Preliminary Assessment of COVID-19 Implications for the Water and Sanitation Sector in Latin America and the Caribbean.

COVID-19 has had a severe impact on human health, as well as in social and economic terms, with implications for the management and governance of the water and sanitation sector. These implications are evident in Latin America and the Caribbean due to existing challenges the region faces in accessing water and sanitation services. In spite of significant advances, around 65 million people in the LAC region currently lack appropriate access to water and soap to wash their hands-one of the most basic measures to prevent the spread of disease. Furthermore, social and economic vulnerabilities have exacerbated the effects of the pandemic in the region, particularly among those living in poverty. The COVID-19 pandemic thus requires the mobilization of frameworks such as the human rights to water and sanitation, specifically considering the region's realities. This paper provides a review of some of the challenges currently faced in the region and advances a series of recommendations for enhancing access to water, sanitation and hygiene. The importance of effective governance, management and communication strategies in the water provisioning sector is highlighted in the context of the pandemic, and the role of science and research for adequate decision making is emphasized.

Occurrence of perfluorinated carboxylic acids in Mexico City's wastewater: A monitoring study in the sewerage and a mega wastewater treatment plant.

An analytical method based on liquid chromatography coupled to mass spectrometry was validated to quantify five perfluorinated carboxylic acids (PFCA) namely, perfluorobutanoic acid (PFBA), perfluorohexanoic acid (PFHxA), perfluoroheptanoic acid (PFHpA), perfluorooctanoic acid (PFOA), and perfluoroundecanoic acid (PFUnA), in wastewater produced in a megacity. Sampling was performed on a monthly basis, obtaining samples from the undergrounded sewerage system and the main open-air canal transporting wastewater out the city. Steady levels of the sum of the target PFCA (Æ©PFCA) were determined on both sites through the study: 419.4 ± 24.3 ng L-1 in undergrounded sewage and 591.1 ± 39 ng L-1 in the open-air canal. Short-chain PFCA (PFBA, PFHxA, and PFHpA) were abundant, while concentrations of PFOA and PFUnA remained lower in both sampling sites. The open-air canal was transected in four sampling points, which were sampled throughout the monitoring campaign, finding that furtive discharges of municipal and industrial wastewater increased the levels of short-chain PFCA, while those of PFOA and PFUnA were depleted. Relevant concentrations of PFBA (176.9 ± 3.3 ng L-1), PFHxA (133.4 ± 2.5 ng L-1), PFHpA (116.6 ± 3.9 ng L-1), PFOA (133.1 ± 3.5 ng L-1), and PFUnA (23.5 ± 6.5 ng L-1) were found 60 km downstream, where the wastewater transported by the open-air canal is used in irrigation. A fraction of sewage is treated in a conventional wastewater treatment plant. The concentration of short-chain PFCA increased in effluent, adding extra loads of PFBA, PFHxA, and PFHpA to the environment.

Scientists raise alarms about fast tracking of transoceanic canal through Nicaragua.

Seeking economic growth and job creation to tackle the nation's extreme poverty, the Nicaraguan government awarded a concession to build an interoceanic canal and associated projects to a recently formed Hong Kong based company with no track record or related expertise. This concession was awarded without a bidding process and in advance of any feasibility, socio-economic or environmental impact assessments; construction has begun without this information. The 278 km long interoceanic canal project may result in significant environmental and social impairments. Of particular concern are damage to Lake Cocibolca, a unique freshwater tropical lake and Central America's main freshwater reservoir; damage to regional biodiversity and ecosystems; and socio-economic impacts. Concerned about the possibly irreparable damage to the environment and to native communities, conservationists and the scientific community at large are urging the Nicaraguan government to devise and reveal an action plan to address and mitigate the possible negative repercussions of this interoceanic canal and associated projects. Critical research needs for preparation of a comprehensive benefit-cost analysis for this megaproject are presented.

Sorption, desorption and displacement of ibuprofen, estrone, and 17ß estradiol in wastewater irrigated and rainfed agricultural soils.

