Physico-chemical characterization and possible uses of sludge processed from an urban sewage treatment plant.

Nowadays, the challenge is to transform dehydrated sewage sludge resulting from wastewater treatment plants from waste into resource. Following this objective, the sludge was further dried and submitted to X-ray diffraction (XRD) and FTIR analysis. The sludge was first dried in ventilated and unventilated spaces at 50 ∘C and 100 ∘C, for 60 and 100 minutes (min) in each case. The final mass and evaporation degree of the sludge depends on the initial mass, ventilation type, drying time, and temperature. The ventilated drying space is preferred for temperature control, homogeneity, and higher evaporation degree. The influence of the drying process on the structure and behavior of the sewage sludge was emphasized through X-ray diffraction (XRD) and FTIR analysis. The XRD shows good structural properties of the sludge samples given by the reduction of the particle size through evaporation. According to FTIR, evaporation influences the depolymerization of the silicate network. The hydroxyl units and metallic ion modifiers can improve the sludge structure, but its intensity decreases through evaporation. With high content of solid substance, and good relation between the composition of the sludge and its structure and behavior, the dried sewage sludge can be used in: (i) agriculture, (ii) construction, (iii) the energy sector.

COVID-19 and Water Variables: Review and Scientometric Analysis.

COVID-19 has changed the world since 2020, and the field of water specifically, boosting scientific productivity (in terms of published articles). This paper focuses on the influence of COVID-19 on scientific productivity with respect to four water variables: (i) wastewater, (ii) renewable water resources, (iii) freshwater withdrawal, and (iv) access to improved and safe drinking water. The field's literature was firstly reviewed, and then the maps were built, emphasizing the strong connections between COVID-19 and water-related variables. A total of 94 countries with publications that assess COVID-19 vs. water were considered and evaluated for how they clustered. The final step of the research shows that, on average, scientific productivity on the water topic was mostly conducted in countries with lower COVID-19 infection rates but higher development levels as represented by gross domestic product (GDP) per capita and the human development index (HDI). According to the statistical analysis, the water-related variables are highly significant, with positive coefficients. This validates that countries with higher water-related values conducted more research on the relationship with COVID-19. Wastewater and freshwater withdrawal had the highest impact on the scientific productivity with respect to COVID-19. Access to safe drinking water becomes insignificant in the presence of the development parameters.

Biological Activated Sludge from Wastewater Treatment Plant before and during the COVID-19 Pandemic.

The COVID-19 pandemic and the related measures brought a change in daily life that affected the characteristics of the municipal wastewater and further, of the biological activated sludge. The activated sludge process is the most widely used biological wastewater treatment process in developed areas. In this paper, we aim to show the situation of specific investigations concerning the variation of the physicochemical parameters and biological composition of the activated sludge from one conventional wastewater treatment plant from a metropolitan area. The investigations were carried out for three years: 2019, 2020 and 2021. The results showed the most representative taxa of microorganisms: Microtrix, Aspidisca cicada, Vorticella convallaria, Ciliata free of the unknown and Epistylis and Rotifers. Even if other microorganisms were found in the sludge flocs, their small presence did not influence in any way the quality of the activated sludge and of the wastewater treatment process. That is why we conclude that protozoa (especially Flagellates and Ciliates) and rotifers were the most important. Together with the values and variation of the physicochemical parameters, they indicated a good, healthy, and stable activated sludge, along with an efficient purifying treatment process, no matter the loading conditions.