effects during intermittent addition. In this study, nine trials were made to assess the application of the free nitrous acid (FNA) as an alternative sulphide control technology in Germany. The sewer pilot plant of the Berlin Water Utility Company was used to perform the trials at a technical scale using a supply of raw sewage. FNA exposure times ranging from 5 to 24 h in varying concentrations were investigated. The effectiveness of the FNA treatment was monitored using the online hydrogen sulphide (H₂S) gas and dissolved-sulphide sensors installed in the sewer pilot plant. Effective sulphide control was only possible during dosing periods, with rapid resumption of sulphide production for the trials with exposure times of <12 h and concentrations ranging from 0.08 to 0.56 mg HNO₂-N L⁻¹ suggesting a slight inhibitory effect. A more pronounced biocidal effect was observed for the trials exposed to FNA treatment for 24 h at concentrations >0.29 mg HNO₂-N L⁻¹. Overall, the trials of this study demonstrated that the biofilms were FNA resistant and that the concentrations and exposure times used were inadequate to develop an effective intermittent dosing strategy. Full article

In large-scale regional models, used for the management of underground resources, it is quite common to find that relationships between the regional aquifer and small wetlands are not included. These models do not consider this connection because of the small amount of water involved, but they should consider the potential for significant ecological impacts if the groundwater resources in the ecosystems associated with these wetlands are mismanaged. The main objective of this work is to investigate the possibilities offered by MODFLOW LGR-V2 to represent (at small scale) the Santa Olalla pond, located in the Doñana Natural Park (South of Spain), and its relationship with the Almonte-Marismas regional aquifer. As a secondary objective, we propose to investigate the advantages and disadvantages that DRAIN, RIVER and LAKE MODFLOW packages offer within the MODFLOW LGR-V2 discretizations. The drain boundary condition with a coarse discretization implemented through ModelMuse allows the most adequate performance of the groundwater levels in the environment of the pond. However, when using lake boundary condition, the use of the MODFLOW LGR-V2 version is particularly useful. The present work also gives some guidelines to employ these packages with the MODFLOW graphical user’s interface, ModelMuse 4.2. Full article

Lake Qinghai in the Qinghai-Tibet plateau is the largest lake in China, but the geochemical understanding of arsenic (As) in the lake is lacking. Water, sediment, and soil samples were collected from Lake Qinghai, rivers flowing into the lake, and lands around the lake. Water samples were analyzed for major ions and As, while sediment and soil samples were analyzed for major elements and As. The average As concentration (25.55 μg L⁻¹) in the lake water was significantly higher than that (1.39 μg L⁻¹) in the river water (p < 0.05), due to the evaporative concentration of lake water. The average As concentration (107.8 μg L⁻¹) in the pore water was significantly higher than that in the lake water, due to its secondary release from sediment solid phases in the reductive condition. The average As/Cl⁻, As/SO₄²⁻ and As/Na molar ratios in the lake water were significantly lower than that in the river water, indicating As was partially transferred from dissolved phase to solid phase in the evaporative concentration process of the lake water. The average As/Ca molar ratio in the lake water was significantly higher than that in the river water, indicating more Ca than As precipitated in the lake water. Furthermore, the average As/Ca molar ratio in the lake water was significantly lower than that in the pore water, indicating more As than Ca was secondarily released from sediment solid phases. The average concentration of As(III) and As(V) were 0.35 and 1.04 μg L⁻¹ for the river water, respectively, and 6.99 and 18.56 μg L⁻¹ for the lake water, indicating As(V) was the predominant As form. The average As concentration was 16.75 mg kg⁻¹ for the lake sediment and 13.14 mg kg⁻¹ for the soil around the lake. Arsenic concentration was significantly negatively correlated with S and Ca concentration in the lake sediments, due to solid dilution effect induced by carbonate and sulfate precipitation. The average As/Sc molar ratio in the sediment (2.06) was significantly higher than that in the soil (1.32), indicating that relatively more As was enriched in the lake sediment. Full article

