Continuous flow operation of solar photo-Fenton fused with NaOCl as a novel tertiary treatment.

A novel strategy based on solar photo-Fenton mediated by ferric nitrilotriacetate (Fe3+-NTA) combined with NaOCl in continuous flow mode for wastewater reclamation has been studied. Escherichia coli (E. coli) inactivation attained ≥ 5 log10-units, meeting the most restrictive EU 2020/741 target (10 CFU/100 mL), and 75% of organic microcontaminant total load was removed. As a remarkable finding, trihalomethanes (THMs) concentration was insignificant, complying by far with the Italian legislation limit. To attain these results, first the effect of liquid depth on E. coli inactivation and imidacloprid (IMD) removal from spiked municipal effluents was evaluated in continuous flow pilot-scale raceway pond reactors at 60-min hydraulic residence time with low reagent concentrations (0.10 mM Fe3+-NTA, 0.73 mM H2O2 and 0.13 mM NaOCl). Disinfection was due to the bactericidal effect of chlorine. In contrast, liquid depth notably influenced microcontaminant removal, highlighting that operation at 10-cm liquid depth allows achieving treatment capacities higher than at 5 cm (16.50 vs 28.20 mg IMD/m2∙day). Next, the monitoring of THMs was carried out to evaluate the generation and degradation of disinfection by-products, along with the removal of actual microcontaminants. These promising results draw attention to the treatment potential and open the way for its commercial application.

Continuous solar photo-Fenton for wastewater reclamation in operational environment at demonstration scale.

For the first time, a continuous flow solar photo-Fenton demonstration plant has been assessed for wastewater reclamation according to the EU 2020/741 regulation. The treated water qualities achieved under two operating strategies (acidic and neutral pH) in a 100-m2 raceway pond reactor were explored in terms of liquid depth, iron source, reagent concentrations, and hydraulic residence time over three consecutive days of operation. The results obtained at acidic pH showed removal percentages of contaminants of emerging concern (CECs) > 75% and water quality classes B, C and D according to EU regulation at both assessed operating conditions, with treatment capacities up to 1.92 m3 m-2 d-1. At neutral pH with ferric nitrilotriacetate (Fe3+-NTA), 50% of CEC removal and only water quality class D were achieved with the most oxidizing condition assessed, giving a treatment capacity of 0.80 m3 m-2 d-1. The treatment capacities obtained in this work, which have never been achieved with solar water treatments, demonstrate the potential of this technology for commercial-scale application.

Photovoltaic and solar disinfection technology meeting the needs of water and electricity of a typical household in developing countries: From a Solar Home System to a full-functional hybrid system.

A novel SolWat system designed exclusively as a Solar Home System that also meets the drinking water access in a family of a rural community in a developing country has been designed, manufactured and tested outdoors. The system is composed of 5 photovoltaic modules of monocrystalline silicon solar cells technology, each 20 Wp, parallel-interconnected, adding up to a 100 Wp system. The modules have a water reactor on top with the capacity of providing a minimum of 37.5 L per day for a family of 5 members, guaranteeing the minimum daily needs. Experimental campaign run tests of SODIS of 3 h each, running the system 3 times per day (with a total of 9 h of experimentation per day). Results show that the water treatment of 3 h should be increased at certain periods of the day when the UV dose is not sufficient (late in the afternoon). E. coli and Enterococcus spp achieved total inactivation or almost total disinfection. Regarding electrical production, although energy losses of 5.6-10% were observed in comparison with a single PV module, it was sufficient to fully meet the load demand of the solar home system. The system could be used in a household of a developing country, using only solar energy to meet the electricity and drinking water demand.

The problem of drinking water access: A review of disinfection technologies with an emphasis on solar treatment methods.