Sorption and leaching potential of ibuprofen, estrone and 17ß estradiol were tested in two agricultural soils: one irrigated using municipal wastewater and the other used in rainfed agriculture. Batch sorption-desorption experiments and undisturbed soil column assays were carried out using both soils to which were added a mixture of the target compounds. The three compounds were sorbed to a different extent by both soils: estrone>17ß estradiol>ibuprofen. Higher sorption was observed in the irrigated soil, which was attributed to the accumulation of organic matter caused by wastewater irrigation. Desorption of hormones was hysteretic in the irrigated soil, while ibuprofen showed low hysteresis in both soils. Retardation of the compounds' displacement was consistent with the sorption pattern observed in the batch tests. Retardation factor (RF) was similar for the three compounds in the two tested soils, indicating that the target compounds are much more mobile in the soil columns than would be predicted based on their equilibrium sorption parameters. The results obtained in the experiments clarify the role of wastewater irrigated soils as a filter and degradation media for the target micropollutants.

The occurrence and distribution of a group of organic micropollutants in Mexico City's water sources.

The occurrence and distribution of a group of 17 organic micropollutants in surface and groundwater sources from Mexico City was determined. Water samples were taken from 7 wells, 4 dams and 15 tanks where surface and groundwater are mixed and stored before distribution. Results evidenced the occurrence of seven of the target compounds in groundwater: salicylic acid, diclofenac, di-2-ethylhexylphthalate (DEHP), butylbenzylphthalate (BBP), triclosan, bisphenol A (BPA) and 4-nonylphenol (4-NP). In surface water, 11 target pollutants were detected: same found in groundwater as well as naproxen, ibuprofen, ketoprofen and gemfibrozil. In groundwater, concentration ranges of salicylic acid, 4-NP and DEHP, the most frequently found compounds, were 1-464, 1-47 and 19-232 ng/L, respectively; while in surface water, these ranges were 29-309, 89-655 and 75-2,282 ng/L, respectively. Eleven target compounds were detected in mixed water. Concentrations in mixed water were higher than those determined in groundwater but lower than the detected in surface water. Different to that found in ground and surface water, the pesticide 2,4-D was found in mixed water, indicating that some pollutants can reach areas where they are not originally present in the local water sources. Concentration of the organic micropollutants found in this study showed similar to lower to those reported in water sources from developed countries. This study provides information that enriches the state of the art on the occurrence of organic micropollutants in water sources worldwide, notably in megacities of developing countries.

Removal and fate of emerging contaminants combining biological, flocculation and membrane treatments.

An experimental study combining biological treatment with flocculation (F) and ultrafiltration (UF) membrane technology was conducted, separately and in combination, seeking to increase insight into the capability of such treatment processes to remove emerging contaminants (ECs). The occurrence and removal efficiencies of 17 ECs are reported for wastewater from Mexico City. Results showed that activated sludge (AS) is the predominant process for removing acidic pharmaceutical compounds, and the use of a cationic flocculant increases the biodegradability of these compounds as well as that of 4-nonylphenol. The UF process alone showed greater removal of phenolic compounds than AS. However, the contribution of flocculation to EC removal by the UF unit was fairly limited. In general, the F + AS + UF processes yielded better results than their separate use, leading to the highest removal rates of 15 of the 17 compounds. In the case of some phenolic compounds and the phthalic acid esters, a competitive sorption process between the membrane and the sludge steps seemed to take place. Bis-2-ethylhexylphthalate (DEHP) was found to be significantly sorbed onto sludge. The F + AS + UF process operated as a membrane bioreactor (MBR) using 16 gL(-1) of suspended solids in the mixed liquor (MLSS) yielded the highest removal efficiencies for the ECs tested.

Mobility of 4-nonylphenol and di(2-ethylhexyl) phthalate in three agricultural soils irrigated with untreated wastewater.

