Studies were conducted evaluating the nature of particles that result from ferrate reduction in a laboratory water matrix and in a natural surface water with a moderate amount of dissolved organic carbon. Particle characterization included size, surface charge, morphology, X-ray photoelectron spectroscopy, and transmission Fourier transform infrared spectroscopy. Characteristics of ferrate resultant particles were compared to particles formed from dosing ferric chloride, a common water treatment coagulant. In natural water, ferrate addition produced significantly more nanoparticles than ferric addition. These particles had a negative surface charge, resulting in a stable colloidal suspension. In natural and laboratory matrix waters, the ferrate resultant particles had a similar charge versus pH relationship as particles resulting from ferric addition. Particles resulting from ferrate had morphology that differed from particles resulting from ferric iron, with ferrate resultant particles appearing smoother and more granular. X-ray photoelectron spectroscopy results show ferrate resultant particles contained Fe2O3, while ferric resultant particles did not. Results also indicate potential differences in the mechanisms leading to particle formation between ferrate reduction and ferric hydrolysis.

Oxygenic photogranules (OPGs) can be directly formed from activated sludge under hydrodynamic conditions, but only with some combinations of different magnitudes of light, mixing, and chemical energies.

Filamentous cyanobacteria are an essential element of oxygenic photogranules for granule-based wastewater treatment with photosynthetic aeration. Currently, mechanisms for the selection of this microbial group and their development in the granular structure are not well understood. Here, we studied the characteristics and fate of iron in photogranulation that proceeds in a hydrostatic environment with an activated sludge (AS) inoculum. We found that the level of Fe in bulk liquids (Fe BL ) sharply increased due to the decay of the inoculum but quickly diminished along with the bloom of microalgae and the advent of the oxic environment. Iron linked with extracellular polymeric substances (Fe EPS ) continued to decline but reached steady low values, which occurred along with the appearance of granular structure. Strong negative correlations were found between Fe EPS and the pigments specific for cyanobacteria. Spectroscopies revealed the presence of amorphous ferric oxides in pellet biomass, which seemed to remain unaltered during the photogranulation process. These results suggest that the availability of Fe EPS in AS inoculumsafter algal bloomselects cyanobacteria, and the limitation of this Fe pool becomes an important driver for cyanobacteria to granulate in a hydrostatic environment. We therefore propose that the availability of iron has a strong influence on the photogranulation process.

Background: There have been notable joint efforts from the private and public sectors in promoting households' access to clean and efficient energy sources. Despite the noteworthy progress realized over the years, the consumption and reliance on clean energy sources are reportedly low. This scenario is evident among households practicing multiple energy use, whereby energy proportions consumed from the clean energy sources are much lower compared to nonclean energy sources. As such, reliance on non-clean energy has greatly hindered the projected welfare and productive gains that comes along with access to clean energy sources. To understand households' energy consumption behavior, this study takes into consideration that energy preference (choice) and intensity (proportions consumed) are two independent decisions. Therefore, a succinct understanding of the factors affecting these decisions acts as a basis for an optimal transition to clean energy sources. Methods: The study utilized a nationally representative cross-sectional household dataset (3663 households) across Kenya. A series of diagnostic and specification tests were carried out so as to identify the most suitable estimation technique in achieving the underlying objectives of the study. The preference for Cragg's double-hurdle model was premised on the fact that the model postulates that households must pass two separate hurdles before a positive level of consuption is observed. Maximum likelihood estimations were derived, followed by the marginal effects for the probability of participation and consumption intensity (conditional and unconditional) to unveil the effects of explanatory variables on the dependent variable. Results: Results show the diversity in magnitude and direction of how various factors affect the preference and consumption intensity among households. For instance, households' energy preference and consumption intensity are predominantly affected by location (rural or urban), household's decision maker on energy use, education level, age of the household head, and the average monthly income. Conclusion: In this regard, the promotion of clean energy use should target households in rural areas and households with lower level of education and lower income brackets. Uptake of clean energy sources such as liquefied petroleum gas should be encouraged among rural and urban poor households through reducing the upfront cost of acquiring cylinders and the refilling costs.