The lack of access to safe drinking water is one of the biggest challenges facing humanity in the 21st century. Despite the collective global effort that has been made, the drinking water sources of at least 2 billion people are faecally contaminated, resulting in more than half a million diarrhoeal deaths each year, with the majority occurring in developing countries. Technologies for the inactivation of pathogenic microorganisms in water are therefore of great significance for human health and well-being. However, conventional technologies to provide drinking water, although effective, present limitations that impede their global application. These treatment methods often have high energy and chemical demands, which limits their application for the prevention of waterborne diseases in the most vulnerable regions. These shortcomings have led to rapid research and development of advanced alternative technologies. One of these alternative methods is solar disinfection, which is recognised by the World Health Organization as one of the most appropriate methods for producing drinkable water in developing countries. This study reviews conventional technologies that are being applied at medium to large scales to purify water and emerging technologies currently in development. In addition, this paper describes the merits, demerits, and limitations of these technologies. Finally, the review focuses on solar disinfection, including a novel technology recently developed in this field.

A critical review on iodine presence in drinking water access at the Saharawi refugee camps (Tindouf, Algeria).

Iodine content in drinking water at the Saharawi refugee camps was analysed to assess the controversy in the origin of the prevalence of goitre among this population. A review on the iodine presence in drinking water reported in the literature was conducted, along with international standards and guidelines for iodine intake and iodine concentration in drinking water were also consulted. Chinese legislation was taken as the reference standard to evaluate the iodine concentration in water as adequate (10-150µg/L) or not (high iodine >150µg/L and iodine excess goitre >300µg/L). Water sampling was conducted in 2015 and 2016 at the Saharawi camps (El Aiun, Awserd, Smara, Boujador and Dakhla) and at the institutional capital of Rabouni. The water supply in the camps is organized in three zones: El Aiun and Awserd where each 'wilaya' receives treated water 20days and raw water another 20days; Smara, Rabouni and Boujador receiving treated water continuously and Dakhla receiving raw water continuously. Results show that Smara, Rabouni and Boujador have access to drinking water with adequate iodine levels, as it occurs in Dakhla where raw water meets the Chinese standard, however in El Aiun and Awserd all population should have access to treated water given the current quality of the raw water supply. External supplies of water and animal milk could be also contributing to the high iodine intake. In conclusion, the contribution of drinking water as the main source of iodine to the urinary iodine concentration (UIC) and goitre prevalence among the Saharawi refugee population is not clear. Further studies should be conducted to assess the iodine content among all the nutritional sources of the population with a detailed study on the daily intake of these foods and drinks, including UIC and goitre prevalence studies.

An insight into the drinking-water access in the health institutions at the Saharawi refugee camps in Tindouf (Algeria) after 40years of conflict.

Drinking water access in the Saharawi refugee camps located in the Algerian desert is a challenge that is still an on-going problem after 40years of conflict. This work presents an analysis of the situation with emphasis on the water supply in health institutions (quantity and quality) including both sanitary inspections and a comprehensive water quality study. Results from sanitary inspections show that only half of the water supply installations at the hospitals are in adequate conditions and the rest present high risk of microbiological contamination. Water access in small medical community centres on the other hand present issues related to the non-availability of food-grade water tanks for the institutions (70%), the use of small 10l containers as the main water supply (40%), poor maintenance (60% under antihygienic conditions and 30% with damaged covers), and insufficient chlorine levels that prevent microbiological contamination. Regarding water quality analyses, raw water supply in Smara, El Aiun and Awserd camps present high conductivity and high levels of fluoride, chloride, nitrate and sulphate, but dropping to normal levels within the drinking-water standards after water treatment via reverse osmosis plants. But for the case of El Aiun and Awserd, the reverse osmosis plant only provides treated water to the population each 20days, so the population receives raw water directly and health risks should be evaluated. Finally, Dakhla water supply is the best in terms of physico-chemical parameters quality, currently providing safe drinking water after a chlorination stage. In summary, drinking water access has improved dramatically in the last years due to the efforts of local and international authorities but several issues remain to be solved: access to treated water for all the population, improved water quality controls (especially in Dakhla), expansion of distribution networks, and adequate storage systems and maintenance.