This study aims to investigate the influence of treated wastewater (TWW) on the hydraulic performance of drip irrigation emitters. A field experiment was conducted in order to test two types of online emitters, a low pressure (LP) and a standard pressure (SP), at different working pressures (0.25 bar, 0.50 bar, and 1.00 bar) using TWW. The emitters were initially evaluated in the laboratory and the field for the discharge exponent (X), discharge coefficient (Kd), average emitter discharge (Q_avg), coefficient of variation (CV), distribution uniformity (DU), the mean discharge ratio (Dra), and the main degree of clogging (DC). The main effect of the emitters on the hydraulic parameters of irrigation performance was not significant, while the operational pressure and operational time of irrigation had a significant effect. For the LP emitter, the average emitter discharge was 7.6, 7.7, and 7.8 Lh⁻¹ at 0.25, 0.50, and 1.00 bar, respectively. For the SP emitter, the average emitter discharge was 7.6, 7.8, and 7.8 Lh⁻¹ at 0.25, 0.50, and 1.00 bar, respectively. The EU values for the LP and SP emitters varied from low to moderate at 0.25 bar, as the EU values at 0.50 and 1.00 bar were considered high for both emitter types. Full article

Climate warming can alter the thermal conditions of reservoirs. However, some hydraulic interventions can be explored to mitigate this impact. This study investigates the long-term effects of climate on the temperature and thermal structure of a monomictic reservoir that has had varying operations from 1959 to 2016. Reservoir progressively operated through three distinct periods, namely, (A) deep penstock withdrawal (DPW; 1959–1991), (B) purely selective withdrawal (SW; 1992–2001), and (C) combination of SW and vertical curtain (VC; 2002–2016). Although annual air temperatures are increasing (+0.15 °C decade⁻¹) in the long term, the reservoir’s surface water temperatures have been found to be decreasing (−0.06 °C decade⁻¹). Periods B and C produced colder profiles and exhibited lower heat content and higher potential energy anomaly than Period A. Furthermore, stronger thermoclines, as indicated by Brunt–Vaisala frequency, were observed in the two latter periods. The results of this study show that varying operations bear a stronger influence on the reservoir’s temperature and thermal structure than climate change itself. Mitigating the thermal impacts of climate warming in reservoirs appears promising with the use of SW and VC. Full article

This paper estimates the prevalence and severity of dental fluorosis among participants in the first wave of The Aguascalientes Longitudinal Study of Child Development (EDNA). The analytical sample includes 1052 children in 100 public elementary schools. Dental fluorosis is determined using the Modified Dean’s Index. There is a 43% general dental fluorosis prevalence, and the estimated Community Fluorosis Index is 0.99. Five municipalities report average groundwater fluoride concentrations above the official Mexican guideline value of 1.5 mg/L. In those municipalities, there is a 50% average dental fluorosis prevalence. An ordered logistic regression analysis indicates that obesity in participants increases the likelihood of suffering more severe dental fluorosis symptoms compared with normal-weight participants (OR = 1.62, p < 0.05). Households consuming tap water are more likely to have children suffering more severe dental fluorosis symptoms (OR = 1.63, p < 0.05). Children aged 8 years are more likely to present more severe dental fluorosis symptoms than their peers aged 7 years (OR = 1.37, p < 0.05). Dental fluorosis will persist as a public health problem in Aguascalientes State unless appropriate technologies for fluoride removal from water are installed and operated. Full article

