Phosphorus adsorption and organic release from dried and thermally treated water treatment sludge.

The study investigated water treatment sludge (WTS) as a phosphorus (P) adsorbent and examined the release of organic matter during the P adsorption process. Previous studies indicated that WTS is an effective adsorbent for P but also releases organic matter, which may affect the organoleptic properties of treated water, but no study has characterised organic release and conducted an in-depth study on its behaviours. This study characterised the organic release during the P adsorption process from four different WTS samples. This study also offers results from a 60-day column experiment that indicate that WTS columns effectively removed the majority of P from the 2 mg/L feed solution. The total organic carbon (TOC) release was gradually reduced from 24.9 mg/L on day 1 to stable levels of 4.4 mg/L to 4.1 mg/L from day 22 onwards. After 60 days, when the organic matter was nearly exhausted, WTS columns were still effective in P adsorption from the solution. In addition, the thermal treatment of WTS at different temperatures was investigated to reduce TOC release and increase P adsorption. The results showed that thermal treatment not only minimized TOC release but also enhanced the P adsorption capacity of the sludge. In a 24-h batch experiment, WTS treated at 600 °C showed the highest P adsorption (1.7 mg/g) with negligible TOC release when compared to sludge treated at 500 °C WTS (1.2 mg/g), 700 °C WTS (1.5 mg/g) and dried WTS (0.75 mg/g). However, the release of inorganic compounds slightly increased after thermal treatment. Future studies could focus on determining whether the thermal processing of WTS which can enhance the WTS's adsorption to emerging pollutants like per- and poly-fluoroalkyl substances and other contaminants. The findings of this study could influence the management practices of water authorities and contribute to the water sector's sustainability objectives.

Comparative analysis of biochar carbon stability methods and implications for carbon credits.

Biochar is an emerging negative emission technology. Its ability to sequester carbon and subsequent carbon credit valuation hinge on the stability of its carbon structure. The widely used indicators of carbon stability H:Corg and O:Corg provide conservative results as these are based on limited incubation experiments and associated modeling results. The results from these accepted methods and other derived methods have not been compared as indicators of carbon stability in a variety of biochar samples. Furthermore, the influence of contrasting feedstock and production techniques on biochar carbon stability is not well explored. Therefore, to address these challenges, a comprehensive stability analysis of 21 different biochar samples with contrasting feedstocks and pyrolysis techniques was conducted using a combination of instrumental methods and derived indicators of carbon stability. Methods such as biochar carbon half-life, thermo-stable fraction, oxidation resistance (R50), and carbon sequestration potential (CS) were used. Based on the initial carbon content of the biochar, simple pyrolysis techniques have similar potential for carbon credits as biochar produced from advanced pyrolysis techniques. Results indicate that the carbon stability of a biochar product is primarily a factor of feedstock type. We found that biochar carbon stability is not related to volatile matter or fixed carbon content for biochar produced using a simple pyrolysis technique and mixed feedstock. Biochars with H:Corg < 0.4 were deemed to have lower carbon stability when compared using different methods. No correlation was observed between the carbon stability of biochar using H:Corg and other methods, however, correlations were observed between half-life, O:Corg, fixed carbon, number of aromatic peaks in FTIR spectrum, R50, and CS. Therefore, it is recommended that data from additional incubation and modeling studies need to be considered to increase the confidence in carbon stability results having major implications to carbon credits.

Cross-informant ratings on emotional and behavioral problems in Nepali adolescents: A comparison of adolescents' self-reports with parents' and teachers' reports.