Agricultural irrigation using raw wastewater is a popular practice in developing countries. However, as endocrine disrupting chemicals have been found in this water, the potential pollution of soil and water sources has become a source of concern. Such pollutants may be removed during the passage of wastewater through the soil by degradation and/or sorption. In this study the sorption and mobility of bis-2-ethyl(hexyl)phthalate (DEHP) and 4-nonylphenol (4-NP) in three different soils (Leptosol, Phaeozem and Vertisol) was compared. The distribution coefficients showed that DEHP is rapidly sorbed onto the three tested soils (K(d) between 1.8 × 10(4) and 4.2 × 0(4) L/kg), while sorption of 4-NP (K(d) between 15 and 80 L/kg) was weaker. In batch experiments the soil sorption capacity observed was as follows: Vertisol > Phaeozem > Leptosol for both compounds. However, in column experiments the retardation factor (R(F)) for 4-NP was higher than for the DEHP in the three soils. This suggests the possible migration of DEHP through the soil via colloids. The column results were found consistent with those observed in the field. It was concluded that the risk of groundwater contamination is higher for Leptosol soil than for Phaeozem and Vertisol soils and that DEHP can reach the aquifer prior to 4-NP.

Sorption and desorption of carbamazepine, naproxen and triclosan in a soil irrigated with raw wastewater: estimation of the sorption parameters by considering the initial mass of the compounds in the soil.

In conventional sorption studies, the prior presence of contaminants in the soil is not considered when estimating the sorption parameters because this is only a transient state. However, this parameter should be considered in order to avoid the under/overestimation of the soil sorption capacity. In this study, the sorption of naproxen, carbamazepine and triclosan was determined in a wastewater irrigated soil, considering the initial mass of the compounds. Batch sorption-desorption tests were carried out at two soil depths (0-10 cm and 30-40 cm), using either 10 mM CaCl(2) solution or untreated wastewater as the liquid phase. Data were satisfactorily fitted to the initial mass model. For the two soils, release of naproxen and carbamazepine was observed when the CaCl(2) solution was used, but not in the soil/wastewater system. The compounds' release was higher in the topsoil than in the 30-40 cm soil. Sorption coefficients (K(d)) for CaCl(2) solution tests showed that in the topsoil, triclosan (64.9 L kg(-1)) is sorbed to a higher extent than carbamazepine and naproxen (5.81 and 2.39 L kg(-1), respectively). In the 30-40 cm soil, carbamazepine and naproxen K(d) values (11.4 and 4.41 L kg(-1), respectively) were higher than those obtained for the topsoil, while the triclosan K(d) value was significantly lower than in the topsoil (19.2 L kg(-1)). Differences in K(d) values were found when comparing the results obtained for the two liquid phases. Sorption of naproxen and carbamazepine was reversible for both soils, while sorption of triclosan was found to be irreversible. This study shows the sorption behavior of three pharmaceuticals in a wastewater irrigated soil, as well as the importance of considering the initial mass of target pollutants in the estimation of their sorption parameters.

Accumulation and leaching potential of some pharmaceuticals and potential endocrine disruptors in soils irrigated with wastewater in the Tula Valley, Mexico.

The reuse of wastewater for irrigation of agricultural land is a well established practice but introduces many contaminants into the terrestrial environment including pharmaceuticals and personal care products. This study reports the persistence and leaching potential of a group of acidic pharmaceuticals, carbamazepine, and three endocrine disruptors in soils from the Tula Valley in Mexico, one of the largest irrigation districts in the world that uses untreated wastewater. After irrigation of soil columns with fortified wastewater over the equivalent of one crop cycle, between 0% and 7% of the total added amounts of ibuprofen, naproxen, and diclofenac and between 0% and 25% of 4-nonylphenol, triclosan, and bisphenol-A were recovered from the soil profiles. Carbamazepine was more persistent, between 55% and 107% being recovered. Amounts in leachates suggested that movement through the soil was possible for all of the analytes, particularly in profiles of low organic matter and clay content. Analysis of soil samples from the Tula Valley confirmed the general lack of accumulation of the acidic pharmaceuticals (concentrations from below the limit of detection to 0.61 µgkg(-1)) and endocrine disruptors (concentrations from below the limit of detection to 109 µgkg(-1)) despite continual addition through regular irrigation with untreated wastewater; there was little evidence of movement through the soil profiles. In contrast, carbamazepine was present in horizon A of the soil at concentrations equivalent to several years of additions by irrigation (2.6-7.5 µgkg(-1)) and was also present in the deeper horizons. The persistence and mobility of carbamazepine suggested a potential to contaminate groundwater.