A key principle of agricultural best management practices (BMPs) is to improve water quality by reducing agricultural-sourced nutrients and associated eutrophication. Long-term (1998–2016) lake summer trophic state index (TSI) trends of an agricultural watershed with agricultural best management practices (BMPs) were assessed. Structural BMPs included vegetative buffers, conservation tillage, conservation reserve, a constructed wetland, and a sediment retention pond. TSI included Secchi visibility (SD), chlorophyll a (Chl), total phosphorus (TP), and total nitrogen (TN). Summer TSI 1977 was >80 in 1998–1999 (hypertrophic) and decreased over the first 10 years to TSI 1977 ≈ 75 (eutrophic). TSI 1977 decrease and changing TSI deviations coincided with vegetative buffers, conservation tillage, and conservation reserve. The TSI(SD) decrease (>90 to <70) coincided with vegetative buffers and TSI(TP) decrease (>90 to <75) coincided primarily with conservation tillage and the sediment retention pond. TSI(Chl) increase (<60 to >70) coincided with conservation tillage and vegetative buffer. Results indicate watershed-wide BMPs can modestly decrease summer trophic state through increased water transparency and decreased TP, but these changes are off-set by increases in chlorophyll a to reach a new stable state within a decade. Future research should assess algal nutrient thresholds, internal nutrient loading, and climate change effects. Full article

The capacity of ecosystems to provide ecosystem services (hereinafter referred to as ES) depends on the state of their structure, processes, and functions, which is determined by interactions with other systems. These interactions are complex and take place in different climatic areas, and have different impacts on ecosystems and the use of ES. As the most sensitive part of the Lithuanian shore zone to climate change is the seaside zone or the coastal zone, which includes the Curonian Lagoon and the sea coast, the said area was therefore chosen for research. The case study examined those ES that were specific to the study area, without attempting to account for absolutely all ES. With an emphasis on the representation of different perspectives (in the process of assessing and preserving the potential of ES), the empirical study involved representatives of different (public and private) sectors. The public sector was represented by elders and eldership employees, the private sector by farmers and businesspeople. Respondents were selected purposefully to reflect the entire existing totality of the existing area. The evaluation of the obtained theoretical and practical results of the research identified the potential of the existing area ecosystem services and perspectives for the implementation of services by assessing their use according to respondents’ opinions, regional climate change, and national scale in EU environmental policy. Full article

Currently, industries seek to optimize the development of technology from energy-saving, economic, and environmental perspectives. Dissolved air flotation (DAF) is one of the most effective wastewater treatment systems. However, it requires considerable energy and causes significant operating costs. A recently emerged application of using fluidic oscillators (FOs) to generate microbubbles has attracted extensive attention, as it consumes much less energy and has proven to be a more energy-efficient technique. In this article, a microbubble generator based on FOs is introduced into the flotation tank, and an energy-saving water treatment system, namely fluidic air flotation (FAF), is presented. Using the computational fluid dynamics (CFD) method, the flow pattern of the FAF is investigated. It is observed that FAF generates a dynamic flow pattern, which is beneficial for bubble removal. At the upper part of the separation zone, the flow pattern exhibits a wavy shape. The flow pattern at the lower part switches between clockwise and counterclockwise. The air distribution of the separation zone is also studied. It is found that the height of the “white water” zone almost linearly decreases with the increase in bubble diameter and diffuser size. FAF consumes almost no energy and occupies a small area, and it is expected to provide a promising solution to develop a new generation of the wastewater treatment system. Full article

This study aims to develop the relational equation between the color and chemical composition of discolored seawater around a submarine volcano, and to examine its relation to the volcanic activity at Nishinoshima Island, Japan, in 2020, using the model applied by atmospheric corrected reflectance 8 day composite of GCOM-C SGLI. To achieve these objectives, the relational equation between the RGB value of the discolored seawater in the submarine volcano and the chemical composition summarized in past studies was derived using the XYZ colorimetric system. Additionally, the relationship between the volcanic activity of the island in 2020 and the chemical composition was compared in chronological order using the GCOM-C SGLI data. The following findings were obtained. First, a significant correlation was observed between the seawater color (x) calculated by the XYZ colorimetric system and the chemical composition such as (Fe + Al)/Si. Second, the distribution of (Fe + Al)/Si in the island, estimated from GCOM-C SGLI data, fluctuated significantly just before the volcanic activity became active (approximately one month prior). These results suggest that the chemical composition estimation of discolored seawater using SGLI data may be a powerful tool in predicting submarine volcanic activity. Full article