BACKGROUND: Studies on cross-informant agreement on adolescents' emotional and behavioral problems (EBPs) are sparse in low- and middle-income countries. This study aimed to assess parent-adolescent and teacher-adolescent agreement on EBPs and associated factors in Nepal. METHODS: This cross-sectional survey included 1904 school-going adolescents aged 11-18, enrolled in government and private schools located in sixteen districts of Nepal. The Nepali versions of the Youth Self Report, Child Behavior Checklist, and Teacher's Report Form were administered to assess EBPs reported by adolescents, their parents, and teachers, respectively. Repeated measures analysis of variance (ANOVA) was done to assess mean differences in problem scores. Pearson's correlation was used to assess cross-informant agreement. Linear regression analysis was used to explore factors associated with cross-informant discrepancies in EBPs. RESULTS: Adolescents reported significantly more problems than their parents and teachers. Mean Total Problem scores for the 90 common items in the adolescents' self-reports, parent reports, and teacher reports were 34.5 (standard deviation [SD]: 21.4), 24.1 (SD = 19.2), and 20.2 (SD = 17.5) respectively. Parent-adolescent agreement on Total Problems was moderate, whereas teacher-adolescent agreement was low. The parent-adolescent agreement was moderate to low for the two broadband scales and all syndrome scales, whereas the teacher-adolescent agreement was low for all scales. Female gender and ethnic minority status impacted both parent-adolescent and teacher-adolescent discrepancies. Family stress/conflicts impacted parent-adolescent discrepancies, while academic performance impacted teacher-adolescent discrepancies. CONCLUSIONS: Nepali adolescents reported more EBPs than their parents and teachers. The agreement between adolescents' self-reports and reports by their parents and teachers was moderate to low. Gender, caste/ethnicity, family stress/conflicts, and academic performance were associated with cross-informant discrepancies. It is crucial to collect information from different sources, consider context-specific needs, and discern factors influencing cross-informant discrepancies to accurately assess adolescents' EBPs and develop personalized approaches to treatment planning.

Evaluating fundamental biochar properties in relation to water holding capacity.

Biochar products that hold and release water within a stable carbonised porous structure provide many opportunities for climate mitigation and a range of applications such as for soil amendments. Biochar that are produced from various organic feedstocks by pyrolysis can provide multiple co-benefits to soil including improving soil health and productivity, pH buffering, contaminant control, nutrient storage, and release, however, there are also risks for biochar application in soils. This study evaluated fundamental biochar properties that influence Water Holding Capacity (WHC) of biochar products and provides recommendations for testing and optimising biochar products prior to soil applications. A total of 21 biochar samples (locally sourced, commercially available, and standard biochars) were characterised for particle properties, salinity, pH and ash content, porosity, and surface area (with N2 as adsorbate), surface SEM imaging, and several water testing methods. Biochar products with mixed particle size, irregular shapes, and hydrophilic properties were able to rapidly store relatively large volumes of water (up to 400% wt.). In contrast, relatively less water (as low as 78% wt.) was taken up by small-sized biochar products with smooth surfaces, along with hydrophobic biochars that were identified by the water drop penetration test (rather than contact angle test). Water was stored mostly in interpore spaces (between biochar particles) although intra-pore spaces (meso-pore and micropore scale) were also significant for some biochars. The type of organic feedstock did not appear to directly affect water holding, although further work is needed to evaluate mesopore scale processes and pyrolytic conditions that could influence the biochemical and hydrological behaviour of biochar. Biochars with high salinity, and carbon structures that are not alkaline pose potential risks when used as soil amendments.

Self-reported emotional and behavioral problems among school-going adolescents in Nepal-A cross-sectional study.