Valuing the subsurface pathogen treatment barrier in water recycling via aquifers for drinking supplies.

A quantitative microbial risk assessment (QMRA) was performed at four managed aquifer recharge (MAR) sites (Australia, South Africa, Belgium, Mexico) where reclaimed wastewater and stormwater is recycled via aquifers for drinking water supplies, using the same risk-based approach that is used for public water supplies. For each of the sites, the aquifer treatment barrier was assessed for its log(10) removal capacity much like for other water treatment technologies. This information was then integrated into a broader risk assessment to determine the human health burden from the four MAR sites. For the Australian and South African cases, managing the aquifer treatment barrier was found to be critical for the schemes to have low risk. For the Belgian case study, the large treatment trains both in terms of pre- and post-aquifer recharge ensures that the risk is always low. In the Mexico case study, the risk was high due to the lack of pre-treatment and the low residence times of the recharge water in the aquifer. A further sensitivity analysis demonstrated that human health risk can be managed if aquifers are integrated into a treatment train to attenuate pathogens. However, reduction in human health disease burden (as measured in disability adjusted life years, DALYs) varied depending upon the number of pathogens in the recharge source water. The beta-Poisson dose response curve used for translating rotavirus and Cryptosporidium numbers into DALYs coupled with their slow environmental decay rates means poor quality injectant leads to aquifers having reduced value to reduce DALYs. For these systems, like the Mexican case study, longer residence times are required to meet their DALYs guideline for drinking water. Nevertheless the results showed that the risks from pathogens can still be reduced and recharging via an aquifer is safer than discharging directly into surface water bodies.

Physico-chemical treatment of Merida landfill leachate for chemical oxygen demand reduction by coagulation.

In order to determine the optimal dosage and type of coagulant for the physico-chemical treatment of leachate from the sanitary landfill of Merida, Mexico, a total of 864 jar tests were performed. Four metallic coagulants (ferric chloride, ferric sulphate, aluminium polychloride and aluminium sulphate) with doses ranging between 50 and 300 mg L(-1) and two polyelectrolytes (high-density anionic and cationic reagents) with doses from 2 to 12 mg L(-1) were tested. Neither an adequate type of coagulant nor an optimal dose could be found. The removal of contaminants was measured as total and dissolved chemical oxygen demand (COD). Soluble COD removal efficiencies were low, from 0 to 47%, with a 4% average value only. These low values of organic material removal were attributed to the particular characteristics of the Merida landfill leachate (low suspended solids concentration), so even with sweep-floc coagulation (300 mg L(-1) dose) only low COD removal efficiencies were obtained. A study of the suspended particle size distribution of the leachate was conducted in order to explain the poor performance. The particle size distribution ranged from 0.375 to 948.2 microm, with an average value of 22.97 microm. In a second step the optimal pH for physico-chemical treatment of these leachates was determined. Finally a greater than 90% removal of organic material, measured as suspended COD, was obtained at pH 2, which was considered as the optimal value.

Estudio de trazado de un modelo de reactor UASB

Este trabajo estudia el comportamiento hidráulico de un modelo a escala de un reactor anaerobio de lecho de lodos con flujo ascendente UASB. En el experimento se usó verde de bromocresol como trazador. El análisis de los resultados se realiza mediante los métodos de dispersión axial, tanques agitados en serie, tiempo promedio y se incorpora a éstos el modelo cinético de Michaelis-Menten. El diseño de reactores UASB vía la determinación de constantes cinéticas en el laboratorio y la información hidráulica proporcionada por el estudio lo hace menos empírico y en algunas circunstancias más preciso

Nuevas tecnologías para la potabilización del agua

Se presentan los orígenes de algunos contaminantes no convencionales, sus efectos y tecnicas de tratamiento

Nuevas tecnologías para la potabilización del agua

Se presentan los orígenes de algunos contaminantes no convencionales, sus efectos y tecnicas de tratamiento