8 research outputs found
Influence of filter age on Fe, Mn and NH4+ removal in dual media rapid sand filters used for drinking water production
Get PDFRapid sand filtration is a common method for removal of iron (Fe), manganese (Mn) and ammonium (NH4+) from anoxic groundwaters used for drinking water production. In this study, we combine geochemical and microbiological data to assess how filter age influences Fe, Mn and NH4+ removal in dual media filters, consisting of anthracite overlying quartz sand, that have been in operation for between ∼2 months and ∼11 years. We show that the depth where dissolved Fe and Mn removal occurs is reflected in the filter medium coatings, with ferrihydrite forming in the anthracite in the top of the filters ( 1 m). Removal of NH4+ occurs through nitrification in both the anthracite and sand and is the key driver of oxygen loss. Removal of Fe is independent of filter age and is always efficient (> 97% removal). In contrast, for Mn, the removal efficiency varies with filter age, ranging from 9 to 28% at ∼2–3 months after filter replacement to 100% after 8 months. After 11 years, removal reduces to 60–80%. The lack of Mn removal in the youngest filters (at 2–3 months) is likely the result of a relatively low abundance of mineral coatings that adsorb Mn2+ and provide surfaces for the establishment of a microbial community. 16S rRNA gene amplicon sequencing shows that Gallionella, which are known Fe2+ oxidizers, are present after 2 months, yet Fe2+ removal is mostly chemical. Efficient NH4+ removal (> 90%) establishes within 3 months of operation but leakage occurs upon high NH4+loading (> 160 µM). Two-step nitrification by Nitrosomonas and Candidatus Nitrotoga is likely the most important NH4+ removal mechanism in younger filters during ripening (2 months), after which complete ammonia oxidation by Nitrospira and canonical two-step nitrification occur simultaneously in older filters. Our results highlight the strong effect of filter age on especially Mn2+but also NH4+ removal. We show that ageing of filter medium leads to the development of thick coatings, which we hypothesize leads to preferential flow, and breakthrough of Mn2+. Use of age-specific flow rates may increase the contact time with the filter medium in older filters and improve Mn2+ and NH4+ removal
Accordion Structure with Box
No full texthttps://stars.library.ucf.edu/bookartsexhibit-14thannual/1008/thumbnail.jp
Is the relationship between empathy and altruism moderated by gender?
No full textThe researchers investigated possible perpetrators of altruistic behavior in Filipino college students and above. This thesis aims to examine the moderation effect of gender in the relationship between empathy and altruism. Since there is a utilization of a moderation analysis, Andrew Hayes process modelling was the main method of statistical analysis alongside multiple linear regression to test possible significance and effects of the variables involved. The target participants were Filipino state and private university students aged 18-25 years old (M=19.6864, SD=1.16165). The universities involved were: Ateneo de Manila University, De La Salle-College of Saint Benilde, De La Salle University-Dasmarinas, De La Salle University-Manila, Polytechnic University of the Philippines, San Beda College, Siliman University, University of Asia and Pacific, University of Santo Tomas, University of the Philippines-Cebu, University of the Philippines-Diliman, University of the Philippines-Los Baños, University of the Philippines-Manila, University of the Philippines-Visayas, and World Citi Colleges-Quezon City. After gathering the empathy and altruism level of 338 participants, findings showed a non-significant moderation effect of gender in the relationship between empathy levels and altruism levels. Results imply that the higher the empathy levels of a person, it is most likely that he/she would have higher altruism levels as well, regardless of his/her gender
