Use of Biochar to Produce Reclaimed Water for Irrigation Reuse Purposes

Contaminants of emerging concern (CECs), especially, pharmaceutical and personal care products (PPCPs) are not removed well during conventional wastewater treatment and hence pose water quality risk to the environment and potentially to public health. The goal of this work was to remove CECs, with emphasis on PPCPs, from treated municipal wastewater using biochar, a low-cost adsorbent, by conducting fixed-bed sorption experiments. The reclaimed water after biochar treatment is intended for use in growing crops/grass for livestock production. If the PPCPs are present in the reclaimed water at high levels, there is greater potential for the PPCPs to enter into human food chain through the meat and its products. Native biochar from slash materials of Jeffrey pine forest was hand ground and sieved to enable its use in column set-up experiments. Chemical activation of native biochar using 1N KOH was performed to obtain KOH-biochar. Initially, total organic carbon (TOC) was used as a surrogate for CECs present in water, and native as well as KOH-biochar were used to remove TOC from treated wastewater. Prior to TOC removal experiments, DI water was pumped through native and KOH-biochar present in column to reduce carbon leaching from biochar. These leaching experiments showed that the TOC leached by native biochar was negligible when compared to KOH-biochar. From breakthrough curves that were plotted for native and KOH-biochar for TOC removal from treated wastewater, It was observed that, even though KOH-biochar removal efficiency for TOC was better at the beginning, both native and KOH-biochar reached their respective saturation capacities within 100 minutes of continuous pumping. Whereas granular activated carbon (GAC) containing column did not reach its saturation capacity during 46 hours of continuous pumping, and reached effluent to influent concentration ratio (Ce/Co) ratio of 0.15 only at the end. The saturation capacities obtained for native and KOH-biochar are 0.05 mg TOC/g and 0.13 mg TOC/g, respectively which were quite low when compared to the adsorption capacities mentioned in the literature. Surprisingly, the results obtained suggest that biochar may not be a potential adsorbent for PPCP removal contradicting the work that has been published till now. The opposing results might be due to interference of leached carbon from biochar itself. Also, it might suggest that TOC cannot be used as surrogate for CECs. Hence, a total of 12 CECs were analyzed using LC-MS/MS, after collecting the effluent samples from KOH-biochar and GAC. Adsorption behavior varied widely among different CECs when KOH-biochar was used as adsorbent. So, compounds were broadly divided into three categories based on their breakthrough behavior and Ce/Co ratios. Caffeine, carbamazepine, DEET and PFOA had a greater range of Ce/Co values with highest value >0.5 during continuous adsorption tests and were included in category I compounds. Breakthrough curve predictions revealed that these compounds follow non-linear Thomas model with adsorption capacities of 396 µg L-1, 391 µg L-1, 1160µg L-1 and 31 µg L-1, respectively for caffeine, carbamazepine, DEET and PFOA. Category II compounds were comprehensively removed throughout the continuous tests. Diphenhydramine, fluoxetine and trimethoprim fall under this category with a narrow range of Ce/Co values and highest of <0.15. Ibuprofen, ketoprofen, meprobamate, primidone and sulfamethoxazole fall under category III whose removal is minimal using KOH-biochar with highest Ce/Co value greater than 1. However, GAC comprehensively removed all the PPCP compounds except for ibuprofen and ketoprofen proving it to be a better adsorbent than biochar. For category I and II compounds, an analysis of compound’s structure, functional groups present and characteristics revealed that π-π electron donor–acceptor might be the most dominant adsorption mechanism. However, no conclusions could be made regarding the reasons for minimal removal of category III compounds. Further, calculations were done to assess if the biochar employed had the potential to remove CECs from reclaimed water used for irrigated animal feed crops when biochar is used as a soil amendment. It was determined that, based on the results from continuous tests, biochar amendment to soils can remove 7 out of 12 CEC compounds analyzed and could possibly reduce their uptake by plants

Numerical integration of singularly perturbed delay differential equations using exponential integrating factor

In this paper, we proposed a numerical integration technique with exponential integrating factor for the solution of singularly perturbed differential-difference equations with negative shift, namely the delay differential equation, with layer behaviour. First, the negative shift in the differentiated term is approximated by Taylor\u27s series, provided the shift is of (o(varepsilon )). Subsequently, the delay differential equation is replaced by an asymptotically equivalent first order neutral type delay differential equation. An exponential integrating factor is introduced into the first order delay equation. Then Trapezoidal rule, along with linear interpolation, has been employed to get a three term recurrence relation. The resulting tri-diagonal system is solved by Thomas algorithm. The proposed technique is implemented on model examples, for different values of delay parameter, $delta$ and perturbation parameter, $varepsilon$. Maximum absolute errors are tabulated and compared to validate the technique. Convergence of the proposed method has also been discussed

Analisis Pemahaman Konsep Matematika pada Materi Operasi Bilangan Bulat di SMP Negeri 4 Gorontalo

This research is a qualitative approach to analyze the understanding of concepts in the material of integer operations. The research was conducted at SMP Negeri 4 Gorontalo involving 25 students as the object of research. This is a descriptive study with indicators used to describe students’ understanding of mathematical concepts, among others (1) Presenting a concept in various forms of mathematical representation, (2) Restating a Concept, (3) classifying objects according to certain properties (according to the concept), (4) Applying the problem-solving concept or algorithm. Furthermore, interviews were conducted to deepen information about students’ understanding of mathematical concepts. The analysis of the results showed that students’ understanding of mathematical concepts on integer operations material was classified as moderate, which was indicated by the ability of students who only met some indicators of understanding the measured mathematical concepts

Wire-arc additive manufacturing: Process optimization, advancements, in-process data monitoring, and material characterization

This thesis explores the optimization and characterization of Wire Arc Additive Manufacturing (WAAM) for low-carbon steel, aiming to enhance deposition quality, geometrical precision, and material properties. Preliminary experiments established a processing window by analyzing the influence of key process parameters power, travel speed, wire feed speed, and stand-off distance on bead geometry and material properties. Advanced methodologies, such as force air cooling, in-process data monitoring and microstructural analysis, were utilized to evaluate the thermal and mechanical behavior of WAAM-fabricated components

Evaluation of flexibility assessment indices upon flexible loading of thermal power plants with high penetration of renewables

In this paper, power system flexibility assessment indices evaluation has been carried out with high penetration of renewables in MATLAB environment, inspired from IRENA FlexTool. The parameters such as magnitude of energy mix, resources available, electricity tariffs and price affordability play a vital role in the proposed research. The developed program has been tested against IEEE 9 bus and IEEE 39 bus systems with and without time-series data and with and without high penetration of renewables. By closely matching the results for various test cases and time series evaluations for IEEE 9 and IEEE 39 bus systems, the developed program has been benchmarked with the IRENA FlexTool and the comparisons have been charted out