BACKGROUND: Studies on self-reported emotional and behavioral problems (EBPs) among adolescents are still sparse in many low- and middle-income countries. In Nepal, no such studies have been performed on a larger scale, and little is known about self-reported EBPs in the adolescent population. METHODS: This cross-sectional, school-based study on EBPs included 1904 adolescents aged 11-18 years, enrolled in government and private schools located in 16 districts in Nepal. The Nepali version of the Youth Self Report form was used to assess self-reported EBPs, and the Teacher Report Form was used to assess academic performance. Analysis of variance (ANOVA) was used for gender comparisons on adolescents' EBPs and on academic competence. Multiple regression analysis was done to explore correlates of self-reported EBPs. RESULTS: The overall prevalence of self-reported EBPs was 14.2%; 15.6% in boys and 12.9% in girls. The mean Total Problems score was 39.27 (standard deviation = 24.16); no gender differences were observed. Boys scored higher on Externalizing Problems and girls scored higher on Internalizing Problems. The effect sizes for gender comparisons were small with Hedges' g ranging from -0.29 to 0.28. Physical illness and negative/traumatic life events were positively correlated with self-reported EBPs, whereas academic performance was negatively correlated. However, the effect sizes were small (η2 < 0.02). CONCLUSION: This study helps to narrow the knowledge gap on the prevalence, magnitude, and types of self-reported EBPs in Nepali adolescents. It demonstrated an association between self-reported EBPs and academic performance and linked self-reported EBPs to other factors such as negative/traumatic life events and physical illness. The findings might assist health authorities in the planning of mental health services and may also provide valuable background information to clinicians dealing with adolescent mental health problems.

Investigation on removal of perfluorooctanoic acid (PFOA), perfluorooctane sulfonate (PFOS), perfluorohexane sulfonate (PFHxS) using water treatment sludge and biochar.

This work assessed the adsorption performance of three common PFAS compounds (PFOA, PFOS and PFHxS) on two water treatment sludges (WTS) and two biochars (commercial biomass biochar and semi-pilot scale biosolids biochar). Of the two WTS samples included in this study, one was sourced from poly-aluminium chloride (PAC) and the other from alum (Al2(SO4)3). The results of experiments using a single PFAS for adsorption reinforced established trends in affinity - the shorter-chained PFHxS was less adsorbed than PFOS, and the sulphates (PFOS) were more readily adsorbed than the acid (PFOA). Interestingly, PAC WTS, showed an excellent adsorption affinity for the shorter chained PFHxS (58.8%), than the alum WTS and biosolids biochar at 22.6% and 41.74%, respectively. The results also showed that the alum WTS was less effective at adsorption than the PAC WTS despite having a larger surface area. Taken together, the results suggest that the hydrophobicity of the sorbent and the chemistry of the coagulant were critical factors for understanding PFAS adsorption on WTS, while other factors, such as the concentration of aluminium and iron in the WTS could not explain the trends seen. For the biochar samples, the surface area and hydrophobicity are believed to be the main drivers in the different performances. Adsorption from the solution containing multiple PFAS was also investigated with PAC WTS and biosolids biochar, demonstrating comparable performance on overall adsorption. However, the PAC WTS performed better with the short-chain PFHxS than the biosolids biochar. While both PAC WTS and biosolids biochar are promising candidates for adsorption, the study highlights the need to explore further the mechanisms behind PFAS adsorption, which could be a highly variable source to understand better the potential for WTS to be utilized as a PFAS adsorbent.

Optimising water holding capacity and hydrophobicity of biochar for soil amendment - A review.

Biochar is a product of the thermal treatment of biomass, and it can be used for enhancing soil health and productivity, soil carbon sequestration, absorbance of pollutants from water and soil, and promoting environmental sustainability. Extensive research has been done on applications of biochar to enhance the Water Holding Capacity (WHC) of biochar amended soil. However, a comprehensive road map of biochar optimised for enhanced WHC, and reduced hydrophobicity is not yet published. This review is the first to provide not only quantitative information on the impacts of biochar properties in WHC and hydrophobicity, but also a road map to optimise biochar for enhanced WHC when applied as a soil amendment. The review shows that straw or grass-derived biochar (at 500-600 °C) increases the WHC of soil if applied at 1 to 3 % in the soil. It is clear from the review that soil of varying texture requires different particle sizes of biochar to enhance the WHC and reduce hydrophobicity. Furthermore, the review concludes that ageing biochar for at least a year with enhanced oxidation is recommended for improving the WHC and reducing hydrophobicity compared to using biochar immediately after production. Additionally, while producing biochar a residence time of 1 to 2 h is recommended to reduce the biochar's hydrophobicity. Finally, a road map for optimising biochar is presented as a schematic that can be a resource for making decisions during biochar production for soil amendment.