The aims of the present paper were to review the knowledge about the Mediterranean non-indigenous species of the taxa Cnidaria and Ctenophora (CC NIS), to screen the risk of 98 species for their potential invasiveness in the Mediterranean Sea and their approach to the Italian waters. Of these, 38% are well established in the basin, 4% are known for their invasiveness, 44% are casual, 11% have a taxonomic status unresolved, and 3% are included in the category ”cryptogenic”. The biodiversity CC NIS of the Mediterranean Sea has changed considerably in the last two decades and 27 out of 98 Mediterranean CC NIS are present in the Italian waters. Fifteen CC NIS, some equipped with high invasive potential, should be regarded as good candidates to become future immigrants of the Italian waters. Anticipatory NIS forecast based on biogeographical and ecological analyses may provide a useful tool for targeted management of the CC NIS issue and for the assessment of the second descriptor of Good Environmental Status. On the other hand, conservation and management of marine ecosystem should be based on the conservation of the essential environmental conditions for the functioning of these ecosystems instead of the contamination or eradication of alien species. Full article

The unsaturated hydraulic characteristics of waste soil are an essential basis for predicting and evaluating leachate migration and distribution in landfills. The saturated water content and permeability coefficient were measured, and a multi-step drainage monitoring experiment was conducted indoors at different dry densities, particle sizes, and degradation ages. Single and dual permeability models were adopted to determine the unsaturated hydraulic characteristic parameters of waste. Results show that dry density and particle size are the key factors affecting the saturated water content and permeability of waste. A single degradation age has little effect on it. Respectively, the saturated water content has a linear relationship with dry density, and permeability has an exponential relationship with dry density under limited experimental data. The overflow numerical inversion method can accurately obtain the unsaturated hydraulic characteristic parameters of wastes and summarizes the values of the unsaturated hydraulic characteristic parameters of wastes with different attributes in the literature and the results of this study. The dual-permeability model performed significantly better than the single-permeability model for water movement, suggesting that a dual-domain description is required for water flow in landfills. Full article

Flow resistance, velocity distribution, and turbulence intensity are significantly influenced by aquatic vegetations (AV) in riparian zones. Understanding the hydraulics of flow with planted floodplains is of great significance for determining the velocity distribution profile and supporting the fluvial processes management. However, the traditional flume experiment method is inefficient. Therefore, the multigroup simultaneous flume test method was carried out to describe the flow patterns affected by emerged rigid (reed and wooden stick) and submerged flexible vegetations (grass and chlorella). The Acoustic Doppler Velocimeter (ADV) was utilized to measure the velocity at one point for different experimental conditions. The results showed that hydraulic features were influenced by different types of vegetation. Furthermore, the relative depth (z/h) was a determining factor of those variations. In addition, the time-averaged velocity distributions of planted floodplains are not logarithmic. Instead, they represented “s-shape” profiles. In detail, for the vegetated floodplains, reed and wood followed an s-shape profile, but for grass and chlorella, they followed reverse s-shape profile. For all cases, turbulence is not isotropic and the change law of turbulence intensity is different in different sections. The flow resistance, turbulence intensities, and Reynold stresses influenced by different types of vegetation were also analyzed. Full article

This study takes Taiwan’s Sun Moon Lake Reservoir as the research object to discuss the sustainable development decision-making of the reservoir water source area in the island area. The grounded theory was adopted to construct the framework; 835 questionnaires were analyzed by statistical test; 10 interviewees’ feelings were collected through interviews and discussions, and multiple verification methods were used for exploration. Conclusion: The study found that the current development of the reservoir water source area of the outlying islands has brought much garbage; affecting the quality of the natural environment; lake; and water source; caused the disappearance of distinctive culture and architecture. The poor interaction between businesses and communities has led to an overlap in the types of industries, consumer goods, attractions and a lack of transportation and medical facilities, affecting people’s desire to travel. The government’s future decisions include: Increasing the variety of consumer goods; improving medical and transportation facilities; preserving unique culture and architecture; linking foreign-invested enterprises with community interactivity; enhancing local people’s interaction; and compensating for the deficiencies in human resources for industrial development are the key points for future improvement of the reservoir water source area of the outlying islands. Full article